The Effects of Hypothalamic Lesions on the Release of Gonadotropins and Prolactin in Response to Estrogen and Progesterone Treatment in Female Rats

Abstract

Plasma gonadotropins and prolactin were measured in rats with hypothalamic lesions. In ovariectomized females estrogen lowered plasma FSH and LH and elevated plasma prolactin. Lesions in the median eminence of ovariectomized rats which lowered plasma gonadotropins and elevated plasma prolactin prevented these effects of estrogen. The ability of progesterone to stimulate FSH and LH release in ovariectomized, estrogenprimed rats was also eliminated by these lesions. Lesions in the suprachiasmatic region which induced constant estrus in animals with intact ovaries failed to block the inhibitory effect of estrogen on gonadotropin release and the rise in prolactin evoked by estrogen still occurred. The stimulation of LH release by progesterone was blocked by these lesions, whereas the stimulation of FSH release was unimpaired. The results are discussed in terms of the sites of the feedback actions of gonadal steroids. (Endocrinology91: 1404, 1972)