ESTROGEN-RECEPTOR AND NEUROTENSIN NEUROMEDIN-N GENE-EXPRESSION IN THEPREOPTIC AREA ARE UNALTERED WITH AGE IN FISCHER-344 FEMALE RATS/

The sensitivity of hypothalamic centers to estrogenic regulation may b e impaired with age and contribute to the loss of reproductive functio n in female rats. Here, we have tested the hypothesis that aging is as sociated with alterations in the level of expression of the estrogen r eceptor (ER) gene and/or the neurotensin/neuromedin-N (NT/N) gene in t he preoptic area (POA) of female rats. We have used in situ hybridizat ion 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 o f 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, est rogenic regulation of both ER messenger RNA levels and NT/N messenger RNA levels did not differ across age groups. These results indicate th at transcription of the ER gene within the POA is not reduced with age and suggest that the receptor translated within the POA functions nor mally in old female rats. Our observations do not support a role for i mpaired expression of the ER gene or impaired estrogenic induction of NT/N gene expression by preoptic neurons in the development of reprodu ctive acyclicity with aging.