THE EFFECT OF 820 nm LASER IRRADIATION UPON CONDUCTION IN THE FROG (RANA TEMPORARIA) SCIATIC NERVE IN VITRO

Abstract

The current study was designed to investigate the effect of pulsed laser irradiation upon conduction latency in the frog sciatic nerve (Rana temporaria) in vitro. Dissected nerves (n = 40) were mounted in an experimental trough at room temperature and irradiated using a GaAlAs laser diode (820 nm, 5 kHz, 70 mW) with 2.38 J or 3.57 J (total delivered energy). In both laser groups there was an increase in negative peak latency following laser irradiation (0.032 ± 0.01 ms with 2.38 J; 0.018 ± 0.01 ms with 3.57 J); this increase was significant with 2.38 J (p < 0.01, ANOVA). An additional study (n=10) showed a significant increase in temperature of the dissected nerve following irradiation with 3.57 J (maximum increase = 0.46 ± 0.13°C: p < 0.01, ANOVA) compared to control group temperature (maximum increase = 0.12 ± 0.03°C). The results of the current study have shown that laser mediated changes in nerve conduction latency are demonstrable in vitro; thus previously reported in vivo findings may be attributable, at least in part, to a direct neurophysiological effect.