Functional reinnervation of sweat glands in the adult cat paw by inappropriate postganglionic axons

Abstract

Sympathetic postganglionic neurons were allowed to reinnervate the hairless skin of the cat paw pad, normally supplied by the tibial nerve, after suturing the central stump of the superficial peroneal nerve (supplying both hairy and hairless skin, eight animals) or of the sural nerve (supplying only hairy skin, seven animals) to the distal stump of the tibial nerve. Neural activation of sweat glands was studied by the starch iodine method and by recording the skin potential from the skin surface. Postganglionic neurons were activated by electrical stimulation of peripheral nerves or reflexly. There was good functional reinnervation of sweat glands by sudomotor neurons in all animals. The superficial peroneal nerve contains a few fibers that normally supply < 20% of the sweat glands on the foot pads. When this nerve regenerated into the innervation territory of the tibial nerve, sudomotor fibers consistently made functional contacts with sweat glands on the pads in all animals. These functional contacts were always weaker than those in the controls. Electrical stimulation of the sural nerve does not activate sweat glands in the paw pads of normal animals, indicating that this nerve does not contain postganglionic sudomotor axons. When the sural nerve regenerated into the foot pads, electrical stimulation activated some sweat glands in five of seven animals. We conclude that sudomotor neurons have a high capacity to functionally reinnervate sweat glands in the adult cat. There was also evidence that some noradrenergic vasoconstrictor neurons might take on ¢holinergic features' in the adult animal when they reinnervate sweat glands suggesting that the peripheral target can specify the phenotypic properties of postganglionic neurons in the adult animal.