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 monkey. After application of a mixture of horseradish peroxidase (HRP) and wheat germ aggulutinin-conjugated HRP to the central cut end of the CSN, sensory ganglion neurons were labeled in the jugular ganglion of the vagus nerve, as well as in the superior and petrosal ganglia of the glossopharyngeal nerve. Many sympathetic ganglion neurons were also labeled retrogradely in the superior cervical ganglion. In the brain, many labeled terminals were seen ipsilaterally in the lateral division of the nucleus of the solitary tract (NST). A few neuronal cell bodies were also labeled ipsilaterally in a reticular region dorsomedial to the caudal one-third of the facial nucleus. The results indicate that the CSN of the Japanese monkey is composed mainly of afferent fibers terminating in the NST, that the afferent fibers in the CSN originate not 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 reticular formation and superior cervical ganglion.