Immunocytochemical localization of the α7 subunit of the nicotinic acetylcholine receptor in the rat central nervous system

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Abstract
Previous molecular cloning studies have revealed that α-bungarotoxin binding proteins present in the brain are members of the neuronal nicotinic acetylcholine receptor gene family. The α7 subunit is structurally related to the agonist binding subunits present in the central and peripheral nervous systems and, when expressed in Xenopus oocytes, forms functional channels blockable by α-bungarotoxin. In the present study, three different monoclonal antibodies raised against the α7 subunit were used to map its distribution throughout the central nervous system of the rat. Immunohistochemical localization revealed that the α7 subunit is expressed in most regions of the brain, being, overall, well correlated with previous “in situ” localization of α7 transcripts and α-bungarotoxin autoradiographic binding studies. Particularly strong immuno-reactivity was observed in several sensory and motor nuclei of the brainstem as well as the red nucleus. At the cellular level, α7 immunostaining was usually found both in somata and dendrites, whereas axonal and terminal labeling was not observed. The widespread distribution of the α7 subunit polypeptide is consistent with immunoprecipitation data demonstrating that it is a component of the predominant subtype of brain α-bungarotoxin-sensitive nicotinic receptors.