Role of Non-Aromatizable Androgens in the Central Control of Pubertation of Female Rats

In 30-postnatal day-old rat females we created a decreased or increased level of 5α-reduced (non-aromatizable) androgens, using injections of an inhibitor of 5α-reductase or exogenous dihydrotestosterone, respectively. In these animals, we measured the levels of noradrenaline (NA) and serotonin (5-HT) in the hypothalamus, those of gonadotropins in the hypophysis, and testosterone and estradiol in the blood plasma; the process of pubertation was also monitored. In rats with a deficiency of non-aromatizable androgens, the NA level increased, while that of 5-HT dropped. In animals with an excess of these hormones, the 5-HT level remained stable against the background of a certain increase in the NA level. In the first group of animals, the estradiol level in the blood increased by a factor of 3, while the testosterone level increased insignificantly. The beginning of pubertation in these animals was not shifted, while the first ovulation occurred somewhat earlier, as compared with the control. In the second group of rats, treatment with exogenous dihydrotestosterone accelerated the beginning of pubertation, but the interval between opening of the vagina and first ovulation even somewhat increased. The neurotransmitter hypothalamic mechanisms mediating acceleration of an initial phase of the female pubertation and retardation of its final phase under the influence of non-aromatizable androgens are discussed.