Effects of distal vagal ganglionectomy and midcervical vagotomy on the ultrastructure of axonal elements in the carotid body of the domestic fowl.

The carotid body of the domestic fowl was examined with the electron microscope after either removal of the distal vagal ganglion or midcervical vagotomy. Almost all the axonal elements of the carotid body degenerated within 5-15 days after ganglionectomy. The degeneration was considered to be due to separation of these axonal elements from their cell bodies (Wallerian degeneration) and indicated that nearly all the nerve supply of the carotid body of Gallus is derived from the vagus nerve. Degeneration of many axonal elements of the carotid body was also seen after midcervical vagotomy, but it took longer (19-41 days) to begin and had greatly increased 207-214 days after operation. It was interpreted as transganglionic degeneration, i.e. severance of the central processes of the distal vagal ganglion cells (by vagotomy) had induced slow degeneration in their peripheral processes (axonal elements in the carotid body). We conclude that the vast majority of the axonal elements in the carotid body of Gallus belong to nerve cell bodies in the distal vagal ganglion and are therefore afferent.