Objective: To observe the expression of inducible nitric oxide synthase(iNOS) in the endothelial cells inside the cerebral micrangium and the effect of electroacupuncture(EA) in vascular dementia(VD) rats.Methods: Thirty Wistar rats were evenly randomized into sham-operation(control)

model and EA groups.VD model was established by occlusion of the bilateral common carotid artery and reperfusion plus intraperitoneal injection of sodium nitroprusside(2.5 mg/kg).In EA group

EA(frequency 5/45 Hz

strength 1.5-3 V) was applied to "Baihui"(GV 20)

"Dazhui"(GV 14)

"Zusanli"(ST 36) and "Geshu"(BL 17) for 20 minutes

once a day

continuously for 7 days.The activity of iNOS in the endothelial cells of right cerebral cortex tissue was assayed with immunohistochemical method.The rat's memory-learning ability was detected by using step-down test(passive avoidance reaction

latency and number of errors of step-down).Results: In comparison with control group

the latency of step-down from the platform of model group shortened significantly

and the number of errors of model group increased remarkably.While compared with model group

the latency of step-down of EA group increased significantly and the number of errors decreased markedly(P<0.01).No significant differences were found between control and EA groups in these two indexes(P>(0.05).) Very weak immunoreaction(IR) of iNOS was found only in fewer slices of the brain tissues in control group;while in majority of the slices of model group

moderate IR and stronger IR were found.In comparison with model group

mild IR of iNOS in EA group was predominant while moderate and strong IR were significantly fewer in the number of slices.There was a significant difference between model group and EA group(P<0.01)

suggesting that after EA

the activity of iNOS in most endothelial cells in cerebral micrangium reduced obviously.Conclusion: Electroacupuncture can obviously reduce the activity of iNOS in the endothelial cells of cerebral micrangium in VD rats

and protect the brain from ischemia/reperfusion injury.