Effect of ethosucximide on the reduction of neuropathic pain due to chronic constriction of the sciatic nerve in rats

Neuropathic pain is caused by a lesion or disease of the peripheral or central nervous system. Since, treatment of neuropathic pains remains a challenge. The purpose of the present study was to examine the effect of ethosuximide, an anti-epileptic and relatively selective T-type calcium blocker, on the behavioral responses following chronic constriction pain (CCI) induced in rats. Experiments were performed on six groups (n=8) of male Sprague-Dawley rats (230-280g).The study consisted of a control and an induced chronic constriction of the sciatic nerve (CCI) groups, 3 groups receiving ethosuximide with concentrations 100, 200, 300 mg/kg,and one group which received normal saline. The cold-and mechano-allodynia and thermal hyperalgesia were measured prior to surgery (the day 0) and 3, 5, 7, 14 and 21 days postsurgery. Statistical analysis of repeated ANOVA was used to compare the results of behavioral tests by means of SPSS software (V:16) It was found that the CCI group significantly produced mechanical and cold allodynia and a hypersensitivity to noxious stimulations. Ethosuximide significantly decreased cold and mechano-allodynia and thermal hyperalgesia. The results suggested that the CCI model significantly influences behavioral responses to both the thermal and mechanical stimulations. Besides, systemic administration of ethosuximide significantly decreases behavioral responses of neuropathic pain induces through CCI. Thus, ethosuximide can be taken as a new potential therapeutic drug used against neuropathic pain