The effects of Botulinum toxin type A on mechanical allodynia and heat hyperalgesia induced by chronic constriction injury of the sciatic nerve in rats

Aim To investigate the antinociceptive effect of Botulinum toxin type A (BoNT-A) in a rat model of neuropathic pain.Methods BoNT-A (7.5,15 and 30 U·kg-1) or vehicle was administered toispilateral side plantar surface of the hindpaw of male Sprague-Dawley rats which were prepared by chronic constriction injury of sciatic nerve to produce neuropathic pain,and BoNT-A(15 and 30 U·kg-1) was administered into contralateral side in order to determine the drug-induced systemic effect.Mechanical allodynia and heat hyperalgesia were observed at pre-administration,1,3,5,7 and 14 days after drug administration,and were quantified by measuring mechanical withdrawal threshold(MWT)and thermal withdrawal latency(TWL).Results Administration of BoNT-A evidently increased the CCI rats MWT and TWL,on the contrary,administration of BoNT-A to contralateral side did not show any significant effect on the MWT and TWL.Conclusion Peripherally administration of BoNT-A remarkably suppressed mechanical allodynia and heat hyperalgesia of rats following neuropathic pain.