Abstract: Objective:To observe the improvement of acidic polysaccharose of Schisandrae Chinensis (SCP-A) on the learning and memory functions of Alzheimer's disease (AD) model mice induced by Aβ_25-35, and to clarify the related mechanisms. Methods:A total of 75 male C57BL mice were randomly divided into control group (injected with saline in intracerebroventricular, given distilled water intragastrically), model group (injected with Aβ_25-35 intracerebroventricularly, given distilled water intragastrically), and 5, 10,20 mg·kg^-1 SCP-A groups (injected with Aβ_25-35 intracerebroventricularly, given SCP-A intragastrically)(n=15). The agents were administered once daily for 14 d, in which Aβ_25-35 was injected intracerebroventricularly on the 8th day. On the 15th day after administration, step-through test and Morris water maze test were used to detect the escape latency, number of errors,and time of finding platform, number of passing platforms,dwell time in target quadrant of the mice; Western blotting method was used to detected the levels of Tau,GSK-3β and their phosphorylated proteins in hippocampus tissue of the mice. Results:The step-through test results showed that compared with control group,the escape latency of the mice in model group was obviously shortened and the number of errors was significantly increased(P<0.01); compared with model group, the escape latencies of the mice in 10 and 20 mg·kg^-1 SCP-A groups were significantly prolonged (P<0.01), the number of errors was significantly decreased (P<0.05 or P<0.01). The Morris water maze test results showed that compared with control group, the time of finding platform of the mice in model group was significantly prolonged,the number of passing platform and dwell time in target quadrant were significantly reduced(P<0.01); compared with model group, the time of finding platform of the mice in 10 and 20 mg·kg^-1 SCP-A groups was significantly shortened(P<0.01),and the number of passing platform and the dwell time in target quadrant were significantly increased (P<0.01). The Western blotting results showed that compared with model group, the expression levels of phosphorylated protein Tau Ser199, Tau Ser396 and Tau Ser404 in hippocampus of the mice in 20 mg·kg^-1 SCP-A group were significantly decreased(P<0.05), and the expression level of GSK-3β was significantly decreased(P<0.01); the expression level of phosphorylated protein GSK-3β Tyr216 was significantly decreased, and the expression level of phosphorylated protein GSK-3β Ser9 was significantly increased (P<0.05). Conclusion:SCP-A has an anti-AD effect, which is related to regulating the activity of GSK-3β to reduce the level of phosphorylated protein Tau in the hippocampus tissue of the mice.

Key words: Alzheimer's disease, Tau, GSK-3β, Schisandra chinensis, acidic polysaccharides