Effects of ovarian hormones on sexual receptivity, proceptivity, and motivation in olfactory bulbectomized female rats.

The purpose of the present experiment was to assess the effect of olfactory bulbectomy and ovarian hormones on female sexual motivation. Ovariectomized female rats underwent either bilateral bulbectomy or sham surgery. Females received one of four subthreshold hormone treatments: 0% estradiol (E2) plus 500 micrograms progesterone (P), 100% E2 alone, 10% E2 plus 500 micrograms P, or 100% E2 plus 500 micrograms P. Sexual motivation (as indicated by a female's preference for a sexually active male over a castrated male) and proceptivity (dart and ear wiggling sequences) were measured in a three compartment partner preference apparatus. Sexual receptivity (lordosis) was measured separately in a glass arena with a sexually active male. Results showed that olfactory bulb removal facilitates sexual receptivity and proceptivity in females exposed to 10% or 100% E2 in combination with 500 micrograms P. In contrast, sexual motivation was only demonstrated by olfactory bulbectomized females which received 100% E2 in combination with 500 micrograms P. These findings support the hypothesis that olfactory bulbectomy induces a behavioral hypersensitivity to estrogen, and suggest that sexual motivation is an estrogen-mediated response which requires a higher level of estrogen stimulation than sexual receptivity and proceptivity.