Effects of soybean isoflavones on cognition and expression of NR2B subtype in hippocampus of Alzheimer's disease rats

Objective To investigate the effects of soybean isoflavones on cognition and expression of NMDA receptor (NR2B) subtype in hippocampus in Alzheimer's disease (AD) rats induced by amyloid β-peptide 25-35(Aβ 25-35).Methods 60 female Wistar rats were randomly divided into five groups: model group, low dose of soybean isoflavone treatment group, high dose of soybean isoflavone treatment group, estrogen group and control group. AD models were made by injection Aβ 25-35 into bilateral hippocampus and normal saline was used in control group. Different dose of soybean isoflavone and estrogen were administered in soybean isoflavone treatment groups and estrogen treatment group for 18 d, respectively. The praxiology of rats was assessed by Morris water maze and the expression of NR2B in hippocampus was detected by immunohistochemistry method.Results Compared with control group,the learning and memory ability of model group obviously damaged and the expression of NR2B in hippocampus decreased (all P0.05). The learning and memory ability in soybean isoflavone treatment groups and estrogen treatment group significantly improved in comparison to model group (all P0.05), and the therapeutic efficacy of high dose of soybean isoflavone treatment group was better than that of low dose of soybean isoflavone treatment group (all P0.05), but no difference in comparison to estrogen treatment group. Compared with model group, the expression of NR2B in hippocampus increased markedly in soybean isoflavone treatment groups and estrogen treatment group (all P0.05), but there was no difference between soybean isoflavone treatment groups and estrogen treatment group.Conclusions Soybean isoflavones may enhance NR2B expression in hippocampus and improve the learning and memory ability of rats just like estrogen. This effect is dose dependent.