Effects of Melatonin on cognition and tau hyperphosphorylation in hippocampus of Alzheimer's disease model rats

Objective To sdudy the effects of Melatonin(MT)on cognition and tau hyperphosphorylation in hippocampus of Alzheimer's disease(AD)model rats.Methods Aβ25-35 was injected into the hippocampus to make AD model rat.MT was injected intraperitoneully into rats of MT group 7 days before and 19 days after modeling.Normal saline(NS)was injected intraperitoneully into rats of AD group after modeling.The cognition was tested by Morris water maze.The pathological changes of hippocampus was observed by Bielschowsky staining and the tau hyperphosphorylation was detected by immunohistochemistry staining.The results were compared with normal control group.Results In MT group,the results of Morris water maze were significant better than those in AD group(all P0.001);and the amount of P-tau positive cells(60.0±2.3)was remarkable decrease than that in AD group(98.4±3.0)(P0.001);but there was no difference between MT group and normal control group.The neurofibrils in hippocampus of MT group were more regular than that in AD group.Conclusions MT improves cognition of AD-rats and inhibits hyperphosphorylation of tau in hippocampus.