EFFECTS OF ESTRADIOL ON SEXUAL RECEPTIVITY, WHEEL-RUNNING BEHAVIOR, AND VAGINAL ESTRUS IN VIRGIN PRAIRIE VOLES

This study examined the effects of estradiol on sexual receptivity and vaginal estrus in experienced and virgin female prairie voles, and ru nning wheel activity in virgin females. Because prairie voles undergo induced ovulation, we predicted that exogenous estradiol would not aff ect activity patterns nor stimulate lordosis in virgins. Females were SC injected with estradiol benzoate (EB) and placed with males, and se xual receptivity was monitored. In experienced females 0.5 mu g of EB resulted in 100% of the females displaying lordosis after 48 h. In con trast, only 20% of the females receiving 0.05 mu g displayed lordosis. Less than 20% of virgin females receiving EB displayed lordosis. Virg ins displayed no change in wheel-running activity after EB treatments, indicating that behaviors that are influenced by estradiol and regula ted by the brain may require previous exposure to males to develop. Al though all females receiving the 0.5 mu g of EB displayed vaginal estr us, virgin females achieved vaginal estrus later than experienced fema les, suggesting that exposure to males has a priming effect resulting in a reduced period to vaginal estrus.