Nerve degeneration study of the source of afferent axonal endings in the carotid baroreceptor zone of the domestic fowl.

Axonal elements of the carotid baroreceptor zone of nine domestic fowls were examined with the electron microscope after either distal vagal ganglionectomy or midcervical vagotomy. The bare baroreceptor endings and the central axon of the encapsulated baroreceptor endings degenerated within 5 to 15 days after ganglionectomy. This was interpreted as Wallerian degeneration and indicated that these two types of baroreceptor endings are derived from the vagus nerve. Similar degenerative changes were not seen after midcervical vagotomy, thus indicating that both types of endings are derived from nerve cell bodies located peripheral to the midcervical site of vagotomy, i.e. in the distal vagal ganglion. The accessory axon of the encapsulated endings and the presumptive aminergic/peptidergic endings of the baroreceptor zone were affected neither by distal vagal ganglionectomy nor by midcervical vagotomy, and therefore were considered not to be derived from the vagus nerve.