The demonstration of the cutaneous distribution of saphenous nerve C-fibres using a plasma extravasation technique in the normal rat and following nerve injury.

The distribution and density of innervation by saphenous nerve C-fibres has been demonstrated, in the intact rat and following nerve injury, using a dye-labelled plasma extravasation technique. In the intact rat the area demarcated by the dye corresponded to the area supplied by the whole nerve as determined by dissection and electrophysiologically. This technique is, therefore, valid for the mapping of the cutaneous distribution of nerves in the normal rat. Under other conditions, e.g. following nerve injury, it cannot be assumed that the distribution of C-fibres capable of evoking the dye response corresponds with that of other types of fibre. After either crush or section injury there was evidence, using the dye technique, of regeneration of saphenous C-fibres. Within 20 weeks of crush injury the extent of the area innervated by these fibres was similar to that in the intact animal, although the density of the reinnervation did not reach normal levels until some time later. There was then a reduction in the extent and particularly in the density of the C-fibre innervation. The possible significance of these observations is discussed. Regeneration after nerve section followed a longer time course and even one year after the injury neither the extent nor density of the reinnervation had reached normal levels.