AN ANTEROGRADE-RETROGRADE LABELING STUDY OF THE CAROTID-SINUS NERVE OF THE JAPANESE MONKEY (MACACA-FUSCATA)

The sites of origin and termination of efferent and afferent fibers in the carotid sinus nerve (CSN) were investigated in the Japanese monke y. After application of a mixture of horseradish peroxidase (HRP) and wheat germ aggulutinin-conjugated HRP to the central cut end of the CS N, sensory ganglion neurons were labeled in the jugular ganglion of th e vagus nerve, as well as in the superior and petrosal ganglia of the glossopharyngeal nerve. Many sympathetic ganglion neurons were also la beled retrogradely in the superior cervical ganglion. In the brain, ma ny labeled terminals were seen ipsilaterally in the lateral division o f the nucleus of the solitary tract (NST). A few neuronal cell bodies were also labeled ipsilaterally in a reticular region dorsomedial to t he caudal one-third of the facial nucleus. The results indicate that t he CSN of the Japanese monkey is composed mainly of afferent fibers te rminating in the NST, that the afferent fibers in the CSN originate no t only from the superior and petrosal ganglia of the glossopharyngeal nerve but also from the jugular ganglion of the vagus nerve, and that efferent fibers contained in the CSN arise from the medullary reticula r formation and superior cervical ganglion.