Interaction of male sensory cues and estradiol in the induction of estrus in the prairie vole.

In the prairie vole, estrus and ovulation are induced by stimulation from a male, which also increases the female's gonadal weight and serum estradiol level. It is not known whether the induction of receptivity is dependent solely on an endogenous increase in circulating estradiol or an interaction of increased estradiol and male sensory stimulation. Using a dose response paradigm, we examined if a dose of estradiol within physiological range was sufficient to induce receptivity. We also examined if extended male contact could induce receptivity in ovariectomized females tested either without estradiol replacement or with a subthreshold dose of estradiol. We found that elevating blood levels of estradiol to those found during estrus was sufficient to induce sexual receptivity; male contact was not necessary. Extended male cohabitation did induce estrus in ovariectomized females treated with a subthreshold dose of estradiol, a dose which without male contact did not support sexual receptivity. In these same females, the extended male contact elevated circulating estradiol levels; the source of the estradiol is unknown.