Sexual receptivity: facilitation by medial preoptic lesions in female rats.

Lesions in the medial preoptic area of ovariectomized female rats reduced the quantity of estrogen needed to induce sexual receptivity in these animals. In addition, the number of days over which receptive behavior could be elicited after a single initial estrogen injection and with subsequent daily progesterone treatment was significantly increased by lesions in the medial preoptic area. These findings support the view that estrogen acts to reduce an inhibitory action that is tonically exerted by the medial preoptic area on pathways mediating estrous behavior.