The estrogen-progesterone induction of mating responses in the spayed female rat

Abstract

A small injection of estrogen followed after a suitable interval by an injection of progesterone is more effective than a larger quantity of estrogen alone in inducing sexual receptivity in the spayed female rat. With respect to length and intensity, the estrogen-progesterone induced heat resembles that of normal animals more nearly than the estrogen induced heat. It seems likely, therefore, that in the normal rat as in the guinea pig sexual receptivity is caused by the synergistic action of estrogen and progesterone produced in the still unruptured follicles. The rat appears to be more sensitive than the guinea pig to estrogen-action and less sensitive to progesterone-action. © 1939 by The Endocrine Society.