Evaluation of myotoxicity and neurotoxicity ( neuromuscular junction focus ) after bupivacaine application followed by laser therapy

Abstract

Local anesthetics are used for pre and postoperative pain and chronic pain. Their two main limitations are inflammation, myotoxicity and neurotoxicity. Bupivacaine is considered among local anesthetics, the most myotoxic. Moreover, laser therapy of low intensity (LLLT) has been prescribed as a complementary therapy that has anti - inflammatory action after tissue injury, it promotes muscle satellite cell proliferation, angiogenesis and expression of growth factors, acting on muscle regeneration. The aim of this project is to investigate the effects of LLLT after bupivacaine injection. 36 adult male Wistar rats will receive bupivacaine 0.5 % application on right antimere, and sodium chloride 0.9 % on left antimere (control). After 24 hours, the animals will be divided into two equal groups: only one group will receive one daily application of LLLT on both antimeres for 5 consecutive days. After this period, the animals will be euthanized, the superficial portion of sternomastoid muscle and the associated nerve will be removed and analyzed by the following methods: a) Levels of inflammation : by Western Blot of TNFalpha b) Myotoxicity: quantification of Creatine Kinase (CK) and Lactate Dehydrogenase (LDH), morphological and ultrastructural analysis of muscle fibers of sternomastoid muscle superficial portion c) Neurotoxicity : morphological, ultrastructural and morphometric analysis of the sternomastoid nerve as well as of the neuromuscular junctions associated ; Analysis of the acetylcholine receptors (nAChRs) distribution by confocal microscopy and Western Blot. (AU)