Coexpression of ER beta with ER alpha and progestin receptor proteins in the female rat forebrain: Effects of estradiol treatment

Estrogen and progestin receptors (ER, PgR) play a critical role in the regu lation of neuroendocrine functions in females. The neuroanatomical distribu tion of the recently cloned, ER beta, overlaps with both Ella and PgR. To d etermine whether ER beta is found within ER alpha- or PgR-containing neuron s in female rat, we used dual label immunocytochemistry. ER beta -immunorea ctivity (ER beta -ir) was primarily detected in the nuclei of cells in the periventricular preoptic area (PvPO), the bed nucleus of the stria terminal is (BNSTpr), the paraventricular nucleus, the supraoptic nucleus, and the m edial amygdala (MEApd). Coexpression of ER beta -ir with ER alpha -ir or Pg R-ir was observed in the PvPO, BNSTpr, and MEApd in ovariectomized rats. E2 treatment decreased the number of ER beta -ir cells in the PvPO and BNSTpr and the number of ER alpha -ir cells in the MEApd and paraventricular nucl eus, and therefore decreased the number of cells coexpressing ER beta -ir a nd ER alpha -ir in the PvPO, BNSTpr, and MEApd. E2 treatment increased the amount of PgR-ir in cells of the PvPO, BNSTpr, and MEApd, a portion of whic h also contained ER beta. These results demonstrate that ER beta is express ed in ER alpha- or PgR-containing cells, and they suggest that E can modula te the ratios of these steroid receptors in a brain region-specific manner.