Influence of Shaoyao Gancao Decoction Effective Ingredients on Mechanica Lallodynia and Heat Hyperalgesia Induced by Chronic Constriction Injury of the Sciatic Nerve in Rats

Objective:To observe the effect and the preemptive analgesia of the extracts of Shaoyao Gancao Decoction(SGM)on mechanical allodynia and heat hyperalgesia induced by chronic constriction injury(CCI)of the sciatic nerve in rats.Methods:Rats were divided into nine groups.Mechanical allodynia and heat hyperalgesia were evaluated by mechanical withdrawal threshold(MWT)and thermalwithdrawal latency(TWL)respectively.In a preemptive treatment groups(BN and BS groups),normal saline(2μL)and SGM(120mg/kg)were orally administered on 7th day before surgery;postoperative treatment groups(AN and AS groups)were administered on 7th day after surgery,pre-postoperative treatment groups(BAN and BAS groups)were administered on 7th day before surgery to 7th day after surgery.All groups were administered twice a day.The TWL and MWT were measured before surgery and on 1st,3rd and 7th day after surgery.Results:PWL and PWT of rats with CCI had a significantly decrease from the first day after surgery to the end of this study(P0.01).MWT and TWL in BS and AS and BAS groups evidently increased(P0.01).MWT and TWL in BS group evidently increased on 1st day(P0.01),but the result was contrary on 7 days after surgery in comparison to AS group(P0.01).Compared to AS group,MWT and TWL in BAS group evidently increased on 1st day(P0.01),but there was no difference on 7 days after surgery.Conclusion: CCI group formed steady mechanical allodynia and heat hyperalgeia from the first day after surgery to the end of this study.SGM orally administered evidently increased MWT and TWL of the CCI rats.Preemptive treatment with SGM remarkably brought the preemptive analgesia and the effects would continue for several days.Compared to AS group,BAS group affected faster for the analgesia.