Noradrenergic-induced expression of c-fos in rat cortex: Neuronal localization

β Adrenoceptors in the rat forebrain have been shown to exist predominantly on astrocytes. Studies were undertaken to determine whether the cellular localization of c-fos expression caused by the activation of brain β receptors would have a similar cellular localization. Double label light and electron microscopic immunohistochemical experiments with a glial (glial fibrillary acidic protein, GFAP) and neuronal marker (neurofilament protein, NFP) were undertaken in rats treated with the adrenergic drug, yohimbine. These studies revealed a predominantly neuronal localization of Fos protein in the cerebral cortex. The latter results indicate that neurons are the postsynaptic noradrenergic target cells in which this immediate early gene is expressed in response to the stimulation of β adrenoceptors. The possible relation of these findings to the glial localization of these receptors is discussed.