Objective: To study the effect of electroacupuncture(EA) on the activity of nitric oxide synthase(NOS) in the colon

dorsal root ganglia and spinal cord in rats with pelvic pain for studying the role of NO in pain transmission.Methods: Twenty-six SD rats were randomly divided into control group(n=6)

model group(n=10) and EA group(n=10).EA(4-(6 Hz)

dense-sparse waves

0.5-(3 V)) was applied to bilateral "Zusanli"(ST 36) for(60 min).Pelvic pain model was established by local injection of 5% formalin((40 μL)) to the colonic wall from the anus.Behavioral reactions were observed.After transcardiac perfusion of saline and paraformaldehyde

the rat's colon near the anus

sacral 2-4 ganglia and the corresponding spinal cord segments were removed to be cut into sections((25 μm)).NOS activity of the colon

dorsal root ganglia and spinal cord tissues was determined by using nicotinamide-adenine dinucleotide phosphate-diaphorase(NADPH-d) histochemistry.Results: In comparison with model group

the cumulative score of pain behavior in EA group was significantly lower(P<0.01).While the integral OD values of NOS of the colonic wall

DRG and spinal cord in model group were significant higher than those in control group(P<0.01).Comparison between model and EA groups showed that the integral OD values of NOS of the 3 types of tissues in EA group were markedly lower than those in model group(P<0.01)

indicating that EA could suppress pelvic pain induced increase of NOS activity.Conclusion: EA can relieve formalin induced pelvic pain and suppress pain produced increase of NOS activity

suggesting NO may be involved in the process of EA analgesia.