Objective: To observe the effect of Yizhiyin on learning and memory ability in the rats with Alzheimers disease induced by Aβ1-42 and the effect of antioxidation. Method: The rat model of AD were established by Aβ1-42 injection into hippocampus

then those rats were treated by three different doses of Yizhiyin. Morris watermaze test was used for detecting learning and memory ability. Immunohistochemisty was used for detecting the expression of β-Amyloid

and the superoxide dismutase (SOD) and the hydroxy radical inhibition of brain were measured. Result: Compared with model group

the ability of learning and memory in high

middle and low doses group were improved (P<0.01).The results of immunohistochemisty showed that there were a lot of β-Amyloid deposition in the brain of model rats and a sprinkle expression in high and middle doses group. The activity of SOD was increased compared to those in model group in brain in each treatment group (P<0.01)

the inhibition of hydroxy radical was increased (P<0.01) in each treatment group except the low dose group. Conclusion: The Yizhiyin could improve the learning and memory capability in AD rats efficiently

and decrease the β-Amyloid deposition. The mechanism of the Yizhiyin should be related to the increase in SOD and the inhibition of hydroxy radical.