Effects of botulinum toxin type A on behavior and Fos protein expression in CCI rat models

Objective To evaluate the analgesic effect of botulinum toxin type A(BoNT-A) against the chronic constriction injury(CCI) of the sciatic nerve and on the expression of Fos protein in rats.Methods BoNT-A or vehicle was administered to the ispilateral side plantar surface of the hindpaw in male SD rats,which were prepared by CCI of the sciatic nerve to induce neuropathic pain.Mechanical and therml allodynia were observed before and on the 1st,3rd,5th,7th and 14th day after drug administration.The expression of Fos protein in the spinal dorsal horn was assessed by immunohistochemical method on the 5th day after drug administration.Results The rats of CCI group formed steady mechanical and heat hyperaglsia from the 7th day after operation to the end of this study.Administration of BoNT-A evidently increased paw mechanical withdrawal threshold(MWT)and thermal withdrawal latency(TWL) in the CCI rats.The expression of Fos protein was increased in CCI rats and BoNT-A 30 U/kg remarkably reduced the expression of Fos protein in the spinal cord.Conclusion Peripherally administration of BoNT-A reduces the expression of Fos protein in the spinal cord and remarkably suppresses mechanical allodynia and heat hyperalgesia of rats with neuropathic pain.