Effects of high frequency electrical stimulation on nerve's conduction of action potentials

Effects of high frequency (HF) electrical stimulation on bullfrog's sciatic nerve were evaluated by analyzing the changes of maximum conducting velocities and amplitudes of compound action potentials (CAPs) recorded after a period (5s or 60s) of HF (5 kHz) electrical stimulation, during which nerve's conduction of action potentials were blocked. The results showed that both conducting velocity and amplitude of CAPs decreased significantly when the induced action potential was crossing the position where HF electrical current had been delivered. The influenced CAPs tended to recover to their normal shape, which usually needed a time of at least 60s. HF stimulation of longer duration (60s, in contrast to 5s duration) affected conducting velocity more than CAPs' amplitude. However, HF stimulation of higher intensity (1.7 mA, in contrast to 0.55 mA) presented relative large influences on CAPs' amplitude, which exhibited slower recovering speed than conducting velocity. The results implicated that high frequency electrical current would introduce damaging effects to nerves to be stimulated, and suggested that safety problem be taken into account and new safe current delivering methods be designed to avoid the side effects before using high frequency electrical current to block nerve conduction clinically.