[alpha]-Subunit Composition of Nicotinic Cholinoreceptors of Neurons of the Guinea Pig Inferior Mesenteric Ganglion: an Immunohistochemical Study

• Published in: Neurophysiology (New York) 2003-03, Vol.35 (2), p.90
• Main Authors: Koval', O M, Voitenko, L P, Skok, M V
• Format: Article
• Language: English
• ISSN: 0090-2977; 1573-9007

Using immunoperoxidase labeling, we studied the subunit composition of nicotinic acetylcholine receptors, nAChR, in preparations of the inferior mesenteric ganglion, IMG, of the guinea pig. Antibodies against synthetic peptides corresponding to agonist-binding membrane components of the [alpha]3, [alpha]4, [alpha]5, and [alpha]7 nAChR subunits were used. The presence of [alpha]3-specific antibodies was revealed on the membranes of about 58% of large neurons and of all small ganglionic cells (means of the greater and smaller diameters of the somata 53.8 + or - 1.8 vs 33.6 + or - 1.4 [mu]m, n = 20, and 14.1 + or - 0.5 vs 7.5 + or - 0.4 [mu]m, n = 50, respectively). Labeled cells of the rostral node were distributed evenly, while those of the caudal node were localized mostly within the regions of branching of the lumbar, colonic, and both hypogastric tracts. Immune labels to the [alpha]4 subunit were observed only on the membranes of small ganglionic cells distributed mostly in the region of the internodal commissural tracts. [alpha]5-Specific labeling was found on the membranes of about 63% large neurons, whose distribution was similar to that of the [alpha]3-labeled units, and on all small cells. Immunoreactivity to the [alpha]7 subunit was observed only on the membranes of small cells concentrated around unlabeled large neurons in the region of branching of the intermesenteric, colonic, and both hypogastric tracts. Thus, nAChR in the guinea pig IMG include [alpha]3, [alpha]4, [alpha]5, and [alpha]7 subunits. The nAChR with [alpha]3 and [alpha]5 subunits are localized on the membranes of large ganglionic neurons, whose number and topographical distribution are very close to each other. Our data agree with our results of earlier electrophysiological experiments and are indicative of the crucial role of the [alpha]3- and [alpha]5-containing nAChR in synaptic transmission via the ganglion under study. The presence of the [alpha]4- and [alpha]7-containing nAChR was found only on small ganglionic cells (which are, probably, not the relay units) and their processes.