Role of angiotensin II receptors in development of neuropathic pain in rats

Objective To evaluate the role of angiotensin Ⅱ receptors in the development of neuropathic pain (NP) in rats.Methods Seventy-five male Sprague-Dawley rats,weighing 230-270 g,were randomly divided into 5 groups (n =15 each) using a random number table:sham operation group (group S),group NP,telmisartan (angiotensin Ⅱ receptor antagonist) 2 mg group (group T1),telmisartan 5 mg group (group T2),and telmisartan 10 mg group (group T3).NP was induced by chronic constrictive injury (CCI) in chloral hydrateanesthetized rats.The sciatic nerve was exposed and 4 loose ligatures were placed on the sciatic nerve at 1 mm intervals with 4-0 silk thread.In S group,the sciatic nerves were exposed but not ligated.Telmisartan 2,5 and 10 mg/kg were perfused via stomach once a day for 14 consecutive days in T1,T2 and T3 groups,respectively,while the equal volume of normal saline was given instead of telmisartan in S and NP groups.Mechanical and thermal pain thresholds were measured at 1 day before CCI and 3,7 and 14 days after CCI in each group.Results The mechanical and thermal pain thresholds were significantly decreased after CCI in NP,T1,T2 and T3 groups as compared with group S.The mechanical and thermal pain thresholds were significantly increased after CCI in T1,T2 and T3 groups as compared with group NP.The mechanical and thermal pain thresholds were significantly higher after CCI in T2 and T3 groups than in group T1.There was no significant difference in the mechanical and thermal pain thresholds between T2 and T3 groups.Conclusion Angiotensin Ⅱ receptors are involved in the development of NP in rats. Key words: Receptor, agiotensin,type 2;  Neuralgia