Evidence for the colocalization of estrogen receptor-β mRNA and estrogen receptor-α immunoreactivity in neurons of the rat forebrain

Abstract

Estrogen receptor β (ERβ) mRNA is expressed in several rat brain regions where ERα is abundant. In vitro studies have shown that ERα and ERβ can heterodimerize and that the activity of this complex may be different than an ERα or ERβ homodimer complex. The purpose of the present study was to ascertain if ERα and ERβ are co-expressed by certain neuronal populations using a double label in situ hybridization/immunocytochemistry method. The results revealed that neurons in the bed nucleus of the stria terminalis, medial amygdala and preoptic area contain both ERs, with the vast majority of the neurons being double labeled. In other brain regions including the arcuate nucleus, cortical amygdaloid nuclei and ventromedial nucleus, only a few double-labeled cells were detected, while neurons in the paraventricular nucleus, supraoptic nucleus, and cerebral cortex expressed only ERβ mRNA. The results of these double label experiments provide the first evidence that ERα and ERβ coexist in neurons under in vivo conditions and suggest that estrogens may differentially modulate the activity of certain neuronal populations depending on whether the cells expresses ERα, ERβ or both ERs.