Refractoriness to short day lengths augments tonic and gonadotrophin-releasing hormone-stimulated lutenising hormone secretion

Journal of Neuroendocrinology
Brian J PrendergastRandy J Nelson

Abstract

Siberian hamsters (Phodopus sungorus) undergo reproductive involution following exposure to short winter day lengths. Following approximately 20 weeks of exposure to short day (SD) lengths, hamsters become refractory to the inhibitory effects of SD, and reproductive competence is restored in anticipation of spring. The extent to which changes in gonadal steroid-dependent and -independent regulation of gonadotrophin secretion participate in this vernal reactivation of the gonads is not known. This experiment tested whether tonic and gonadotrophin-releasing hormone (GnRH)-stimulated regulation of lutenising hormone (LH) secretion differs between photoresponsive and photorefractory Siberian hamsters. Male hamsters born into long day (LD) lengths were castrated or subjected to a sham-castration surgery at 17 days of age, implanted s.c. with blank or testosterone-filled capsules, and housed in LD or SD thereafter. Baseline LH and LH responses to GnRH (200 ng/kg, s.c) were measured at 14 (photoresponsive) and 40 (photorefractory) weeks of age. Despite lower circulating testosterone concentrations in gonadally regressed SD hamsters on week 14, tonic LH concentrations were comparable among all groups of gonad-intact hamsters on weeks 1...Continue Reading

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Citations

Jul 20, 2010·Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology·Frank Scherbarth, Stephan Steinlechner
Sep 1, 2012·Behavioral Ecology : Official Journal of the International Society for Behavioral Ecology·James C Dooley, Brian J Prendergast
Mar 29, 2014·Hormones and Behavior·Sean P Bradley, Brian J Prendergast

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