Distribution of estrogen receptor alpha and beta in the mouse central nervous system: in vivo autoradiographic and immunocytochemical analyses.

Although the distribution of estrogen receptor beta (ERbeta) immunoreactivity in the rat central nervous has been reported, no such data are available in the mouse. The present study used in vivo autoradiography utilizing a (125)I-estrogen that has equal binding affinity for both receptors as well as immunohistochemistry for ERbeta and ERalpha, to investigate and compare the distribution of the two ERs in the mouse CNS. The use specific antisera against ERalpha and ERbeta allowed us to evaluate the contribution of these receptors to the binding detected with autoradiography. In addition, data were collected in ovariectomized wildtype and ERalpha KO (knockout) mice to examine developmental regulation of ERbeta expression by ERalpha. These studies revealed that in the mouse CNS, combining immunoreactivity for ERalpha with that for ERbeta accounted for all regions where binding was seen using autoradiography. Therefore, these data strongly suggest that the major contributors of estrogen binding in the mouse CNS are ERalpha and ERbeta. Together, these data provide an anatomical foundation for future studies and advance our understanding of estrogen action in the CNS. Moreover, since the immunocytochemical images were similar in wildtype and ERalpha KO mice, these studies suggest that the lack of ERalpha does not influence the expression of ERbeta in the central nervous system.