Cyclic activity in the male hypothalamus.

Abstract

IT is well known that the administration of testosterone to female rats shortly after birth induces the differentiation of an acyclic male type of hypothalamus, resulting in permanent sterility and cystic ovaries lacking in corporalutea1. The role of testosterone in the genetic male rat has been examined by the method of castration during infancy2,3. The findings have shown that deprivation of endogenous testosterone within 3 days of birth is followed by the differentiation of a cyclic female type of hypothalamus as seen by the presence of corpora lutea in ovarian transplants made during adult life. Castration more than 3 days after birth does not prevent the differentiation of the male type of hypothalamus, for ovaries grafted into animals so treated contained no corpora lutea in adulthood. These and other investigations4 raised the possibility that the findings would be different if the transplantation and examination of the ovaries were carried out in the immature animal.