Effects of Testosterone, Dihydrotestosterone, and Estradiol on the Impaired Prolactin Response to Metoclopramide in the Castrated Rat

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Abstract
This study was designed to assess the effect of three testicular steroids, testosterone, dihydrotestosterone, and estradiol, on PRL secretion in castrated rats. This has been done by evaluating the effect of androgens and estrogens and their antagonists, alone or in combination, on metoclopramide (MET)-induced PRL secretion in the castrated male rat. Ventral prostate and seminal vesicles retained normal weight after treatment of castrated rats with testosterone propionate (TP) and dihydrotestosterone (DHT). This effect was partially antagonized by the antiandrogen cyproterone acetate (CA) which in itself had no effect. TP, as well as DHT and EB, prevented the rise of plasma and pituitary LH and plasma FSH consequent to castration. CA partially blunted the TP and completely blocked the DHT effect, indicating that it acts as an antiandrogen. Nafoxidine hydrochloride (NH) antagonized the effect of EB, but not of TP on gonadotropins. This indicates that in combination with EB, NH acts as an antiestrogen.