Meeting Abstract
P1.213 Friday, Jan. 4 Seasonal Differences in RFamide Peptide Regulation of the Reproductive Endocrine Axis in Siberian Hamsters BAILEY, A.M.*; LONG, K.L.; GREIVES, T.J.; ZHAO, S.; KRIEGSFELD, L.J.; DEMAS, G.E.; Indiana Univ., Bloomington; Indiana Univ., Bloomington; Indiana Univ., Bloomington; Univ. of California, Berkeley; Univ. of California, Berkeley; Indiana Univ., Bloomington allibail@indiana.edu
Seasonally breeding animals use photoperiod to limit reproduction to favorable conditions. Changes in day length cause neuroendocrine adjustments in the reproductive endocrine axis, resulting in activation or suppression of reproduction. Recently, two RFamide neuropeptides, kisspeptin and RFamide related peptide 3 (RFRP-3) have been characterized as seasonal stimulatory and inhibitory regulators of the axis, respectively. We examined seasonal differences in gene expression of these peptides in the gonads and hypothalamus in Siberian hamsters (Phodopus sungorus). In long-day (LD) reproductively active males, expression of kisspeptin in the testes is constant over 30 weeks, whereas RFRP-3 expression increases over time. In short-day (SD) reproductively regressed males, kisspeptin expression similarly remains constant over 30 weeks, while RFRP-3 shows an initial maximum expression during reproductive regression and subsequently decreases. We assessed functional endocrine responses to kisspeptin and RFRP-3 by administering exogenous peptides in combination. In LD males, kisspeptin consistently stimulates the reproductive axis except when combined with a high dose of RFRP-3. In SD reproductively active males (i.e., SD non-responders), RFRP-3 appears to have a dose-response-like stimulatory effect on the axis, which is enhanced when combined with kisspeptin. These effects will subsequently be assessed in females. Collectively, these results will show the differential role of RFamides in regulating seasonal reproductive function and will broaden our understanding of the neuroendocrinology of seasonal breeding.
