Objective: To investigate the effects of nao-an capsule (a traditional Chinese medicine) on oxidative stress and Tau protein hyperphosphorylated in hippocampal neurons of diabetic rats. Method: Thirty-six-4-week-old Male SD rats were randomly divided into 3 group: the diabetic model group(untreaed).Naoan capsule 1 Group

treated with Naoan atonin (30 mg ·kg-1 ·d-1)by gavage

Naoan 2 Group

treated with Naoan atonin (200 mg ·kg-1 ·d-1)by gavage. Rat diabetic model was produced by streptozotocin

12 normal rats were assigned to the normal control group. The Y-electrical-maze test was used to verify the changes of learning and memory functions of the two groups at 8-week

12-week and 16-week.The hippocampus of rats were tested by immunohistochemical method.After 16-weeks the contents malondialhyde (MDA)

activity of glutathione peroxidase (GSH-Px)

and superoxide dismutase (SOD) of plasma and the hippocamp were measured. Result: The total reaction time and error number of diabetic rats in Y-electrical-maze was prolonged significantly. The contents of Tau hyperphosphorylation in the hippocampal neurons of the diabetic rat brain increased .Compared with the control group

plasma and hippocampal MDA of DM group rats increased

both GSH-Px and SOD activity decreased.Naoan capsule atonin increased reamakabli superoxide dismutase and glutathione peroxidase activities and reduced malonaldehyde levels in plasma and hippocamp

and increased ability of learning and memory

reduced Tau hyperphosphorylation in the hippocampal neurons than DM group P<0.05. Conclusion:The cognitive dysfunctions may be caused by diabetes

which might be associated to increasingthe Tau hyperphosphorylation in the hippocampal neurons of the rat brain.Overproduction of reactive oxygen species and defficieny in antioxidant enzymes may contribute to the development of the diabetes’s pathological changes central nervous system. Naoan capsule may inhibit oxidative stress in plasma and hippocamp

amendment the cognition and Tau protein hyperphosphorylated in hippocampal neurons of diabetic rats.