Objective To establish an animal model of aging,to observe changes related to cognitive impairment and depression-like behavior,and to explore the mechanisms of the two diseases caused by the model.Methods Male Sprague-Dawley (SD) rats were treated with D-galactose and alchlor;after simultaneous administration of both drugs,their learning and memory abilities were assessed using the Morris water maze test.The depression-like behavioral changes were observed in the forced swimming test.Golgi staining was performed to observe the development of hippocampal neurons;oxidative stress index changes in superoxide dismutase (SOD) activity and malondialdehyde (MDA) levels were analyzed in the hippocampus.Results Compared with a control group,rats in the model group showed reduced escape latency (P ＜ 0.05) from the platform in the water maze,reduced residence time on and a reduced number of times passing through the platform (P ＜ 0.05);the real time in the water during the forced swimming test was significantly prolonged (P ＜ 0.01).Golgi staining indicated that dendritic spine density in the hippocampus in model rats was decreased (P ＜ 0.01),as was hippocampus SOD activity (P ＜ 0.05),while MDA levels were increased (P ＜ 0.05).Conclusion We established a new animal model of aging with cognitive impairment and depression.The common disease mechanisms of these two diseases might be related to the destruction of the nervous system during the process of overload caused by free radicals and the resulting metabolic imbalance.