No effect of GA-AS (904 nm) laser irradiation on the intact skin of the injured rat sciatic nerve

Abstract

We evaluated the electrophysiological and histopathological effects of low-energy gallium arsenide (904 nm) laser irradiation on the intact skin injured rat sciatic nerve. Twenty-four male Wistar rats were divided into three groups ( n=8 each). At the level of proximal third of the femur the sciatic nerve was crushed bilaterally with an aneurysm clip (Aesculap FE 751, Tuttingen, Germany) for half a second. A gallium arsenide laser (wavelength 904 nm, pulse duration 220 ns, peak power per pulse 27 W, spot size 0.28 cm2, pulse repetition rate 16, 128 and 1000 Hz; total applied energy density 0.31, 2.48 and 19 J/cm2) was applied to the right sciatic nerve for 15 min daily at the same time on 7 consecutive days. The same procedure was performed on the left sciatic nerve of same animal, but without radiation emission, and this was accepted as control. Compound muscle action potentials were recorded from right and left sides in all three groups before surgery, just at the end of injury, at the 24th hour and on the 14th and 21st days of injury in all rats using a BIOPAC MP 100 Acquisition System Version 3.5.7 (Santa Barbara, USA). BIOPAC Acknowledge Analysis Software (ACK 100 W) was used to measure CMAP amplitude, area, proximal and distal latency, total duration and conduction velocity. Twenty-one days after injury, the rats were sacrificed. The sciatic nerves of the operated parts were harvested from the right and left sides. Histopathological evaluation was performed by light microscopy. Statistical evaluation was done using analysis of variance for two factors (right and left sides) repeated-measures (CMAP variables within groups) and the Tukey-Kramer Honestly Significant Difference test (CMAP variables between laser groups). The significance was set at p < 0.05. No statistically significant difference (p > 0.05) was found regarding the amplitude, area, duration and conduction velocity of CMAP for each applied dose (0.31, 2.48 and 19 J/cm2) on the irradiated (right) side and the control (left) side, or between irradiated groups. Twenty-one days after injury there were no qualitative differences in the morphological pattern of the regenerated nerve fibres in either irradiated (0.31, 2.48 and 19 J/cm2) or control nerves when evaluated by light microscopy. This study showed that low-energy GaAs irradiation did not have any effect on the injured rat sciatic nerve.

Influência da irradiação do laser na regeneração nervosa em diferentes locais de tratamento

“…17 Rochkind et al 17 , Khullar et al 6 and Gigo-Benato et al 13 studied the influence of low-intensity laser, irradiated along the nerve path, on peripheral nerve injuries and found positive effects for nerve regeneration. In studying low-intensity laser irradiation in the spinal cord, in the region corresponding to the injured nerve, Rochkind et al 4 reported an improvement in the recovery of the corresponding injured peripheral nerve, while Bagis et al, 5 in conducting a study with the crushing of rat sciatic nerves, used the same irradiation site with the GaAs laser and declared that it is inefficient in the repair of nerve lesions. In the study by Bagis et al 5 two factors might have influenced the fact that no improvement was found in nerve regeneration, the probably short application time of the laser in seven consecutive days, and the pulsed emission of the low-intensity laser chosen for the study.…”

“…In studying low-intensity laser irradiation in the spinal cord, in the region corresponding to the injured nerve, Rochkind et al 4 reported an improvement in the recovery of the corresponding injured peripheral nerve, while Bagis et al, 5 in conducting a study with the crushing of rat sciatic nerves, used the same irradiation site with the GaAs laser and declared that it is inefficient in the repair of nerve lesions. In the study by Bagis et al 5 two factors might have influenced the fact that no improvement was found in nerve regeneration, the probably short application time of the laser in seven consecutive days, and the pulsed emission of the low-intensity laser chosen for the study. Anders et al 3 proposed that the effect of low-intensity laser beams on peripheral nerve recovery can be increased if both the nerve path and the corresponding segment of the spinal cord are irradiated.…”

Stimulation Effect of Low Level Laser Therapy on Sciatic Nerve Regeneration in Rat

“…19 Since then, many other studies on the effect of different wavelengths of LLLT on slight and mild peripheral nerve lesion have been reported. 14,[20][21][22][23][24][25] In addition, combination of laser therapy with entubulation to reconstruct massive segmental loss of peripheral nerve has shown very promising outcomes. [26][27][28] Most reports on the effect of LLLT on PNS injury are in cases of axonotmesis.…”

Análise da dose do laser de baixa potência em equipamentos nacionais

“…It may be presumed that there were differences in the obtained results because the samples were not identical. However, Bagis et al 25 also studied the effect of laser energy on the nerve tissue of rats and did not obtain significant results, using ΔEs between 0.31 and 19 J/cm 2 and energy levels between 0.09 and 5.3 J. To reach these final energy values, the authors used a prolonged application time (900s) for their equipment with a low Pm (0.02-0.08 mW).…”