BERN.1 Wednesday, Jan. 5 Putting the brakes on reproduction. Implications for conservation? Global climate change? WINGFIELD, J.C.; Univ. of California, Davis firstname.lastname@example.org
Seasonal breeding is widespread in vertebrates and involves development of the gonads, actual onset of breeding activities (e.g. cycling in females) and termination resulting in regression of the reproductive system. Whereas males generally show complete spermatogenesis prior to and after onset of breeding, females of many vertebrate species show partial ovarian development and may delay onset of cycling (e.g. estrous), yolk deposition or germinal vesicle breakdown until conditions conducive for ovulation and onset of breeding are favorable. Regulation of this "brake" on the onset of breeding remains relatively unknown, but could have profound implications for conservation efforts and for "mismatches" of breeding in relation to global climate change. Using avian models it is proposed that a brain peptide, gonadotropin-inhibitory hormone (GnIH), may be the brake preventing onset of breeding in females. Evidence to date suggests that although GnIH may be involved in the regulation of gonadal development and regression, it plays more regulatory roles in the process of final ovarian development leading to ovulation, transitions from sexual to parental behavior and suppression of reproductive function by environmental stress. Accumulating experimental evidence strongly suggests that GnIH inhibits actions of gonadotropin-releasing hormones and may also have direct actions in the gonad. Thus, actual onset of breeding activities leading to ovulation may involve environmental cues releasing an inhibition (brake) on the hypothalamo-pituitary-gonad axis.