Influence of testosterone upon sexual maturation in the rat.

1. Testosterone injected into the neonatal female rat induces permanent sterility. This study was carried out in an endeavour to determine where this change is induced.2. Hypophysectomized, but otherwise normal, female rats bearing anterior pituitary transplants from androgen-sterilized female rats under the median eminence of the hypothalamus and vascularized from it, show oestrous cycles in the vaginal smear, have corpora lutea in the ovaries and are fertile.3. Hypophysectomized androgen-sterilized female rats bearing anterior pituitary transplants from normal female rats under the median eminence and vascularized from it show persistent oestrus in the vaginal smear, have small ovaries containing large follicles but no corpora lutea and are sterile.4. Testosterone injected into the female rat, and leading to sterility and ovarian malfunction, does not act at the level of the anterior pituitary, which retains the ability to function normally. It is considered that it may act upon the central nervous system to cause a disturbance of the gonadotrophin-releasing mechanism.