Effects of Low Power Laser on Pain Response and Axonal Regeneration in Rat Models with Sciatic Nerve Crush Injury

This study purposed to examine the effect of low power laser on pain response and axonal regeneration. In order to prepare peripheral nerve injury models, we crushed the sciatic nerve of Sprague-Dawley rats and treated them with low power laser for 21 days. The rats were divided into 4 groups: normal group(n=10); control group(n=10) without any treatment after the induction of sciatic nerve crush injury; experimental group I(n=10) treated with low power laser(0.21$mJ/mm^2$) after the induction of sciatic nerve crush injury; and experimental group II(n=10) treated with low power laser(5.25$mJ/mm^2$) after the induction of sciatic nerve crush injury. We measured spontaneous pain behavior(paw withdrawal latency test) and mechanical allodynia(von Frey filament test) for evaluating pain behavioral response, and measured the sciatic function index for evaluating the functional recovery of peripheral nerve before the induction of sciatic nerve crush injury and on day 1, 7, 14 and 21 after the induction. After the experiment was completed, changes in the H & E stain and toluidine blue stain were examined histopathologically, and changes in MAG(myelin associated glycoprotein) and c-fos were examined immunohistologically. According to the results of this study, when low power laser was applied to rat models with sciatic nerve crush injury for 21 days and the results were examined through pain behavior evaluation and neurobehavioral, histopathological and immunohistological analyses, low power laser was found to affect pain response and axonal regeneration in both experimental group I and experimental group II. Moreover, the effect on pain response and axonal regeneration was more positive in experimental group I to which output 0.21$mJ/mm^2$ was applied than in experimental group II to which 5.25$mJ/mm^2$ was applied.