Neuroendocrine Regulation of Seasonal Reproduction
- Elisabetta Tolla, Elisabetta TollaUniversity of Glasgow College of Medical Veterinary and Life Sciences
- Jonathan H. Pérez, Jonathan H. PérezUniversity of Glasgow College of Medical Veterinary and Life Sciences
- Ian C. Dunn, Ian C. DunnUniversity of Edinburgh, Roslin Institute
- Simone L. MeddleSimone L. MeddleUniversity of Edinburgh, Roslin Institute
- and Tyler J. StevensonTyler J. StevensonUniversity of Glasgow College of Medical Veterinary and Life Sciences
Neuroendocrine mechanisms control the seasonal reproduction in birds and mammals. Seasonal reproduction is ubiquitous across vertebrate and invertebrate species, and its timing is extremely crucial in order to maximize offspring survival. The hypothalamus is the key brain region that integrates environmental cues. An endogenous circannual timer with oscillations that approximate one year is also localized in the hypothalamus. Successful timing of reproduction involves the combination of endogenous internal timers that are entrained by local environmental cues. Photoperiod, or the annual change in day length, is the primary cue most temperate animals use to predict future environmental conditions. Birds are able to detect light through photoreceptors located in the medio-basal hypothalamus. These photoreceptors are localized in neuroendocrine regions and regulate the key reproductive neuropeptide gonadotropin-releasing hormone (GnRH). In mammals, retinal photoreceptors transduce light information the suprachiasmatic nucleus in the hypothalamus, which then modulates the nocturnal duration of melatonin. Melatonin in mammals is crucial, as it regulates the neuroendocrine release of GnRH and downstream transitions across seasonal reproductive states. The tanycyte cells lining the third ventricle (3rdV) of the hypothalamus are the critical node for the integration of internal (i.e., circannual timing) and external (e.g., photoperiod) information necessary for the regulation of seasonal reproduction.