Effect on the action potential of the low power Nd: YAG laser as irradiated directly to the nerve.

The present paper reports our studies of changes in the compound action potential after Nd: YAG laser irradiation of the rat's sciatic nerve. The nerve on one side was exposed and irradiated by Nd: YAG laser directly. The temperature of the irradiated nerve was also measured. 1) Under 100 mW irradiation the compound action potential and the temperature of the surface of the sciatic nerve did not show a detectable change. 2) Under 300 mW irradiation the compound action potential showed an increase in amplitude, and shortening in latency. A negative after-potential appeared within 30 secs of irradiation. The temperature on the sciatic nerve rose by 3 degrees C during the irradiation. 3) Under 500 mW irradiation the compound action potential decreased gradually in amplitude and ultimately disappeared. The temperature on the sciatic nerve reached more than 47 degrees C.