Objective To observe the effect of electroacupuncture(EA) on expression of neuronal nitric oxide synthase(nNOS) protein and mRNA in the spinal cord in rats with chronic constrictive injury(CCI) of the sciatic nerve so as to explore its mechanisms underlying pain relief.Methods Thirty-six male SD rats were randomly divided into sham operation(control) group(n=12)

CCI model group(n=12) and EA group(n=12).EA was applied to bilateral "Weizhong"(BL 40) and "Huantiao"(GB 30) on the injured side for 30 min

once a day for 7 days(from the 11th day on after CCI).The mechanical and thermal pain thresholds were measured before and after CCI.Spinal nNOS protein and mRNA expression levels were detected by Western blot and reverse transcription-polymerase chain reaction(RT-PCR)

respectively.Results In comparison with the control group

both mechanical and thermal pain thresholds were significantly lower in the model group(P<0.01).Compared with the model group

the two types of pain threshold were increased considerably on the 16th day in the EA group(P<0.01).In comparison with the control group

the spinal nNOS protein and mRNA expression levels were increased significantly in the model group(P<0.05

P<0.01).In comparison with the model group

both nNOS protein and mRNA expression levels in the spinal cord were down-regulated obviously in the EA group(P<0.05).Conclusion Electroacupuncture can alleviate neuropathic pain in CCI rats

which is closely related to its effect in down-regulating the expression of nNOS protein and mRNA in the spinal cord.