Poster Presentation The International Congress of Neuroendocrinology 2014

Food restriction-induced increases in GnIH cellular activation are attenuated at the time of estrous in Syrian hamsters (Mesocrietus auratus) (#267)

Noah Benton 1 , Jeremy Brozek 1 , Ryan Andrews 1 , Lance Kriegsfeld 2 , Jill Schneider 1
  1. Biological Sciences, Lehigh University, Bethlehem, PA, United States
  2. Department of Psychology, University of California, Berkeley, 94720, USA
In estrous cycling females, hunger for food is lowest when sexual motivation and circulating estradiol concentrations are highest, and these fluctuations are amplified when food availability is limited. We hypothesize that the amplifying effects of mild food restriction are mediated by increases in the secretion of gonadotropin-inhibiting hormone (GnIH) and its interaction with ovarian steroids. GnIH treatment increases food hoarding and inhibits sexual motivation in Syrian hamsters, and thus, we predicted that levels of cellular activation in GnIH-immunoreactive (ir) cells would be increased by mild food restriction on most days of the estrous cycle, except on the day of estrous in this species. Female Syrian hamsters were either fed ad libitum or food restricted to 75% of their average ad libitum intake for a period of 8 days. After treatment, blood and brains were collected from groups representing every day of the 4-day estrous cycle. Brain sections were double-labeled for GnIH-ir and for the protein Fos, a marker for cellular activation. Food restriction 1) significantly elevated Fos-ir/GnIH-ir on all days of the estrous cycle except the periovulatory day, 2) had no effect on circulating concentrations of estradiol or progesterone, and 3) decreased circulating concentrations of leptin similarly on every day of the estrous cycle. In summary, food restriction, and possibly decreased plasma leptin, activates GnIH cells differentially according to the day of the estrous cycle, ensuring that food hoarding is increased in preparation for the energetic costs of pregnancy and lactation, and mating is restricted to the most fertile period. This work was funded by NSF grants IOS-1257638 and IOS-1257876.