Leptin facilitates and inhibits sexual behavior in female hamsters

Food deprivation decreases fertility in female mammals in part by inhibiting sexual behaviors. Genetically obese ob/ob mice, like food-deprived wild-type animals, are also infertile; treatment of ob/ob mice with leptin, the adipocyte-derived protein that they lack, corrects some of their reproductive deficiencies. We tested the hypothesis that leptin treatment would prevent the suppression of sexual receptivity that is caused by food deprivation in female Syrian hamsters. Instead, we found that treatment with murine leptin facilitated female sexual behavior in ad libitum-fed hamsters, but not in food-deprived animals. In food-deprived hamsters, leptin treatment actually intensified the inhibition of lordosis. Food deprivation decreased detectable estrogen receptor immunoreactivity (ERIR) in the ventromedial hypothalamus (VMH), but the leptin-induced changes in female sexual behavior were not accompanied by parallel changes in VMH ERIR. Thus leptin facilitates estrous behavior in hamsters, but it does not overcome the lordosis-inhibiting metabolic cues produced by acute food deprivation. Because circulating leptin levels are directly related to body fat content, an implication of these findings is that elevated levels of adipose tissue could have a positive influence on sexual responsiveness.