The role of ovarian hormones in sexual reward states of the female rat.

To what extent does the reward value of sexual stimulation in females depend on ovarian hormones? The effects of estradiol benzoate (EB) and progesterone (P) were examined on the acquisition and expression of sexual reward induced by paced copulation and clitoral stimulation (CLS) in ovariectomized (OVX) rats. In experiment 1 we examined the expression of a pacing-induced conditioned place preference (CPP). Ovariectomized, hormone-primed rats were given experience with paced copulation associated with one side of a CPP apparatus. Changing hormonal status prior to the final CPP test did not alter pacing-induced CPP. However, subsequent partial extinction of CPP was observed only in rats primed with EB+P, a treatment previously shown to induce sexual desire and receptivity. In Experiment 2, significant CLS-induced CPP developed in ovariectomized rats regardless of hormone priming. Our results show that the expression of the sexual reward state induced by paced copulation, and CLS in particular, is independent of hormone priming. We propose that ovarian hormones sensitize sensory and motor pathways necessary for sexual behavior and stimulation to induce reward.