Mechanism of Soybean Isoflavones Improving Learning and Memory Abilities of Rats with Alzheimer's Disease

Objective To investigate the mechanism of soybean isoflavones(SIFs) improving the learning and memory abilities of rats with Alzheimer's disease(AD).Methods A total of 70 rats were randomized into normal control group,sham-operation group,model group,estrogen treatment group,and high-,medium-and low-dose SIF treatment groups.A rat model of AD was induced by injecting β-amyloid peptide(Aβ) into the right amygdala.The AD rats in the SIF treatment groups were treated with different doses of SIFs.The learning and memory abilities of AD rats were evaluated based on escape latency,swimming time percentage,and times of passing through platform within 2 minutes.The activities of choline acetyltransferase(ChAT) and cysteinyl aspartate-specific protease 3(caspase-3) in the hippocampus were observed and compared among all groups.Results Compared with those in the model group,the escape latency was significantly decreased and the swimming time percentage and times of passing through platform within 2 minutes were significantly increased in the high-,medium-and low-dose SIF treatment groups(P0.01);the activity of hippocampus ChAT was significantly increased in the high-and medium-dose SIF treatment groups(P0.01);the activity of caspase-3 was significantly decreased in the high-,medium-and low-dose SIF treatment groups(P0.01).There were significant differences in escape latency,times of passing through platform within 2 minutes,and activities of ChAT and caspase-3 between the high-dose SIF treatment group and low-dose SIF treatment group(P0.01).Conclusion SIFs can improve the learning and memory abilities of AD rats by regulating the activities of ChAT and caspase-3 in the hippocampus in a dose dependent manner.