Perinatal development of hypothalamic and cortical estrogen receptors in mouse brain: methodological aspects

Binding of the estrogen, [3H]moxestrol, to fetal and neonatal mouse brain cytosol receptors was examined to determine the ontogeny of estrogen receptors in the hypothalamus and cerebral cortex from embryonic (E) day 15 to postnatal (P) day 18. Cytosol receptor assays were performed under exchange conditions at 25 degrees C for 4 h in order to measure receptors which had become occupied by estradiol during tissue homogenization. Scatchard analysis revealed high affinity (Kd = 0.4 nM) sites and was in good agreement with single point assays at 1 nM, which measured 70% of binding capacity. Binding was initially examined in the whole forebrain. Total binding of [3H]moxestrol in the forebrain increases between E15 and E18 and reaches adult levels at P9. The increase in binding relative to protein content peaks at P9 and then decreases, whereas the amount of binding relative to DNA content reaches a maximum between P12 and P15. The developmental time-course of the estrogen receptors was studied in the hypothalamus and 3 cortical regions. In the hypothalamus binding of [3H]moxestrol increases from P5 to P18 of the cortical areas. The cingulate cortex shows the highest amount of binding, increasing until P9 and then declining. In the other two cortical areas studied, the lateral and posterior cortex, binding expressed per mg DNA, is somewhat higher between P7 and P15 than in adults. When the binding is expressed per mg protein there is a sharp decline after P7, the magnitude of which is probably a result of a large increase in protein content relative to amount of receptor.(ABSTRACT TRUNCATED AT 250 WORDS)