Reinnervation of Free Skin Autografts in the Rat

The objective of the present work is to study, using histochemical techniques, the regeneration of cholinesterase-positive and adrenergic nerves in free skin grafts which were applied to the dorsal muscle fascia of the rat. The first signs of regeneration of single free nerves which showed nonspecific cholinesterase (nsChE) activity were observed four weeks postoperatively in the dermis of the skin graft. The first nerves occurring in the vicinity of hair follicles were observed eight weeks after grafting. The regeneration progressed steadily and, twelve weeks postoperatively, nerve trunks, nerve plexi and nerves following blood vessels were observed. The first signs of regeneration of the fluorescent adrenergic nerves following blood vessels in the regenerated connective tissue under the graft were observed twelve weeks postoperatively, but the regeneration of adrenergic nerves was still incomplete even after 20 weeks and most blood vessels remained without nerves. The grafted skin itself remained without adrenergic nerves. In the present study the ingrowth of nerves was observed to occur randomly, although the reinnervation of some target structures such as hair follicles and blood vessels was apparent. This can probably be explained on the basis of chemotactical factors, which work at very short distances from the target organ. Only free nonspecific cholinesterase-positive nerves or nerves in association with hair follicles were observed in the grafts in the present study. The recovery sensation in the skin grafts, as demonstrated in clinical works, is discussed on the basis of regenerated free nerve endings. A suggestion is made on the role of different transmitters in sensory discrimination.