Abstract：
OBJECTIVE: Pharmacologic pain treatments lack specific targeting and often produce unwanted side effects (eg, addiction, additional hyperalgesia). We previously established that the direct application of laser irradiation (direct photobiomodulation [PBM]) of the sural nerve reduces thermal hypersensitivity in a rodent model of chronic pain, but not mechanical hypersensitivity. These observations were consistent with a selective reduction in the small-diameter fiber contribution to electrophysiologically measured evoked response after direct PBM of a sensory nerve (saphenous). However, to our knowledge, direct application of laser irradiation has never been performed in an animal model of acute nociceptive pain or on a mixed nerve in which sensory and motor outcomes can be observed.
METHODS: In this study, we describe the effects of direct application of laser irradiation (808 nm, 60 mW, 4 minutes) on a mixed nerve (sciatic nerve) in an acute nociceptive pain model (intradermal capsaicin injection) in rats over the course of two weeks. To investigate whether laser irradiation of a mixed nerve alters motor function, in separate experiments, we applied laser irradiation to the sciatic nerve (using the same parameters as in the chronic pain experiments), and force generation of the gastrocnemius was measured.
RESULTS: Capsaicin-induced hypersensitivities to mechanical (pin prick) and thermal (Hargreaves) noxious stimuli, associated with Aδ- and C-fibers, showed a maximal reduction of 70% and 56.2%, respectively, by direct PBM, when compared with a control group (vehicle injection, no PBM) on the same day. This reduction was determined to be significant using a mixed-design analysis of variance with a p value < 0.05. Force generation remained unchanged for up to 120 minutes after laser irradiation. In summary, direct PBM selectively inhibits C- and Aδ-fiber transmission while leaving Aɑ-, Aβ-, and motor-fiber activity intact.
CONCLUSIONS: These results, in conjunction with our previous analyses of laser irradiation effects on the sural nerve in a chronic spared nerve injury pain model, suggest that direct PBM is a promising candidate for treating pain induced by small-diameter fiber activity.
METHODS: In this study, we describe the effects of direct application of laser irradiation (808 nm, 60 mW, 4 minutes) on a mixed nerve (sciatic nerve) in an acute nociceptive pain model (intradermal capsaicin injection) in rats over the course of two weeks. To investigate whether laser irradiation of a mixed nerve alters motor function, in separate experiments, we applied laser irradiation to the sciatic nerve (using the same parameters as in the chronic pain experiments), and force generation of the gastrocnemius was measured.
RESULTS: Capsaicin-induced hypersensitivities to mechanical (pin prick) and thermal (Hargreaves) noxious stimuli, associated with Aδ- and C-fibers, showed a maximal reduction of 70% and 56.2%, respectively, by direct PBM, when compared with a control group (vehicle injection, no PBM) on the same day. This reduction was determined to be significant using a mixed-design analysis of variance with a p value < 0.05. Force generation remained unchanged for up to 120 minutes after laser irradiation. In summary, direct PBM selectively inhibits C- and Aδ-fiber transmission while leaving Aɑ-, Aβ-, and motor-fiber activity intact.
CONCLUSIONS: These results, in conjunction with our previous analyses of laser irradiation effects on the sural nerve in a chronic spared nerve injury pain model, suggest that direct PBM is a promising candidate for treating pain induced by small-diameter fiber activity.
摘要：
目的：药物疼痛治疗缺乏特异性靶向性，常产生不良副作用（如，上瘾,额外的痛觉过敏)。我们先前确定，在慢性疼痛的啮齿动物模型中，腓肠神经的直接激光照射（直接光生物调节[PBM]）可降低热超敏反应，但不是机械性过敏.这些观察结果与感觉神经（隐神经）的直接PBM后，小直径纤维对电生理测量的诱发反应的贡献的选择性减少是一致的。然而,根据我们的知识，在急性伤害性疼痛的动物模型或可以观察到感觉和运动结果的混合神经上，从未直接应用激光照射。
方法：在本研究中，我们描述了直接应用激光照射(808nm，60mW,4分钟）在大鼠急性伤害性疼痛模型（皮内辣椒素注射）中的混合神经（坐骨神经）上持续两周。为了研究激光照射混合神经是否改变运动功能，在单独的实验中，我们对坐骨神经进行激光照射（使用与慢性疼痛实验相同的参数），测量腓肠肌的力产生。
结果：辣椒素诱导的对机械（针刺）和热（哈格里夫斯）有害刺激的超敏反应，与Aδ和C纤维相关，显示最大减少70%和56.2%，分别,通过直接PBM，当与对照组(载体注射，没有PBM)在同一天。使用p值<0.05的混合设计方差分析确定该减少是显著的。在激光照射后的120分钟内，力的产生保持不变。总之,直接PBM选择性地抑制C-和Aδ-光纤传输，同时离开Aα-，Aβ-,和运动纤维活动完好无损。
结论：这些结果，结合我们先前在慢性备用神经损伤疼痛模型中对激光照射对腓肠神经的影响的分析，表明直接PBM是治疗小直径纤维活性引起的疼痛的有希望的候选药物。
方法：在本研究中，我们描述了直接应用激光照射(808nm，60mW,4分钟）在大鼠急性伤害性疼痛模型（皮内辣椒素注射）中的混合神经（坐骨神经）上持续两周。为了研究激光照射混合神经是否改变运动功能，在单独的实验中，我们对坐骨神经进行激光照射（使用与慢性疼痛实验相同的参数），测量腓肠肌的力产生。
结果：辣椒素诱导的对机械（针刺）和热（哈格里夫斯）有害刺激的超敏反应，与Aδ和C纤维相关，显示最大减少70%和56.2%，分别,通过直接PBM，当与对照组(载体注射，没有PBM)在同一天。使用p值<0.05的混合设计方差分析确定该减少是显著的。在激光照射后的120分钟内，力的产生保持不变。总之,直接PBM选择性地抑制C-和Aδ-光纤传输，同时离开Aα-，Aβ-,和运动纤维活动完好无损。
结论：这些结果，结合我们先前在慢性备用神经损伤疼痛模型中对激光照射对腓肠神经的影响的分析，表明直接PBM是治疗小直径纤维活性引起的疼痛的有希望的候选药物。
