Age differentially influences estrogen receptor-α (ERα) and estrogen receptor-β (ERβ) gene expression in specific regions of the rat brain

Estradiol's ability to influence neurochemical events that are critical to female reproductive cyclicity and behavior decreases with age. We tested the hypothesis that decreases in estrogen receptor-α (ERα) and/or ERβ mRNA explain the brain's declining responsiveness to estradiol. We assessed ERα and ERβ mRNA levels in intact and ovariectomized estradiol-treated rats. ERβ mRNA was detected in several brain regions and decreased by middle-age in the cerebral cortex and supraoptic nucleus of estradiol-treated rats. ERβ mRNA levels exhibited a diurnal rhythm in the suprachiasmatic nucleus of young and middle-aged rats and this rhythm was blunted in old rats. We examined ERα mRNA in the periventricular preoptic, medial preoptic, ventromedial and arcuate nuclei, and it was decreased only in the periventricular preoptic nucleus of the old rats. In summary, the expression of ERα and ERβ mRNAs is differentially modulated in the aging brain and changes are region specific.