Males increase serum estrogen and estrogen receptor binding in brain of female voles.

Sexual development of female prairie voles does not occur unless females are exposed to stimuli from an unfamiliar male. Three experiments were conducted to determine whether a saturable high-affinity estradiol binding site (ERN) is present in cell nuclei of brain tissue from females exposed to male stimuli and whether serum estradiol and brain ERN are correlated with the duration of male exposure. Brain ERN were detected and found to be correlated with serum estradiol levels. Significant increases in brain ERN were observed within 18 hours after females were exposed to a male for either a continuous (uninterrupted) or transient (1 1/4 hour) period. A significant increase in serum estradiol was observed for females given continuous male exposure. The rate of increase of ERN in brain was significantly higher for females given continuous as opposed to transient male exposure. The results suggest that the continued presence of a male can accelerate the rate of increase of ERN in the brain, presumably through increases in circulating estradiol.