Quantitative autoradiographic studies of 5-HT-accumulating neurones in the nodose ganglia of the cat after perikaryal or terminal uptake.

The distributions of ganglionar cell bodies, specifically labeled with 3H-5-HT, were studied in light microscope autoradiographs of the cat nodose ganglion. The size, number and localization of labeled cells were examined under different experimental conditions: after in vitro incubation of the ganglion with 3H-5-HT and after retrograde transport of 3H-5-HT injected into the nucleus of the solitary tract (NST) which receives primary visceral sensory projections from nodose ganglia cells of the vagal nerve. Following incubation of the nodose ganglia with a low concentration of 3H-5-HT (10(-6) M), some ganglionar cell bodies took up and retained the tracer. In both the right and left ganglia, they were significantly smaller in size than the unreactive neurones. The mean diameter of their perikaryon was 36.97 +/- 0.52 microns, compared with 45.76 +/- 0.87 microns in unreactive neurones. About 600 labeled cell bodies were counted in each ganglion, corresponding to 2-3% of the total nodose ganglion cell population. These reactive neurones were not localized in one particular area of the ganglia, but scattered throughout both of them. Following bilateral or unilateral microinjections of 3H-5-HT in the NST, retrogradely labeled cell bodies were observed, 24 h later, in the nodose ganglia. Their mean diameter was estimated to be 36.14 +/- 0.69 microns and they represented approximately 2% of the total ganglion cell population. As in in vitro experiments, the labeled cells were not grouped in any particular region of the ganglion. These experiments show that the distribution of both populations of labeled cells, observed under these conditions, are comparable. On an anatomical and quantitative basis one may reasonably suppose that the perikaryal or terminal uptakes concern the same neuronal population.