Sweat gland reinnervation by sudomotor regeneration after different types of lesions and graft repairs

Clinical and experimental investigations have shown that recovery of motor and sensory functions after a nerve lesion varies with the type of lesion and the repair technique. We report a study on regeneration of sudomotor axons to sweat glands (SGs) in the mouse paw following different sciatic nerve injury procedures: freezing, crushing, and sectioning. After sectioning, repair was by primary suture or by grafting with the resected section or with conduits of plastic or collagen. Successful regeneration was marked by the reappearance of SG reactivity to pilocarpine. After a freezing or crushing lesion, SGs activated by pilocarpine reappeared by 17 days postoperation and then increased progressively in number until the preoperative number of SGs were again active at 41 days. Cutting the nerve followed by primary repair resulted in a short delay and a significant deficiency in reinnervation. Results obtained with a graft of a segment of resected nerve were similar to primary repair after nerve section and better than when grafts of plastic or collagen tubes were used. This suggests that substances provided by the grafted nerve segment and the type of conduit provided play important roles in the regeneration of unmyelinated axons.