EFFECTS OF ANDROGEN AND ESTROGEN-RECEPTOR LIGANDS ON EARLY POSTNATAL EXPRESSION OF VP MESSENGER-RNA IN THE BNST AND MA

Early postnatal expression of VP mRNA in the bed nucleus of the stria terminalis (BNST) and medial amygdala (MA) of the male rat has been sh own to be testosterone (T) dependent, However, it remains unclear whet her these effects of T are mediated exclusively through androgen or es trogen receptors, or both. This study was performed to determine which gonadal hormone receptor(s) is (are) responsible for the neonatal exp ression of VP and mRNA expression in the BNST and MA. Male and female: rats were given early postnatal (day 1-5) treatment with estrogen or a ndrogen receptor agonists or antagonists and VP mRNA was then detected by in situ hybridization in the BNST and MA. In male rats, tamoxifen (estrogen antagonist) blocked T effects on VP mRNA expression in postn atal day six animals; while the estrogen agonist diethylstilbestrol mi micked the effects of T in the female rat. The data clearly indicate a primary role of the estrogen receptor in mediating the initial expres sion of VP mRNA in the BNST and MA of male and female rats.