Pharyngeal branch of the vagus nerve carries intraepithelial afferent fibers in the cat pharynx: An elucidation of the origin and central and peripheral distribution of these components

The presence of a sensory component in the pharyngeal branch of the vagus n erve (PhB), including its peripheral distribution and central projection, w as studied by denervation and tracer experiments in the cat. The distributi on of nerve fibers immunoreactive to protein gene product 9.5, a sensitive neuronal marker; calcitonin gene-related peptide; and substance P in the ph aryngeal epithelium was analyzed in both intact animals and animals subject ed to partial denervation by means of sectioning two of the three nerve tru nks, the glossopharyngeal nerve, the superior laryngeal nerve, and the PhB, while leaving one intact. The results of this study show that the glossoph aryngeal nerve and superior laryngeal nerve carry nerve fibers to the phary ngeal epithelium rostral and caudal to the middle level of the epiglottis, respectively, whereas the PhB carries nerve fibers to the mesopharyngeal ep ithelium. Tracer experiments, by applying wheat germ agglutinin-horseradish peroxidase to the PhB, demonstrated retrogradely labeled primary sensory n eurons in the jugular ganglion and transganglionic labeling of terminals in the interstitial subnucleus of the nucleus of the tractus solitarius. Thes e results indicate that the PhB contains a sensory component that originate s from the jugular ganglion, innervates the mesopharyngeal epithelium, and projects to the nucleus of the tractus solitarius.