Objective:To observe changes of nitric oxide synthase(NOS) activity and neuropathic pain responses and the effect of electroacupuncture(EA) of "Huantiao"(GB 30)-"Yanglingquan"(GB 34) on NOS activity in rats with chronic constriction injury(CCI) of sciatic nerve.Methods:Seventy-two SD rats were evenly randomized into control

model and EA groups.CCI model was established by wrapping the sciatic nerve(4-5 mm proximal to the furcated site) with a thin polyethylene cannula((2-3) mm long) according to Mosconi's method.Electroacupuncture(4-16 Hz

1-3 V

intermittent dense-sparse waves) was given to "Huantiao"(GB 30) and "Yanglingquan"(GB 34) for 30 min

once every other day and beginning from the 2

(nd)

day on after operation.The pain threshold(hind-paw withdrawal latency) was measured by giving plantar radiation thermal stimulation at different time(2 d

4 d

7 d

14 d

28 d after establishing model).NOS activity of tissues of the lumbar spinal cord was detected by using histochemical method(NADPH-d).Results:Compared with pre-operation

the paw withdrawal latency(PWL) reduced significantly in all the 3 groups(P

<

0.05

0.01) after operation and recovered 7 days and 14 days later in control and EA groups respectively.The PWL values of model group were significantly shorter than those of control group from the 2(nd) day on after operation.The pain threshold(hind-paw withdrawal latency) was measured by giving plantar radiation thermal stimulation at different time(2 d

4 d

7 d

14 d

28 d after establishing model).NOS activity of tissues of the lumbar spinal cord was detected by using histochemical method(NADPH-d).Results:Compared with pre-operation

the paw withdrawal latency(PWL) reduced significantly in all the 3 groups(P

<

0.05

0.01) after operation and recovered 7 days and 14 days later in control and EA groups respectively.The PWL values of model group were significantly shorter than those of control group from the 2

(nd)

day to the 28(nd) day to the 28

(th)

day after operation(P

<

0.05

0.01).Compared with model group

PWL values of EA group from the 4(th) day after operation(P

<

0.05

0.01).Compared with model group

PWL values of EA group from the 4

(th)

day to 28(th) day to 28

(th)

day after operation were significantly higher(P

<

0.05

0.01)

suggesting that EA could evidently raise pain threshold to relieve pain.The optical density(OD) values of NOS of the spinal dorsal horn in model group were significantly lower than those in control group from the 4(th) day after operation were significantly higher(P

<

0.05

0.01)

suggesting that EA could evidently raise pain threshold to relieve pain.The optical density(OD) values of NOS of the spinal dorsal horn in model group were significantly lower than those in control group from the 4

(th)

day to 28(th) day to 28

(th)

day after operation(P

<

0.05

0.01).Compared with model group

OD values of NOS in EA group were significantly higher from the 4(th) day after operation(P

<

0.05

0.01).Compared with model group

OD values of NOS in EA group were significantly higher from the 4

(th)

day to 28(th) day to 28

(th)

day after operation(P

<

0.05

0.01)

suggesting that EA could raise NOS activity in CCI rats.Conclusion:EA of "Huantiao"(GB 30) and "Yanglingquan"(GB 34) can effectively inhibit chronic neuropathic pain and upregulate the expression of NOS in the spinal dorsal horn of CCI rats.