Collateral sprouting of sensory axons in the hairy skin of the trunk: a morphological study in adult rats.

The capacity of sensory axons in the hairy skin of adult rats to extend branches into adjacent denervated skin has been studied by anterograde tracing with wheat germ agglutinin-horseradish peroxidase conjugate. In one series of experiments the Th10 intercostal nerve area was isolated and the distribution of sensory axons from the lateral cutaneous nerve was examined in control experiments and at various times after the denervation. In a second series of experiments, the entire Th10 was isolated, and the caudal extension of sensory axons from the Th10 spinal nerve was examined in control experiments and at various times after the denervation. The findings indicate that thin as well as coarse cutaneous sensory nerve axons can extend collateral sprouts within their 'own' dermatome as well as outside their normal segmental territory. Thus the dermatomal border does not seem to be a limit for collateral sprouting of coarse sensory nerve axons.