Ascending collaterals of cutaneous neurons in the fasciculus gracilis of the cat during peripheral nerve regeneration.

Dorsal column projection patterns and conduction velocities of regenerating myelinated sensory neurons were studied at intervals between 1 and 12 months after transection of the sural nerve. The neurons had significantly decreased conduction velocities, both in the fasciculus gracilis and in the periphery. Although dorsal root reflexes were temporarily abolished, there was no evidence of gross rearrangement of the neurons' ascending collaterals in the dorsal columns in response to transection of their peripheral processes or as a result of reestablishment of functional peripheral connections. These findings support the hypothesis that when a regenerating cutaneous sensory neuron reforms functional peripheral connections in tissue it originally innervated, its receptor properties are similar to those it had before the nerve was lesioned.