\[Abstract\]ObjectiveTo investigate the relation of diabetic encephalopathy with oxidative stress and hippocampus expression of inducible nitric oxide synthase(iNOS) in rats and to study the therapeutic effects of curcumin. MethodsDiabetes mellitus was induced by injection of Streptozotocin in rats. The experiment animals were randomly divided into control group, diabetic group, diabetes plus curcumin group and control plus curcumin group; animals in the latter two groups received 60 mg·kg-1·d-1 curcumin treatment. Superoxide dismutase(SOD),catalase(CAT), malondialdehyde(MDA) and nitric oxide(NO) in the hippocampal tissues were measured 12 weeks after treatment. The expression of iNOS mRNA and the mean optical density (MOD) of immunoreactive neurons were evaluated by RT-PCR and immunohistochemistry method, respectively. ResultsCompared with the control group, diabetic group had significantly lower activities of SOD and CAT, higher contents of NO and MDA, and increased expression of iNOS mRNA and protein in the hippocampal tissues (P<0.01). Compared with the diabetic group, diabetic plus curcumin group had significantly higher activities of SOD and CAT, lower contents of NO and MDA and decreased expression of iNOS mRNA and the MOD of immunoreactive neurons in hippocampus (P<0.01). ConclusionDiabetic encephalopathy is associated with oxidative stress and increased expression of iNOS; curcumin may protect diabetic encephalopathy by inhibiting oxidative stress and down-regulating the iNOS expression.