Distribution of estrogen receptor beta immunoreactivity in the rat centralnervous system

The discovery of estrogen receptor beta (ER beta) and subsequent localizati on of its mRNA in the rat central nervous system (CNS) has provided new ins ights about estrogen action in brain. A critical step in understanding the role of ER beta is demonstrating that the mRNA is translated into functiona l protein. The present study used a new ER beta -specific polyclonal. antis erum (Z8P) and immunocytochemistry (ICC) to investigate the distribution of ER beta in the rat CNS. Ovariectomized female rats were perfusion fixed, a nd free-floating sections were incubated with Z8P. After visualization with a standard ABC method, nuclear immunoreactivity was seen in neurons throug hout the brain, including the olfactory nuclei, laminae TV-VI of the cerebr al cortex, medial septum, preoptic area, bed nucleus of the stria terminali s, supraoptic nucleus, paraventricular nucleus, zona incerta, medial and co rtical amygdaloid nuclei, cerebellum, nucleus of the solitary tract, ventra l tegmental area, and spinal trigeminal nucleus. Moreover, the results of a double-label ICC/ in situ hybridization study revealed that ER beta mRNA a nd immunoreactivity were colocalized in neurons of the brain, thus confirmi ng the specificity of the antiserum. Through the use of Western blot analys is, Z8P was shown to recognize in vitro translated ER beta, but not ER alph a, as well as a 60-kDa protein from rat granulosa cells and ovary extracts. The results of these studies have demonstrated that(1) ER beta mRA is tran slated into immunoreactive protein throughout the rat brain, and (2) ER bet a resides in the cell nucleus. Together, these data provide an anatomic fou ndation for future studies and advance our understanding of estrogen action in hypothalmic and extrahypothalamic brain regions. J. Comp. Neural. 436:6 4-81, 2001. (C) 2001 Wiley-Liss, Inc.