Objective:To investigate the relevance between spatial learning and memory impairment and the changes of inducible nitric oxide synthase (iNOS) activity,superoxide dismutase (SOD) activity and malondiadehyde (MDA) content in hippocampus from Type 1 diabetic mice.Methods:Sixty male mice were randomly assigned into a control group (NC group,20 mice) and a Type 1 diabetic group (DM group,40 mice).Type 1 diabetic mouse models were established by a large dose intraperitoneal injection of streptozotocin (100 mg/kg).The spatial learning and memory abilities of mice were assessed by Morris water maze (MWM) test.After MWM test,we chose 20 mice (diabetic encephalopathy mice) with the worst spatial learning and memory abilities from diabetic model group,and detected the iNOS activity,SOD activity and MDA content in hippocampus in both groups.Results:Compared with the NC group,the escape latency was significantly extended and platform crossings were significantly declined in diabetic mice (P＜0.01).Furthermore,the activity of iNOS and the content of MDA were markedly increased,and the activity of SOD was significantly decreased in hippocampus of diabetic encephalopathy mice (P＜0.01).Conclusion:The established Type 1 diabetic mice show symptoms of cognitive dysfunction,which might be related to the increase of oxidative stress in hippocampus.