Continuous Stimulation of Transected Distal Nerves Fails to Prolong Action Potential Propagation
Wallerian degeneration of the distal portion of a cut nerve is considered irreversible. A possible reason for degeneration is lack of axon stimulation in the distal, cut nerves. We hypothesized greater rates of stimulation of distal nerve stumps would prolong time to action potential propagation failure, and uncut nerves would not be damaged by implanted nerve stimulators. We also hypothesized that action potentials measured from the body of the sciatic nerve would show similar response as motor-evoked potentials measured in the muscles innervated by branches of the sciatic nerve. We implanted a nerve stimulator onto distal cut sciatic nerves of rats and recorded motor-evoked potentials. Three groups were stimulated at 1 Hz (once per second), 0.1 Hz (once per 10 seconds), and 0.01 Hz (once per 100 seconds) respectively. Motor-evoked potentials progressively declined after nerve transection, failing faster at 1 Hz (26.8 hours +/- 108 minutes) and 0.1 Hz (22 hours +/- 66 minutes) compared with stimulation at 0.01 Hz (36.75 hours +/- 83 minutes). Intact axons were not damaged by implanted nerve stimulators. Action potentials recorded directly from nerves were equivalent to motor- evoked potentials. Failure of motor-evoked potential transmission in a transected nerve is accelerated by a greater rate of continuous stimulation of the distal stump.