We examined the effects of Ar+ laser (457, 488, 514nm; 25, 50, 100mW) irradiation on the law of polar excitation using frog sciatic nerve. The law of polar excitation is well known, as both cathode-make-excitation (CE) and anode-break-excitation (AE) are elicited when nerves are extracellularly stimulated with a longer pulse at suprathreshold intensity. Compound action potentials (CAP) were suppressed by the laser irradiation. Furthermore, the existence of irradiation conditions (power, wavelength) for greatly suppressing AE in comparison with CE was demonstrated. Ar+ laser irradiation did not suppress conduction but did suppress generation of CAP. It seems possible that only AE generation is suppressed by local irradiation using the Ar+ laser. Since the contribution of Hyperpolarization-activated channels (Ih) to AE generation had been demonstrated and Ih expression is associated with intractable epilepsy, the present results suggest a novel LLLT for intractable epilepsy as an alternative to Ih blockers.
