Meeting Abstract

P1.136  Saturday, Jan. 4 15:30  RFamide peptides differentially regulate HPG axis activity according to seasonal reproductive condition in female Siberian hamsters BAILEY, A.M.*; GREIVES, T.J.; LEGAN, S.J.; DEMAS, G.E.; Indiana University, Bloomington; North Dakota State University, Fargo; University of Kentucky, Lexington; Indiana University, Bloomington allibail@indiana.edu

Seasonally breeding mammals use photoperiod to limit reproduction to favorable conditions. Changes in day length trigger endocrine adjustments in the hypothalamo-pituitary-gonadal (HPG) axis, resulting in activation or suppression of reproduction. Recently, two RFamide neuropeptides, kisspeptin and RFamide related peptide (RFRP-3), have been hypothesized as seasonal regulators of the HPG axis. Exogenous kisspeptin imparts a robust stimulatory effect on the HPG axis, whereas the function of RFRP-3 is less clear and varies across species and reproductive conditions. In this study, we investigated the function of these two neuropeptides across photoperiods and subsequent reproductive states in female Siberian hamsters (Phodopus sungorus). We examined the HPG axis response to exogenous kisspeptin and RFRP-3 by administering each neuropeptide alone, as well as combining an effective dose of kisspeptin (10µM) with each of three doses of RFRP-3 (10µM, 20µM, 40µM). We measured serum luteinizing hormone in three groups of female Siberian hamsters: long-day (LD) reproductively active females, short-day responsive (SD-R) reproductively quiescent females, and short-day unresponsive (SD-NR) reproductively active females. Kisspeptin alone stimulated the HPG axis in all three groups of females. RFRP-3 alone appeared to generally have a stimulatory effect, particularly in SD-R females. When the two were combined, kisspeptin’s stimulatory effect was attenuated in LD females, but enhanced in SD-NR females. These results suggest complex interactions of these peptides in relation to reproductive context and contribute to our understanding of the neuroendocrinology of seasonal reproduction.