Acute electrophysiologic effect of pulsed gallium-arsenide low energy laser irradiation on configuration of compound nerve action potential and nerve excitability

Abstract

Background and objectives: We evaluated the acute electrophysiologic effects of low-energy pulsed laser irradiation, measured by extracellular recording technique on compound action potential configuration and nerve excitability in the isolated frog sciatic nerve

Study design/materials and methods: A pulsed gallium-arsenide (GaAs) laser (wavelength, 904 nm; pulse duration, 220 nanoseconds; peak power per pulse, 27 W; spot size, 0.28 cm(2); total applied energy density, 0.005-2.5 J/cm(2)) was used for the experiment. Sixty isolated nerves were divided into six groups (n = 10), each of which received a different repetition frequency. In each group, action potentials were recorded, before laser irradiation, which served as the control data. The extracellular action potentials were recorded for each combination of 1, 3, 5, 7, 10, 13, and 15 minutes of irradiation time and 4, 8, 16, 32, 64, 128 repetition frequency by using a BIOPAC MP 100 Acquisition System Version 3.5.7 (Santa Barbara USA). Action potential latency, duration of depolarization and repolarization, and the stimulating voltage were measured. Statistical evaluation was performed using linear correlation analysis by SPSS 9.05.

Results: Although there was no correlation between applied energy density and action potential latency, the duration of depolarization and repolarization phases (P > 0.05), there was a weak correlation between applied energy density and stimulating voltage.

Conclusions: The study showed that low-energy GaAs irradiation at 42 different energy density between 0.005 and 2.5 J/cm(2) generates no effect on action potential configuration and nerve excitability.