Effects of Low Dosages of Androgen on the Differentiation of Hypothalamic Regulatory Control of Ovulation in the Rat

In these studies a single injection of 10 μg of testosterone propionate at 5 days of age resulted in permanent anovulatory sterility in 96 of 136 female rats. Studies of the hypothalamic refractoriness produced by this dosage revealed that ovulation could be induced in 5 of 10 sterile rats by electrical stimulation of the median eminence, whereas preoptic-suprachiasmatic stimulation was ineffective. However, if sterile rats were pretreated with progesterone and electrical stimulation was performed on the day of vaginal proestrus, then ovulation could be induced by stimulation of the preoptic area. These findings differ from those in rats sterilized by comparable administration of 1.25 mg of androgen. It is suggested that the degree of hypothalamic alteration produced by androgen treatment is dosage-dependent.