Innervation of scar tissue in the skin of the rat.

In this study the reinnervation of scar tissue was investigated histochemically to demonstrate catecholamine fluorescence and nonspecific cholinesterase activity. The scarring was produced by healing and contraction of a defect in the dorsal skin of the rat. The first regenerating nerves showing nonspecific cholinesterase activity were observed in the scar four weeks postoperatively. Throughout the investigation period, that is up to twenty weeks after the operation, only free regenerated nerves were found in the scar; no encapsulated nerve endings were observed. No fluorescent adrenergic nerves were found in the dense collagenous part of the scar tissue. Regenerated fluorescent nerves were, however, observed in the loose regenerated connective tissue under the scar. Most of these nerves followed the course of blood vessels. In the present work a vigorous contraction of the scar tissue was noted and a poor innervation of the scar tissue with free nerves was observed. The role of these regenerated nerve endings in sensory discrimination, and the importance of different transmitters acting in the sensory system are discussed.