Neurosteroid Actions in Memory and Neurologic/Neuropsychiatric Disorders

Abstract

Memory dysfunction is a symptomatic feature of many neurologic and neuropsychiatric disorders; however, the basic underlying mechanisms of memory and altered states of circuitry function associated with disorders of memory remain a vast unexplored territory. The initial discovery of endogenous neurosteroids triggered a quest to elucidate their role as neuromodulators in normal and diseased brain function. In this review, based on the perspective of our own research, the advances leading to the discovery of positive and negative neurosteroid allosteric modulators of GABA type-A (GABA_A), NMDA, and non-NMDA type glutamate receptors are brought together in a historical and conceptual framework. We extend the analysis toward a state-of-the art view of how neurosteroid modulation of neural circuitry function may affect memory and memory deficits. By aggregating the results from multiple laboratories using both animal models for disease and human clinical research on neuropsychiatric and age-related neurodegenerative disorders, elements of a circuitry level view begins to emerge. Lastly, the effects of both endogenously active and exogenously administered neurosteroids on neural networks across the life span of women and men point to a possible underlying pharmacological connectome by which these neuromodulators might act to modulate memory across diverse altered states of mind.

Introduction

A major question in neuroscience since the initial discovery that somatically released gut peptides could alter central nervous system (CNS) function relates to whether and how the body can influence or modulate brain function. The science of neuroendocrinology was advanced conceptually 50 years ago by the independent discoveries of Schally, Leeman and Reichlin, demonstrating that the gut peptides thyrotropin-releasing hormone (TRH) (1, 2) and substance P (3, 4) were synthesized, stored, and released in the hypothalamus as endogenous neuromodulators. The demonstration of local synthesis of neuropeptides within the CNS presented a non-canonical mechanism for gut peptides to act as chemical neurotransmitters at synapses, without transport via the systemic circulation and transport across the blood-brain barrier (BBB).

The BBB does not impair access of sex steroids to the CNS to the same extent as gut peptides. Lipophilic steroid hormones, such as progesterone, estradiol and testosterone cross the BBB and readily gain access to the CNS (5) where they can serve as agonists of steroid hormone receptors that in turn act at genomic response elements. In the early 1980s, several lines of evidence from Etienne, Baulieu, and Robel (6–9) challenged the central dogma that neuroactive steroids were exclusively synthesized peripherally, demonstrating for the first time that steroids could be synthesized from cholesterol within the CNS.

Such steroids were called neurosteroids and an intensive search began to identify which steroids belonged to this group and to define their function. An early clue came from the research of Selye (10) showing that steroids could have anesthetic effects. Four decades later, in 1983, radiolabeling studies by Sapolsky, McEwen, and Rainbow revealed uptake of corticosterone in the stratum oriens and apical dendrite regions of the hippocampus, suggesting that GABAergic interneurons in these regions might possess corticosterone receptors (11). Corticosterone treatment had been shown to affect GABA uptake in the hippocampus, possibly suggesting a mechanism for hormonal modulation of memory. In a seemingly unrelated study, while investigating the pharmacological mechanism of action of the synthetic steroid anesthetic alphaxalone, Harrison and Simmonds (12) demonstrated that alphaxalone and barbiturates shared a common mechanism of action via augmenting GABA_AR action. Subsequent research by multiple investigators demonstrated that several reduced metabolites of progesterone and deoxycorticosterone act as positive allosteric modulators of GABA_ARs (13–17), much like benzodiazepines (18, 19). Other research (20, 21) also suggested that neurosteroids might be capable of modulating inhibitory GABAergic neurotransmission.

As new ideas emerged from clinical studies by Andrew Herzog in the mid 1980s concerning the possible role of estrogen and progesterone in catamenial epilepsy (22), we hypothesized that progesterone might act as a positive allosteric modulator of the GABA_AR. This led to the early work of Fong-sen Wu and Terrell Gibbs in my lab (23) showing that progesterone did in fact modulate GABA_A and glycine receptors. Unexpectedly, we also found that pregnenolone sulfate (PregS), a novel negatively charged steroid derived from the sulfation of pregnenolone (PREG), potentiated N-methyl-D-aspartate receptor (NMDAR) function (24) (Figure 1 and Table 1).

Figure 1

Over the ensuing 25 years, endogenous neurosteroids have been implicated in learning and memory function, hippocampal information processes, and synaptic plasticity (28, 29, 48, 59–63). Neurosteroids have also been implicated in the etiology and treatment of learning and memory disturbances associated with certain neuropsychiatric disorders, including schizophrenia, depression, and anxiety (50, 64–66) (Table 2).

Memory dysfunction is frequently comorbid with age-related neurodegenerative diseases, such as Alzheimer's disease (AD) (84). From a therapeutic standpoint, the lack of an effective treatment for memory disorders extends beyond neurodegeneration to a wide range of neuropsychiatric disorders, such as depression and schizoprhenia.

Memory dysfunction seriously impacts performance of routine tasks necessary for a productive and healthy life, including the ability to maintain gainful employment and compliance with treatment plans (85). This review summarizes the field from the perspective of our own research, which has spanned the past three decades, and attempts to bring together state-of-the-art findings related to the role of neurosteroids in memory dysfunction, as seen in patients with schizophrenia, depression, and anxiety disorders. We believe that a greater understanding of how steroids modulate neural network activity will help lay the foundation for a unifying theory of neurosteroid action in the brain centered on a systems level “pharmacological connectome.”

Synthesis, Structure, Transport and Cellular Targets of Neurosteroids

Synthesis and Translocation

Neurosteroid synthesis involves translocation of cholesterol across the mitochondrial membrane by transport proteins, such as the steroidogenic acute regulatory protein (StAR protein), the translocator protein (TSPO), voltage-dependent anion channel (VDAC) protein and the adenine nucleotide transporter (ANT) protein (86–89). The conversion of cholesterol to PREG is catalyzed by the enzyme cytochrome P450 side chain cleavage (P450 scc) located on chromosome 15 in humans (90). Other enzymes that play a role in the biosynthesis of neurosteroids include 5α-reductase and 3α-hydroxysteroid dehydrogenase (91–93). These two enzymes are involved in the biosynthesis of allopregnanolone (ALLO) and tetrahydrodeoxycorticosterone (THDOC); the identification of neurons that express these enzymes in the rodent cerebral cortex, hippocampus, olfactory bulb, amygdala, and thalamus suggests that ALLO and THDOC can be synthesized locally from precursors within the CNS (94).

The sulfation and desulfation of neurosteroids further alters both the pharmacokinetic and pharmacodynamic properties of these endogenous neuromodulators (95). In humans, sulfation of PREG to PregS is catalyzed by SULT2B1a, whereas SULT2B1b preferentially catalyzes the sulfation of 3beta-hydroxysteroids. Non-human primate studies suggest that age-dependent changes in the expression of these enzymes could play a role in age-related changes in cognitive function (96, 97).

Neurosteroids and their sulfated conjugates can be characterized based on their core backbone structures as pregnanes, pregnenes, androstanes, progesterones, and deoxycorticosterones. Neurosteroids in these respective subcategories include: pregnanolone and pregnanolone sulfate; PREG and PregS; dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEAS); progesterone and ALLO; and, deoxycorticosterone and THDOC (98). While delineating the neurological function of sulfated neurosteroids remains a frontier in neuroendocrinology, some fundamental progress has been made these past few decades.

Physiological Actions

The physiologic effects of neurosteroids are mediated through direct interactions with neurotransmitter receptors and transporters, and indirectly via promotion of second-messenger signaling cascades (47, 48, 99–103). Their rapid non-genomic effects are exerted via the allosteric modulation of inhibitory and excitatory receptors located in the surface membrane. In some cases, neurosteroids exert genomic effects, at least in part, by activation of intracellular steroid receptors (104). The degree to which neurosteroids produce genomic and non-genomic effects depends on the extent to which they are metabolized (e.g., PREG to progesterone), and the extent to which the parent molecule and its neuroactive metabolites modulate extra- and intracellular receptors (104).

The modulation of GABAergic neurotransmission by neurosteroids is mediated by interactions with allosteric sites on GABA_ARs (105–109), and neurosteroids appear to play a role in regulating the expression of specific GABA_AR subunits (63). Classical uncharged neurosteroids modulate inhibitory GABA receptors and neurotransmission. Neurosteroids that are known to be relatively potent positive modulators of GABAergic neurotransmission include ALLO, pregnanolone, and TDHOC.

PregS is a relatively potent positive allosteric modulator of NMDAR-mediated synaptic transmission, while pregnanolone sulfate is a relatively potent negative allosteric modulator of NMDAR-mediated glutamatergic neurotransmission (24, 35, 110).

PregS is the most widely studied neurosteroid that potentiates NMDARs (111, 112). 17-hydroxy-PREG is metabolized to DHEA by cytochrome P450 17α-hydroxylase/17,20-lyase. The sulfated form of DHEA, like the sulfated form of PREG (i.e., PregS), is also an NMDAR potentiator. Electrophysiology studies of recombinant NMDARs expressed in Xenopus oocytes have established that the effects of PregS are dependent on NMDAR subunit composition. PregS potentiates GluN2A- and GluN2B-NMDARs, whereas it negatively modulates GluN2C- and GluN2D-NMDARs (38). Long known to be critical for learning and memory, transient activation of NMDARs is required for induction of long-term potentiation (LTP) or strengthening of synaptic transmission, as well as long-term depression (LTD) or weakening of synaptic transmission (113). Activation of NMDARs is crucial for many forms of activity-dependent plasticity responsible for learning and memory in the hippocampus and other brain nuclei (114–118).

PregS also acts as a negative allosteric modulator of GABA, glycine, kainate, and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors (34). The synthetic analog of PregS, PREG hemisuccinate, and other related PREG derivatives bearing a negative charge, potentiate the NMDA response (119). This observation suggests that positive modulation of NMDARs is not mediated by the sulfate group per se. Additional studies using other synthetic analogs of PregS revealed that a negatively charged moiety at the C3 position is, however, essential for positive modulation of NMDARs (35). PregS may also influence NMDAR-dependent responses via a phosphorylation-dependent mechanism (46). Low nanomolar concentrations of PregS induce a delayed onset increase of the neuronal response to NMDA and trafficking of NMDAR to the cell surface through an intracellular Ca²⁺ ([Ca²⁺]i)-dependent and non-canonical mechanism involving G-proteins (47) (Figure 2). Moreover, low picomolar PregS concentrations appear to be sufficient to increase [Ca²⁺]i and CREB phosphorylation (48).

Figure 2

Effects of PregS on NMDARs are diverse (15). NMDARs possess at least two distinct modulatory sites (38). PregS increases the frequency and duration of NMDA-mediated channel opening while it inhibits AMPA and GABA_ARs (24, 110). PregS effects are dependent on the subunit composition of NMDARs (45, 120). PregS potentiates recombinant NMDARs with GluN1-1a/GluN2B through a steroid modulating domain in GluN2B that also modulates tonic proton inhibition and is pH independent. PregS-mediated potentiation of GluN-2C-NMDARs is similarly pH-dependent. On the other hand, PregS-mediated potentiation of GluN2A and 2D-NMDARs is enhanced at reduced pH. The presence of GluN1-1b subunit with an N-terminal exon-5 splicing insert modulates the extent of proton-dependent PregS potentiation (43, 45). The differential pH sensitivity of the NMDAR isoforms to modulation by PregS is likely to be critical in view of the importance of proton sensors in CNS health and disease (45). PregS acts at a site distinct from the PregS site and inhibits NMDARs irrespective of subunit composition (35, 38, 46).

PregS increases spontaneous excitatory post-synaptic currents (sEPSC) frequency but not amplitude. This demonstrates PregS-mediated presynaptic regulation of spontaneous glutamate release and points to a potential significant impact of PregS on hippocampal function. Presynaptic transient receptor potential channel (TRP channel) receptor activation by PregS modulates glutamate release and increases sEPSC in acutely isolated hilar neurons of the dentate gyrus, an increase that is blocked by TRP channel antagonists (121). Dong et al. (122) had previously demonstrated presynaptic effects of PregS. Lee et al. (121) identified a role for PregS in eliciting presynaptic plasticity by altering intracellular Ca²⁺ via Ca²⁺-induced Ca²⁺ release (CICR). Moreover, PregS modulates CICR, which is a key mediator of neuronal plasticity. PregS may affect CICR indirectly by activation of NMDARs or L-type voltage-gated Ca²⁺ channels (L-Type VGCCs) and not by direct activation of the Ca²⁺ release-activated Ca²⁺ channel protein 1 (ORAI1) or stromal interaction molecule 1 (STIM1).

DHEA, which is structurally similar to PREG, is the most abundantly expressed neurosteroid in the human body. This neurosteroid is synthesized in the brain, and higher concentrations are found in the brain than in plasma (123). DHEA and DHEAS are neuroprotective, acting via NMDA and AMPA receptors (124, 125). DHEA also appears to play a role in neuronal cell differentiation and programmed cell death via interactions with neurotrophic tyrosine kinase receptors (126, 127). DHEAS, which is structurally similar to PregS except for substitution of carbonyl oxygen for the acetyl group at C17 on the steroid D ring, potentiates NMDA-mediated Ca²⁺ currents and inhibits GABA_AR-mediated chloride currents (124, 128–131). Neurosteroids are neuroprotective and reduce neuroinflammation (124, 125, 132, 133).

The Modulatory Recognition Sites

There is a paucity of information on the direct binding of neurosteroids to receptors and of the mechanisms underpinning neuromodulation (39, 134). The ability of neurosteroids to bind to and activate specific categories and subtypes of neuronal receptors is influenced by: (1) conjugation of the parent molecule with a sulfate group; (2) geometry (planar vs. bent); and (3) charge (38, 119). The complexity of neurosteroid-mediated effects, for instance gating of GABA_AR (109, 135–139) and subunit-specific modulation of glycine and NMDARs (140), suggest the likelihood of multiple binding sites that contribute to potentiating and inhibitory effects (39). The effects of neurosteroids on GABA_ARs also appears to involve modulation of δ subunit-containing receptors which play a role in tonic inhibition (141–145).

The receptor transmembrane domain plays a role in neurosteroid-mediated modulation of NMDARs (43) (Figure 3) and GABA_ARs (109, 146, 147). Residues in the α1-subunit M1 and/or M2 membrane domains of the GABA_ARs are critical for neurosteroid action (109) (Figure 4) Recent studies using Gloeobacter ligand-gated ion channels (GLIC), a prototypic pentameric ligand-gated ion channel that is a homolog to the nicotinic acetylcholine receptor, have identified putative intersubunit and intrasubunit neurosteroid binding sites for ALLO within the transmembrane domain (134) (Figure 5). Using this innovative approach, Cheng et al. (134) found that substitutions at the 12 and 15 positions on the neurosteroid backbone altered modulation of GLIC channel activity, demonstrating the functional role of both sites. The interaction of neurosteroids with GABA_AR is stereoselective, suggesting that the binding sites for these compounds are of a specific dimension and shape (12, 34, 148).

Figure 3

Figure 4

Figure 5

The results suggest that interactions between the extracellular domain and transmembrane domains play an essential role in the positive and negative modulatory actions of neurosteroids (149). Another important factor determining neurosteroid-dependent modulation of cell function is localization of the neurosteroid. Recent studies have started investigating this aspect using both endogenous neurosteroids and their synthetic analogs. Neurosteroids that can permeate cell membranes can be localized within different intracellular compartments. This compartmentalization is likely to be of importance to the therapeutic function of the neurosteroid (150).

Other known molecular targets of neurosteroids include various TRP channels (151, 152), serotonin receptors and L-Type VGCCs (42). Subtypes of the TRP channels expressed in mammals include TRPC (canonical), TRPV (vallinoid), TRPM (melastatin), and TRPA (ankyrin) channels. PregS modulates Ca²⁺ influx via TRPM3 channels in pancreatic beta cells (151). In addition, TRPM3 is also activated by related substances PREG, DHEA and DHEA sulfate in these studies. Although previous studies by Chen and Wu (153) suggest that PregS activates TRPV1, also known as the capsaicin receptor, other members of the TRPV and TRPM subfamily tested by Wagner and colleagues were not activated by PregS.

TRPM3 channels are expressed at glutamatergic synapses in neonatal Purkinje cells (154). The effect of PregS on AMPA receptor-mediated miniature excitatory post-synaptic current (mEPSC) frequency is blocked by lanthanide³⁺, a non-selective TRP channel blocker (155), providing support for TRPM3 as a target for PregS modulation of glutamate release. Valenzuela et al. (156) demonstrated that PregS activates silent synapses by promoting Ca²⁺ influx in a TRP channel-dependent manner, increasing presynaptic glutamate release, and insertion of AMPARs into the post-synaptic membrane (Figure 6). Based on these results, Valenzuela et al. developed a working model to explain the actions of PregS at glutamatergic synapses (Figure 7). This model is consistent with the recent discovery of delayed onset potentiation of the NMDA response reported by Kostakis et al. (47). We subsequently demonstrated that the phenomenon of delayed onset potentiation of the NMDAR response induced by PregS occurs at physiologically relevant picomolar concentrations and is coupled to a downstream signal transduction pathway associated with learning and memory function (Figures 8, 9).

Figure 6

Figure 7

Figure 8

Figure 9

Modulation of TRP channels has been proposed as a therapeutic target for age-related neurologic disorders, such as AD (157). TRPA1 channels regulate astrocyte resting Ca²⁺ and inhibitory synapse efficacy (158). The TRPA1 channel has also been implicated in astrocytic hyperactivity and synaptic dysfunction mediated by Aβ in mouse models of AD (159). Recognized differences in TRPA1 channels across species have been cited as confounding the translational value of results from preclinical rodent models (160). For example, human TRPA1 activity is suppressed by caffeine but mouse TRPA1 channels are activated (161). More work is needed to fully elucidate the role of neurosteroids as functional modulators of the different subtypes of TRPs expressed in the brain.

Transport of Negatively Charged Steroids Across Cell Membranes

Sulfated steroids, namely PregS and DHEAS, are unique in that they are highly negatively charged and thus do not pass across cell membranes without specific transporters. It therefore seems unlikely, although not impossible, that PregS or DHEAS could rapidly associate with a receptor present within the cell without a specific membrane transporter. Our results show that PregS acts extracellularly (35) and that PREG is inactive as a modulator (36–38, 162). For these reasons, PregS more closely resembles the characteristics of classical neurotransmitters, such as acetylcholine, in which the parent molecule bears a full positive charge and is active only at an extracellularly directed recognition site while the immediate breakdown products (choline + acetic acid) are inactive. However, with respect to the neuronal membrane, PregS exhibits full effect even when applied extracellularly to cultured cortical and hippocampal neurons (27, 48) internally dialyzed with the same concentration of PregS via the whole cell patch clamp recording configuration (47).

The recognition site for steroids, such as estrogen (ER), progesterone and its metabolite ALLO is now relatively well-described. For instance, membrane-bound ER receptors, such as ERα localize at the cell surface where they regulate cell signaling mediated by ER produced in the CNS; this function is in addition to their well-recognized classical intracellular localizations where these receptors function to modulate transcription (163–166). Interestingly, activation of these membrane receptors leads to rapid, non-genomic effects and regulates neuronal plasticity in the CNS (166–171).

An extracellular site of activation for PregS on endogenous NMDARs in primary rat hippocampal and chick spinal cord neurons in culture, as well as receptors expressed in Xenopus oocytes, was demonstrated by Farb et al. (26). Extracellular application of PregS activates NMDARs, whereas intracellular dialysis with PregS fails to elicit a neuronal response or to inhibit PregS applied extracellularly (35). An extracellularly directed PregS -binding domain and obligatory transmembrane domain TM4 participate in the positive allosteric modulation of NMDAR activation by neurotransmitter co-agonists glutamate and glycine [(43, 44) and reviewed by (62, 172)].

These findings were recently confirmed and extended by Wilding et al. (54), who generated chimeric receptors by replacing specific domains of the NMDAR with homologous domains from kainate receptors expressed in non-neuronal HEK293 cells to elucidate the contribution of specific domains to pore formation and allosteric modulation of the NMDARs. By contrast, potentiation by the dihydroxysterol does not require the ligand-binding domain but instead requires a membrane proximal portion of the carboxy terminal domain of the NMDAR, consistent with an intracellularly directed site for receptor activation. Recently, Chisari et al. (58) have described the characterization of compound analogs of PregS, such as KK169. Like PregS, KK169 has the ability to potentiate NMDAR function, and possesses several characteristics that are consistent with an action for PregS and related sulfated steroids at a cell surface-oriented activation domain (35, 43). Interestingly, KK169 does not inhibit oxysterol potentiation of the NMDAR, consistent with its action at an extracellularly directed binding site (similar to that for PregS). However, some sequestration of KK169 was observed in cultured hippocampal neurons, revealing a possible mechanism for membrane transport and accumulation.

These considerations also relate to question of whether PregS might be able to cross the BBB, with the clear expectation that a specific transmembrane transporter would be needed. In fact, such a transporter has been observed in non-fenestrated intracerebral capillaries (173–177) and could well be present in glia and/or neurons, providing a possible pathway toward sequestration.

Neurosteroids and Memory Function

PREG was initially thought of only as a precursor for other steroids and not as an active modulator. Fluorescence spectroscopy studies of the binding of PREG and the related sulfated neurosteroid 3α-hydroxy-5β-pregnan-20-one sulfate, which differentially modulate NMDA and AMPA receptors, suggest that the differential effects of these sulfated neurosteroids on current flow may be related to their binding at the SIS2 and amino terminal domains of these receptors (39). Cannabinoid receptor 1 (CB1) has been identified as a molecular target for PREG (178). Tetrahydrocannabinol or THC, the active ingredient in cannabis, induces PREG synthesis in a CB1 receptor-dependent manner. PREG then acts as an allosteric negative modulator of CB1 receptor in an autocrine-paracrine loop in the brain acting to ameliorate cannabis intoxication. CB1 receptor activation is well-known to modulate learning and memory function by depressing neurotransmitter release. Interestingly, two cannabinoid receptor-mediated signaling cascades have been identified: one is PREG sensitive and targets the vesicular protein Munc-18-1, thereby depressing transmitter release; the other is PREG-insensitive and involves the lateral perforant path of the hippocampus (179). When given as an adjunctive treatment to patients diagnosed with schizophrenia, PREG both improves negative symptoms and ameliorates cognitive deficits (50).

Although controversy still remains with respect to the ability of systemically administered sulfated neurosteroids to cross the BBB, acute treatment with PregS, which is well-recognized for its actions as a positive allosteric modulator of NMDARs, has been associated with an improvement in learning and memory function (21, 24, 31, 34, 35, 162, 180–185). The influx of the sulfated compounds is dependent upon transporters, such as organic anion transporting peptides (OATPs) situated in the BBB and choroid plexus (173, 177, 186) (Figure 10).

Figure 10

The role of these transporters in the efflux of negatively charged sulfate steroids across the BBB from the CNS into the systemic circulation is fairly well-established; however, the specific mechanisms associated with brain influx have not been fully elucidated, despite the finding that systemic administration of sulfated steroids produces effects on cognition including improved learning and memory function (31, 173, 176). It had been suggested, based on studies looking at the expression of 17α-Hydroxylase/C17-20-lyase and hydroxysteroid sulfotransferase, that sulfated steroids, such as DHEAS are unlikely to be synthesized de novo within the human hippocampus (186). This work has led to the suggestion that sulfated neurosteroids must be transported from the periphery into the CNS, but this hypothesis has not been validated (186). Using in situ rat brain perfusion, Qaiser et al. (176) found that PregS enters the brain more rapidly than DHEAS and that both sulfated steroids undergo extensive desulfation mediated by sulfatase located in the capillary fraction of the BBB. While more work is clearly needed to parse out these complex relationships (95), systemic administration of conjugated neurosteroids can nevertheless result in increased CNS levels of the unsulfated neurosteroids (176).

Whether or not the cognitive enhancing effects are due to PregS or PREG remains to be determined. However, the cognitive enhancing effects of PregS in healthy subjects are unlikely to be due to the PREG metabolite ALLO since acute administration of this and other GABAergic modulating neurosteroids to healthy subjects inhibits learning and memory function in a manner similar to benzodiazepines (187–191). On the contrary, ALLO may play a role in the effects of PREG seen in patients with schizophrenia and other neuropsychiatric and neurologic disorders in which neural network activity is dysregulated (51).

Unlike synthetic pharmaceuticals, the literature reporting on the role of neurosteroids in learning and memory function includes some studies looking at the role of endogenous levels and other studies looking at the effects of systemically administered neurosteroids. Because of this, there are several important factors that must be considered when interpreting the results of these studies, including: (1) metabolism of the parent neurosteroid molecule and active metabolites may have a different mechanisms of action; (2) dosing schedules can be acute or chronic; and (3) pharmacokinetic and pharmacodynamic interactions between the neurosteroids and endogenous levels of circulating steroid hormones can fluctuate over time.

Performance on tests of memory function also depends on when neurosteroids are administered in relationship to training or testing. For example, administration of neurosteroids before training can influence both acquisition and consolidation of new information, whereas administration after training is expected to influence consolidation and recall but not acquisition. The type of memory function being assessed (e.g., working memory vs. long-term memory) may also be more or less sensitive to the effects of neurosteroids. Finally, the age and cognitive status of the study subjects must be considered. Each of these factors is explored in greater detail below.

Mechanism of Action and Metabolism of Parent Molecule to Active Metabolites

Neurosteroids are metabolized to other neurosteroids that can also influence neurologic function. For example, PREG is a lipophilic precursor of ALLO, which is also a metabolite of progesterone. Administration of a loading dose of PREG is associated with an increase in serum ALLO levels (192). Although PREG is preferentially metabolized to ALLO, it is also metabolized to progesterone and DHEA (51, 52, 104). The extent to which a neurosteroid, such as PREG is metabolized to progesterone and vice versa determines whether the dose administered will modulate extra- or intracellular receptors to produce non-genomic vs. genomic effects (104).

Administration of 5α-reductase inhibitors, such as finasteride appears to prevent the metabolism of progesterone to ALLO and may thereby influence the neuromodulatory effects of endogenous as well as exogenous sources of these neurosteroids (193–195). Studies looking at the direct infusion of PregS into the nucleus basalis show that this neurosteroid improves spatial memory function in rats and increases acetylcholine release in the basolateral amygdala and frontoparietal cortex (196). Despite these promnestic effect, the metabolism of sulfated neurosteroids, such as PregS by sulfatases, coupled with limited transport across the BBB, has impeded the development of this compound as a novel therapeutic. This limitation can be overcome by using synthetic analogs (132).

Acute vs. Chronic Dosing Schedules

Acute administration of ALLO improves memory function in one mouse model of AD (197), but other studies using rodent models suggest that chronic exposure to ALLO may actually cause memory deficits and exacerbate disease-related functional impairments (198–200). The observation that ALLO transiently increases CREB phosphorylation and increases indicators of neurogenesis in wildtype rats (201) suggests that the acute and chronic effects may not be the same. The translational relevance of these observations to human subjects is unclear since, although men show an age-related decrease in serum ALLO, a similar age-dependent reduction in circulating levels of this neurosteroid is not seen in women (202). On the contrary, women show changes in circulating levels of ALLO that correlate with transient changes in circulating levels of steroid hormones (202). Interestingly, acute systemic administration of ALLO appears to interfere with episodic memory function in healthy women without impairing semantic or working memory function (203), suggesting that brain regions involved in these distinct memory processes, such as the frontal lobes and hippocampus are differentially modulated by this neurosteroid.

Studies looking at brain region-specific effects of neurosteroids on memory function have served to further elucidate the role these neuromodulators play in the acquisition, consolidation and retrieval of information. Systemic administration of the GABA_AR positive modulator ALLO to mice interferes with acquisition and consolidation on a hippocampal-dependent novel object recognition task (204, 205). ALLO impairs memory acquisition/encoding in rodent models when it is injected into the nucleus basalis magnocellularis before an acquisition trial, implicating inhibition of cholinergic neurotransmission in the effects of ALLO on memory acquisition (181). Intrahippocampal administration of ALLO into the CA1 subregion after the acquisition phase of a passive avoidance paradigm has no measurable effect on retention (206).

Age-Dependent Effects of Neurosteroids

Neuroactive steroid hormones levels change during development, with aging and across the estrous cycle (207, 208). Age-dependent effects of neurosteroids on memory function are seen in rodents and humans. For example, neonatal exposure of female rats to estradiol has been associated with reduced brain levels of ALLO and improved learning and memory function in adulthood (209). It has been suggested, based largely on work in animal models, that enduring changes in GABA_ARs expression induced by developmental exposure to steroid hormones, such as progesterone and its metabolites play a role in hippocampal neuronal excitability and in the etiology of sex-dependent neuropsychiatric disorders and memory deficits later in life (209–211). Administration of the 5α-reductase inhibitor, finasteride to pregnant rat dams late in gestation impairs cognitive and neuroendocrine function in their juvenile offspring (210). Treatment of neonatal female rats with estradiol increases the expression of extrasynaptic α4/δ subunit-containing GABA_ARs and improves performance in the Morris water maze during adulthood (209).

In humans, serum levels of ALLO are normally stable during the first 2 years of life (212). Obese children have been reported to have elevated circulating levels of ALLO, but how this influences their learning and memory function later in life has not been elucidated (213). In post-menopausal women, the effects of ALLO on mood appears to be dose dependent and to follow an inverted U-shaped cure (214). The major contributor to endogenous levels of ALLO is the corpus luteum of the ovary and, not too surprisingly, serum levels of ALLO increase during puberty and with polycystic ovary syndrome (PCOS) (202, 212, 215–218). Functional imaging studies indicate that activity within the right superior and inferior parietal lobes is increased during performance of working memory tasks in untreated women with PCOS. The observed increase in neuronal activity is attenuated by antiandrogen therapy (219).

During the menstrual cycle in humans, ALLO and progesterone levels rise together, with the highest concentrations reached in the luteal phase (202, 220–223). Encoding of emotional memories appears to be better in the luteal phase than in follicular phase (207). It has been suggested that cyclical fluctuations in circulating steroid hormone levels can influence encoding and recall of emotional stimuli, and therefore may play a role in the expression of post-traumatic stress disorder (PTSD) symptomology (224, 225).

In rodents, the onset of puberty is associated with an increase in the expression α4βδ GABA_ARs on dendrites of CA1 hippocampal pyramidal cells (226–228). There is also evidence to suggest that synaptic pruning is influenced by neurosteroids during puberty. Optimal spine density may depend in part on expression and modulation of α4βδ GABA_ARs during puberty, which in turn appears necessary for optimal learning and memory function in adulthood (229). The estrus cycle influences memory function in female rodents (230). Spatial learning and memory deficits observed on the morning of proestrus phase in rodent are associated with an increased expression of α4βδ GABA_ARs on CA1 pyramidal cell dendrites (230). There is a reversible decrease in the expression of δ-GABA_ARs in parvalbumin containing interneurons in the CA3 hippocampal subregion during pregnancy in rodents, and this change is associated with increased levels of ALLO (231). Reduced expression of δ-GABA_ARs and increased ALLO may serve to counterbalance each other during pregnancy so that tonic inhibition is maintained. It has been suggested that dysregulation of this delicate balance alters cortical activity in the γ frequency range and that measuring drug-induced changes in cortical γ activity could serve as a non-invasive objective biomarker for predicting the efficacy of pharmacological interventions (231). A non-invasive objective biomarker of this type could prove to be very useful in open label studies.

Timing of Neurosteroid Administration in Relationship to Effect on Memory Function

Learning and memory function can be broken down into three phases: (1) acquisition; (encoding); (2) consolidation; and (3) retrieval (recall). As a result, in addition to their unique and sometimes complex mechanisms of action, the timing of neurosteroid administration can also influence performance on specific tests sensitive to the different aspects of learning and memory function. For example, post-acquisition administration of PregS is associated with improved retention in rodents on a passive avoidance paradigm, indicating that this positive modulator of glutamatergic neurotransmission facilitates consolidation (206). Systemic administration of PregS enhances acquisition (31), while direct infusion of this neurosteroid into the lateral septum 30 min before training appears to interfere with acquisition (185). This seeming discrepancy between the two studies can likely be explained by the complexity of the septo-hippocampal interaction and Pregs-induced increase in excitation and/or decreased excitation within the septum (232).

Specific Type of Memory Function Being Assessed

But what about the specific type of memory function being assessed with a specific task; how might this affect interpretation of behavioral response to neurosteroids? Different types of memories require activation of different brain regions. Regional changes in activation are also associated with specific neuropsychiatric and neurologic disorders. Problems with attention, concentration, and motivation can interfere with encoding of new information and, thus, with performance on tests of memory function (233). While the hippocampus is involved in most aspects of learning and memory function, certain types of memory appear to depend less on activation of this brain region than on other regions (234).

The role of neurosteroids in semantic memory function can only be effectively studied in humans who have the inherent ability to verbally express what they know about the world (235). Humans are also capable of using non-episodic strategies on tests looking at the temporal aspects of an episodic memory (236). This distinction can be very important when parsing out the effects of neurosteroid on episodic vs. semantic memory function. For example, systemic administration of ALLO impairs episodic memory but not working or semantic memory function in healthy adult women (203). The effects of neurosteroids on semantic memory function in schizophrenia has not been elucidated; however, PREG is metabolized to ALLO and PregS, both of which appear to improve working memory function in this patient population (51, 52, 65, 237, 238). Whether this effect on performance is mediated by PREG, ALLO, or PregS alone or via a combination of all three neurosteroids has not been determined.

The effects of neurosteroids on learning and memory for fear-inducing stimuli appears to be different in males and females, who show different brain levels of ALLO at baseline as well. Augmenting levels of ALLO in the bed nucleus of the stria terminalis (BNST) of males, who have lower levels of ALLO at baseline, promotes contextual freezing. By contrast, reducing intra-BNST levels of ALLO in females, who have higher brain ALLO levels at baseline, enhances the expression of contextual freezing (239). In addition to differences in responding due to sex-related baseline levels of neurosteroids, different aspects of memory function depend on recruitment of different brain regions, as well as on activation of different subregions within the hippocampus (e.g., dorsal vs. ventral hippocampus) (240).

Learning and memory of coordinated motor activities involves activation of the cerebellum where neurosteroids are synthesized de novo by Purkinje cells (241–243). It has recently been suggested that 17β-estradiol may also play a role in cerebellar motor memory formation in male rats (244). Animal studies also suggest that the glutamate-nitric oxide-cyclic GMP pathway is impaired in the cerebellum and cortex of subjects with hyperammonemia due to hepatic failure. Ammonia-induced disruption of this pathway has been implicated in impaired performance on certain types of procedural tasks that depend in part on optimization of motor performance. Restoring the pathway and cyclic GMP levels in the brain restores learning ability. The role of neurosteroids in cerebellar function and the acquisition of motor skills has not been fully elucidated. Elevated levels of GABAergic neurosteroids have been associated with hepatic failure, and it has been suggested that PregS may be of clinical benefit in the treatment of deficits in motor coordination and memory disturbances associated with hyperammonia seen in this patient population (245).

Where within the pharmacological connectome do neurosteroids act to modulate different types of learning and memory function in vivo? Not too surprisingly, direct infusion of agonists and antagonists into the brain regions implicated in these different types of memory can either augment or inhibit learning and memory function. For example, the effects of the neurosteroid ALLO on acquisition and extinction of memories associated with exposure to powerful emotion-evoking or fear-inducing stimuli are state independent when it is injected into the amygdala and hippocampus, but state-dependent when injected into the BNST (246). Due to the high concentration of GABA_A receptors in the basolateral amygdala, infusion of GABAergic neurosteroids, such as ALLO into this brain region interferes with the acquisition and expression of the contextual and auditory cue-induced freezing responses in male rats (246).

Age and Cognitive Status of Subjects at Time of Testing

Neurosteroids are implicated in age- and disease state-dependent impairments in learning and memory function (247–249). Because aging subjects can be comorbid for neuropsychiatric disorders, such as depression and age-related neurodegenerative diseases that both affect memory function (250), understanding the role of neurosteroids in age-related changes in memory function can shed light on potential therapeutic targets suitable for this unique patient population.

Low brain levels of ALLO have been associated with memory impairments in aged rats as well as in human subjects diagnosed with AD (67, 248). In addition, post-mortem studies of human subjects with AD reveal increased brain levels of DHEA and PREG (67). Autopsy studies in humans indicate that brain testosterone levels are lower in patients with AD in comparison to normal men (251) and free testosterone has been implicated as a risk factor for probable AD based on clinical diagnostic criteria (252). However, although low testosterone has been implicated in cognitive deficits in healthy men, testosterone replacement therapy does not appear to significantly improve memory function in cognitively impaired older men with low testosterone (253). It is important to point out that although in vivo biomarkers are expected to enhance the pathophysiological specificity of the diagnosis of AD dementia in future studies, most published studies to date looking at the role of neurosteroids on memory function have used core clinical criteria for the diagnosis of possible/probable AD type dementia. Interpretation of such results is hampered in human studies as inclusion of subjects who will ultimately not meet the definitive diagnostic criteria for AD at autopsy is a possible confounding factor.

Decreased plasma levels of DHEA and DHEAS have also been reported in humans with AD (71). It has been suggested that patients meeting clinical criteria for probable AD who have higher baseline levels of DHEAS may perform better on memory tasks than those with lower levels, while by contrast patients with lower circulating levels of cortisol may perform better than those with higher plasma cortisol (68). Men with probable AD based on clinical features of the disease show diurnal changes in cortisol levels characterized by a significant increases at 03 h 00 not seen in healthy elderly men. This increase in cortisol levels occurs despite a slight decrease in levels of adrenocorticotropic hormone (70). Increased levels of DHEA, adrenocorticotropic hormone (ACTH), and interleukin-6 (IL-6) are seen in the morning in women diagnosed with clinical symptoms consistent with AD (70). Cortisol levels are important to the different sleep stages.

Although sleep disturbances are implicated in AD, it is not entirely clear how the aforementioned diurnal changes in cortisol influence sleep and memory consolidation. Sleep plays a role in memory consolidation, and neurosteroids, such as PregS and ALLO can modulate activity within brain regions, such as the pedunculopontine tegmentum nucleus implicated in regulation of sleep (248, 254, 255). Neurosteroids, such as PregS have been implicated in disturbances of sleep and cognitive dysfunction in AD rodent models (247, 256). It has been suggested that the promnestic effects of PregS are mediated by an increase in paradoxical (a.k.a., rapid eye movement; REM) sleep (257, 258), but whether or not the effects of PregS on memory function in subjects with neuropsychiatric disorders and age-related neurodegenerative disease are mediated by enhancement of REM and/or non-REM sleep has not been fully elucidated (259, 260).

Positron emission tomography (PET) imaging studies using the high-affinity sigma-1 (σ-1) receptor selective PET tracer [18F]1-(3-Fluoropropyl)-4-[4-cyanophenoxy) methyl]piperidine ([18F]FPS) as a radioligand suggest that neurosteroids including DHEA bind to σ-1 receptors in vivo (261). Sigma-1 receptors modulate NMDA-mediated responses (262, 263). Agonists of the σ-1 receptor, which acts as a molecular chaperone on mitochondria-associated endoplasmic reticulum membranes, appear to provide neuroprotection in rodent models of AD (264).

PET scans using the radiotracer [carbonyl-(11)C]WAY-100635 indicate that progesterone and DHEAS modulate serotonin 1A (5-HT1A) receptor binding in vivo (265, 266). While there is evidence of disrupted serotonergic neurotransmission in AD (267), the role of neurosteroids, such as DHEAS in the progression of this age-related neurodegenerative disease has not been fully elucidated.

Hyperactivity of entorhinal cortical and hippocampal circuits are also thought to underlie neurodegenerative disorders, such as AD and mild cognitive impairment (MCI) (268–272). Early synaptic dysfunction or “synaptopathy” at the level of inhibitory interneurons within the entorhinal cortex and CA3 hippocampal subregion leads to hyperactivity of pyramidal cells, which appears to play a role in the progression of AD neuropathology (e.g., tauopathy) (271, 272). This hyperactivity may be due in part to reduced responsiveness of pyramidal neurons to GABAergic inhibitory inputs (272). Other studies implicate a loss of GABAergic interneurons in aging rat models of MCI, suggesting that multiple mechanisms may play a role and/or may interact to contribute to hyperactivity (273, 274). Studies using human tissue from patients with late stage AD reveal hippocampal subregion- and strata specific changes in receptor subunit expression that could potentially influence memory function (275). For example, α5 subunit expression, which is implicated in learning and memory function, is increased in the pyramidal layer and oriens of the CA1 subregion. In addition, expression of the α1 subunit, which is implicated in sedation, is increased in all strata of the CA3 subregion and in the granule cell layer and hilus of the dentate gyrus. An increase in α2 subunit expression, which has been implicated in anxiety, is seen in the oriens and radiatum in the CA3 subregion. Expression of α2 is increased in the oriens of the CA1 subregion, but is decreased in the pyramidal layer. There is a decrease in β3 subunit expression in the granular and molecular layers of the dentate gyrus, while expression of α3 and β1 subunits remain unchanged.

ALLO may be useful in attenuating the hyperactivity implicated in early stage AD (201, 276). In mouse models, ALLO appears to increase neurogenesis, reduce amyloid deposition and improve performance on learning and memory tests, suggesting that it may serve as a regenerative therapeutic (197, 277–279). A clinical trial for ALLO is ongoing. Other investigations indicate that chronic treatment with riluzole, which includes a reduction in glutamatergic neurotransmission among its mechanisms of action, attenuates the spread of tauopathy in rodent models (280). Is it possible that neurosteroids, such as pregnanolone sulfate and its synthetic analog pregnanolone hemisuccinate, which negatively modulate glutamatergic neurotransmission, may also have potential therapeutic applications in AD and age-related MCI.

Upregulation of TSPO expression has been implicated in neuropsychiatric disorders and neurodegenerative disease (281–283). Oxidative stress is associated with induction of neurosteroid biosynthesis in the human brain (284), and TSPO ligands (N,N-dialkyl-2-phenylindol-3-ylglyoxylamides) that also show anxiolytic activity promote a reduction in oxidative stress and pro-inflammatory enzymes in glial cells via promotion of neurosteroid synthesis (133). The role of this pathway in the progression of neurodegenerative diseases associated with memory impairments, such as AD has not been fully elucidated. However, increasing oxidative stress by treating oligodendrocytes with beta-amyloid is associated with an increase in the synthesis of DHEA (284), which provides some neuroprotection in a rodent model of AD (285).

Radioligands are being used to measure TSPO expression in vivo. PET scans using 11C-PBR28 as a radiolabeled tracer indicate that binding to TSPO is greater in patients with early-onset AD than in those with late-onset disease. Binding to TSPO is also inversely correlated with gray matter volume and performance on measures of cognitive function in all patients with AD. Early-onset patients have greater 11C-PBR28 binding than late-onset patients. Additionally, an increase in TSPO binding is not seen in patients with age-related MCI, even though these patients show increased amyloid pathology as assessed by Pittsburgh Compound B PET scans and hippocampal atrophy as assessed by volumetric analysis of MRI scans (282). The largest differences in TSPO binding in these groups are seen in the temporal and parietal cortices.

These findings collectively point to a potential therapeutic use for neurosteroids in age-related neurodegenerative diseases. The unique modulatory properties of neurosteroids make these particularly well-suited for targeting comorbid anxiety and depression as well as memory deficits in these patient populations.

The Role of Neurosteroids in Memory Deficits Associated With Stress and Anxiety Disorders

Three large scale major neural networks—the default mode network, central executive network, and salience network—contribute to cognitive processing within the human brain and function together to facilitate adaptive responses of the CNS (286). The default mode network plays a role in episodic memory function and self-related cognitive activities including autobiographical memories. Key functional nodes within the default mode network, which includes the hippocampus, amygdala, and medial prefrontal cortex, have been implicated in AD and epilepsy (287, 288). The frontal parietal connections of the central executive network control attention, working memory, and executive function.

Connections within the central executive network have been implicated in schizophrenia (289). Responses to emotional changes and reward stimuli are dependent on intact function of the salience network, within which the anterior insula, anterior cingulate cortex and amygdala, ventral tegmental area, and thalamus function together to segregate the most relevant and rewarding among internal and extra-personal stimuli in order to guide behavior. Stronger connectivity within the salience network has been associated with increased anxiety (290, 291). Pathological activation of the salience and default networks can interfere with the process of switching between these two networks, which would have a differential impact on mood and memory functionality. Neurosteroids can therefore differentially modulate these three major neural networks central to memory processing.

Neurosteroids play a role in anxiety and in the learning and memory deficits associated with certain anxiety disorders. Treatment of subjects under acute psychosocial stress with DHEA (50 mg/day) both improves attention but also impairs declarative memory function (78), suggesting that the benefits in one cognitive domain may be offset by deficits in another at this dose. Neurosteroid modulation of GABAergic neurotransmission in the central amygdala has been implicated in anxiety (131) and the effects of ALLO on anxiety appear to be mediated in part via modulation of activity within the amygdala, which in turn influences neural activity in brain regions involved in learning and memory function (64, 192, 292) (Figures 11, 12). Although the role of 5α-reductase inhibition in the memory deficits associated with anxiety disorders has not been fully elucidated, it has nevertheless been suggested that serum and brain levels of ALLO are increased by 5α-reductase inhibition.

Figure 11

Figure 12

The BNST, which is also referred to as the extended amygdala, receives input from the hippocampus and shares reciprocal projections with the paraventricular nucleus of the thalamus (246, 293–296). This brain regions play a role in adaptive responses of the hypothalamic-pituitary-adrenal axis (HPA axis) to fear-inducing stimuli (239, 246, 296). The effects of ALLO on acquisition and extinction of hippocampal-dependent memories associated with fear-inducing stimuli appear to be state-dependent following direct injections of this neurosteroid into the BNST. Direct injections of ALLO into the BNST during conditioning or testing suppressed contextual fear, but this effect was not seen when the neurosteroid was injected into the BNST during both procedures (246).

Selective serotonin reuptake inhibitors (SSRIs) increase brain levels of ALLO in humans and animals, suggesting that the anxiolytic effects of SSRIs may be related in part to their effect on CNS levels of this endogenous GABAergic modulator (93, 297–301). Patients with anxiety disorders often self-medicate with ethanol. Acute exposure to ethanol also increases brain levels of ALLO (302). By contrast, preclinical studies in a rat model suggest that chronic intermittent exposure to ethanol is associated with decreased ALLO levels in the hippocampus. Although protein levels were not reported, in this study, mRNA levels for 5alpha-reductase and 3alpha-HSD were noted to be reduced in the hippocampus of these rats, which also had impaired performance on a hippocampal-dependent memory test and increased sensitivity to the anxiolytic effects of alphaxalone (303). Could targeting neurosteroidogenesis (304) and/or steroid metabolism be a viable strategy for the treatment of patients presenting with comorbid anxiety and alcohol use disorders?

When compared with normal subjects and patients with major depression, elderly patients with generalized anxiety disorder (GAD) show more deficits on tests of short-term memory function (305). The severity of GAD has been found to positively correlate with cortisol levels in saliva of older adults (73). Elevated salivary cortisol in older adults is associated with impaired performance on tests of memory function (306). Treatment of older adults presenting with GAD and elevated baseline cortisol with SSRIs is associated with a reduction in salivary cortisol that correlates with reductions in anxiety (307). SSRIs increase levels of ALLO (299). and ALLO restores hippocampal-dependent learning and memory function in a rodent model of AD (308). AD is associated with non-cognitive behavioral and psychological symptoms, which can include paranoia and anxiety; therefore, ALLO may be well-suited for targeting these as well as the cognitive deficits associated with this form of dementia (309).

Cortisol seems to enhance treatment outcomes in a small group (males and females) treated with exposure-based group therapy (310). In addition, high endogenous estradiol vs. low estradiol correlates with better treatment outcomes in exposure therapy (311) in female patients with spider phobias. Investigations of neural network activity using intracranial electroencephalography in human subjects indicate that β-frequency coherence (13–30 Hz) between the amygdala and hippocampus encodes variations in mood (312). Stress may mediate changes in mood and cognition in early adolescence and may play a role in the expression of psychopathologies in adulthood. During stress, corticotropin-releasing hormone promotes an increase in adrenocorticotropic hormone release. This promotes an increase in the concentration of cholesterol at the inner mitochondria membrane of the adrenal cortical cell via activation of the steroidogenic acute regulatory protein. Cholesterol is then converted to PREG and its steroid metabolites, including PregS, cortisol, corticosterone, DHEA, and ALLO (77, 87, 313, 314).

DHEA and DHEAS appear to counteract the negative effects of increased cortisol on working memory function in women and men, respectively (315, 316). A dose-dependent inverted U-shaped response to DHEAS is observed on tests of learning and memory function in male mice (30). By contrast, DHEA is effective in a wider range of doses, suggesting it would be a better choice as a therapeutic (30). Although a positive correlation between DHEAS and cognitive function has been observed in women and men, more research is needed to determine if the effects of DHEA and DHEAS on learning and memory function in humans are sex, dose, and disease state dependent (30, 317, 318).

The response to stress appears to be influenced in part by circulating steroid hormones. Stress increases associative learning and dendritic spine density in the hippocampus of male rats, but impairs associative learning and reduces spine density in females (319). The potential effects of neurosteroids on development of anxiety disorders can be observed during puberty, which is not only associated with increase in levels of reproductive hormones but also with the onset of many psychiatric disorders, including GAD, social anxiety, and panic attacks (320–326). Anxiety symptoms have been found to increase from middle to late adolescence (323), with a particularly high prevalence of all anxiety disorders reported among adolescent girls (324, 327, 328). Of particular interest in this setting are the neurosteroids ALLO (in human and rat) and pregnanolone (in human only), metabolites of the reproductive hormone progesterone that are also produced in the brain in response to stress (79, 329).

Animal studies suggest that developmental exposure to ALLO influences subsequent responsivity to anxiolytics in adulthood (206, 330–332). Acute stress is associated with an increase in plasma ALLO levels that correlates with an increase in expression of the TSPO, also known as the peripheral benzodiazepine receptor. Because the TSPO plays a role in steroidogenesis, it has been considered as a therapeutic target for treatment of anxiety disorders (77, 333). It is interesting to note, that ALLO levels have been found to be decreased relative to controls in the CSF of women with chronic stress disorders, such as PTSD (75). A subsequent study from this group observed a negative correlation between CSF levels of total GABAergic neurosteroids levels (ALLO plus pregnanolone) and PTSD symptoms in men (76). This study also found an association between PTSD and reduced 5α-reductase mediated biosynthesis of ALLO in men, which is in contrast to the block at 3α-HSD previously observed in women with PTSD. Other studies have found that administration of sodium lactate and cholecystokinin tetrapeptide to persons diagnosed with panic disorder decreases plasma concentrations of both pregnanolone and ALLO, and increases the concentration of the functional antagonistic isomer 3β,5α-tetrahydroprogesterone (334). These findings suggest that both acute stress and chronic stress give rise to unique effects on ALLO levels in men and women. Although studies in post-menopausal women did not reveal any benefit on tests of short-term memory function, it has nevertheless been suggested that replenishing this neurosteroid may have beneficial effects on memory function in certain populations with age-related memory deficits (335, 336).

Restoration of altered endogenous neurosteroid levels via modulation of steroidogenesis mediated by pregnane xenobiotic receptors (PXR) and the endocannabinoid system has been suggested as an alternative to direct administration of neurosteroids (89, 178, 337). Because PREG is a precursor for all steroid hormones, it seems plausible that promotion of cortisol synthesis during stress may attenuate synthesis of other steroid hormones, but this suggestion has not been substantiated.

These findings suggest that changes in endogenous brain levels of neurosteroids associated with age, sex, stress, and administration of SSRIs may play a key role in the onset and clinical response to pharmacologic interventions in certain anxiety disorders. Supporting this hypothesis are findings related to the effects of ALLO on gonadotrophin-releasing hormone (GnRH), the primary chemical messenger implicated in the onset of puberty and sexual maturation (338). Central precocious puberty is associated with ALLO, which has been found to suppress the release of hypothalamic GnRH via allosteric modulation of GABA_ARs (339, 340). Although inhibition of GnRH release is increased by ALLO administration before puberty and in adulthood, it is paradoxically reduced during puberty (212).

The reduction in GnRH release during puberty is also associated with increased excitability of pyramidal cells in hippocampal region CA1. This effect appears to be due in part to inhibition of α4-containing GABA_ARs, which are expressed at higher levels than normal in the CA1 region of the hippocampus during puberty. GABA_ARs of the α4β2δ subtype, which have a δ subunit instead of a γ subunit, play a role in tonic inhibition in areas, such as the dentate gyrus and cortex (341). GABA_AR-mediated conductance is normally inhibitory; however, the reversal potential of GABA_AR-mediated post-synaptic current in dentate gyrus granule cells is “positive” to the resting membrane potential, making membrane hyperpolarization of GABA_ARs unlikely in this region. Inhibition of shunting appears to play a role in overcoming this process, such that non-hyperpolarizing inhibitory conductance reduces the depolarizing effect of post-synaptic potentials by decreasing proximal membrane resistance (342). In the dentate gyrus and cortex, the GABAergic current is inward (i.e., chloride flux is outward) (342, 343), and thus inhibition in these areas is enhanced by ALLO. However, in the CA1 hippocampal subregion the current is normally outward (344), and thus increased expression of α4β2δ GABA receptors paradoxically results in ALLO attenuating rather than enhancing inhibition. The reduction in currents generated by ALLO at α4β2δ GABA_AR is dependent upon the presence of arginine 353 in the intracellular loop of α4, where it may serve as a chloride modulatory site (345). This polarity-dependent decrease in inhibition mediated by ALLO may have important implications for how we approach the memory deficits associated with anxiety disorders, which may prove to be amenable to therapeutic strategies targeting the expression and/or activity of GABA_ARs of the α4β2δ subtype (346).

The Role of Neurosteroids in Memory Deficits Associated With Depression

Changes in neurosteroid levels have been implicated in onset of depression and in the actions of medications used to treat depression. Animal studies using a synthetic analog of ALLO suggest that fluctuations in neurosteroids levels may also influence motivation to learn via modulation of dopaminergic pathways (347). The effects of ALLO on mood in women appear to follow an inverted U-shaped curve (214). SSRI treatment has been associated with increased brain levels of ALLO, suggesting that the memory enhancing effects of SSRIs in this patient population may be related in part to the actions of this neurosteroid (93, 297, 348, 349). Preclinical animal studies suggest that modulation of GABAergic neurotransmission by DHEA may also have therapeutic potential in the treatment of memory deficits associated with depression (350).

It is not entirely clear how ALLO, which is a positive allosteric modulator of GABAergic neurotransmission, acts to improve memory function in this patient population, but it has been suggested that stress-induced changes in GABA receptor expression levels are likely to play a role in the etiology of depression. This hypothesis is supported by preclinical studies showing that early life traumatic stress is associated with chronic anxiety, spatial memory deficits and reduced expression of GABA_AR subunits in the adult rat brains (351).

It has been suggested that PREG and its metabolites may be efficacious in the treatment of depressive disorders. Treatment of depression poses several challenges and this is especially true in the treatment of depression in bipolar disorder (BPD). In a study conducted by Brown et al. (352), 80 adults with BPD and depressive mood state were treated with PREG or placebo as add-on therapy for 12 weeks. Outcome measures included the 17-item Hamilton Scale for Depression, Hamilton Rating Scale for Anxiety (HRSA) and Young Mania Rating Scale. Assessment of serum neurosteroid levels at baseline and treatment completion (week 12) revealed large baseline-to exit changes in neurosteroids in the PREG treatment group. In the PREG group, unlike the placebo group, HRSA changes negatively correlated with ALLO and PREG levels, indicative of reduced anxiety. The results of this small study should be interpreted with caution because subjects were taking a wide variety of medications including lithium, antidepressants (unspecified), sedative hypnotics/anxiolytics (unspecified), antipsychotics (unspecified), and stimulants (unspecified) and they were not stratified based on the drugs they were taking for their depression.

The Role of Neurosteroids in Memory Deficits Associated With Schizophrenia

The cognitive deficits associated with schizophrenia are caused by multiple factors, and elucidating a single causative part of the cognitive component would provide some hope for understanding memory and a basis for therapeutic discovery. Neural circuitry-based studies highlight cortical disinhibition as a critical factor in schizophrenia affecting GABAergic interneurons (parvalbumin, SOM/NPY/CCK/expressing interneurons). GAD67 deficiencies together with changes in GABA_AR expression, in particular the α2 subunit, are known (353–356). Hypofunction of NMDARs, particularly in inhibitory parvalbumin (PV) interneurons (357), may initiate the disease process, leading to decreased inhibition of pyramidal neurons. NMDAR hypofunction in inhibitory interneurons is implicated in the observed GABAergic deficits (358–364). Whatever the specific path for initiating dynamical imbalance or dysregulation of the circuitry, the resultant hyperactivity of downstream pyramidal neurons ultimately leads to dysregulated neural network activity, excitotoxicity, and eventually frank neuronal loss. Note that hypofunction of NMDARs expressed in pyramidal neurons themselves is also likely (365). Disruptions of neural network activity during sleep, including reduced sleep spindle activity, has been associated with impaired sleep dependent memory consolidation in schizophrenia (260).

Synchronous activity of PV interneurons generates gamma oscillations which are observed during performance of cognitive tasks. Cognitive deficits are thought to arise from a disturbance of these high frequency oscillations in the gamma range due to reduced excitatory drive to cortical PV interneurons (366, 367) with resultant network hypersynchrony (368, 369). Manipulations of various receptors such as α5 type GABA_ARs and sodium channels have been shown to enhance cognition (356). The glutamate hypothesis of schizophrenia underscores the importance of NMDARs in neuropsychiatric disorders. NMDARs are critical for the generation of gamma oscillations, and dysfunctional NMDARs result in psychosis and deficits in specific cognitive domains. Genetically engineered mice lacking NMDARs show deficits in habituation, working memory and associative learning (370).

Enhancing NMDAR function is therefore vital for enhancing cognition in healthy individuals and those with neuropsychiatric disorders (111). However, attempts to enhance NMDAR neurotransmission thus far have not been successful (371). A recent meta-analysis of currently available NMDAR positive allosteric modulators reveals that these are ineffective in alleviating cognitive impairments (371). Maintaining a critical balance in NMDAR activation is optimal for avoiding the negative consequences of NMDAR stimulation a, making PregS, DHEAS and their analogs highly suitable candidates. Subunit selective modulation, combined with its ability to potentiate receptor function without overstimulation, renders PregS a likely and highly suitable positive modulator of NMDARs (111, 371).

PREG and ALLO have been investigated as potential therapeutics for treating memory deficits associated with schizophrenia (50, 65, 238). Acute administration of either clozapine or olanzapine increases brain and plasma levels of PREG, which is a precursor of ALLO and PregS (372). Adrenalectomy prevents clozapine-induced increase in hippocampal PREG. By contrast, significant increases in PREG levels in rat hippocampus are not observed following acute administration of aripiprazole, quetiapine, or ziprasidone administration. This suggests that the effects of second-generation antipsychotics on memory function may be due in part to increased brain levels of PREG and/or PregS (28, 48, 51, 62, 373).

We have previously demonstrated that low picomolar concentrations of PregS are sufficient to increase [Ca²⁺]i and CREB phosphorylation (48). There is some evidence that sulfotransferase 4A1 haplotype 1 (SULT4A1-1)-positive subjects show a better response to olanzapine than do SULT4A1-1 negative subjects. However, the exact role this sulfotransferase isozyme plays in the formation of PregS from PREG and the amelioration of learning and memory deficits in humans with schizophrenia treated with second-generation antipsychotics has not yet been established (374). ALLO-mediated modulation of GABAergic neurotransmission has also been implicated in the antipsychotic effects of clozapine and olanzapine in rodent models (375–377).

Multiple clinical and preclinical studies have examined the effects of neurosteroids, PREG, PregS and DHEA on memory and other cognitive attributes. Cognitive deficits are a core feature of schizophrenia (378). Recent clinical trials in patients with schizophrenia suggest that treatment with PREG as add-on therapy alleviates cognitive deficits (50). In patients receiving PREG, plasma levels of its immediate metabolite, PregS (positive modulator of NMDARs) and ALLO (positive modulator of GABA_ARs) are elevated, suggesting a possible role for PregS in improvement of learning and memory function (50). Earlier studies (28) had also described the cognition enhancing effects of PregS (29).

Neurosteroids, Dopamine Knockout Mouse Model and Schizophrenia

Dopamine (DA) is a neuromodulator and a key player in several neural disorders in which cognitive deficits are characteristic, such as schizophrenia, attention deficit hyperactivity disorder, and depression (379–381). The dopamine transporter (DAT) mediates re-uptake of extracellular DA, thus terminating DA receptor activation. DAT, a member of the Na⁺/Cl⁻-dependent family of neurotransmitter transporters (382) is therefore a major therapeutic target for schizophrenia and other disorders (383–385). Several transgenic models have been generated with changes in DAT expression or function or mutations in the DAT gene (386). These models have proven to be crucial in elucidating neurotransmitter and neuromodulator function (or mechanistic underpinnings) of neuropsychiatric disorders (381, 387).

Wong et al. (373) have used a DAT knockout (DAT KO) mouse model exhibiting symptoms characteristic of schizophrenia to investigate the effects of PregS treatment on learning and memory function. Systemic administration of PregS, which is able to cross the BBB, alleviates positive and negative symptoms as well as cognitive deficits in the DAT KO mouse. Long-term systemic treatment with PregS rescues impaired episodic memory and poor discriminative abilities in the DAT KO mice without adverse effects. Consistent with observed reductions in cognitive deficits, long-term PregS treatment increases expression of the obligatory NMDAR subunit GluN1 in the hippocampus. Earlier, our laboratory characterized some of the mechanisms involved in increased expression of NMDAR subunits and demonstrated that PregS increases surface GluN1 in oocytes expressing recombinant NMDAR subunits in a non-canonical GPCR- and Ca²⁺-dependent manner (47) (Figure 2).

Synthetic Neurosteroids as Potential Cognitive Enhancers

The findings reviewed herein suggest that the memory deficits seen in patients with schizophrenia, depression and anxiety disorders are influenced by changes in endogenous neurosteroid levels. Because not all systemically administered endogenously occurring neurosteroids readily cross the BBB and because these compounds can be metabolized to hormonally active steroids with different mechanisms of action, the therapeutic potential of these compounds is limited. For this reason, synthetic analogs of neurosteroids, which are more resistant to metabolism and better able to cross the BBB, are under investigation for use as anxiolytics, antidepressants, cognitive enhancers, anesthetics, and anticonvulsants (132, 388, 389). For example, synthetic neuroactive steroids bearing a hemisuccinate group are more resistant to hydrolysis than the corresponding sulfate esters and are partly unionized at physiological pH, allowing increased passage across the BBB. One such synthetic neuroactive steroid, pregnanolone hemisuccinate, produces sedation and neuroprotection in mice and rats (132). Weaver et al. (132) demonstrated that pregnanolone hemisuccinate (PAHS) inhibits NMDA-induced currents and cell death in primary cultures of hippocampal neurons. Additionally, administration of a non-sedating dose of PAHS to rats following focal cerebral ischemia reduces cortical and subcortical infarct size (Figure 13).

Figure 13

Ganaxolone (3-hydroxy-3-methyl-5-pregnane-20-one), an orally bioavailable synthetic analog of ALLO, is a positive allosteric modulator of GABA_AR with promising basic and early-stage clinical outcomes as a potential novel treatment for PTSD (388, 390–392). Based on the mechanism of action of ganaxolone and work in preclinical animal models suggesting improved spatial memory function in an animal model of Angelman Syndrome (393), future investigation looking at the clinical value of this agent in anxiety disorders appears warranted. Another synthetic analog of ALLO, 3β-ethenyl-3α-hydroxy-5α-pregnan-20-one (Co 3-0593), has been found to have anxiolytic effects comparable to benzodiazepines after both subcutaneous and oral administration in rodents. An absence of tolerance to this synthetic neuroactive steroid is suggested by the observation that its effects were maintained with chronic administration (394).

Current research into the function of PregS is impeded by the lack of selective/specific antagonists and by a lack of knowledge of validated binding site(s). These drawbacks are further exacerbated by the susceptibility of the essential 3-hydroxysulfate to hydrolysis by sulfatases. To overcome these limitations, we and others are using PregS analogs to decipher mechanistic aspects of PregS-mediated effects on learning and memory function. We recently reported that low nanomolar concentration of PregS induce a delayed-onset increase of the neuronal response to NMDA and trafficking of NMDAR to the cell surface through an intracellular ([Ca²⁺]i)-dependent mechanism (47) (Figure 2). Moreover, we have demonstrated that low picomolar PregS increases [Ca²⁺]i and CREB phosphorylation and the frequency of spontaneous excitatory post-synaptic currents (48) (Figures 8, 9). More work is needed to determine if the synthetic analog of PregS, PREG hemisuccinate, has the potential to overcome the limitations associated with systemic administration of PregS.

Conclusions

The effects of neurosteroids in memory function in neuropsychiatric and neurologic disorders reflect their modulatory interactions exerted via selective binding at the amino and transmembrane domains of specific subunits comprising GABA and glutamate receptors, among others. Age- and disease state-dependent changes in endogenous levels of neurosteroids appear to play a role in the emergence of the unique functional imbalances implicated in specific neuropsychiatric disorders and the associated memory deficits, which are mediated in part by changes in neural network activity within specific brain regions implicated in the encoding, consolidation, and retrieval of memories. It may be helpful to think of these findings in terms of a pharmacological connectome that reflects the interactions of neurosteroids with various neural networks involved with the encoding and recall of memories. We believe that a neural circuitry framework will help to guide future investigations into the potential role of neurosteroids and their synthetic analogs as neurotherapeutics for memory dysfunction (Figure 14).

Figure 14

References

• 1.

  SchallyAVReddingTWBowersCYBarrettJF. Isolation and properties of porcine thyrotropin-releasing hormone. J Biol Chem. (1969) 244:4077–88.

  • Pubmed Abstract
  • Google Scholar

• 2.

  MitnickMReichlinS. Thyrotropin-releasing hormone: biosynthesis by rat hypothalamic fragments in vitro. Science. (1971) 172:1241–3. 10.1126/science.172.3989.124

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 3.

  LeemanSEHammerschlagR. Stimulation of salivary secretion by a factor extracted from hypothalamic tissue. Endocrinology. (1967) 81:803–10. 10.1210/endo-81-4-803

  • CrossRef
  • Google Scholar

• 4.

  ChangMMLeemanSE. Isolation of a sialogogic peptide from bovine hypothalamic tissue and its characterization as substance P. J Biol Chem. (1970) 245:4784–90.

  • Pubmed Abstract
  • Google Scholar

• 5.

  PardridgeWMMietusLJ. Transport of steroid hormones through the rat blood-brain barrier. Primary role of albumin-bound hormone. J Clin Invest. (1979) 64:145–54. 10.1172/JCI109433

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 6.

  CorpéchotCRobelPAxelsonMSjövallJBaulieuEE. Characterization and measurement of dehydroepiandrosterone sulfate in rat brain. Proc Natl Acad Sci USA. (1981) 78:4704–7.

  • Pubmed Abstract
  • Google Scholar

• 7.

  CorpéchotCSynguelakisMTalhaSAxelsonMSjövallJVihkoRet al. Pregnenolone and its sulfate ester in the rat brain. Brain Res. (1983) 270:119–25. 10.1016/0006-8993(83)90797-7

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 8.

  RobelPBourreauECorpéchotCDangDCHalbergFClarkeCet al. Neuro-steroids: 3 beta-hydroxy-delta 5-derivatives in rat and monkey brain. J Steroid Biochem. (1987) 27:649–55.

  • Pubmed Abstract
  • Google Scholar

• 9.

  MorfinRYoungJCorpéchotCEgestadBSjövallJBaulieuEE. Neurosteroids: pregnenolone in human sciatic nerves. Proc Natl Acad Sci USA. (1992) 89:6790–3. 10.1073/pnas.89.15.6790

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 10.

  SelyeH. Anaesthetic effects of steroid hormones. Proc Soc Exp Biol Med. (1941) 46:116–21.

  • Google Scholar

• 11.

  SapolskyRMMcEwenBSRainbowTC. Quantitative autoradiography of [3H]corticosterone receptors in rat brain. Brain Res. (1983) 271:331–4.

  • Google Scholar

• 12.

  HarrisonNLSimmondsMA. Modulation of the GABA receptor complex by a steroid anaesthetic. Brain Res. (1984) 323:287–92. 10.1016/0006-8993(84)90299-3

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 13.

  HarrisonNLViciniSBarkerJL. A steroid anesthetic prolongs inhibitory postsynaptic currents in cultured rat hippocampal neurons. J Neurosci. (1987) 7:604–9. 10.1523/JNEUROSCI.07-02-00604.1987

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 14.

  BarkerJLHarrisonNLLangeGDOwenDG. Potentiation of gamma-aminobutyric-acid-activated chloride conductance by a steroid anaesthetic in cultured rat spinal neurones. J Physiol. (1987) 386:485–501.

  • Pubmed Abstract
  • Google Scholar

• 15.

  CallachanHCottrellGAHatherNYLambertJJNooneyJMPetersJA. Modulation of the GABAA receptor by progesterone metabolites. Proc R Soc Lond B Biol Sci. (1987) 231:359–69. 10.1098/rspb.1987.0049

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 16.

  GeeKWChangWCBrintonREMcEwenBS. GABA-dependent modulation of the Cl- ionophore by steroids in rat brain. Eur J Pharmacol. (1987) 136:419–23. 10.1016/0014-2999(87)90317-7

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 17.

  PetersJAKirknessEFCallachanHLambertJJTurnerAJ. Modulation of the GABAA receptor by depressant barbiturates and pregnane steroids. Br J Pharmacol. (1988) 94:1257–69.

  • Pubmed Abstract
  • Google Scholar

• 18.

  ChoiDWFarbDHFischbachGD. Chlordiazepoxide selectively augments GABA action in spinal cord cell cultures. Nature. (1977) 269:342–4.

  • Pubmed Abstract
  • Google Scholar

• 19.

  MacdonaldRLBarkerJL. Different actions of anticonvulsant and anesthetic barbiturates revealed by use of cultured mammalian neurons. Science. (1978) 200:775–7.

  • Pubmed Abstract
  • Google Scholar

• 20.

  MajewskaMDHarrisonNLSchwartzRDBarkerJLPaulSM. Steroid hormone metabolites are barbiturate-like modulators of the GABA receptor. Science. (1986) 232:1004–7. 10.1126/science.2422758

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 21.

  MajewskaMDSchwartzRD. Pregnenolone-sulfate: an endogenous antagonist of the gamma-aminobutyric acid receptor complex in brain?Brain Res. (1987) 404:355–60. 10.1016/0006-8993(87)91394-1

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 22.

  HerzogAG. Intermittent progesterone therapy and frequency of complex partial seizures in women with menstrual disorders. Neurology. (1986) 36:1607–10.

  • Pubmed Abstract
  • Google Scholar

• 23.

  WuFSGibbsTTFarbDH. Inverse modulation of gamma-aminobutyric acid- and glycine-induced currents by progesterone. Mol Pharmacol. (1990) 37:597–602.

  • Pubmed Abstract
  • Google Scholar

• 24.

  WuFSGibbsTTFarbDH. Pregnenolone sulfate: a positive allosteric modulator at the N-methyl-D-aspartate receptor. Mol Pharmacol. (1991) 40:333–6.

  • Pubmed Abstract
  • Google Scholar

• 25.

  MajewskaMD. Interaction of ethanol with the GABAA receptor in the rat brain: possible involvement of endogenous steroids. Alcohol. (1988) 5:269–73. 10.1016/0741-8329(88)90064-X

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 26.

  FarbDHGibbsTTWuFSGyenesMFriedmanLRussekSJ. Steroid modulation of amino acid neurotransmitter receptors. Adv Biochem Psychopharmacol. (1992) 47:119–31.

  • Pubmed Abstract
  • Google Scholar

• 27.

  IrwinRPMaragakisNJRogawskiMAPurdyRHFarbDHPaulSM. Pregnenolone sulfate augments NMDA receptor mediated increases in intracellular Ca²⁺ in cultured rat hippocampal neurons. Neurosci Lett. (1992) 141:30–4. 10.1016/0304-3940(92)90327-4

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 28.

  FloodJFMorleyJERobertsE. Memory-enhancing effects in male mice of pregnenolone and steroids metabolically derived from it. Proc Natl Acad Sci USA. (1992) 89:1567–71. 10.1073/pnas.89.5.1567

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 29.

  FloodJFMorleyJERobertsE. Pregnenolone sulfate enhances post-training memory processes when injected in very low doses into limbic system structures: the amygdala is by far the most sensitive. Proc Natl Acad Sci USA. (1995) 92:10806–10. 10.1073/pnas.92.23.10806

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 30.

  FloodJFSmithGERobertsE. Dehydroepiandrosterone and its sulfate enhance memory retention in mice. Brain Res. (1988) 447:269–78. 10.1016/0006-8993(88)91129-8

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 31.

  PlesciaFMarinoRACannizzaroEBrancatoACannizzaroC. The role of pregnenolone sulphate in spatial orientation-acquisition and retention: an interplay between cognitive potentiation and mood regulation. Behav Processes. (2013) 99:130–7. 10.1016/j.beproc.2013.07.001

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 32.

  PlesciaFSardoPRizzoVCacaceSMarinoRABrancatoAet al. Pregnenolone sulphate enhances spatial orientation and object discrimination in adult male rats: evidence from a behavioural and electrophysiological study. Behav Brain Res. (2014) 258:193–201. 10.1016/j.bbr.2013.10.026

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 33.

  Abdel-HafizLChaoOYHustonJPNikolausSSpielerREde Souza SilvaMAet al. Promnestic effects of intranasally applied pregnenolone in rats. Neurobiol Learn Mem. (2016) 133:185–95. 10.1016/j.nlm.2016.07.012

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 34.

  Park-ChungMWuFSFarbDH. 3 alpha-Hydroxy-5 beta-pregnan-20-one sulfate: a negative modulator of the NMDA-induced current in cultured neurons. Mol Pharmacol. (1994) 46:146–50.

  • Pubmed Abstract
  • Google Scholar

• 35.

  Park-ChungMWuFSPurdyRHMalayevAAGibbsTTFarbDH. Distinct sites for inverse modulation of N-methyl-D-aspartate receptors by sulfated steroids. Mol Pharmacol. (1997) 52:1113–23. 10.1124/mol.52.6.1113

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 36.

  Park-ChungMMalayevAPurdyRHGibbsTTFarbDH. Sulfated and unsulfated steroids modulate gamma-aminobutyric acidA receptor function through distinct sites. Brain Res. (1999) 830:72–87.

  • Pubmed Abstract
  • Google Scholar

• 37.

  YaghoubiNMalayevARussekSJGibbsTTFarbDH. Neurosteroid modulation of recombinant ionotropic glutamate receptors. Brain Res. (1998) 803:153–60. 10.1016/S0006-8993(98)00644-1

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 38.

  MalayevAGibbsTTFarbDH. Inhibition of the NMDA response by pregnenolone sulphate reveals subtype selective modulation of NMDA receptors by sulphated steroids. Br J Pharmacol. (2002) 135:901–9. 10.1038/sj.bjp.0704543

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 39.

  CameronKBartleERoarkRFanelliDPhamMPollardBet al. Neurosteroid binding to the amino terminal and glutamate binding domains of ionotropic glutamate receptors. Steroids. (2012) 77:774–9. 10.1016/j.steroids.2012.03.011

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 40.

  PartridgeLDValenzuelaCF. Neurosteroid-induced enhancement of glutamate transmission in rat hippocampal slices. Neurosci Lett. (2001) 301:103–6. 10.1016/S0304-3940(01)01613-5

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 41.

  SliwinskiAMonnetFPSchumacherMMorin-SurunMP. Pregnenolone sulfate enhances long-term potentiation in CA1 in rat hippocampus slices through the modulation of N-methyl-D-aspartate receptors. J Neurosci Res. (2004) 78:691–701. 10.1002/jnr.20332

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 42.

  SabetiJNelsonTEPurdyRHGruolDL. Steroid pregnenolone sulfate enhances NMDA-receptor-independent long-term potentiation at hippocampal CA1 synapses: role for L-type calcium channels and sigma-receptors. Hippocampus. (2007) 17:349–69. 10.1002/hipo.20273

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 43.

  JangMKMierkeDFRussekSJFarbDH. A steroid modulatory domain on NR2B controls N-methyl-D-aspartate receptor proton sensitivity. Proc Natl Acad Sci USA. (2004) 101:8198–203. 10.1073/pnas.0401838101

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 44.

  HorakMVlcekKChodounskaHVyklickyLJr. Subtype-dependence of N-methyl-D-aspartate receptor modulation by pregnenolone sulfate. Neuroscience. (2006) 137:93–102. 10.1016/j.neuroscience.2005.08.058

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 45.

  KostakisEJangMKRussekSJGibbsTTFarbDH. A steroid modulatory domain in NR2A collaborates with NR1 exon-5 to control NMDAR modulation by pregnenolone sulfate and protons. J Neurochem. (2011) 119:486–96. 10.1111/j.1471-4159.2011.07442.x

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 46.

  PetrovicMSedlacekMCaisOHorakMChodounskaHVyklickyLJr. Pregnenolone sulfate modulation of N-methyl-D-aspartate receptors is phosphorylation dependent. Neuroscience. (2009) 160:616–28. 10.1016/j.neuroscience.2009.02.052

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 47.

  KostakisESmithCJangMKMartinSCRichardsKGRussekSJet al. The neuroactive steroid pregnenolone sulfate stimulates trafficking of functional N-methyl D-aspartate receptors to the cell surface via a noncanonical, G protein, and Ca²⁺-dependent mechanism. Mol Pharmacol. (2013) 84:261–74. 10.1124/mol.113.085696

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 48.

  SmithCCMartinSCSugunanKRussekSJGibbsTTFarbDH. A role for picomolar concentrations of pregnenolone sulfate in synaptic activity-dependent Ca²⁺ signaling and CREB activation. Mol Pharmacol. (2014) 86:390–8. 10.1124/mol.114.094128

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 49.

  AdamusováECaisOVyklickýVKudováEChodounskáHHorákMet al. Pregnenolone sulfate activates NMDA receptor channels. Physiol Res. (2013) 62:731–6.

  • Pubmed Abstract
  • Google Scholar

• 50.

  MarxCELeeJSubramaniamMRapisardaABautistaDCChanEet al. Proof-of-concept randomized controlled trial of pregnenolone in schizophrenia. Psychopharmacology (Berl). (2014) 231:3647–62. 10.1007/s00213-014-3673-4

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 51.

  MarxCEKeefeRSBuchananRWHamerRMKiltsJDBradfordDWet al. Proof-of-concept trial with the neurosteroid pregnenolone targeting cognitive and negative symptoms in schizophrenia. Neuropsychopharmacology. (2009) 34:1885–903. 10.1038/npp.2009.26

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 52.

  MarxCEBradfordDWHamerRMNaylorJCAllenTBLiebermanJAet al. Pregnenolone as a novel therapeutic candidate in schizophrenia: emerging preclinical and clinical evidence. Neuroscience. (2011) 191:78–90. 10.1016/j.neuroscience.2011.06.076

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 53.

  RitsnerMSBawaknyHKreininA. Pregnenolone treatment reduces severity of negative symptoms in recent-onset schizophrenia: an 8-week, double-blind, randomized add-on two-center trial. Psychiatry Clin Neurosci. (2014) 68:432–40. 10.1111/pcn.12150

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 54.

  WildingTJLopezMNHuettnerJE. Chimeric glutamate receptor subunits reveal the transmembrane domain is sufficient for NMDA receptor pore properties but some positive allosteric modulators require additional domains. J Neurosci. (2016) 36:8815–25. 10.1523/JNEUROSCI.0345-16.2016

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 55.

  PaulSMDohertyJJRobichaudAJBelfortGMChowBYHammondRSet al. The major brain cholesterol metabolite 24(S)-hydroxycholesterol is a potent allosteric modulator of N-methyl-D-aspartate receptors. J Neurosci. (2013) 33:17290–300. 10.1523/JNEUROSCI.2619-13.2013

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 56.

  LinsenbardtAJTaylorAEmnettCMDohertyJJKrishnanKCoveyDFet al. Different oxysterols have opposing actions at N-methyl-D-aspartate receptors. Neuropharmacology. (2014) 85:232–42. 10.1016/j.neuropharm.2014.05.027

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 57.

  VyklickyVKrausovaBCernyJLadislavMSmejkalovaTKysilovBet al. Surface expression, function, and pharmacology of disease-associated mutations in the membrane domain of the human GluN2B Subunit. Front Mol Neurosci. (2018) 11:110. 10.3389/fnmol.2018.00110

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 58.

  ChisariMWildingTJBrunwasserSKrishnanKQianMBenzAet al. Visualizing pregnenolone sulfate-like modulators of NMDA receptor function reveals intracellular and plasma-membrane localization. Neuropharmacology. (2018) 144:91–103. 10.1016/j.neuropharm.2018.10.015

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 59.

  ValléeMMayoWDarnaudéryMCorpéchotCYoungJKoehlMet al. Neurosteroids: deficient cognitive performance in aged rats depends on low pregnenolone sulfate levels in the hippocampus. Proc Natl Acad Sci USA. (1997) 94:14865–70. 10.1073/pnas.94.26.14865

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 60.

  Weill-EngererSDavidJPSazdovitchVLierePEychenneBPianosAet al. Neurosteroid quantification in human brain regions: comparison between Alzheimer's and nondemented patients. J Clin Endocrinol Metab. (2002) 87:5138–43. 10.1210/jc.2002-020878

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 61.

  ScullinCSPartridgeLD. Modulation by pregnenolone sulfate of filtering properties in the hippocampal trisynaptic circuit. Hippocampus. (2012) 22:2184–98. 10.1002/hipo.22038

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 62.

  SmithCCGibbsTTFarbDH. Pregnenolone sulfate as a modulator of synaptic plasticity. Psychopharmacology (Berl). (2014) 231:3537–56. 10.1007/s00213-014-3643-x

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 63.

  ReddyDSGangisettyOWuX. PR-independent neurosteroid regulation of α2-GABA-A receptors in the hippocampus subfields. Brain Res. (2017) 1659:142–7. 10.1016/j.brainres.2017.01.030

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 64.

  van WingenGvan BroekhovenFVerkesRJPeterssonKMBäckströmTBuitelaarJet al. How progesterone impairs memory for biologically salient stimuli in healthy young women. J Neurosci. (2007) 27:11416–23. 10.1523/JNEUROSCI.1715-07.2007

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 65.

  KreininABawaknyNRitsnerMS. Adjunctive pregnenolone ameliorates the cognitive deficits in recent-onset schizophrenia: an 8-week, randomized, double-blind, placebo-controlled trial. Clin Schizophr Relat Psychoses. (2017) 10:201–10. 10.3371/CSRP.KRBA.013114

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 66.

  FarbDHRatnerMH. Targeting the modulation of neural circuitry for the treatment of anxiety disorders. Pharmacol Rev. (2014) 66:1002–32. 10.1124/pr.114.009126

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 67.

  NaylorJCKiltsJDHuletteCMSteffensDCBlazerDGErvinJFet al. Allopregnanolone levels are reduced in temporal cortex in patients with Alzheimer's disease compared to cognitively intact control subjects. Biochim Biophys Acta. (2010) 1801:951–9. 10.1016/j.bbalip.2010.05.006

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 68.

  CarlsonLESherwinBBChertkowHM. Relationships between dehydroepiandrosterone sulfate (DHEAS) and cortisol (CRT) plasma levels and everyday memory in Alzheimer's disease patients compared to healthy controls. Horm Behav. (1999) 35:254–63. 10.1006/hbeh.1999.1518

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 69.

  CsernanskyJGDongHFaganAMWangLXiongCHoltzmanDMet al. Plasma cortisol and progression of dementia in subjects with Alzheimer-type dementia. Am J Psychiatry. (2006) 163:2164–9. 10.1176/ajp.2006.163.12.2164

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 70.

  RasmusonSNäsmanBOlssonT. Increased serum levels of dehydroepiandrosterone (DHEA) and interleukin-6 (IL-6) in women with mild to moderate Alzheimer's disease. Int Psychogeriatr. (2011) 23:1386–92. 10.1017/S1041610211000810

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 71.

  AldredSMecocciP. Decreased dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEAS) concentrations in plasma of Alzheimer's disease (AD) patients. Arch Gerontol Geriatr. (2010) 51:e16–8. 10.1016/j.archger.2009.07.001

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 72.

  CherrierMMAndersonKShoferJMillardSMatsumotoAM. Testosterone treatment of men with mild cognitive impairment and low testosterone levels. Am J Alzheimers Dis Other Demen. (2015) 30:421–30. 10.1177/1533317514556874

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 73.

  MantellaRCButtersMAAmicoJAMazumdarSRollmanBLBegleyAEet al. Salivary cortisol is associated with diagnosis and severity of late-life generalized anxiety disorder. Psychoneuroendocrinology. (2008) 33:773–81. 10.1016/j.psyneuen.2008.03.002

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 74.

  HeydariBLeMellédo JM. Low pregnenolone sulphate plasma concentrations in patients with generalized social phobia. Psychol Med. (2002) 32:929–33. 10.1017/S0033291702005238

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 75.

  RasmussonAMPinnaGPaliwalPWeismanDGottschalkCCharneyDet al. Decreased cerebrospinal fluid allopregnanolone levels in women with posttraumatic stress disorder. Biol Psychiatry. (2006) 60:704–13. 10.1016/j.biopsych.2006.03.026

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 76.

  RasmussonAMKingMWValovskiIGregorKScioli-SalterEPinelesSLet al. Relationships between cerebrospinal fluid GABAergic neurosteroid levels and symptom severity in men with PTSD. Psychoneuroendocrinology. (2018) 102:95–104. 10.1016/j.psyneuen.2018.11.027

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 77.

  Droogleever FortuynHAvan BroekhovenFSpanPNBäckströmTZitmanFGVerkesRJ. Effects of PhD examination stress on allopregnanolone and cortisol plasma levels and peripheral benzodiazepine receptor density. Psychoneuroendocrinology. (2004) 29:1341–4. 10.1016/j.psyneuen.2004.02.003

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 78.

  WolfOTKudielkaBMHellhammerDHHellhammerJKirschbaumC. Opposing effects of DHEA replacement in elderly subjects on declarative memory and attention after exposure to a laboratory stressor. Psychoneuroendocrinology. (1998) 23:617–29. 10.1016/S0306-4530(98)00032-8

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 79.

  GirdlerSSStranevaPALightKCPedersenCAMorrowAL. Allopregnanolone levels and reactivity to mental stress in premenstrual dysphoric disorder. Biol Psychiatry. (2001) 49:788–97. 10.1016/S0006-3223(00)01044-1

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 80.

  KanesSJColquhounHDohertyJRainesSHoffmannERubinowDRet al. Open-label, proof-of-concept study of brexanolone in the treatment of severe postpartum depression. Hum Psychopharmacol. (2017) 32:e2576. 10.1002/hup.2576

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 81.

  KanesSColquhounHGunduz-BruceHRainesSArnoldRSchacterleAet al. Brexanolone (SAGE-547 injection) in post-partum depression: a randomised controlled trial. Lancet. (2017) 390:480–9. 10.1016/S0140-6736(17)31264-3

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 82.

  HerzogAGFryeCAProgesterone Trial Study Group. Allopregnanolone levels and seizure frequency in progesterone-treated women with epilepsy. Neurology. (2014) 83:345–8. 10.1212/WNL.0000000000000623

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 83.

  Valencia-SanchezCCrepeauAZHoerthMTButlerKAAlmader-DouglasDWingerchukDMet al. Is adjunctive progesterone effective in reducing seizure frequency in patients with intractable catamenial epilepsy? A critically appraised topic. Neurologist. (2018) 23:108–12. 10.1097/NRL.0000000000000167

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 84.

  CaraciFSpampinatoSFMorgeseMGTasceddaFSalluzzoMGGiambirtoneMCet al. Neurobiological links between depression and AD: the role of TGF-β1 signaling as a new pharmacological target. Pharmacol Res. (2018) 130:374–84. 10.1016/j.phrs.2018.02.007

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 85.

  McIntyreRSChaDSSoczynskaJKWoldeyohannesHOGallaugherLAKudlowPet al. Cognitive deficits and functional outcomes in major depressive disorder: determinants, substrates, and treatment interventions. Depress Anxiety. (2013) 30:515–27. 10.1002/da.22063

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 86.

  KallenCBBillheimerJTSummersSAStayrookSELewisMStraussJFIII. Steroidogenic acute regulatory protein (StAR) is a sterol transfer protein. J Biol Chem. (1998) 273:26285–8.

  • Pubmed Abstract
  • Google Scholar

• 87.

  LiuJRoneMBPapadopoulosV. Protein-protein interactions mediate mitochondrial cholesterol transport and steroid biosynthesis. J Biol Chem. (2006) 281:38879–93. 10.1074/jbc.M608820200

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 88.

  BoseMWhittalRMMillerWLBoseHS. Steroidogenic activity of StAR requires contact with mitochondrial VDAC1 and phosphate carrier protein. J Biol Chem. (2008) 283:8837–45. 10.1074/jbc.M709221200

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 89.

  PorcuPBarronAMFryeCAWalfAAYangSYHeXYet al. Neurosteroidogenesis today: novel targets for neuroactive steroid synthesis and action and their relevance for translational research. J Neuroendocrinol. (2016) 28:12351. 10.1111/jne.12351

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 90.

  ChungBCMattesonKJVoutilainenRMohandasTKMillerWL. Human cholesterol side-chain cleavage enzyme, P450scc: cDNA cloning, assignment of the gene to chromosome 15, and expression in the placenta. Proc Natl Acad Sci USA. (1986) 83:8962–6. 10.1073/pnas.83.23.8962

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 91.

  PenningTMPawlowskiJESchlegelBPJezJMLinHKHoogSSet al. Mammalian 3 alpha-hydroxysteroid dehydrogenases. Steroids. (1996) 61:508–23. 10.1016/S0039-128X(96)00093-1

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 92.

  PenningTMJinYHerediaVVLewisM. Structure-function relationships in 3alpha-hydroxysteroid dehydrogenases: a comparison of the rat and human isoforms. J Steroid Biochem Mol Biol. (2003) 85:247–55. 10.1016/S0960-0760(03)00236-X

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 93.

  GriffinLDMellonSH. Selective serotonin reuptake inhibitors directly alter activity of neurosteroidogenic enzymes. Proc Natl Acad Sci USA. (1999) 96:13512–7. 10.1073/pnas.96.23.13512

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 94.

  Agís-BalboaRCPinnaGZhubiAMalokuEVeldicMCostaEGuidottiA. Characterization of brain neurons that express enzymes mediating neurosteroid biosynthesis. Proc Natl Acad Sci USA. (2006) 103:14602–7. 10.1073/pnas.0606544103

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 95.

  MuellerJWGilliganLCIdkowiakJArltWFosterPA. The regulation of steroid action by sulfation and desulfation. Endocr Rev. (2015) 36:526–63. 10.1210/er.2015-1036

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 96.

  SorwellKGKohamaSGUrbanskiHF. Perimenopausal regulation of steroidogenesis in the nonhuman primate. Neurobiol Aging. (2012) 33:1487.e1–13. 10.1016/j.neurobiolaging.2011.05.004

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 97.

  SorwellKGRennerLWeissARNeuringerMKohamaSGUrbanskiHF. Cognition in aged rhesus monkeys: effect of DHEA and correlation with steroidogenic gene expression. Genes Brain Behav. (2017) 16:361–8. 10.1111/gbb.12351

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 98.

  BaulieuEERobelPSchumacherM. Neurosteroids: beginning of the story. Int Rev Neurobiol. (2001) 46:1–32. 10.1016/S0074-7742(01)46057-0

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 99.

  ChenLCaiWChenLZhouRFuruyaKSokabeM. Modulatory metaplasticity induced by pregnenolone sulfate in the rat hippocampus: a leftward shift in LTP/LTD-frequency curve. Hippocampus. (2010) 20:499–512. 10.1002/hipo.20649

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 100.

  CarriganCNPatelSACoxHDBolstadESGerdesJMSmithWEet al. The development of benzo- and naphtho-fused quinoline-2,4-dicarboxylic acids as vesicular glutamate transporter (VGLUT) inhibitors reveals a possible role for neuroactive steroids. Bioorg Med Chem Lett. (2014) 24:850–4. 10.1016/j.bmcl.2013.12.086

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 101.

  ShimizuHIshizukaYYamazakiHShiraoT. Allopregnanolone increases mature excitatory synapses along dendrites via protein kinase A signaling. Neuroscience. (2015) 305:139–45. 10.1016/j.neuroscience.2015.07.079

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 102.

  MillerPSScottSMasiulisSDe ColibusLPardonESteyaertJAricescuAR. Structural basis for GABAA receptor potentiation by neurosteroids. Nat Struct Mol Biol. (2017) 24:986–992. 10.1038/nsmb.3484

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 103.

  GrosserGBennienJSánchez-GuijoABakhausKDöringBHartmannMet al. Transport of steroid 3-sulfates and steroid 17-sulfates by the sodium-dependent organic anion transporter SOAT (SLC10A6). J Steroid Biochem Mol Biol. (2018) 179:20–5. 10.1016/j.jsbmb.2017.09.013

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 104.

  RupprechtRBerningBHauserCAHolsboerFReulJM. Steroid receptor-mediated effects of neuroactive steroids: characterization of structure-activity relationship. Eur J Pharmacol. (1996) 303:227–34. 10.1016/0014-2999(96)00036-2

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 105.

  YangPJonesBLHendersonLP. Mechanisms of anabolic androgenic steroid modulation of alpha(1)beta(3)gamma(2L) GABA(A) receptors. Neuropharmacology. (2002) 43:619–33. 10.1016/S0028-3908(02)00155-7

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 106.

  LambertJJPetersJASturgessNCHalesTG. Steroid modulation of the GABAA receptor complex: electrophysiological studies. Ciba Found Symp. (1990) 153:56–71. 10.1016/1044-5765(91)90020-O

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 107.

  BelelliDCasulaALingALambertJJ. The influence of subunit composition on the interaction of neurosteroids with GABA(A) receptors. Neuropharmacology. (2002) 43:651–61. 10.1016/S0028-3908(02)00172-7

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 108.

  HarneySCFrenguelliBGLambertJJ. Phosphorylation influences neurosteroid modulation of synaptic GABAA receptors in rat CA1 and dentate gyrus neurones. Neuropharmacology. (2003) 45:873–83. 10.1016/S0028-3908(03)00251-X

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 109.

  HosieAMWilkinsMEda SilvaHMSmartTG. Endogenous neurosteroids regulate GABAA receptors through two discrete transmembrane sites. Nature. (2006) 444:486–9. 10.1038/nature05324

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 110.

  BowlbyMR. Pregnenolone sulfate potentiation of N-methyl-D-aspartate receptor channels in hippocampal neurons. Mol Pharmacol. (1993) 43:813–9.

  • Pubmed Abstract
  • Google Scholar

• 111.

  CollingridgeGLVolianskisABannisterNFranceGHannaLMercierMet al. The NMDA receptor as a target for cognitive enhancement. Neuropharmacology. (2013) 64:13–26. 10.1016/j.neuropharm.2012.06.051

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 112.

  HackosDHHansonJE. Diverse modes of NMDA receptor positive allosteric modulation: mechanisms and consequences. Neuropharmacology. (2017) 112:34–45. 10.1016/j.neuropharm.2016.07.037

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 113.

  CollingridgeGLKehlSJMcLennanH. Excitatory amino acids in synaptic transmission in the Schaffer collateral-commissural pathway of the rat hippocampus. J Physiol. (1983) 334:33–46. 10.1113/jphysiol.1983.sp014478

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 114.

  MorrisRGAndersonELynchGSBaudryM. Selective impairment of learning and blockade of long-term potentiation by an N-methyl-D-aspartate receptor antagonist, AP5. Nature. (1986) 319:774–6. 10.1038/319774a0

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 115.

  BashirZIAlfordSDaviesSNRandallADCollingridgeGL. Long-term potentiation of NMDA receptor-mediated synaptic transmission in the hippocampus. Nature. (1991) 349:156–8. 10.1038/349156a0

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 116.

  AsztelyFWigströmHGustafssonB. The relative contribution of NMDA receptor channels in the expression of long-term potentiation in the hippocampal CA1 region. Eur J Neurosci. (1992) 4:681–90. 10.1111/j.1460-9568.1992.tb00177.x

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 117.

  CuiLNInenagaKNagatomoTYamashitaH. Sodium nitroprusside modulates NMDA response in the rat supraoptic neurons in vitro. Brain Res Bull. (1994) 35:253–60. 10.1016/0361-9230(94)90131-7

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 118.

  TraynelisSFWollmuthLPMcBainCJMennitiFSVanceKMOgdenKKet al. Glutamate receptor ion channels: structure, regulation, and function. Pharmacol Rev. (2010) 62:405–96. 10.1124/pr.109.002451

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 119.

  WeaverCELandMBMalayevAAPurdyRHRichardsKGGibbsTTFarbDH. Geometry and charge determine the pharmacological effects of steroids on the N-methyl-D-aspartate receptor. J Pharmacol Exp Ther. (2000) 293:747–54.

  • Pubmed Abstract
  • Google Scholar

• 120.

  KorinekMKaprasVVyklickyVAdamusovaEBorovskaJValesKet al. Neurosteroid modulation of N-methyl-D-aspartate receptors: molecular mechanism and behavioral effects. Steroids. (2011) 76:1409–18. 10.1016/j.steroids.2011.09.002

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 121.

  LeeKHChoJHChoiISParkHMLeeMGChoiBJJangIS. Pregnenolone sulfate enhances spontaneous glutamate release by inducing presynaptic Ca²⁺-induced Ca²⁺ release. Neuroscience. (2010) 171:106–16. 10.1016/j.neuroscience.2010.07.057

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 122.

  DongYFuYMSunJLZhuYHSunFYZhengP. Neurosteroid enhances glutamate release in rat prelimbic cortex via activation of alpha1-adrenergic and sigma1 receptors. Cell Mol Life Sci. (2005) 62:1003–14. 10.1007/s00018-005-5004-8

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 123.

  ManingerNWolkowitzOMReusVIEpelESMellonSH. Neurobiological and neuropsychiatric effects of dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEAS). Front Neuroendocrinol. (2009) 30:65–91. 10.1016/j.yfrne.2008.11.002

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 124.

  KimonidesVGKhatibiNHSvendsenCNSofroniewMVHerbertJ. Dehydroepiandrosterone (DHEA) and DHEA-sulfate (DHEAS) protect hippocampal neurons against excitatory amino acid-induced neurotoxicity. Proc Natl Acad Sci USA. (1998) 95:1852–7. 10.1073/pnas.95.4.1852

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 125.

  BorowiczKKPiskorskaBBanachMCzuczwarSJ. Neuroprotective actions of neurosteroids. Front Endocrinol (Lausanne). (2011) 2:50. 10.3389/fendo.2011.00050

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 126.

  UlmannLRodeauJLDanouxLContet-AudonneauJLPaulyGSchlichterR. Dehydroepiandrosterone and neurotrophins favor axonal growth in a sensory neuron-keratinocyte coculture model. Neuroscience. (2009) 159:514–25. 10.1016/j.neuroscience.2009.01.018

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 127.

  LazaridisICharalampopoulosIAlexakiVIAvlonitisNPediaditakisIEfstathopoulosPet al. Neurosteroid dehydroepiandrosterone interacts with nerve growth factor (NGF) receptors, preventing neuronal apoptosis. PLoS Biol. (2011) 9:e1001051. 10.1371/journal.pbio.1001051

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 128.

  ShenWMennerickSZorumskiECCoveyDFZorumskiCF. Pregnenolone sulfate and dehydroepiandrosterone sulfate inhibit GABA-gated chloride currents in Xenopus oocytes expressing picrotoxin-insensitive GABA(A) receptors. Neuropharmacology. (1999) 38:267–71. 10.1016/S0028-3908(98)00172-5

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 129.

  JohanssonTLeGrevès P. The effect of dehydroepiandrosterone sulfate and allopregnanolone sulfate on the binding of [(3)H]ifenprodil to the N-methyl-d-aspartate receptor in rat frontal cortex membrane. J Steroid Biochem Mol Biol. (2005) 94:263–6. 10.1016/j.jsbmb.2005.01.020

  • CrossRef
  • Google Scholar

• 130.

  TwedeVTartagliaALCoveyDFBamberBA. The neurosteroids dehydroepiandrosterone sulfate and pregnenolone sulfate inhibit the UNC-49 GABA receptor through a common set of residues. Mol Pharmacol. (2007) 72:1322–9. 10.1124/mol.107.034058

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 131.

  WangCMarxCEMorrowALWilsonWAMooreSD. Neurosteroid modulation of GABAergic neurotransmission in the central amygdala: a role for NMDA receptors. Neurosci Lett. (2007) 415:118–23. 10.1016/j.neulet.2007.01.004

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 132.

  WeaverCEMarekPPark-ChungMTamSWFarbDH. Neuroprotective activity of a new class of steroidal inhibitors of the N-methyl-D-aspartate receptor. Proc Natl Acad Sci USA. (1997) 94:10450–4. 10.1073/pnas.94.19.10450

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 133.

  SantoroAMattace RasoGTalianiSDa PozzoESimoriniFCostaBet al. TSPO-ligands prevent oxidative damage and inflammatory response in C6 glioma cells by neurosteroid synthesis. Eur J Pharm Sci. (2016) 88:124–31. 10.1016/j.ejps.2016.04.006

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 134.

  ChengWWLChenZWBracamontesJRBudelierMMKrishnanKShinDJet al. Mapping two neurosteroid-modulatory sites in the prototypic pentameric ligand-gated ion channel GLIC. J Biol Chem. (2018) 293:3013–27. 10.1074/jbc.RA117.000359

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 135.

  MajewskaMDDemirgörenSLondonED. Binding of pregnenolone sulfate to rat brain membranes suggests multiple sites of steroid action at the GABAA receptor. Eur J Pharmacol. (1990) 189:307–15. 10.1016/0922-4106(90)90124-G

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 136.

  MajewskaMDDemirgörenSSpivakCELondonED. The neurosteroid dehydroepiandrosterone sulfate is an allosteric antagonist of the GABAA receptor. Brain Res. (1990) 526:143–6. 10.1016/0006-8993(90)90261-9

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 137.

  AkkGBracamontesJRCoveyDFEversADaoTSteinbachJH. Neuroactive steroids have multiple actions to potentiate GABAA receptors. J Physiol. (2004) 558:59–74. 10.1113/jphysiol.2004.066571

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 138.

  AkkGCoveyDFEversASSteinbachJHZorumskiCFMennerickS. Mechanisms of neurosteroid interactions with GABA(A) receptors. Pharmacol Ther. (2007) 116:35–57. 10.1016/j.pharmthera.2007.03.004

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 139.

  AkkGCoveyDFEversASMennerickSZorumskiCFSteinbachJH. Kinetic and structural determinants for GABA-A receptor potentiation by neuroactive steroids. Curr Neuropharmacol. (2010) 8:18–25. 10.2174/157015910790909458

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 140.

  MaksayGLaubeBBetzH. Subunit-specific modulation of glycine receptors by neurosteroids. Neuropharmacology. (2001) 41:369–76. 10.1016/S0028-3908(01)00071-5

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 141.

  MihalekRMBanerjeePKKorpiERQuinlanJJFirestoneLLMiZPet al. Attenuated sensitivity to neuroactive steroids in gamma-aminobutyrate type A receptor delta subunit knockout mice. Proc Natl Acad Sci USA. (1999) 96:12905–10. 10.1073/pnas.96.22.12905

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 142.

  MihalekRMBowersBJWehnerJMKralicJEVanDorenMJMorrowALet al. GABA(A)-receptor delta subunit knockout mice have multiple defects in behavioral responses to ethanol. Alcohol Clin Exp Res. (2001) 25:1708–18. 10.1111/j.1530-0277.2001.tb02179.x

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 143.

  SpigelmanILiZLiangJCagettiESamzadehSMihalekRMet al. Reduced inhibition and sensitivity to neurosteroids in hippocampus of mice lacking the GABA(A) receptor delta subunit. J Neurophysiol. (2003) 90:903–10. 10.1152/jn.01022.2002

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 144.

  StellBMBrickleySGTangCYFarrantMModyI. Neuroactive steroids reduce neuronal excitability by selectively enhancing tonic inhibition mediated by delta subunit-containing GABAA receptors. Proc Natl Acad Sci USA. (2003) 100:14439–44. 10.1073/pnas.2435457100

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 145.

  WhissellPDLeckerIWangDSYuJOrserBA. Altered expression of δGABAA receptors in health and disease. Neuropharmacology. (2015) 88:24–35. 10.1016/j.neuropharm.2014.08.003

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 146.

  RickCEYeQFinnSEHarrisonNL. Neurosteroids act on the GABAA receptor at sites on the N-terminal side of the middle of TM2. Neuroreport. (1998) 9:379–83. 10.1097/00001756-199802160-00004

  • CrossRef
  • Google Scholar

• 147.

  HosieAMClarkeLda SilvaHSmartTG. Conserved site for neurosteroid modulation of GABA_Areceptors. Neuropharmacology. (2009) 56:149–54. 10.1016/j.neuropharm.2008.07.050

  • CrossRef
  • Google Scholar

• 148.

  CoveyDFNathanDKalkbrennerMNilssonKRHuYZorumskiCFet al. Enantioselectivity of pregnanolone-induced gamma-aminobutyric acid(A) receptor modulation and anesthesia. J Pharmacol Exp Ther. (2000) 293:1009–16.

  • Pubmed Abstract
  • Google Scholar

• 149.

  GhoshBTsaoTWCzajkowskiC. A chimeric prokaryotic-eukaryotic pentameric ligand gated ion channel reveals interactions between the extracellular and transmembrane domains shape neurosteroid modulation. Neuropharmacology. (2017) 125:343–52. 10.1016/j.neuropharm.2017.08.007

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 150.

  JiangXShuHJKrishnanKQianMTaylorAACoveyDFet al. Clickable neurosteroid photolabel reveals selective Golgi compartmentalization with preferential impact on proximal inhibition. Neuropharmacology. (2016) 108:193–206. 10.1016/j.neuropharm.2016.04.031

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 151.

  WagnerTFLochSLambertSStraubIMannebachSMatharIet al. Transient receptor potential M3 channels are ionotropic steroid receptors in pancreatic beta cells. Nat Cell Biol. (2008) 10:1421–30. 10.1038/ncb1801

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 152.

  HarteneckC. Pregnenolone sulfate: from steroid metabolite to TRP channel ligand. Molecules. (2013) 18:12012–28. 10.3390/molecules181012012

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 153.

  ChenSCWuFS. Mechanism underlying inhibition of the capsaicin receptor-mediated current by pregnenolone sulfate in rat dorsal root ganglion neurons. Brain Res. (2004) 1027:196–200. 10.1016/j.brainres.2004.08.053

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 154.

  Zamudio-BulcockPAEverettJHarteneckCValenzuelaCF. Activation of steroid-sensitive TRPM3 channels potentiates glutamatergic transmission at cerebellar Purkinje neurons from developing rats. J Neurochem. (2011) 119:474–85. 10.1111/j.1471-4159.2011.07441.x

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 155.

  Zamudio-BulcockPAValenzuelaCF. Pregnenolone sulfate increases glutamate release at neonatal climbing fiber-to-Purkinje cell synapses. Neuroscience. (2011) 175:24–36. 10.1016/j.neuroscience.2010.11.063

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 156.

  ValenzuelaCFPartridgeLDMameliMMeyerDA. Modulation of glutamatergic transmission by sulfated steroids: role in fetal alcohol spectrum disorder. Brain Res Rev. (2008) 57:506–19. 10.1016/j.brainresrev.2007.04.009

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 157.

  YamamotoSWajimaTHaraYNishidaMMoriY. Transient receptor potential channels in Alzheimer's disease. Biochim Biophys Acta. (2007) 1772:958–67. 10.1016/j.bbadis.2007.03.006

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 158.

  ShigetomiETongXKwanKYCoreyDPKhakhBS. TRPA1 channels regulate astrocyte resting calcium and inhibitory synapse efficacy through GAT-3. Nat Neurosci. (2011) 15:70–80. 10.1038/nn.3000

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 159.

  BossonAPaumierABoisseauSJacquier-SarlinMBuissonAAlbrieuxM. TRPA1 channels promote astrocytic Ca²⁺ hyperactivity and synaptic dysfunction mediated by oligomeric forms of amyloid-β peptide. Mol Neurodegener. (2017) 12:53. 10.1186/s13024-017-0194-8

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 160.

  BianchiBRZhangXFReillyRMKymPRYaoBBChenJ. Species comparison and pharmacological characterization of human, monkey, rat, and mouse TRPA1 channels. J Pharmacol Exp Ther. (2012) 341:360–8. 10.1124/jpet.111.189902

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 161.

  NagatomoKKuboY. Caffeine activates mouse TRPA1 channels but suppresses human TRPA1 channels. Proc Natl Acad Sci USA. (2008) 105:17373–8. 10.1073/pnas.0809769105

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 162.

  WhittakerMTGibbsTTFarbDH. Pregnenolone sulfate induces NMDA receptor dependent release of dopamine from synaptic terminals in the striatum. J Neurochem. (2008) 107:510–21. 10.1111/j.1471-4159.2008.05627.x

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 163.

  SadlerSEMallerJL. Identification of a steroid receptor on the surface of Xenopus oocytes by photoaffinity labeling. J Biol Chem. (1982) 257:355–61.

  • Pubmed Abstract
  • Google Scholar

• 164.

  SadlerSEBowerMAMallerJL. Studies of a plasma membrane steroid receptor in Xenopus oocytes using the synthetic progestin RU 486. J Steroid Biochem. (1985) 22:419–26.

  • Pubmed Abstract
  • Google Scholar

• 165.

  MicevychPEMermelsteinPG. Membrane estrogen receptors acting through metabotropic glutamate receptors: an emerging mechanism of estrogen action in brain. Mol Neurobiol. (2008) 38:66–77. 10.1007/s12035-008-8034-z

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 166.

  StormanEMLiuNJWessendorfMWGintzlerAR. Physical linkage of estrogen receptor α and aromatase in rat: oligocrine and endocrine actions of CNS-produced estrogens. Endocrinology. (2018) 159:2683–97. 10.1210/en.2018-00319

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 167.

  McEwenBSGouldEOrchinikMWeilandNGWoolleyCS. Oestrogens and the structural and functional plasticity of neurons: implications for memory, ageing and neurodegenerative processes. Ciba Found Symp. (1995) 191:52–66; discussion 66–73.

  • Pubmed Abstract
  • Google Scholar

• 168.

  AbrahámIMTodmanMGKorachKSHerbisonAE. Critical in vivo roles for classical estrogen receptors in rapid estrogen actions on intracellular signaling in mouse brain. Endocrinology. (2004) 145:3055–61. 10.1210/en.2003-1676

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 169.

  MukaiHKimotoTHojoYKawatoSMurakamiGHigoSet al. Modulation of synaptic plasticity by brain estrogen in the hippocampus. Biochim Biophys Acta. (2010) 1800:1030–44. 10.1016/j.bbagen.2009.11.002

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 170.

  OoishiYKawatoSHojoYHatanakaYHigoSMurakamiGet al. Modulation of synaptic plasticity in the hippocampus by hippocampus-derived estrogen and androgen. J Steroid Biochem Mol Biol. (2012) 131:37–51. 10.1016/j.jsbmb.2011.10.004

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 171.

  TabatadzeNSmejkalovaTWoolleyCS. Distribution and posttranslational modification of synaptic ERα in the adult female rat hippocampus. Endocrinology. (2013) 154:819–30. 10.1210/en.2012-1870

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 172.

  GibbsTTRussekSJFarbDH. Sulfated steroids as endogenous neuromodulators. Pharmacol Biochem Behav. (2006) 84:555–67. 10.1016/j.pbb.2006.07.031

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 173.

  AsabaHHosoyaKTakanagaHOhtsukiSTamuraETakizawaTTerasakiT. Blood-brain barrier is involved in the efflux transport of a neuroactive steroid, dehydroepiandrosterone sulfate, via organic anion transporting polypeptide 2. J Neurochem. (2000) 75:1907–16. 10.1046/j.1471-4159.2000.0751907.x

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 174.

  SuzukiMSuzukiHSugimotoYSugiyamaY. ABCG2 transports sulfated conjugates of steroids and xenobiotics. J. Biol.Chem. (2003) 278:22644–9. 10.1074/jbc.M212399200

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 175.

  MiyajimaMKusuharaHFujishimaMAdachiYSugiyamaY. Organic anion transporter 3 mediates the efflux transport of an amphipathic organic anion, dehydroepiandrosterone sulfate, across the blood-brain barrier in mice. Drug Metab Dispos. (2011) 39:814–9. 10.1124/dmd.110.036863

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 176.

  QaiserMZDolmanDEMBegleyDJAbbottNJCazacu-DavidescuMCorolDIet al. Uptake and metabolism of sulphated steroids by the blood-brain barrier in the adult male rat. J Neurochem. (2017) 142:672–85. 10.1111/jnc.14117

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 177.

  GrubeMHagenPJedlitschkyG. Neurosteroid transport in the brain: role of ABC and SLC transporters. Front Pharmacol. (2018) 9:354. 10.3389/fphar.2018.00354

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 178.

  ValléeMVitielloSBellocchioLHébert-ChatelainEMonlezunSMartin-GarciaEet al. Pregnenolone can protect the brain from cannabis intoxication. Science. (2014) 343:94–8. 10.1126/science.1243985

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 179.

  WangWJiaYPhamDTPalmerLCJungKMCoxCDet al. Atypical endocannabinoid signaling initiates a new form of memory-related plasticity at a cortical input to hippocampus. Cereb Cortex. (2018) 28:2253–66. 10.1093/cercor/bhx126

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 180.

  KnapsteinPDavidAWuCHArcherDFFlickingerGLTouchstoneJC. Metabolism of free and sulfoconjugated DHEA in brain tissue in vivo and in vitro. Steroids. (1968) 11:885–96. 10.1016/S0039-128X(68)80102-3

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 181.

  MayoWDelluFRobelPCherkaouiJLe MoalMBaulieuEEet al. Infusion of neurosteroids into the nucleus basalis magnocellularis affects cognitive processes in the rat. Brain Res. (1993) 607:324–8. 10.1016/0006-8993(93)91524-V

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 182.

  WongMMossRL. Patch-clamp analysis of direct steroidal modulation of glutamate receptor-channels. J Neuroendocrinol. (1994) 6:347–55. 10.1111/j.1365-2826.1994.tb00592.x

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 183.

  HigashiTSugitaniHYagiTShimadaK. Studies on neurosteroids XVI. Levels of pregnenolone sulfate in rat brains determined by enzyme-linked immunosorbent assay not requiring solvolysis. Biol Pharm Bull. (2003) 26:709–711. 10.1248/bpb.26.709

  • CrossRef
  • Google Scholar

• 184.

  SchumacherMLierePAkwaYRajkowskiKGriffithsWBodinKet al. Pregnenolone sulfate in the brain: a controversial neurosteroid. Neurochem Int. (2008) 52:522–40. 10.1016/j.neuint.2007.08.022

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 185.

  NanfaroFCabreraRBazzocchiniVLaconiMYunesR. Pregnenolone sulfate infused in lateral septum of male rats impairs novel object recognition memory. Pharmacol Rep. (2010) 62:265–72. 10.1016/S1734-1140(10)70265-6

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 186.

  SteckelbroeckSNassenAUgeleBLudwigMWatzkaMReissingerAet al. Steroid sulfatase (STS) expression in the human temporal lobe: enzyme activity, mRNA expression and immunohistochemistry study. J Neurochem. (2004) 89:403–17. 10.1046/j.1471-4159.2004.02336.x

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 187.

  Bruins SlotLAPiazzaPVColpaertFC. Neuroactive steroids and the constraint of memory. Eur J Neurosci. (1999) 11:4081–8. 10.1046/j.1460-9568.1999.00824

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 188.

  MatthewsDBMorrowALTokunagaSMcDanielJR. Acute ethanol administration and acute allopregnanolone administration impair spatial memory in the Morris water task. Alcohol Clin Exp Res. (2002) 26:1747–51. 10.1097/01.ALC.0000037219.79257.17

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 189.

  JohanssonIMBirznieceVLindbladCOlssonTBäckströmT. Allopregnanolone inhibits learning in the Morris water maze. Brain Res. (2002) 934:125–31. 10.1016/S0006-8993(02)02414-9

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 190.

  WiltgenBJSandersMJFergusonCHomanicsGEFanselowMS. Trace fear conditioning is enhanced in mice lacking the delta subunit of the GABAA receptor. Learn Mem. (2005) 12:327–33. 10.1101/lm.89705

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 191.

  AmatoRJMoerschbaecherJMWinsauerPJ. Effects of pregnanolone and flunitrazepam on the retention of response sequences in rats. Pharmacol Biochem Behav. (2011) 99:391–8. 10.1016/j.pbb.2011.05.023

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 192.

  SripadaRKMarxCEKingAPRamptonJCHoSSLiberzonI. Allopregnanolone elevations following pregnenolone administration are associated with enhanced activation of emotion regulation neurocircuits. Biol Psychiatry. (2013) 73:1045–53. 10.1016/j.biopsych.2012.12.008

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 193.

  van DorenMJMatthewsDBJanisGCGrobinACDevaudLLMorrowAL. Neuroactive steroid 3alpha-hydroxy-5alpha-pregnan-20-one modulates electrophysiological and behavioral actions of ethanol. J Neurosci. (2000) 20:1982–9. 10.1523/JNEUROSCI.20-05-01982.2000

  • CrossRef
  • Google Scholar

• 194.

  GorinRECrabbeJCTanchuckMALongSLFinnDA. Effects of finasteride on chronic and acute ethanol withdrawal severity in the WSP and WSR selected lines. Alcohol Clin Exp Res. (2005) 29:939–48. 10.1097/01.ALC.0000167742.11566.01

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 195.

  ArdeshiriAKelleyMHKornerIPHurnPDHersonPS. Mechanism of progesterone neuroprotection of rat cerebellar Purkinje cells following oxygen-glucose deprivation. Eur J Neurosci. (2006) 24:2567–74. 10.1111/j.1460-9568.2006.05142.x

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 196.

  PallarésMDarnaudéryMDayJLe MoalMMayoW. The neurosteroid pregnenolone sulfate infused into the nucleus basalis increases both acetylcholine release in the frontal cortex or amygdala and spatial memory. Neuroscience. (1998) 87:551–8. 10.1016/S0306-4522(98)00174-2

  • CrossRef
  • Google Scholar

• 197.

  WangJMSinghCLiuLIrwinRWChenSChungEJet al. Allopregnanolone reverses neurogenic and cognitive deficits in mouse model of Alzheimer's disease. Proc Natl Acad Sci USA. (2010) 107:6498–503. 10.1073/pnas.1001422107

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 198.

  BengtssonSKJohanssonMBäckströmTWangM. Chronic allopregnanolone treatment accelerates Alzheimer's disease development in AβPP(Swe)PSEN1(ΔE9) mice. J Alzheimers Dis. (2012) 31:71–84. 10.3233/JAD-2012-120268

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 199.

  BengtssonSKJohanssonMBackstromTNitschRMWangM. Brief but chronic increase in allopregnanolone cause accelerated AD pathology differently in two mouse models. Curr Alzheimer Res. (2013) 10:38–47. 10.2174/1567205011310010006

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 200.

  BengtssonSKJohanssonMBäckströmT. Long-term continuous allopregnanolone elevation causes memory decline and hippocampus shrinkage, in female wild-type B6 mice. Horm Behav. (2016) 78:160–7. 10.1016/j.yhbeh.2015.10.010

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 201.

  IrwinRWSolinskyCMLoyaCMSalituroFGRodgersKEBauerGet al. Allopregnanolone preclinical acute pharmacokinetic and pharmacodynamic studies to predict tolerability and efficacy for Alzheimer's disease. PLoS ONE. (2015) 10:e0128313. 10.1371/journal.pone.0128313

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 202.

  GenazzaniARPetragliaFBernardiFCasarosaESalvestroniCTonettiAet al. Circulating levels of allopregnanolone in humans: gender, age, and endocrine influences. J Clin Endocrinol Metab. (1998) 83:2099–103. 10.1210/jcem.83.6.4905

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 203.

  KaskKBäckströmTNilssonLGSundström-PoromaaI. Allopregnanolone impairs episodic memory in healthy women. Psychopharmacology (Berl). (2008) 199:161–8. 10.1007/s00213-008-1150-7

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 204.

  RabinowitzACohenSJFinnDAStackmanRWJr. The neurosteroid allopregnanolone impairs object memory and contextual fear memory in male C57BL/6J mice. Horm Behav. (2014) 66:238–46. 10.1016/j.yhbeh.2014.05.005

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 205.

  CohenSJStackmanRWJr. Assessing rodent hippocampal involvement in the novel object recognition task. A review. Behav Brain Res. (2015) 285:105–17. 10.1016/j.bbr.2014.08.002

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 206.

  MòdolLDarbraSPallarèsM. Neurosteroids infusion into the CA1 hippocampal region on exploration, anxiety-like behaviour and aversive learning. Behav Brain Res. (2011) 222:223–9. 10.1016/j.bbr.2011.03.058

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 207.

  ErtmanNAndreanoJMCahillL. Progesterone at encoding predicts subsequent emotional memory. Learn Mem. (2011) 18:759–63. 10.1101/lm.023267.111

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 208.

  NielsenSEErtmanNLakhaniYSCahillL. Hormonal contraception usage is associated with altered memory for an emotional story. Neurobiol Learn Mem. (2011) 96:378–84. 10.1016/j.nlm.2011.06.013

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 209.

  LocciAPorcuPTalaniGSantoruFBerrettiRGiuntiEet al. Neonatal estradiol exposure to female rats changes GABAA receptor expression and function, and spatial learning during adulthood. Horm Behav. (2017) 87:35–46. 10.1016/j.yhbeh.2016.10.005

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 210.

  ParisJJBruntonPJRussellJAWalfAAFryeCA. Inhibition of 5α-reductase activity in late pregnancy decreases gestational length and fecundity and impairs object memory and central progestogen milieu of juvenile rat offspring. J Neuroendocrinol. (2011) 23:1079–90. 10.1111/j.1365-2826.2011.02219.x

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 211.

  PorcuPLallaiVLocciACatzedduSSerraVPisuMGet al. Changes in stress-stimulated allopregnanolone levels induced by neonatal estradiol treatment are associated with enhanced dopamine release in adult female rats: reversal by progesterone administration. Psychopharmacology (Berl). (2017) 234:749–60. 10.1007/s00213-016-4511-7

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 212.

  FadaltiMPetragliaFLuisiSBernardiFCasarosaEFerrariEet al. Changes of serum allopregnanolone levels in the first 2 years of life and during pubertal development. Pediatr Res. (1999) 46:323–7. 10.1203/00006450-199909000-00013

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 213.

  GrossoSLuisiSMostardiniRMateraMBarloccoEGCasarosaEet al. Circulating levels of allopregnanolone, a neuroactive steroid, and leptin during treatment with valproic acid in children with epilepsy. Neuroendocrinology. (2011) 93:159–64. 10.1159/000321664

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 214.

  AndréenLSundström-PoromaaIBixoMNybergSBäckströmT. Allopregnanolone concentration and mood–a bimodal association in postmenopausal women treated with oral progesterone. Psychopharmacology (Berl). (2006) 187:209–21. 10.1007/s00213-006-0417-0

  • CrossRef
  • Google Scholar

• 215.

  WangMSeippelLPurdyRHBãckströmT. Relationship between symptom severity and steroid variation in women with premenstrual syndrome: study on serum pregnenolone, pregnenolone sulfate, 5 alpha-pregnane-3,20-dione and 3 alpha-hydroxy-5 alpha-pregnan-20-one. J Clin Endocrinol Metab. (1996) 81:1076–82.

  • Pubmed Abstract
  • Google Scholar

• 216.

  OttanderUPoromaaISBjurulfESkyttABäckströmTOlofssonJI. Allopregnanolone and pregnanolone are produced by the human corpus luteum. Mol Cell Endocrinol. (2005) 239:37–44. 10.1016/j.mce.2005.04.007

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 217.

  BixoMAnderssonAWinbladBPurdyRHBäckströmT. Progesterone, 5alpha-pregnane-3,20-dione and 3alpha-hydroxy-5alpha-pregnane-20-one in specific regions of the human female brain in different endocrine states. Brain Res. (1997) 764:173–8. 10.1016/S0006-8993(97)00455-1

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 218.

  HedströmHBäckströmTBixoMNybergSWangMGideonssonITurkmenS. Women with polycystic ovary syndrome have elevated serum concentrations of and altered GABA(A) receptor sensitivity to allopregnanolone. Clin Endocrinol (Oxf). (2015) 83:643–50. 10.1111/cen.12809

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 219.

  SolemanRSKreukelsBPCVeltmanDJCohen-KettenisPTHompesPGADrentMLet al. Does polycystic ovary syndrome affect cognition? A functional magnetic resonance imaging study exploring working memory. Fertil Steril. (2016) 105:1314–21.e1. 10.1016/j.fertnstert.2016.01.034

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 220.

  SchmidtPJPurdyRHMoorePHJrPaulSMRubinowDR. Circulating levels of anxiolytic steroids in the luteal phase in women with premenstrual syndrome and in control subjects. J Clin Endocrinol Metab. (1994) 79:1256–60. 10.1210/jcem.79.5.7962316

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 221.

  BicíkováMLapcíkOHamplRStárkaLKnuppenRHauptOet al. A novel radioimmunoassay of allopregnanolone. Steroids. (1995) 60:210–3. 10.1016/0039-128X(94)00039-F

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 222.

  InnalaEBäckströmTPoromaaISAnderssonCBixoM. Women with acute intermittent porphyria have a defect in 5α-steroid production during the menstrual cycle. Acta Obstet Gynecol Scand. (2012) 91:1445–52. 10.1111/j.1600-0412.2012.01536.x

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 223.

  NybergSBäckströmTZingmarkEPurdyRHPoromaaIS. Allopregnanolone decrease with symptom improvement during placebo and gonadotropin-releasing hormone agonist treatment in women with severe premenstrual syndrome. Gynecol Endocrinol. (2007) 23:257–66. 10.1080/09513590701253511

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 224.

  FerreeNKKamatRCahillL. Influences of menstrual cycle position and sex hormone levels on spontaneous intrusive recollections following emotional stimuli. Conscious Cogn. (2011) 20:1154–62. 10.1016/j.concog.2011.02.003

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 225.

  FerreeNKWheelerMCahillL. The influence of emergency contraception on post-traumatic stress symptoms following sexual assault. J Forensic Nurs. (2012) 8:122–30. 10.1111/j.1939-3938.2012.01134.x

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 226.

  ShenHGongQHYuanMSmithSS. Short-term steroid treatment increases delta GABAA receptor subunit expression in rat CA1 hippocampus: pharmacological and behavioral effects. Neuropharmacology. (2005) 49:573–86. 10.1016/j.neuropharm.2005.04.026

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 227.

  SmithCCVedderLCMcMahonLL. Estradiol and the relationship between dendritic spines, NR2B containing NMDA receptors, and the magnitude of long-term potentiation at hippocampal CA3-CA1 synapses. Psychoneuroendocrinology. (2009) 34(Suppl. 1):S130–42. 10.1016/j.psyneuen.2009.06.003

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 228.

  ShenHSabaliauskasNSherpaAFentonAAStelzerAAokiCSmithSS. A critical role for alpha4betadelta GABAA receptors in shaping learning deficits at puberty in mice. Science. (2010) 327:1515–8. 10.1126/science.1184245

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 229.

  AfrozSShenHSmithSS. α4βδ GABAA receptors reduce dendritic spine density in CA1 hippocampus and impair relearning ability of adolescent female mice: effects of a GABA agonist and a stress steroid. Neuroscience. (2017) 347:22–35. 10.1016/j.neuroscience.2017.01.051

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 230.

  SabaliauskasNShenHMollaJGongQHKuverAAokiCSmithSS. Neurosteroid effects at α4βδ GABAA receptors alter spatial learning and synaptic plasticity in CA1 hippocampus across the estrous cycle of the mouse. Brain Res. (2015) 1621:170–86. 10.1016/j.brainres.2014.12.026

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 231.

  FerandoIModyI. Altered gamma oscillations during pregnancy through loss of δ subunit-containing GABA(A) receptors on parvalbumin interneurons. Front Neural Circuits. (2013) 7:144. 10.3389/fncir.2013.00144

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 232.

  MüllerCRemyS. Septo-hippocampal interaction. Cell Tissue Res. (2018) 373:565–75. 10.1007/s00441-017-2745-2

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 233.

  MuzzioIAKentrosCKandelE. What is remembered? Role of attention on the encoding and retrieval of hippocampal representations. J Physiol. (2009) 587:2837–54. 10.1113/jphysiol.2009.172445

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 234.

  AndreescuCEMilojkovicBAHaasdijkEDKramerPDe JongFHKrustAet al. Estradiol improves cerebellar memory formation by activating estrogen receptor beta. J Neurosci. (2007) 27:10832–9. 10.1523/JNEUROSCI.2588-07.2007

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 235.

  KonradCEngelienASchöningSZwitserloodPJansenAPletzigerEet al. The functional anatomy of semantic retrieval is influenced by gender, menstrual cycle, and sex hormones. J Neural Transm (Vienna). (2008) 115:1327–37. 10.1007/s00702-008-0073-0

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 236.

  EastonAWebsterLAEacottMJ. The episodic nature of episodic-like memories. Learn Mem. (2012) 19:146–50. 10.1101/lm.025676.112

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 237.

  RobertsE. Pregnenolone from Selye to Alzheimer and a model of the pregnenolone sulfate binding site on the GABAA receptor. Biochem Pharmacol. (1995) 49:1–16. 10.1016/0006-2952(94)00258-N

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 238.

  RitsnerMSGibelAShleiferTBoguslavskyIZayedAMaayanRet al. Pregnenolone and dehydroepiandrosterone as an adjunctive treatment in schizophrenia and schizoaffective disorder: an 8-week, double-blind, randomized, controlled, 2-center, parallel-group trial. J Clin Psychiatry. (2010) 71:1351–62. 10.4088/JCP.09m05031yel

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 239.

  NagayaNAccaGMMarenS. Allopregnanolone in the bed nucleus of the stria terminalis modulates contextual fear in rats. Front Behav Neurosci. (2015) 9:205. 10.3389/fnbeh.2015.00205

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 240.

  Sierra-MercadoDPadilla-CoreanoNQuirkGJ. Dissociable roles of prelimbic and infralimbic cortices, ventral hippocampus, and basolateral amygdala in the expression and extinction of conditioned fear. Neuropsychopharmacology. (2011) 36:529–38. 10.1038/npp.2010.184

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 241.

  SakamotoHUkenaKTsutsuiK. Effects of progesterone synthesized de novo in the developing Purkinje cell on its dendritic growth and synaptogenesis. J Neurosci. (2001) 21:6221–32. 10.1523/JNEUROSCI.21-16-06221.2001

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 242.

  TsutsuiKSakamotoHUkenaK. Biosynthesis and action of neurosteroids in the cerebellar Purkinje neuron. J Steroid Biochem Mol Biol. (2003) 85:311–21. 10.1016/S0960-0760(03)00229-2

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 243.

  WulffPSchonewilleMRenziMViltonoLSassoe-PognettoMBaduraAet al. Synaptic inhibition of Purkinje cells mediates consolidation of vestibulo-cerebellar motor learning. Nat Neurosci. (2009) 12:1042–9. 10.1038/nn.2348

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 244.

  DieniCVSullivanJAFaralliMContemoriSBiscariniAPettorossiVEet al. 17 beta-estradiol synthesis modulates cerebellar dependent motor memory formation in adult male rats. Neurobiol Learn Mem. (2018) 155:276–86. 10.1016/j.nlm.2018.08.011

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 245.

  Gonzalez-UsanoACauliOAgustiAFelipoV. Pregnenolone sulfate restores the glutamate-nitric-oxide-cGMP pathway and extracellular GABA in cerebellum and learningand motor coordination in hyperammonemic rats. ACS Chem Neurosci. (2014) 5:100–5. 10.1021/cn400168y

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 246.

  AccaGMMathewASJinJMarenSNagayaN. Allopregnanolone induces state-dependent fear via the bed nucleus of the stria terminalis. Horm Behav. (2017) 89:137–44. 10.1016/j.yhbeh.2017.01.002

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 247.

  MayoWGeorgeODarbraSBouyerJJValléeMDarnaudéryMet al. Individual differences in cognitive aging: implication of pregnenolone sulfate. Prog Neurobiol. (2003) 71:43–8. 10.1016/j.pneurobio.2003.09.006

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 248.

  GeorgeOValléeMVitielloSLe MoalMPiazzaPVMayoW. Low brain allopregnanolone levels mediate flattened circadian activity associated with memory impairments in aged rats. Biol Psychiatry. (2010) 68:956–63. 10.1016/j.biopsych.2010.03.022

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 249.

  CarusoDBarronAMBrownMAAbbiatiFCarreroPPikeCJet al. Age-related changes in neuroactive steroid levels in 3xTg-AD mice. Neurobiol Aging. (2013) 34:1080–9. 10.1016/j.neurobiolaging.2012.10.007

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 250.

  KlöppelSKotschiMPeterJEggerKHausnerLFrölichLet al. Separating symptomatic Alzheimer's disease from depression based on structural MRI. J Alzheimers Dis. (2018) 63:353–63. 10.3233/JAD-170964

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 251.

  RosarioERChangLHeadEHStanczykFZPikeCJ. Brain levels of sex steroid hormones in men and women during normal aging and in Alzheimer's disease. Neurobiol Aging. (2011) 32:604–13. 10.1016/j.neurobiolaging.2009.04.008

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 252.

  HogervorstEBandelowSCombrinckMSmithAD. Low free testosterone is an independent risk factor for Alzheimer's disease. Exp Gerontol. (2004) 39:1633–9. 10.1016/j.exger.2004.06.019

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 253.

  ResnickSMMatsumotoAMStephens-ShieldsAJEllenbergSSGillTMShumakerSAet al. Testosterone treatment and cognitive function in older men with low testosterone and age-associated memory impairment. JAMA. (2017) 317:717–27. 10.1001/jama.2016.21044

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 254.

  DarbraSGeorgeOBouyerJJPiazzaPVLe MoalMMayoW. Sleep-wake states and cortical synchronization control by pregnenolone sulfate into the pedunculopontine nucleus. J Neurosci Res. (2004) 76:742–7. 10.1002/jnr.20074

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 255.

  GeorgeOValléeMLe MoalMMayoW. Neurosteroids and cholinergic systems: implications for sleep and cognitive processes and potential role of age-related changes. Psychopharmacology (Berl). (2006) 186:402–13. 10.1007/s00213-005-0254-6

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 256.

  MayoWLe MoalMAbrousDN. Pregnenolone sulfate and aging of cognitive functions: behavioral, neurochemical, and morphological investigations. Horm Behav. (2001) 40:215–7. 10.1006/hbeh.2001.1677

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 257.

  DarnaudéryMBouyerJJPallarésMLe MoalMMayoW. The promnesic neurosteroid pregnenolone sulfate increases paradoxical sleep in rats. Brain Res. (1999) 818:492–8. 10.1016/S0006-8993(98)01338-9

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 258.

  DarnaudéryMKoehlMPiazzaPVLe MoalMMayoW. Pregnenolone sulfate increases hippocampal acetylcholine release and spatial recognition. Brain Res. (2000) 852:173–9. 10.1016/S0006-8993(99)01964-2

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 259.

  RiemannDHohagenFKriegerSGannHMüllerWEOlbrichRet al. Cholinergic REM induction test: muscarinic supersensitivity underlies polysomnographic findings in both depression and schizophrenia. J Psychiatr Res. (1994) 28:195–210. 10.1016/0022-3956(94)90006-X

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 260.

  BaranBCorrellDVuperTCMorganADurrantSJManoachDSet al. Spared and impaired sleep-dependent memory consolidation in schizophrenia. Schizophr Res. (2018) S0920-9964:30231–7. 10.1016/j.schres.2018.04.019

  • CrossRef
  • Google Scholar

• 261.

  WaterhouseRNChangRCAtueheneNCollierTL. In vitro and in vivo binding of neuroactive steroids to the sigma-1 receptor as measured with the positron emission tomography radioligand [18F]FPS. Synapse. (2007) 61:540–6. 10.1002/syn.20369

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 262.

  MauriceTRomanFJPrivatA. Modulation by neurosteroids of the in vivo (+)-[3H]SKF-10,047 binding to sigma 1 receptors in the mouse forebrain. J Neurosci Res. (1996) 46:734–43. 10.1002/(SICI)1097-4547(19961215)46:6<734::AID-JNR10>3.0.CO;2-U

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 263.

  GibbsTTFarbDH. Dueling enigmas: neurosteroids and sigma receptors in the limelight. Sci STKE. (2000) 2000:pe1. 10.1126/stke.2000.60.pe1

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 264.

  MauriceTStrehaianoMDuhrFChevallierN. Amyloid toxicity is enhanced after pharmacological or genetic invalidation of the σ1 receptor. Behav Brain Res. (2018) 339:1–10. 10.1016/j.bbr.2017.11.010

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 265.

  LanzenbergerRMitterhauserMKranzGSSpindeleggerCWadsakWSteinPet al. Progesterone level predicts serotonin-1a receptor binding in the male human brain. Neuroendocrinology. (2011) 94:84–8. 10.1159/000328432

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 266.

  SteinPBaldingerPKaufmannUChristinaRMHahnAHöflichAet al. Relation of progesterone and DHEAS serum levels to 5-HT1A receptor binding potential in pre- and postmenopausal women. Psychoneuroendocrinology. (2014) 46:52–63. 10.1016/j.psyneuen.2014.04.008

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 267.

  VidalBSebtiJVerdurandMFieuxSBillardTStreichenbergerNet al. Agonist and antagonist bind differently to 5-HT1A receptors during Alzheimer's disease: a post-mortem study with PET radiopharmaceuticals. Neuropharmacology. (2016) 109:88–95. 10.1016/j.neuropharm.2016.05.009

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 268.

  KohMTHabermanRPFotiSMcCownTJGallagherM. Treatment strategies targeting excess hippocampal activity benefit aged rats with cognitive impairment. Neuropsychopharmacology. (2010) 35:1016–25. 10.1038/npp.2009.207

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 269.

  YassaMAMattfeldATStarkSMStarkCE. Age-related memory deficits linked to circuit-specific disruptions in the hippocampus. Proc Natl Acad Sci USA. (2011) 108:8873–8. 10.1073/pnas.1101567108

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 270.

  BakkerAKraussGLAlbertMSSpeckCLJonesLRStarkCEet al. Reduction of hippocampal hyperactivity improves cognition in amnestic mild cognitive impairment. Neuron. (2012) 74:467–74. 10.1016/j.neuron.2012.03.023

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 271.

  WuJWHussainiSABastilleIMRodriguezGAMrejeruARilettKet al. Neuronal activity enhances tau propagation and tau pathology in vivo. Nat Neurosci. (2016) 19:1085–92. 10.1038/nn.4328

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 272.

  NurielTAnguloSLKhanUAshokAChenQFigueroaHYet al. Neuronal hyperactivity due to loss of inhibitory tone in APOE4 mice lacking Alzheimer's disease-like pathology. Nat Commun. (2017) 8:1464. 10.1038/s41467-017-01444-0

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 273.

  ShettyAKTurnerDA. Hippocampal interneurons expressing glutamic acid decarboxylase and calcium-binding proteins decrease with aging in Fischer 344 rats. J Comp Neurol. (1998) 394:252–69. 10.1002/(SICI)1096-9861(19980504)394:2<252::AID-CNE9>3.0.CO;2-1

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 274.

  StanleyEMFadelJRMottDD. Interneuron loss reduces dendritic inhibition and GABA release in hippocampus of aged rats. Neurobiol Aging. (2012) 33:431.e1–13. 10.1016/j.neurobiolaging.2010.12.014

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 275.

  KwakowskyACalvo-FloresGuzmán BPandyaMTurnerCWaldvogelHJFaullRL. GABAA receptor subunit expression changes in the human Alzheimer's disease hippocampus, subiculum, entorhinal cortex and superior temporal gyrus. J Neurochem. (2018) 145:374–92. 10.1111/jnc.14325

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 276.

  ReddyDSEstesWA. Clinical potential of neurosteroids for CNS disorders. Trends Pharmacol Sci. (2016) 37:543–61. 10.1016/j.tips.2016.04.003

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 277.

  ChenSWangJMIrwinRWYaoJLiuLBrintonRD. Allopregnanolone promotes regeneration and reduces β-amyloid burden in a preclinical model of Alzheimer's disease. PLoS ONE. (2011) 6:e24293. 10.1371/journal.pone.0024293

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 278.

  BrintonRD. Neurosteroids as regenerative agents in the brain: therapeutic implications. Nat Rev Endocrinol. (2013) 9:241–50. 10.1038/nrendo.2013.31

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 279.

  ZhangPXieMQDingYQLiaoMQiSSChenSXet al. Allopregnanolone enhances the neurogenesis of midbrain dopaminergic neurons in APPswe/PSEN1 mice. Neuroscience. (2015) 290:214–26. 10.1016/j.neuroscience.2015.01.019

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 280.

  PereiraACGrayJDKoganJFDavidsonRLRubinTGOkamotoMet al. Age and Alzheimer's disease gene expression profiles reversed by the glutamate modulator riluzole. Mol Psychiatry. (2017) 22:296–305. 10.1038/mp.2016.33

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 281.

  GirardCLiuSCadepondFAdamsDLacroixCVerleyeMet al. Etifoxine improves peripheral nerve regeneration and functional recovery. Proc Natl Acad Sci USA. (2008) 105:20505–10. 10.1073/pnas.0811201106

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 282.

  KreislWCLyooCHMcGwierMSnowJJenkoKJKimuraNet al. In vivo radioligand binding to translocator protein correlates with severity of Alzheimer's disease. Brain. (2013) 136:2228–38. 10.1093/brain/awt145

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 283.

  SetiawanEWilsonAAMizrahiRRusjanPMMilerLRajkowskaGet al. Role of translocator protein density, a marker of neuroinflammation, in the brain during major depressive episodes. JAMA Psychiatry. (2015) 72:268–275. 10.1001/jamapsychiatry.2014.2427

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 284.

  BrownRCCascioCPapadopoulosV. Pathways of neurosteroid biosynthesis in cell lines from human brain: regulation of dehydroepiandrosterone formation by oxidative stress and beta-amyloid peptide. J Neurochem. (2000) 74:847–59. 10.1046/j.1471-4159.2000.740847.x

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 285.

  AlyHFMetwallyFMAhmedHH. Neuroprotective effects of dehydroepiandrosterone (DHEA) in rat model of Alzheimer's disease. Acta Biochim Pol. (2011) 58:513–20. 10.18388/abp.2011_2218

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 286.

  MenonV. Large-scale brain networks and psychopathology: a unifying triple network model. Trends Cogn Sci. (2011) 15:483–506. 10.1016/j.tics.2011.08.003

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 287.

  HodgettsCJShineJPWilliamsHPostansMSimsRWilliamsJet al. Increased posterior default mode network activity and structural connectivity in young adult APOE-ε4 carriers: a multimodal imaging investigation. Neurobiol Aging. (2019) 73:82–91. 10.1016/j.neurobiolaging.2018.08.026

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 288.

  OferILeRoseCMastHLeVanPMetternichBEggerKet al. Association between seizure freedom and default mode network reorganization in patients with unilateral temporal lobe epilepsy. Epilepsy Behav. (2018) S1525-5050:30822–3. 10.1016/j.yebeh.2018.10.025

  • CrossRef
  • Google Scholar

• 289.

  WhiteTPJosephVFrancisSTLiddlePF. Aberrant salience network (bilateral insula and anterior cingulate cortex) connectivity during information processing in schizophrenia. Schizophr Res. (2010) 123:105–15. 10.1016/j.schres.2010.07.020

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 290.

  SripadaRKKingAPGarfinkelSNWangXSripadaCSWelshRCet al. Altered resting-state amygdala functional connectivity in men with posttraumatic stress disorder. J Psychiatry Neurosci. (2012) 37:241–9. 10.1503/jpn.110069

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 291.

  SripadaRKKingAPWelshRCGarfinkelSNWangXSripadaCSet al. Neural dysregulation in posttraumatic stress disorder: evidence for disrupted equilibrium between salience and default mode brain networks. Psychosom Med. (2012) 74:904–11. 10.1097/PSY.0b013e318273bf33

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 292.

  SripadaRKWelshRCMarxCELiberzonI. The neurosteroids allopregnanolone and dehydroepiandrosterone modulate resting-state amygdala connectivity. Hum Brain Mapp. (2014) 35:3249–61. 10.1002/hbm.22399

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 293.

  CanterasNSSwansonLW. Projections of the ventral subiculum to the amygdala, septum, and hypothalamus: a PHAL anterograde tract-tracing study in the rat. J Comp Neurol. (1992) 324:180–94. 10.1002/cne.903240204

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 294.

  LiSKirouacGJ. Projections from the paraventricular nucleus of the thalamus to the forebrain, with special emphasis on the extended amygdala. J Comp Neurol. (2008) 506:263–87. 10.1002/cne.21502

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 295.

  LiSKirouacGJ. Sources of inputs to the anterior and posterior aspects of the paraventricular nucleus of the thalamus. Brain Struct Funct. (2012) 217:257–73. 10.1007/s00429-011-0360-7

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 296.

  PenzoMARobertVTucciaroneJDe BundelDWangMVan AelstLet al. The paraventricular thalamus controls a central amygdala fear circuit. Nature. (2015) 519:455–9. 10.1038/nature13978

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 297.

  UzunovaVShelineYDavisJMRasmussonAUzunovDPCostaEet al. Increase in the cerebrospinal fluid content of neurosteroids in patients with unipolar major depression who are receiving fluoxetine or fluvoxamine. Proc Natl Acad Sci USA. (1998) 95:3239–44. 10.1073/pnas.95.6.3239

  • CrossRef
  • Google Scholar

• 298.

  KhistiRTChopdeCTJainSP. Antidepressant-like effect of the neurosteroid 3alpha-hydroxy-5alpha-pregnan-20-one in mice forced swim test. Pharmacol Biochem Behav. (2000) 67:137–43. 10.1016/S0091-3057(00)00300-2

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 299.

  PinnaGDongEMatsumotoKCostaEGuidottiA. In socially isolated mice, the reversal of brain allopregnanolone down-regulation mediates the anti-aggressive action of fluoxetine. Proc Natl Acad Sci USA. (2003) 100:2035–40. 10.1073/pnas.0337642100

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 300.

  PinnaGCostaEGuidottiA. Fluoxetine and norfluoxetine stereospecifically facilitate pentobarbital sedation by increasing neurosteroids. Proc Natl Acad Sci USA. (2004) 101:6222–5. 10.1073/pnas.0401479101

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 301.

  DevallAJSantosJMFryJPHonourJWBrandãoMLLovickTA. Elevation of brain allopregnanolone rather than 5-HT release by short term, low dose fluoxetine treatment prevents the estrous cycle-linked increase in stress sensitivity in female rats. Eur Neuropsychopharmacol. (2015) 25:113–23. 10.1016/j.euroneuro.2014.11.017

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 302.

  MorrowALJanisGCVanDorenMJMatthewsDBSamsonHHJanakPHGrantKA. Neurosteroids mediate pharmacological effects of ethanol: a new mechanism of ethanol action?Alcohol Clin Exp Res. (1999) 23:1933–40. 10.1111/j.1530-0277.1999.tb04094.x

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 303.

  CagettiEPinnaGGuidottiABaicyKOlsenRW. Chronic intermittent ethanol (CIE) administration in rats decreases levels of neurosteroids in hippocampus, accompanied by altered behavioral responses to neurosteroids and memory function. Neuropharmacology. (2004) 46:570–9. 10.1016/j.neuropharm.2003.10.001

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 304.

  FinnDAJimenezVA. Dynamic adaptation in neurosteroid networks in response to alcohol. Handb Exp Pharmacol. (2017). 10.1007/164_2017_82. [Epub ahead of print].

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 305.

  MantellaRCButtersMADewMAMulsantBHBegleyAETraceyBet al. Cognitive impairment in late-life generalized anxiety disorder. Am J Geriatr Psychiatry. (2007) 15:673–9. 10.1097/JGP.0b013e31803111f2

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 306.

  LeeBKGlassTAMcAteeMJWandGSBandeen-RocheKBollaKIet al. Associations of salivary cortisol with cognitive function in the Baltimore memory study. Arch Gen Psychiatry. (2007) 64:810–8. 10.1001/archpsyc.64.7.810

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 307.

  LenzeEJMantellaRCShiPGoateAMNowotnyPButtersMAet al. Elevated cortisol in older adults with generalized anxiety disorder is reduced by treatment: a placebo-controlled evaluation of escitalopram. Am J Geriatr Psychiatry. (2011) 19:482–90. 10.1097/JGP.0b013e3181ec806c

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 308.

  SinghCLiuLWangJMIrwinRWYaoJChenSet al. Allopregnanolone restores hippocampal-dependent learning and memory and neural progenitor survival in aging 3xTgAD and nonTg mice. Neurobiol Aging. (2012) 33:1493–506. 10.1016/j.neurobiolaging.2011.06.008

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 309.

  LoiSMEratneDKelsoWVelakoulisDLooiJC. Alzheimer disease: non-pharmacological and pharmacological management of cognition and neuropsychiatric symptoms. Australas Psychiatry. (2018) 26:358–65. 10.1177/1039856218766123

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 310.

  SoraviaLMHeinrichsMWinzelerLFislerMSchmittWHornHet al. Glucocorticoids enhance in vivo exposure-based therapy of spider phobia. Depress Anxiety. (2014) 31:429–35. 10.1002/da.22219

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 311.

  LiSGrahamBM. Estradiol is associated with altered cognitive and physiological responses during fear conditioning and extinction in healthy and spider phobic women. Behav Neurosci. (2016) 130:614–23. 10.1037/bne0000166

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 312.

  KirkbyLALuongoFJLeeMBNahumMVan VleetTMRaoVRet al. An amygdala-hippocampus subnetwork that encodes variation in human mood. Cell. (2018) 175:1688–700.e14. 10.1016/j.cell.2018.10.005

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 313.

  AlfanoJPedersenRCKramerREBrownieAC. Cholesterol metabolism in the rat adrenal cortex: acute temporal changes following stress. Can J Biochem Cell Biol. (1983) 61:708–13. 10.1139/o83-089

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 314.

  AguileraGKissALuACamachoC. Regulation of adrenal steroidogenesis during chronic stress. Endocr Res. (1996) 22:433–43. 10.1080/07435809609043729

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 315.

  do ValeSSelingerLMartinsJMGomesACBichoMdo CarmoIet al. The relationship between dehydroepiandrosterone (DHEA), working memory and distraction–a behavioral and electrophysiological approach. PLoS ONE. (2014) 9:e104869. 10.1371/journal.pone.0104869

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 316.

  ShiaRMHagenJAMcIntireLKGoodyearCDDykstraLNNarayananL. Individual differences in biophysiological toughness: sustaining working memory during physical exhaustion. Mil Med. (2015) 180:230–6. 10.7205/MILMED-D-14-00363

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 317.

  DiamondDMFleshnerMRoseGM. The enhancement of hippocampal primed burst potentiation by dehydroepiandrosterone sulfate (DHEAS) is blocked by psychological stress. Stress. (1999) 3:107–21. 10.3109/10253899909001116

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 318.

  CastanhoTCMoreiraPSPortugal-NunesCNovaisACostaPSPalhaJAet al. The role of sex and sex-related hormones in cognition, mood and well-being in older men and women. Biol Psychol. (2014) 103:158–66. 10.1016/j.biopsycho.2014.08.015

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 319.

  DallaCWhetstoneASHodesGEShorsTJ. Stressful experience has opposite effects on dendritic spines in the hippocampus of cycling versus masculinized females. Neurosci Lett. (2009) 449:52–6. 10.1016/j.neulet.2008.10.051

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 320.

  HaywardCSanbornK. Puberty and the emergence of gender differences in psychopathology. J Adolesc Health. (2002) 30:49–58. 10.1016/S1054-139X(02)00336-1

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 321.

  KesslerRCBerglundPDemlerOJinRMerikangasKRWaltersEE. Lifetime prevalence and age-of-onset distributions of DSM-IV disorders in the National Comorbidity Survey Replication. Arch Gen Psychiatry. (2005) 62:593–602. 10.1001/archpsyc.62.6.593

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 322.

  ReardonLELeen-FeldnerEWHaywardC. A critical review of the empirical literature on the relation between anxiety and puberty. Clin Psychol Rev. (2009) 29:1–23. 10.1016/j.cpr.2008.09.005

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 323.

  Van OortFVGreaves-LordKVerhulstFCOrmelJHuizinkAC. The developmental course of anxiety symptoms during adolescence: the TRAILS study. J Child Psychol Psychiatry. (2009) 50:1209–17. 10.1111/j.1469-7610.2009.02092.x

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 324.

  MerikangasKRNakamuraEFKesslerRC. Epidemiology of mental disorders in children and adolescents. Dialogues Clin Neurosci. (2009) 11:7–20.

  • Pubmed Abstract
  • Google Scholar

• 325.

  MerikangasKRHeJPBrodyDFisherPWBourdonKKoretzDS. Prevalence and treatment of mental disorders among US children in the 2001-2004 NHANES. Pediatrics. (2010) 125:75–81. 10.1542/peds.2008-2598

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 326.

  MerikangasKRHeJPBursteinMSwansonSAAvenevoliSCuiLet al. Lifetime prevalence of mental disorders in U.S. adolescents: results from the National Comorbidity Survey Replication–Adolescent Supplement (NCS-A). J Am Acad Child Adolesc Psychiatry. (2010) 49:980–9. 10.1016/j.jaac.2010.05.017

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 327.

  LeikangerEIngulJMLarssonB. Sex and age-related anxiety in a community sample of Norwegian adolescents. Scand J Psychol. (2012) 53:150–7. 10.1111/j.1467-9450.2011.00915.x

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 328.

  LegersteeJSVerhulstFCRobbersSCOrmelJOldehinkelAJvan OortFV. Gender-specific developmental trajectories of anxiety during adolescence: determinants and outcomes. the TRAILS study. J Can Acad Child Adolesc Psychiatry. (2013) 22:26–34.

  • Pubmed Abstract
  • Google Scholar

• 329.

  PurdyRHMorrowALMoorePHJrPaulSM. Stress-induced elevations of gamma-aminobutyric acid type A receptor-active steroids in the rat brain. Proc Natl Acad Sci USA. (1991) 88:4553–7. 10.1073/pnas.88.10.4553

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 330.

  DarbraSPallarèsM. Neonatal allopregnanolone increases novelty-directed locomotion and disrupts behavioural responses to GABA(A) receptor modulators in adulthood. Int J Dev Neurosci. (2009) 27:617–25. 10.1016/j.ijdevneu.2009.05.008

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 331.

  MòdolLDarbraSVallèeMPallarèsM. Alteration of neonatal Allopregnanolone levels affects exploration, anxiety, aversive learning and adult behavioural response to intrahippocampal neurosteroids. Behav Brain Res. (2013) 241:96–104. 10.1016/j.bbr.2012.11.043

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 332.

  DarbraSMòdolLLlidóACasasCValléeMPallarèsM. Neonatal allopregnanolone levels alteration: effects on behavior and role of the hippocampus. Prog Neurobiol. (2014) 113:95–105. 10.1016/j.pneurobio.2013.07.007

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 333.

  AnsseauMvon FrenckellRCerfontaineJLPapartP. Pilot study of PK 11195, a selective ligand for the peripheral-type benzodiazepine binding sites, in inpatients with anxious or depressive symptomatology. Pharmacopsychiatry. (1991) 24:8–12. 10.1055/s-2007-1014425

  • CrossRef
  • Google Scholar

• 334.

  StröhleARomeoEdi MicheleFPasiniAHermannBGajewskyGet al. Induced panic attacks shift gamma-aminobutyric acid type A receptor modulatory neuroactive steroid composition in patients with panic disorder: preliminary results. Arch Gen Psychiatry. (2003) 60:161–8. 10.1001/archpsyc.60.2.161

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 335.

  MerrittPStanglBHirshmanEVerbalisJ. Administration of dehydroepiandrosterone (DHEA) increases serum levels of androgens and estrogens but does not enhance short-term memory in post-menopausal women. Brain Res. (2012) 1483:54–62. 10.1016/j.brainres.2012.09.015

  • CrossRef
  • Google Scholar

• 336.

  IrwinRWWangJMChenSBrintonRD. Neuroregenerative mechanisms of allopregnanolone in Alzheimer's disease. Front Endocrinol. (2012) 2:117. 10.3389/fendo.2011.00117

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 337.

  FryeCAParisJJWalfAARusconiJC. Effects and mechanisms of 3α,5α,-THP on emotion, motivation, and reward functions involving pregnane xenobiotic receptor. Front Neurosci. (2012) 5:136. 10.3389/fnins.2011.00136

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 338.

  MoguilevskyJAWuttkeW. Changes in the control of gonadotrophin secretion by neurotransmitters during sexual development in rats. Exp Clin Endocrinol Diabetes. (2001) 109:188–95. 10.1055/s-2001-15105

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 339.

  CalogeroAEPalumboMABosboomAMBurrelloNFerraraEPalumboGet al. The neuroactive steroid allopregnanolone suppresses hypothalamic gonadotropin-releasing hormone release through a mechanism mediated by the gamma-aminobutyric acidA receptor. J Endocrinol. (1998) 158:121–5. 10.1677/joe.0.1580121

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 340.

  SimJASkynnerMJHerbisonAE. Direct regulation of postnatal GnRH neurons by the progesterone derivative allopregnanolone in the mouse. Endocrinology. (2001) 142:4448–53. 10.1210/endo.142.10.8451

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 341.

  WisdenWLaurieDJMonyerHSeeburgPH. The distribution of 13 GABAA receptor subunit mRNAs in the rat brain. I. Telencephalon, diencephalon, mesencephalon. J Neurosci. (1992) 12:1040–62. 10.1523/JNEUROSCI.12-03-01040.1992

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 342.

  StaleyKJModyI. Shunting of excitatory input to dentate gyrus granule cells by a depolarizing GABAA receptor-mediated postsynaptic conductance. J Neurophysiol. (1992) 68:197–212. 10.1152/jn.1992.68.1.197

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 343.

  GulledgeATStuartGJ. Excitatory actions of GABA in the cortex. Neuron. (2003) 37:299–309. 10.1016/S0896-6273(02)01146-7

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 344.

  AlgerBENicollRA. Pharmacological evidence for two kinds of GABA receptor on rat hippocampal pyramidal cells studied in vitro. J Physiol. (1982) 328:125–41. 10.1113/jphysiol.1982.sp014256

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 345.

  ShenHGongQHAokiCYuanMRudermanYDattiloMet al. Reversal of neurosteroid effects at alpha4beta2delta GABAA receptors triggers anxiety at puberty. Nat Neurosci. (2007) 10:469–77. 10.1038/nn1868

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 346.

  KuverASmithSS. Flumazenil decreases surface expression of α4β2δ GABAA receptors by increasing the rate of receptor internalization. Brain Res Bull. (2016) 120:131–43. 10.1016/j.brainresbull.2015.11.015

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 347.

  VashchinkinaEMannerAKVekovischevaOden HollanderBUusi-OukariMAitta-AhoTet al. Neurosteroid Agonist at GABAA receptor induces persistent neuroplasticity in VTA dopamine neurons. Neuropsychopharmacology. (2014) 39:727–37. 10.1038/npp.2013.258

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 348.

  KhistiRTChopdeCT. Serotonergic agents modulate antidepressant-like effect of the neurosteroid 3alpha-hydroxy-5alpha-pregnan-20-one in mice. Brain Res. (2000) 865:291–300. 10.1016/S0006-8993(00)02373-8

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 349.

  NelsonMPinnaG. S-norfluoxetine microinfused into the basolateral amygdala increases allopregnanolone levels and reduces aggression in socially isolated mice. Neuropharmacology. (2011) 60:1154–9. 10.1016/j.neuropharm.2010.10.011

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 350.

  SamardzicJHencicBJancicJJadzicDDjuricMObradovicDIet al. Neurosteroid dehydroepiandrosterone improves active avoidance retrieval and induces antidepressant-like behavior in rats. Neurosci Lett. (2017) 660:17–21. 10.1016/j.neulet.2017.09.013

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 351.

  LuCYLiuXJiangHPanFHoCSHoRC. Effects of traumatic stress induced in the juvenile period on the expression of gamma-aminobutyric acid receptor type A subunits in adult rat brain. Neural Plast. (2017) 2017:5715816. 10.1155/2017/5715816

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 352.

  BrownESParkJMarxCEHynanLSGardnerCDavilaDet al. A randomized, double-blind, placebo-controlled trial of pregnenolone for bipolar depression. Neuropsychopharmacology. (2014) 39:2867–73. 10.1038/npp.2014.138

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 353.

  LismanJECoyleJTGreenRWJavittDCBenesFMHeckersSet al. Circuit-based framework for understanding neurotransmitter and risk gene interactions in schizophrenia. Trends Neurosci. (2008) 31:234–42. 10.1016/j.tins.2008.02.005

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 354.

  MurrayJDAnticevicAGancsosMIchinoseMCorlettPRKrystalJHet al. Linking microcircuit dysfunction to cognitive impairment: effects of disinhibition associated with schizophrenia in a cortical working memory model. Cereb Cortex. (2014) 24:859–72. 10.1093/cercor/bhs370

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 355.

  de JongeJCVinkersCHHulshoff PolHEMarsmanA. GABAergic mechanisms in schizophrenia: linking postmortem and in vivo studies. Front Psychiatry. (2017) 8:118. 10.3389/fpsyt.2017.00118

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 356.

  MöhlerHRudolphU. Disinhibition, an emerging pharmacology of learning and memory. F1000Res. (2017) 6:F1000 Faculty Rev-101. 10.12688/f1000research.9947.1

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 357.

  BillingsleaENTatard-LeitmanVMAnguianoJJutzelerCRSuhJSaundersJAet al. Parvalbumin cell ablation of NMDA-R1 causes increased resting network excitability with associated social and self-care deficits. Neuropsychopharmacology. (2014) 39:1603–13. 10.1038/npp.2014.7

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 358.

  CoyleJTTsaiGGoffD. Converging evidence of NMDA receptor hypofunction in the pathophysiology of schizophrenia. Ann N Y Acad Sci. (2003) 1003:318–27. 10.1196/annals.1300.020

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 359.

  PilowskyLSBressanRAStoneJMErlandssonKMulliganRSKrystalJHet al. First in vivo evidence of an NMDA receptor deficit in medication-free schizophrenic patients. Mol Psychiatry. (2006) 11:118–9. 10.1038/sj.mp.4001751

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 360.

  SohalVSZhangFYizharODeisserothK. Parvalbumin neurons and gamma rhythms enhance cortical circuit performance. Nature. (2009) 459:698–702. 10.1038/nature07991

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 361.

  FazzariPPaternainAVValienteMPlaRLujánRLloydKet al. Control of cortical GABA circuitry development by Nrg1 and ErbB4 signalling. Nature. (2010) 464:1376–80. 10.1038/nature08928

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 362.

  BaluDTCoyleJT. Glutamate receptor composition of the post-synaptic density is altered in genetic mouse models of NMDA receptor hypo- and hyperfunction. Brain Res. (2011) 1392:1–7. 10.1016/j.brainres.2011.03.051

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 363.

  PitcherGMKaliaLVNgDGoodfellowNMYeeKTLambeEKet al. Schizophrenia susceptibility pathway neuregulin 1-ErbB4 suppresses Src upregulation of NMDA receptors. Nat Med. (2011) 17:470–8. 10.1038/nm.2315

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 364.

  Gonzalez-BurgosGLewisDA. NMDA receptor hypofunction, parvalbumin-positive neurons, and cortical gamma oscillations in schizophrenia. Schizophr Bull. (2012) 38:950–7. 10.1093/schbul/sbs010

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 365.

  ForrestADBangJFeatherstoneREBloomJHLuminaisMSZhangRVet al. Pyramidal cell-selective GluN1 knockout causes impairments in salience attribution and related EEG activity. Exp Brain Res. (2018) 236:837–46. 10.1007/s00221-017-5152-8

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 366.

  RotaruDCLewisDAGonzalez-BurgosG. The role of glutamatergic inputs onto parvalbumin-positive interneurons: relevance for schizophrenia. Rev Neurosci. (2012) 23:97–109. 10.1515/revneuro-2011-0059

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 367.

  ChungDWWillsZPFishKNLewisDA. Developmental pruning of excitatory synaptic inputs to parvalbumin interneurons in monkey prefrontal cortex. Proc Natl Acad Sci USA. (2017) 114:E629–37. 10.1073/pnas.1610077114

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 368.

  VerretLMannEOHangGBBarthAMCobosIHoKet al. Inhibitory interneuron deficit links altered network activity and cognitive dysfunction in Alzheimer model. Cell. (2012) 149:708–21. 10.1016/j.cell.2012.02.046

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 369.

  PalopJJMuckeL. Network abnormalities and interneuron dysfunction in Alzheimer disease. Nat Rev Neurosci. (2016) 17:777–92. 10.1038/nrn.2016.141

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 370.

  CarlénMMeletisKSiegleJHCardinJAFutaiKVierling-ClaassenDet al. A critical role for NMDA receptors in parvalbumin interneurons for gamma rhythm induction and behavior. Psychiatry. (2012) 17:537–48. 10.1038/mp.2011.31

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 371.

  IwataYNakajimaSSuzukiTKeefeRSPlitmanEChungJKet al. Effects of glutamate positive modulators on cognitive deficits in schizophrenia: a systematic review and meta-analysis of double-blind randomized controlled trials. Mol Psychiatry. (2015) 20:1151–60. 10.1038/mp.2015.68

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 372.

  MarxCEShampineLJDuncanGEVanDorenMJGrobinACMassingMWet al. Clozapine markedly elevates pregnenolone in rat hippocampus, cerebral cortex, and serum: candidate mechanism for superior efficacy?Pharmacol Biochem Behav. (2006) 84:598–608. 10.1016/j.pbb.2006.07.026

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 373.

  WongPSzeYChangCCLeeJZhangX. Pregnenolone sulfate normalizes schizophrenia-like behaviors in dopamine transporter knockout mice through the AKT/GSK3β pathway. Transl Psychiatry. (2015) 5:e528. 10.1038/tp.2015.21

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 374.

  RamseyTLLiuQBrennanMD. Replication of SULT4A1-1 as a pharmacogenetic marker of olanzapine response and evidence of lower weight gain in the high response group. Pharmacogenomics. (2014) 15:933–9. 10.2217/pgs.14.54

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 375.

  MarxCEDuncanGEGilmoreJHLiebermanJAMorrowAL. Olanzapine increases allopregnanolone in the rat cerebral cortex. Biol Psychiatry (2000) 47:1000–4. 10.1016/S0006-3223(99)00305-4

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 376.

  UgaleRRHiraniKMorelliMChopdeCT. Role of neuroactive steroid allopregnanolone in antipsychotic-like action of olanzapine in rodents. Neuropsychopharmacology. (2004) 29:1597–609. 10.1038/sj.npp.1300460

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 377.

  MarxCEVanDorenMJDuncanGELiebermanJAMorrowAL. Olanzapine and clozapine increase the GABAergic neuroactive steroid allopregnanolone in rodents. Neuropsychopharmacology. (2003) 28:1–13. 10.1038/sj.npp.1300015

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 378.

  GrimesKMZanjaniAZakzanisKK. Memory impairment and the mediating role of task difficulty in patients with schizophrenia. Psychiatry Clin Neurosci. (2017) 71:600–11. 10.1111/pcn.12520

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 379.

  KapurSRemingtonGJonesCWilsonADaSilvaJHouleSet al. High levels of dopamine D2 receptor occupancy with low-dose haloperidol treatment: a PET study. Am J Psychiatry. (1996) 153:948–50. 10.1176/ajp.153.7.948

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 380.

  DoughertyDDBonabAASpencerTJRauchSLMadrasBKFischmanAJ. Dopamine transporter density in patients with attention deficit hyperactivity disorder. Lancet. (1999) 354:2132–3. 10.1016/S0140-6736(99)04030-1

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 381.

  EfimovaEVGainetdinovRRBudyginEASotnikovaTD. Dopamine transporter mutant animals: a translational perspective. J Neurogenet. (2016) 30:5–15. 10.3109/01677063.2016.1144751

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 382.

  ReithMEXuCChenNH. Pharmacology and regulation of the neuronal dopamine transporter. Eur J Pharmacol. (1997) 324:1–10. 10.1016/S0014-2999(97)00065-4

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 383.

  AmaraSGKuharMJ. Neurotransmitter transporters: recent progress. Annu Rev Neurosci. (1993) 16:73–93. 10.1146/annurev.ne.16.030193.000445

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 384.

  GirosBJaberMJonesSRWightmanRMCaronMG. Hyperlocomotion and indifference to cocaine and amphetamine in mice lacking the dopamine transporter. Nature. (1996) 379:606–12. 10.1038/379606a0

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 385.

  MadrasBKFaheyMAMillerGMDe La GarzaRGouletMSpealmanRDet al. Non-amine-based dopamine transporter (reuptake) inhibitors retain properties of amine-based progenitors. Eur J Pharmacol. (2003) 479:41–51. 10.1016/j.ejphar.2003.08.055

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 386.

  GainetdinovRR. Dopamine transporter mutant mice in experimental neuropharmacology. Naunyn Schmiedebergs Arch Pharmacol. (2008) 377:301–13. 10.1007/s00210-007-0216-0

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 387.

  GainetdinovRRCaronMG. Monoamine transporters: from genes to behavior. Annu Rev Pharmacol Toxicol. (2003) 43:261–84. 10.1146/annurev.pharmtox.43.050802.112309

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 388.

  GasiorMCarterRBWitkinJM. Neuroactive steroids: potential therapeutic use in neurological and psychiatric disorders. Trends Pharmacol Sci. (1999) 20:107–12. 10.1016/S0165-6147(99)01318-8

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 389.

  ParésysLHoffmannKFrogerNBianchiMVilleyIBaulieuEEet al. Effects of the synthetic neurosteroid: 3β-methoxypregnenolone (MAP4343) on behavioral and physiological alterations provoked by chronic psychosocial stress in tree shrews. Int J Neuropsychopharmacol. (2016) 19:pyv119. 10.1093/ijnp/pyv119

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 390.

  CarterRBWoodPLWielandSHawkinsonJEBelelliDLambertJJet al. Characterization of the anticonvulsant properties of ganaxolone (CCD 1042; 3α-hydroxy-3β-methyl-5α-pregnan-20-one), a selective, high-affinity, steroid modulator of the γ-aminobutyric acidA receptor. J Pharmacol Exp Ther. (1997) 280:1284–95.

  • Google Scholar

• 391.

  PinnaGRasmussonAM. Ganaxolone improves behavioral deficits in a mouse model of post-traumatic stress disorder. Front Cell Neurosci. (2014) 8:256. 10.3389/fncel.2014.00256

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 392.

  RasmussonAMMarxCEJainSFarfelGMTsaiJSunXet al. A randomized controlled trial of ganaxolone in posttraumatic stress disorder. Psychopharmacology (Berl). (2017) 234:2245–57. 10.1007/s00213-017-4649-y

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 393.

  CiarloneSLWangXRogawskiMAWeeberEJ. Effects of the synthetic neurosteroid ganaxolone on seizure activity and behavioral deficits in an Angelman syndrome mouse model. Neuropharmacology. (2017) 116:142–50. 10.1016/j.neuropharm.2016.12.009

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 394.

  WielandSBelluzziJHawkinsonJEHogenkampDUpasaniRSteinLet al. Anxiolytic and anticonvulsant activity of a synthetic neuroactive steroid Co 3-0593. Psychopharmacology (Berl). (1997) 134:46–54. 10.1007/s002130050424

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 395.

  FerreeNKCahillL. Post-event spontaneous intrusive recollections and strength of memory for emotional events in men and women. Conscious Cogn. (2009) 18:126–34. 10.1016/j.concog.2008.11.008

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 396.

  Mohedano-MorianoAMartinez-MarcosAPro-SistiagaPBlaizotXArroyo-JimenezMMMarcosPet al. Convergence of unimodal and polymodal sensory input to the entorhinal cortex in the fascicularis monkey. Neuroscience. (2008) 151:255–71. 10.1016/j.neuroscience.2007.09.074

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 397.

  SripadaRKMarxCEKingAPRajaramNGarfinkelSNAbelsonJLet al. DHEA enhances emotion regulation neurocircuits and modulates memory for emotional stimuli. Neuropsychopharmacology. (2013) 38:1798–807. 10.1038/npp.2013.79

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 398.

  WahlstromKLHuffMLEmmonsEBFreemanJHNarayananNSMcIntyreCKet al. Basolateral amygdala inputs to the medial entorhinal cortex selectively modulate the consolidation of spatial and contextual learning. J Neurosci. (2018) 38:2698–712. 10.1523/JNEUROSCI.2848-17.2018

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 399.

  LussierALRomay-TallónRCarunchoHJKalynchukLE. Altered GABAergic and glutamatergic activity within the rat hippocampus and amygdala in rats subjected to repeated corticosterone administration but not restraint stress. Neuroscience. (2013) 231:38–48. 10.1016/j.neuroscience.2012.11.037

  • CrossRef
  • Google Scholar

• 400.

  LeeVMacKenzieGHooperAMaguireJ. Reduced tonic inhibition in the dentate gyrus contributes to chronic stress-induced impairments in learning and memory. Hippocampus. (2016) 26:1276–90. 10.1002/hipo.22604

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 401.

  PinelesSLNillniYIPinnaGIrvineJWebbAArditte HallKAet al. PTSD in women is associated with a block in conversion of progesterone to the GABAergic neurosteroids allopregnanolone and pregnanolone measured in plasma. Psychoneuroendocrinology. (2018) 93:133–41. 10.1016/j.psyneuen.2018.04.024

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 402.

  LeeALOgleWOSapolskyRM. Stress and depression: possible links to neuron death in the hippocampus. Bipolar Disord. (2002) 4:117–28. 10.1034/j.1399-5618.2002.01144.x

  • Pubmed Abstract
  • CrossRef
  • Google Scholar

• 403.

  NishimuraKJOrtizJBConradCD. Antagonizing the GABAA receptor during behavioral training improves spatial memory at different doses in control and chronically stressed rats. Neurobiol Learn Mem. (2017) 145:114–8. 10.1016/j.nlm.2017.09.002

  • Pubmed Abstract
  • CrossRef
  • Google Scholar