Coexpression of ERβ with ERα 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 regulation of neuroendocrine functions in females. The neuroanatomical distribution of the recently cloned, ER , overlaps with both ER and PgR. To determine whether ER is found within ER or PgR-containing neurons in female rat, we used dual label immunocytochemistry. ER immunoreactivity (ER -ir) was primarily detected in the nuclei of cells in the periventricular preoptic area (PvPO), the bed nucleus of the stria terminalis (BNSTpr), the paraventricular nucleus, the supraoptic nucleus, and the medial amygdala (MEApd). Coexpression of ER -ir with ER -ir or PgR-ir was observed in the PvPO, BNSTpr, and MEApd in ovariectomized rats. E2 treatment decreased the number of ER -ir cells in the PvPO and BNSTpr and the number of ER -ir cells in the MEApd and paraventricular nucleus, and therefore decreased the number of cells coexpressing ER -ir and ER -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 which also contained ER . These results demonstrate that ER is expressed in ER or PgRcontaining cells, and they suggest that E can modulate the ratios of these steroid receptors in a brain region-specific manner. (Endocrinology 142: 5172–5181, 2001)