Progesterone receptor isoforms are differentially regulated by sex steroids in the rat forebrain

WE studied the effects of estradiol (E2) and progesterone (P4) on expressio n of genes coding for PR isoforms in the forebrain of ovariectomized rats b y RT-PCR analysis. In the hypothalamus the expression of both PR isoforms w as induced by E2 and down-regulated by P4. In the preoptic area these chang es were only observed in the PR-B isoform. In contrast, in the hippocampus PR induction by E2 was only observed for PR-A. In this region P4 did not mo dify the expression of any PR isoform. These results indicate that PR isofo rms expression is differentially regulated by sex steroid hormones in disti nct forebrain regions and suggest that the tissue-specific regulation of ei ther PR-A or PR-B may be involved in the physiological actions of P4 upon t he rat brain. (C) 1998 Lippincott Williams & Wilkins.