Failure of intact cutaneous mechanosensory axons to sprout functional collaterals in skin of adult rabbits

The original evidence that spared cutaneous nerves will sprout following partial denervation of skin was obtained in adult rabbits, in which nociceptive function returned to the deprived areas. Recently we reported that in the adult rat intact touch-sensitive (low-threshold mechanosensory) nerves fail to establish new functional endings in adjacent denervated skin. We have now investigated low-threshold mechanosensory nerves in the skin of adult rabbits after partially denervating the ear or hind limb; the sprouting of new functional endings into neighboring skin would be revealed by an expansion of the low-threshold receptive fields of cutaneous nerves (the areas of skin from which impulses could be evoked by stroking with a bristle). The results show that intact low-threshold mechanosensory nerves do not establish functional endings in adjacent denervated skin in the adult rabbit. These findings, together with those now reported for the cat as well as the rat, support the conclusion that possibly in all adult mammals intact low- and high-threshold nerves differ in their ability to respond to the presence of adjacent denervated skin by sprouting.