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 running wheel activity in virgin females. Because prairie voles undergo induced ovulation, we predicted that exogenous estradiol would not affect activity patterns nor stimulate lordosis in virgins. Females were SC injected with estradiol benzoate (ED) and placed with males, and sexual receptivity was monitored. In experienced females 0.5 micrograms of EB resulted in 100% of the females displaying lordosis after 48 h. In contrast, only 20% of the females receiving 0.05 micrograms displayed lordosis. Less than 20% of virgin females receiving EB displayed lordosis. Virgins displayed no change in wheel-running activity after EB treatments, indicating that behaviors that are influenced by estradiol and regulated by the brain may require previous exposure to males to develop. Although all females receiving the 0.5 micrograms of EB displayed vaginal estrus, virgin females achieved vaginal estrus later than experienced females, suggesting that exposure to males has a priming effect resulting in a reduced period to vaginal estrus.