Low intensity laser therapy effectiveness in controlling neuropathic pain in mice

ABSTRACT Low-level laser therapy (LLLT) has been widely discussed in the literature as an alternative form of treatment for several types of pain, especially neuropathic pain. This kind of therapy stands out for not being invasive, rarely causing side effects and being cost effective. However, for its effectiveness, it is necessary more detailed parameters, which are still very discrepant in the literature. Thus, this study aims to investigate the effect of LLLT, in the infrared range, with 30J/cm² fluency, on the control of neuropathic pain in animal models. A total of 24 male Swiss albino mice, weighing 25.30 grams, were divided into three groups: the Control Group (CG), the Laser Group (L30G) and the Sham Group (SG). The induction of neuropathy was held through the model of chronic constriction of the sciatic nerve (CCI), and the LLLT treatment was conducted as follows: The CG was treated with 0 J/cm2 fluency, whereas the L30G was treated with 30 J/cm2 fluency, and the SG with simulation of surgery without intervention. The irradiations were performed 3 times a week, for 90 days, at the nerve’s point of compression, using the contact technique. For the evaluation, the Hot Plate Test was used for thermal hyperalgesia, and the Randall-Selitto test was used for mechanical hyperalgesia. In the CG’s results, we observed no significant improvement in the days after surgery in any of the tests conducted, and, in the GL30, a significant improvement in both tests was observed: from the 30th day of treatment for the Hot Plate Test, and from the 45th for the Randall-Selitto Test, in which the mice showed total restoration of sensitivity. We thus conclude that the use of LLLT with 30 J/cm2 fluency in the treatment of neuropathic pain in animal models is effective.摘要 低强度激光疗法（Low-level laser therapy, LLLT）作为多种疼痛（尤其是神经病理性疼痛）的替代治疗手段，已在学界被广泛探讨。该疗法以非侵入性、极少引发不良反应及成本效益良好的优势脱颖而出。然而，其临床有效性的相关参数仍存在较大分歧，且有待进一步细化。为此，本研究旨在探究红外波段、辐照通量为30 J/cm²的低强度激光疗法对动物模型中神经病理性疼痛的调控效果。本研究共纳入24只体重为25.30 g的雄性瑞士白化小鼠，随机分为三组：对照组（Control Group, CG）、激光组（Laser Group, L30G）与假手术组（Sham Group, SG）。采用慢性坐骨神经压迫损伤（Chronic Constriction Injury, CCI）模型诱导神经病变。激光干预方案如下：对照组给予0 J/cm²辐照通量处理，激光组给予30 J/cm²辐照通量处理，假手术组仅实施模拟手术而无实际激光干预。照射采用接触式技术，于神经受压位点进行，每周3次，持续90天。本研究采用热板试验（Hot Plate Test）评估热痛觉过敏（thermal hyperalgesia），采用兰德尔-塞利托试验（Randall-Selitto test）评估机械痛觉过敏（mechanical hyperalgesia）。结果显示，对照组在术后各时间点的两项试验中均未出现显著改善；而激光组则在两项试验中均呈现显著改善：热板试验自治疗第30天起出现改善，兰德尔-塞利托试验自第45天起出现改善，此时小鼠的痛觉敏感性已完全恢复。综上，本研究表明，采用辐照通量为30 J/cm²的低强度激光疗法，对动物模型中的神经病理性疼痛具有明确的治疗效果。