Immunocytochemical localization of estrogen receptor beta in the rat brain

The localization of the new estrogen receptor, ER-beta, in the rat brain was studied by immunocytochemical technique, and the results revealed that ER-beta immunoactive material was predominantly localized in the neuronal nucleus, but it was also detectable in the cytoplasm and neuronal processes. High levels of ER-beta immunopositive signals were detected in the cerebral cortex, vertical limb of the diagonal band, Purkinje cells, locus ceruleus, and motor trigeminal nucleus. Moderate levels were found in the medial septum, lateral amygdaloid nucleus, substantia nigra, and central gray. Weak signals were localized in some subregions of the hypothalamus and amygdaloid complex. Some differences of the expression of ER-beta immunoreactivity between male and female rats were also noticed. The above results provide the first detailed evidence that ER-beta protein is widely distributed in the rat brain, and ER-beta may be involved in some important brain function such as learning and memory.