Estrogen receptor and neurotensin/neuromedin-N gene expression in the preoptic area are unaltered with age in Fischer 344 female rats.

Abstract

The sensitivity of hypothalamic centers to estrogenic regulation may be impaired with age and contribute to the loss of reproductive function in female rats. Here, we have tested the hypothesis that aging is associated with alterations in the level of expression of the estrogen receptor (ER) gene and/or the neurotensin/neuromedin-N (NT/N) gene in the preoptic area (POA) of female rats. We have used in situ hybridization histochemistry and quantitative autoradiography to compare ER gene expression and NT/N gene expression in the POA of ovariectomized and ovariectomized/estradiol-treated female rats at 3, 11, and 20 months of age. We found no evidence for an age-related impairment of either ER or NT/N gene expression in two subdivisions of the POA: the anterior medial preoptic nucleus and the medial preoptic nucleus. Likewise, estrogenic regulation of both ER messenger RNA levels and NT/N messenger RNA levels did not differ across age groups. These results indicate that transcription of the ER gene within the POA is not reduced with age and suggest that the receptor translated within the POA functions normally in old female rats. Our observations do not support a role for impaired expression of the ER gene or impaired estrogenic induction of NT/N gene expression by preoptic neurons in the development of reproductive acyclicity with aging.