EFFECT OF SEX STEROIDS ON HYPOTHALAMIC GABA

Orchidectomy decreased gamma-aminobutyric acid (GABA) levels and the activity of glutamic acid decarboxylase (GAD) in the acurate/median eminence area (ARC/ME). The replacement treatment with estradiol benzoate (E2) or testosterone propionate (T) restored both paramenters back to the levels of the control intact rats. Dihydrotestosterone propionate (DHT) administration did not reverse the effect of castration. Hypophysectomy diminished GABA content and E2 and T treatments can not reverse this action. Administration of an antiserum to rat prolactin (PRL) blocked the stimulatory action of E2 on GABA concentration and GAD activity in the ARC/ME. Implants of anterior pituitaries or the combination of both grafting pituitaries and E2 administration increased GABA content in the ARC/ME and anterior pituitary glands. These results indicate that PRL may mediate the stimulatory effect of estrogen on ARC/ME GABA neurons.