Abstract: Objective: To investigate the effects of ginsenoside-Rg₂ on mechanical allodynia, heat hyperalgeia, depressive state of rats with chronic sciatic nerve constriction injury. Methods: Fifty SD rats were randomly divided into 5 groups: blank control group (Normal, normal + saline),sham operation group (Sham, sham operation + saline),chronic constriction injury of the sciatic nerve group (CCI, CCI + saline),ginsenoside-Rg₂ low dose group (CCI + Rg₂ 5 mg/kg), and ginsenoside-Rg₂ high dose group (CCI + Rg₂ 10 mg/kg).After the CCI model was established,drug were injected into the abdominal cavity through the syringe once a day,for 14 consecutive days.The mechanical shrinkage foot reflex threshold (MWT) and thermal withdrawal latency(TWL) were determined at 1 d before the operation and at 1,3,5,7,10 and 14 d after the operation.Light-dark transition test, forced swimming test were determined at 1 d before the operation and at 14 d after the operation.Results: Compared with the sham group, the MWL and TWL of the CCI rats were decreased significantly (P＜0.01), time in the light compartment and number of transition were decreased (P＜0.01), the immobility time in FST was also prolonged significantly (P＜0.01). At 14 days after CCI operation, the MWL and TWL of the ginsenoside-Rg₂ groups were increased significantly (P＜0.01), time in the light compartment and number of transition were also shortened significantly (P＜0.01), the immobility time in FST was also shortened significantly (P＜0.01). Conclusion: Intraperitoneal injection of ginsenoside-Rg₂ can inhibit the mechanical and thermal pain sensitivity of CCI rats,and can relieve depressive state.

Key words: ginsenoside-Rg₂, chronic constriction injury of the sciatic nerve, mechanical allodynia, heat hyperalgeia, depressive state, rat