Carotid body grafts induce chemosensitivity in muscle nerve fibers of the cat.

The ability of carotid body parenchymal cells to change the physiological properties of nerve fibers was tested in 8 cats by transplanting the carotid body to the tenuissimus muscle and reinnervating the organ with the muscle nerve. Ninety-five to 174 days after the transplant, electrophysiological recordings were obtained from the reinnervating tenuissimus nerves. Forty percent of the regenerating nerve fibers having spontaneous activity responded to muscle stretch, hypoxia, NaCN, ACh, nicotine and dopamine, apparently because of dual innervation of glomus cells and muscle spindles. Five of 6 transplants, examined electron microscopically, contained viable glomus cells innervated by axon terminals. Neither the normal tenuissimus nerve nor the same nerve regenerating into adipose tissue grafts or to one non-viable carotid body transplant showed chemosensory properties although these grafts contained numerous, small myelinated axons indicative of extensive nerve regeneration. It is concluded that carotid body cells are capable of inducing chemosensory properties in axons that, normally, subserve a mechanosensory function.