Cannabinoids and Stress Steroids modify intrinsic properties of clasp-controlling neurons in the hindbrain of an amphibian
-
1
Willamette University, Biology Department, United States
Appropriate behavioral responses to acute stress are critical for an animal’s health and survival. The behavior that is selected as appropriate is guided by the current state of the animal, including external (predatory threat) and internal states (breeding condition). Many of these external and internal states are conveyed to the brain by neuroendocrine signals. Exactly how these neuroendocrine signals modify behavioral decisions on a rapid non-genomic time scale is not well understood. It has been hypothesized that stress steroid hormones, such as corticosterone, rapidly switch behaviors by upregulating endocannabinoid signaling, a model that has much theoretical support in the literature but has only been directly tested in one animal model. The goal of our research is to investigate whether and how stress steroid hormones and endocannabinoids modify intrinsic properties of behavior-controlling neurons in rough skin newts, Taricha granulosa. Taricha are a powerful animal model for this study because endocrine regulation of clasping behavior has been well characterized, and the clasp is a robust behavior controlled by reticulospinal neurons and modified by interneurons located in the rostromedial reticular formation of the hindbrain. I have developed a slice preparation of Taricha hindbrain for whole cell recordings; Coronal slices of hindbrain tissue from wild-caught sexually mature male Taricha are prepared at room temperature in modified extracellular solution. Single cells are visualized using DodT contrast on an Axioexaminer Microscope with a 40x water-immersion objective. Low resistance glass electrodes are filled with modified intracellular solution. Recordings are performed in current- and voltage-clamp using an Axopatch 200B amplifier, Digidata 1440A, and pClamp 10 software. Recordings are included for analysis only from neurons that show less than 20% change in their series resistance (<20 MΩ) or input resistance over the course of the experiment (50 - 60 min). Our data show that agonists of cannabinoid receptors (WIN55,212-2 and CP 55,940) decrease the excitability of 70% target neurons, as measured by the lowest current required to elicit an action potential. In these same neurons, we also observed a 30% decrease in the number of excitatory post-synaptic potentials received by target neurons after cannabinoid agonists are bath applied. A decreased frequency of spontaneous EPSCs suggests that cannabinoids are acting presynaptically to inhibit the release of glutamate. This result is consistent with the known role of endocannabinoids in decreasing probability of neurotransmitter release. As a first step towards understanding whether stress steroid hormones act by upregulating cannabinoid signaling, we examined neuronal responses to corticosterone; only 25% neurons responded to bath-applied corticosterone. In most of these neurons, we observed a decrease in membrane excitability, an increase in spike adaptation, a decrease in membrane potential response to step current injection, and a decrease in the frequency of EPSCs. Partnering analysis of intrinsic properties with morphological analysis may allow us to understand the heterogeneous effects of corticosterone. Furthermore, by incorporating antagonists to cannabinoid receptors in our protocol we will be able to directly test the hypothesis that endocannabinoids provide the link to specific stress-related behaviors.
Acknowledgements
Funded by the Research Corporation and M.J. Murdock Charitable Trust.
Keywords:
Corticosterone,
Endocannabinoids,
Neuromodulation,
sex behavior,
stress
Conference:
Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012.
Presentation Type:
Poster (but consider for Participant Symposium)
Topic:
Neuromodulation
Citation:
Coddington
E
(2012). Cannabinoids and Stress Steroids modify intrinsic properties of clasp-controlling neurons in the hindbrain of an amphibian.
Conference Abstract:
Tenth International Congress of Neuroethology.
doi: 10.3389/conf.fnbeh.2012.27.00413
Copyright:
The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers.
They are made available through the Frontiers publishing platform as a service to conference organizers and presenters.
The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated.
Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed.
For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions.
Received:
02 May 2012;
Published Online:
07 Jul 2012.
*
Correspondence:
Dr. Emma Coddington, Willamette University, Biology Department, Salem, OR, 97301, United States, resilience4DJ@gmail.com