Low-intensity laser therapy improves tetanic contractions in mouse anterior tibialis muscle injected with Bothrops jararaca snake venom

Abstract Introduction Envenomation by Bothrops snakes can produce local pain, edema, hemorrhage and myonecrosis. However, standard antivenom therapy is generally ineffective in neutralizing these effects so that alternative methods of treatment have been investigated. In experimental animals, low-level laser therapy (LLLT) attenuates the local effects of Bothrops venoms, but the benefits of LLLT on muscle function after envenomation are unclear. In this study, we examined the influence of LLLT on the contractile activity of mouse skeletal muscle injected with venom from Bothrops jararaca, the principal cause of snakebite in southeastern Brazil. Methods Twenty-seven male mice were used. Mice were injected with venom (40 μg in 50 μl) in the right anterior tibialis muscle, after which the muscle tendon was exposed, connected to an isometric transducer and subjected to a resting tension of 1 g. A bipolar electrode was attached to the tibial nerve for electrical stimulation. The mice were randomly allocated to five groups: A – Control (n = 3), B – Venom 3 h (n = 6), C – Venom 9 h (n = 6), D – Venom + Laser 3 h (n = 6), E – Venom + Laser 9 h (n = 6). Results The two groups that received LLLT post-venom showed improved muscle contraction and contracture in relation to muscle treated with venom alone. Conclusion These results indicate that LLLT can improve muscle function after damage induced by B. jararaca venom.

摘要 引言
矛头蝮属（Bothrops）蛇类咬伤可引发局部疼痛、水肿、出血及肌坏死。然而，标准抗蛇毒血清疗法（antivenom therapy）通常无法中和此类毒性反应，因此学界已探索多种替代治疗方案。在实验动物中，低强度激光疗法（low-level laser therapy, LLLT）可缓解矛头蝮蛇毒的局部毒性作用，但低强度激光疗法对咬伤后肌肉功能的获益效果尚不明确。本研究针对巴西东南部蛇咬伤的主要致病原——巴西矛头蝮（Bothrops jararaca）蛇毒注射至小鼠骨骼肌后的情况，考察了低强度激光疗法对骨骼肌收缩功能的影响。

方法
本研究共使用27只雄性小鼠。将40 μg（溶于50 μl溶媒中）的巴西矛头蝮蛇毒注射至小鼠右侧胫骨前肌（anterior tibialis muscle），随后暴露肌肉肌腱，将其连接至等长换能器（isometric transducer）并施加1 g的静息张力。于胫神经（tibial nerve）处附着双极电极（bipolar electrode）以实施电刺激。将小鼠随机分为5组：A组——对照组（n=3），B组——蛇毒注射后3 h组（n=6），C组——蛇毒注射后9 h组（n=6），D组——蛇毒+低强度激光疗法3 h组（n=6），E组——蛇毒+低强度激光疗法9 h组（n=6）。

结果
相较于仅接受蛇毒处理的肌肉，两个在蛇毒注射后接受低强度激光疗法的实验组，其肌肉收缩与挛缩情况均得到改善。

结论
本研究结果表明，低强度激光疗法可改善巴西矛头蝮蛇毒诱导的肌肉损伤后的肌肉功能。