Nerve growth factor and neurotrophin-3 affect functional recovery following peripheral nerve injury differently

Many studies have investigated the roles of neurotrophic factors in nerve regeneration by examining either anatomical recovery (regenerated axon count) or functional recovery as measured by sensory and motor behavior. This longitudinal study examined the effects of NGF and NT3 on functional and anatomical recovery following transection of tbc sciatic nerve.

Alzet osmotic pumps were implanted to deliver a continuous supply of NGF, NT3 or buffer solution to the stumps of the transected sciatic nerve for the first 28 days following implantation. Rats were tested weekly to determine the extent of recovery of motor (footprint gait analysis) or nociceptive (warm water withdrawal), and mechanoreceptive (skin pinch) function.

Neither NT3-, nor NGF-treatment significantly enhanced motor recovery as examined by gait analysis. At the end of 12 weeks of behavioral testing, there was no difference in motor recovery. In addition, the recovery of withdrawal response to warm water stimulus was delayed in NGF treated animals. After twelve weeks, nerves were removed for anatomical analysis. Regenerated sciatic nerves from NT3 treated animals had slightly more axons than control- or NGF-treated animals.

This work shows that there were no long-lasting improvements of anatomical or functional recovery in NGF- or NT3-treated animals 12 weeks following sciatic nerve transection.