The effects of olfactory bulbectomy and chronic psychosocial stress on serum glucocorticoids and sexual behavior in female rats

Abstract

The effects of olfactory bulb removal (OBX) and chronic psychosocial stress on serum glucocorticoids and sexual behavior were assessed in female rats primed with a subthreshold level of estradiol (E2). Ovariectomized females underwent either OBX or sham surgery. Half of the OBX and half of the sham animals were exposed to chronic psychosocial stress (crowding, strobe light, and intermittent noise) for one-half h per day for 27 days. On day 22, three blood samples were collected from each animal for serum corticosterone analysis; 1) before, 2) during, and 3) after acute stress (one-half h restraint). On day 28, females were exposed to either 4 or 24 h of E2. On day 29, all females received 500 micrograms progesterone (P) 4 h prior to sexual behavior testing. Sexual receptivity was measured using the lordosis quotient (LQ = [number of lordotic responses/10 mounts] x 100). Sexual proceptivity (dart and ear wiggling sequences) and rejection (number of nonlordotic responses to mount attempts) were measured throughout a 10-min test period. Results showed that chronic psychosocial stress dramatically increased sexual receptivity and proceptivity while decreasing sexual rejection in female rats primed with a subthreshold level of E2. Chronic psychosocial stress also elevated serum glucocorticoids and significantly exacerbated the glucocorticoid response to acute stress. OBX, while increasing sexual receptivity and decreasing sexual rejection, had no effect on serum glucocorticoids. These findings support the hypothesis that OBX potentiates female sexual behavior directly through an increase in neural sensitivity to E2. In contrast, the enhancing effect of chronic psychosocial stress on female sexual behavior may result from alterations of the hypothalamo-pituitary-adrenal system.