To determine whether there are sex differences in the distribution of type II corticosteroid receptor-immunoreactive (type Il-ir) cells in the rat hippocampus, we carried out a quantitative morphometric immunocytochemical study using a mouse monoclonal antibody, BUGR2. We report that in adrenally intact male and female rats, high densities of cells with nuclear type Il-ir were observed in the pyramidal layer of field CA1 and the granular layer of the dentate gyrus. In intact males very few cells, presumably glia, in the stratum oriens showed type Il-ir. In contrast, in females, interneurons with diffuse or cytoplasmic type Il-ir were observed in the stratum oriens of CAl and CA3. There were also sex differences in the regulation of type Il-ir by corticosterone, the predominant glucocorticoid, and female sex steroids. In male rats the density of cells with nuclear type Il-ir in all parts of Ammon’s horn and the dentate gyrus was decreased significantly after adrenalectomy (adx). In contrast, in females such reductions were observed only in the pyramidal layer of CAl and the granular layer of the dentate gyrus. In both sexes, cells with intense diffuse or mainly cytoplasmic type Il-ir were observed in the pyramidal layer and stratum oriens after adx. The loss of nuclear type Il-ir in the hippocampus of adx females was not affected significantly by ovariectomy. In adx males, nuclear Type Il-ir was restored in CAl and the dentate gyrus after treatment with corticosterone or progesterone. Cells in CA3 were, however, unresponsive to treatment with either hormone. In contrast, in adx females, treatment with either corticosterone or progesterone restored nuclear type Il-ir to cells in all regions of the hippocampus. In both adx males and females, cytoplasmic type Il-ir observed in some cells in the pyramidal layer and stratum oriens, was abolished completely by corticosterone, and partially by progesterone treatment. In both adx males and females, estradiol treatment did not affect significantly the pattern of type Il-ir. Sex differences in the distribution of type Il-ir interneurons in intact rats and the regulation of the intracellular location of type Il-ir of adx rats by corticosterone and progesterone, may be important determinants of sex differences in the modulation of hippocampal function by glucocorticoids.
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