The effects of chronic neonatal denervation and a crush lesion on the regenerative capacity of sensory nerve fibers were studied in rats. After 50 weeks of postnatal denervation, the amplitudes of compound action potentials (CAPs) of Aab-, Ad- and C-fibers were reduced to 14.3%, 18.2% and 37.4%, respectively (P < 0.005). Similarly, after a crush lesion, the amplitudes of CAPs were reduced to 34.3%, 38.8% and 51.6%, respectively (P < 0.005). The conduction velocities, thresholds and maximum strength of stimulation of nerve fibers were normal. Neurogenic plasma extravasation into the skin due to antidromic nerve stimulation was reduced to 27.5% and 30.3% after postnatal denervation and the crush lesion, respectively (P < 0.005). These results indicate that neonatal sensory nerve injury induces permanent neurodegeneration of peripheral sensory nerve fibers as demonstrated by the inhibition of afferent conduction property and efferent neurogenic plasma extravasation response.

The effects of chronic neonatal denervation and a crush lesion on the regenerative capacity of sensory nerve fibers were studied in rats. After 50 weeks of postnatal denervation, the amplitudes of compound action potentials (CAPs) of Aab-, Ad- and C-fibers were reduced to 14.3%, 18.2% and 37.4%, respectively (P < 0.005). Similarly, after a crush lesion, the amplitudes of CAPs were reduced to 34.3%, 38.8% and 51.6%, respectively (P < 0.005). The conduction velocities, thresholds and maximum strength of stimulation of nerve fibers were normal. Neurogenic plasma extravasation into the skin due to antidromic nerve stimulation was reduced to 27.5% and 30.3% after postnatal denervation and the crush lesion, respectively (P < 0.005). These results indicate that neonatal sensory nerve injury induces permanent neurodegeneration of peripheral sensory nerve fibers as demonstrated by the inhibition of afferent conduction property and efferent neurogenic plasma extravasation response.