Role of oxytocin in the hypothalamic regulation of sexual receptivity in hamsters.

Oxytocin (OXT) has been implicated in the control of a variety of social and reproductive behaviors in several species. The purpose of the present study was to test the hypothesis that OXT activity within the medial preoptic-anterior hypothalamus (MPOA-AH) and the ventromedial hypothalamus (VMH) plays a critical role in the expression of sexual receptivity in Syrian hamsters. The first 2 experiments investigated whether OXT would stimulate sexual receptivity in female hamsters in a dose-dependent manner. A 3rd experiment investigated whether sexual receptivity would be inhibited when endogenous OXT activity was blocked. Microinjection of OXT into the MPOA-AH or the VMH induced sexual receptivity in a dose-dependent manner in ovariectomized (OVX) hamsters primed with estradiol. Microinjection of a selective OXT antagonist, d(CH2)5[Tyr(Me)2Thr4,Tyr-NH29] ornithine vasotocin into the MPOA-AH or the VMH significantly reduced the levels of sexual receptivity exhibited by OVX hamsters administered estradiol and progesterone. These findings support the hypothesis that OXT activity in the MPOA-AH and the VMH plays an important role in the regulation of sexual receptivity in hamsters.