Cutaneous nerve regeneration in the rat: reinnervation of the denervated skin by regenerative but not by collateral sprouting.

The functional regeneration of cutaneous chemosensitive nerves responsible for the initiation of the neurogenic inflammatory response has been studied in rat hind paw skin. The qualitative and quantitative estimation of plasma extravasation induced by mustard oil, a skin irritant which induces an inflammatory response by the neurogenic route, proved to be a reliable and objective method for studying the regeneration of these cutaneous nerves. The results indicate a complete functional reinnervation by chemosensitive sensory nerves of the skin area previously denervated by crushing the corresponding peripheral nerve. It is concluded that these particular unmyelinated sensory nerves regenerate by means of regenerative sprouting but apparently lack the ability for collateral sprouting. The significance of the present findings in relation to the mechanisms of cutaneous nerve regeneration is discussed.