The arcuate nucleus and RF-amide neuropeptides in the seasonal adaptation of mammals
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1
University Sidi Mohammed Ben Abdellah, Faculty of Sciences Dhar El Mehraz, Biology, Morocco
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2
CNRS UPR 3212 and University of Strasbourg, Department of Neurobiology of Rhythms, France
Many species of temperate regions show seasonal variations in several aspects of physiology and behaviour, including reproduction, hibernation and body weight. They typically inhibit reproduction during winter to conserve scarce energetic resources. This is the case of the jerboa, a rodent adapted to the semi desert-environment of Morocco. The seasonal changes are triggered by the annual changes of photoperiod which in mammals is decoded by a photo-neuroendocrine system composed of the retina, the suprachiasmatic nucleus and the pineal melatonin.
In nature, seasonal adaptations are regulated by both day length and non-photoperiodic cues which vary seasonally such as food availability and/or energy stores. The arcuate nucleus is a potent structure involved in the long-term control of energy stores. It contains peptidergic POMC and NPY neurons which are responsive to a wide array of hormones and nutrients.
In the jerboa (Jaculus orientalis), reproductive activity is seasonal; it’s activated in spring-early summer and inhibited in autumn. We have previously demonstrated that the GnRH neurosecretory system displays seasonal variations. The seasonal plasticity was also observed in the expression of neuropeptides which regulate gonadotropic activity such as POMC neurons within the arcuate nucleus. In seasonal mammals, the melatonin and sex steroids control reproductive activity by indirectly modulating gonadotropin secretion through an action in the mediobasal hypothalamus. The discovery of the two RF-amide peptides, Kisspeptin and RFRP-3 in seasonal rodents during the last years has helped in uncovering the mechanisms of seasonal reproduction. Kisspeptin neurons were found in the anteroventral periventricular nucleus (AVPV) and in the arcuate nucleus (ARC), whereas RFRP-3 cells were found in the dorsomedial hypothalamus (DMN). kisspeptin is well known as potent stimulator of GnRH secretion and the principal conduit mediating sex steroids feed-back. Several studies suggest a role of RFRP-3 as inhibitory regulator of the mammalian reproductive axis. Photoperiodic and seasonal variations in the expression level of these peptides have been reported in seasonal species such as hamsters, sheep….with large differences between species. We have recently reported seasonal changes of Kp and RFRP-3 expression within the arcuate nucleus and DMN of the jerboa. A high content of Kp and RFRP was obtained during the sexually active period, suggesting that the two RF-amide neuropeptides act in concert to regulate the gonadotropic activity of this species.
All recent studies point to Kisspeptin and RFRP-3, in the mediation of photic and non photic cues on the reproductive system, and suggest that they play different roles. Seasonal adaptation is a complex process which involves RF-amides peptides, which may communicate with neurochemical systems regulating feeding notably POMC and NPY neurons in the arcuate nucleus and other neuropeptides. Discerning how and why differences in the mechanisms governing seasonal adaptation may help us to understand how some environmental cues drive to divergent patterns of regulatory mechanisms across a wide range of habitats.
Acknowledgements
Supported by grant PICS (CNRST-Maroc/CNRS France) and GDRI Neuro.
Keywords:
Kisspeptin,
RFRP-3,
Season,
Reproduction,
jerboa
Conference:
4th Conference of the Mediterrarnean Neuroscience Society, Istanbul, Türkiye, 30 Sep - 3 Oct, 2012.
Presentation Type:
Symposium
Topic:
Abstracts
Citation:
El Ouezzani
S and
Simonneaux
V
(2013). The arcuate nucleus and RF-amide neuropeptides in the seasonal adaptation of mammals.
Conference Abstract:
4th Conference of the Mediterrarnean Neuroscience Society.
doi: 10.3389/conf.fnhum.2013.210.00027
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Received:
20 Mar 2013;
Published Online:
11 Apr 2013.
*
Correspondence:
Prof. Seloua El Ouezzani, University Sidi Mohammed Ben Abdellah, Faculty of Sciences Dhar El Mehraz, Biology, Fez, 30000, Morocco, elouezzani@yahoo.com