Effects of treadmill exercise on thermal hyperalgesia in CCI male rats

Introduction: Injury or disease of central or peripheral nervous system leads to neuropathic pain. Threshold of pain conducting neurons is reduced following neuronal lesion which causes neuropathic pain. Pain has two characteristic allodynia (painful response to non-noxious stimulus) and hyperalgesia (increased response to painful stimulus). There are several reports about reducing effect of exercise on neuropathic hyperalgesia. The aim of the present study was evaluation of pre lesion exercise on thermal hyperalgesia. Materials and methods: 58 male rats, weighing 200±20 (gr) randomly divided into 5 groups (Intact, Sham, chronic constriction injury=CCI, pre cci exercise, and post cci exercise). After anesthesia, CCI was done on the sciatica nerve. Rats run on treadmill with medium intensity for 3 weeks. Plantar test was used to detect hyperalgesia. TNF-a level in the cerebrospinal fluid was detected through western blot analysis test. Data were analyzed by one-way ANOVA followed by Tukey’s multiple comparison post hoc tests using the GraphPad Prism 5 Demo. P values less than 0.05 were considered significant. All data are expressed as mean ± SEM. Results: Threshold of thermal pain in CCI group significantly decreased compared to sham group, meanwhile Post cci exercise significantly increased it respect to CCI group. TNF-a level significantly increased in CCI group compared to sham group, however this cytokine reduced significantly in post cci exercise group compared to CCI group. Conclusion: Exercise following neuropathic pain attenuates thermal hyperalgesia due to at least decrease in proinflammatory cytokine TNF-a.