IMMUNOCYTOCHEMICAL LOCALIZATION OF THE ALPHA-7 SUBUNIT OF THE NICOTINIC ACETYLCHOLINE-RECEPTOR IN THE RAT CENTRAL-NERVOUS-SYSTEM

Previous molecular cloning studies have revealed that alpha-bungarotox in binding proteins present in the brain are members of the neuronal n icotinic acetylcholine receptor gene family. The alpha 7 subunit is st ructurally related to the agonist binding subunits present in the cent ral and peripheral nervous systems and, when expressed in Xenopus oocy tes, forms functional channels blockable by a-bungarotoxin. In the pre sent study, three different monoclonal antibodies raised against the a lpha 7 subunit were used to map its distribution throughout the centra l nervous system of the rat. Immunohistochemical localization revealed that the alpha 7 subunit is expressed in most regions of the brain, b eing, overall, well correlated with previous ''in situ'' localization of alpha 7 transcripts and alpha-bungarotoxin autoradiographic binding studies. Particularly strong immunoreactivity was observed in several sensory and motor nuclei of the brainstem as well as the red nucleus. At the cellular level, alpha 7 immunostaining was usually found both in somata and dendrites, whereas axonal and terminal labeling was not observed. The widespread distribution of the alpha 7 subunit polypepti de is consistent with immunoprecipitation data demonstrating that it i s a component of the predominant subtype of brain alpha-bungarotoxin-s ensitive nicotinic receptors. (C) 1994 Wiley-Liss, Inc.