The Role Played by the Preoptic Region and the Hypothalamus in Spontaneous Ovulation and Ovulation Induced by Progesterone

Abstract

In female rats, cuts were made with the use of the Halasz technique around the preoptic area, leaving the connections between the preoptic area and hypothalamus intact. Such cuts do not interfere with spontaneous ovulation, as opposed to cuts made at the level of the optic chiasm. In addition, the effects of cuts around the preoptic area on progesterone-induced secretion of gonadotrophins were studied. In acute experiments, these cuts blocked the activity of progesterone injected on the third day of dioestrus of the 5-day cycle or at pro-oestrus of the 4-day cycle. However, in chronic experiments, progesterone injected at pro-oestrus, followed by pentobarbital, did induce ovulation.