Meeting Abstract

29.3  Jan. 5  A role for kisspeptin in seasonal reproduction? GREIVES, Timothy*; MASON, Alex; SCOTTI, Melissa-Ann; KETTERSON, Ellen; KRIEGSFELD, Lance; DEMAS, Gregory; Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405 USA; Department of Psychology and Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720 USA tjgreive@indiana.edu

Most temperate zone species exhibit seasonal breeding, coordinating reproduction with optimal environmental conditions. This coordination requires integration of relevant environmental signals by the hypothalamo-pituitary-gonadal (HPG) axis. Photoperiod provides a noise-free cue, triggering gonadal regression or hastening recrudescence via direct actions on the HPG axis. Kisspeptin, a recently identified peptide hormone, induces secretion of pituitary gonadotropins in laboratory animals. Because seasonal breeding is associated with changes in HPG activity, seasonal variation in secretion or sensitivity to kisspeptin in response to photoperiod may underlie seasonal changes in reproduction. To test this idea, Siberian hamsters (Phodopus sungorus) were held in long (LD 16:8) or short (LD 8:16) days for 2 or 8 weeks and differences in hypothalamic kisspeptin staining and gonadotropin (LH) response to injections of kisspeptin were compared. Short-day housed (non-reproductive) animals displayed a marked reduction in kisspeptin staining in the AVPV compared with long-long-day, reproductive animals, whereas short-day animals displayed increased kisspeptin staining in the ARC. Kisspeptin injections significantly elevated LH levels in both long and short day hamsters. These data indicate that kisspeptin release from the hypothalamus changes in response to photoperiod whereas exogenous kisspeptin induces LH secretion, regardless of photoperiod. Ongoing studies will examine the precise role of kisspeptin in mediating reproduction in seasonally breeding animals.