Estrogen receptor α and β mRNA expressions by proliferating and differentiating cells in the adult rat dentate gyrus and subventricular zone

Numerous factors modulate neurogenesis in the adult dentate gyrus and subventricular zone, but it is often not clear if the modulation is mediated by direct effects on the proliferating and differentiating cells or secondary to effects on other cells. Also, while some factors selectively affect neurogenesis in one of the neurogenetic zones, it is not clear how selectivity is achieved. Estrogen is a hormonal modulator of neurogenesis. To address the issues of direct versus indirect control and regional specificity we investigated the colocalization of immunoreactivity for a proliferating cell marker, Ki-67, and a marker for migrating and differentiating cells with a neuronal phenotype, doublecortin, with the expressions of mRNA for estrogen receptors a and P. We found an extensive colocalization of estrogen receptor a with both markers in the dentate gyrus and only with Ki-67 in the subventricular zone. An extensive colocalization of estrogen receptor P with both markers was found in the dentate gyrus, but only a few Ki-67-immunoreactive and no doublecortin-immunoreactive cells of the subventricular zone expressed estrogen receptor p mRNA. Estrogen receptor a and P mRNAs were not expressed in other telencephalic Ki-67-immunoreactive cells or in constitutively doublecortin-immunoreactive cells of the piriform cortex. The extensive colocalization of immunoreactive markers for cell proliferation and differentiation with mRNAs for estrogen receptor a and estrogen receptor P points to the direct modulation of dentate cell proliferation, differentiation and survival by estrogen, while direct effects of estrogen in the subventricular zone appear restricted to estrogen receptor a-mediated effects operating at the time of cell proliferation. (c) 2005 IBRO. Published by Elsevier Ltd. All rights reserved.