Simultaneous visualization of aortic and [3H]5-hydroxytryptamine-accumulating cell bodies in the nodose ganglion of the cat.

1. Single- and double-tracer experiments were performed in cats to investigate the relationship between the aortic cells and the cell bodies accumulating 5-hydroxytryptamine (5-HT) in the nodose ganglion. In one series of experiments, horseradish peroxidase (HRP) was applied to the central end of the aortic nerve, anterogradely transported and accumulated in ganglionar perikarya. The distribution of HRP-positive neurones was reconstructed in serial sections through the nodose ganglion. In a second series of experiments, the distribution of [(3)H]5-HT-accumulating cell bodies was assessed following incubation of the nodose ganglion in [(3)H]5-HT. The third series of experiments combined the treatments of the preceding ones: anterograde transport of HRP in the aortic nerve followed by incubation of the nodose ganglion in [(3)H]5-HT.2. The results from these experiments provide more information with regard to (i) the topographical relationship between the aortic and [(3)H]5-HT-accumulating cell bodies in the same ganglion and (ii) the distribution and number of double-labelled neurones, giving further indications about histochemical components of the aortic nerve.3. The HRP experiments demonstrated that HRP-positive cells show a preferential pattern of topographical organization. They were mostly located in the medial border of the ganglion where the laryngeal and aortic nerves enter. On the other hand, [(3)H]5-HT-accumulating neurones were scattered throughout the ganglion.4. In double-tracer experiments, three populations of labelled cell bodies were distinguished in the same nodose ganglion: (1) single HRP-cells; (2) single [(3)H]5-HT-accumulating cells and (3) double-labelled cells. The distribution of the latter population exhibited no preferential localization. Quantitative estimates indicated that double-labelled neurones constituted 65-85% of the population of HRP-positive cell bodies.5. These results show that most aortic neurones are able to take up exogenous serotonin and may be serotonergic neurones. They suggest that serotonin may be involved in physiological effects mediated via the aortic nerves.