The effect of medial preoptic-anterior hypothalamic lesions on testosterone plasma levels and testosterone conversion in the hypothalamus of male rats.

Male Wistar rats were submitted to bilateral high frequency lesions in the medial preoptic-anterior hypothalamic area or to sham procedure. The behavioral effect of the lesions was observed and plasma testosterone (T) and estradiol (E2) were measured by radioimmunoassay. In vitro metabolism of T was studied in the hypothalamus. Lesions produced a permanent deficit in male sexual behavior, an increase of plasma T and E2, and of hypothalamic T aromatization, and a decrease of T conversion to 5 alpha-dihydrotestosterone (DHT).

Effect of castration on hypothalamic testosterone metabolism in the male rat.

In vitro studies were performed of hypothalamic testosterone (T) metabolism 30 days after castration of adult male rats. No changes were seen in T conversion into dihydrotesterone and estrogens in the castrated rats. Plasma T levels were decreased while plasma estradiol concentrations did not differ from those of intact controls. It was suggested that the hypothalamic T metabolism probably is not androgen dependent.