Age-related changes in cytoplasmic estradiol receptor concentrations in microdissected brain nuclei: correlations...

The purpose of this study was to; determine at what age changes in cytoplasmic estradiol receptors are evident in specific microdissected brain areas of the female rat; assess whether alterations parallel previous changes observed when large brain areas were used for determination of receptor concentrations; and assess whether changes in cytoplasmic estradiol receptors are correlated with changes in steroid-mediated physiological functions. To assess the effects of age on cytoplasmic estradiol receptor concentrations, we used virgin female Sprague-Dawley rats at 3-4 months, 7-8 months and 10-11 months of age. They were ovariectomized 7-14 days prior to use to allow maximal translocation of receptors to the cytoplasm. The animals were anesthetized and perfused with a 10% (v/v) solution of dimethylsulfoxide to protect the receptor proteins from the effects of freezing. Brains were removed and frozen. This procedure of freezing the brains caused a minimal (15-18%) loss in the number of receptors and no change in the dissociation constant. Consecutive 300 micron sections were sliced and the following nuclei and brain areas were microdissected: bed nucleus of the stria terminalis, suprachiasmatic-preoptic area, medial preoptic nucleus, periventricular preoptic nucleus, periventricular anterior hypothalamic area, paraventricular nucleus, dorsomedial nucleus, ventromedial nucleus, arcuate-median eminence, medial amygdala, and cortical amygdala. The pituitary gland was also removed and analyzed. The cytoplasmic fraction from a tissue pool from 3 animals was prepared and aliquots were incubated with [3H]estradiol at a final concentration of 1.5 nM in the presence or absence of 100-fold excess moxestrol. Receptor-bound [3H]estradiol was separated from free hormone by gel filtration.(ABSTRACT TRUNCATED AT 250 WORDS)