| Objective:To explore the effect of AngⅣon cognition function of diabetic rat,and the expression of synaptophysin and receptor AT4 on hippocampus.Methods:Sixty-five SD male rats were divided into the normal group for fifteen, diabetic model group for twenty-five,AngⅣtreatment group for twenty-five randomly.Streptozotocin-diabetic rat model was induced by a single intraperitoneal injection of STZ at a dose of 60 mg/kg.12 weeks after model was established,the learning and memory abilities of rats were tested with the Morris water maze.Then,AngⅣwas injected into the lateral ventricle of AngⅣtreatment group rats at a dose of 5nmol(1nmol/μL)for each rat,once a day lasted for a week,normal sodium was injected into diabetic model group and normal group rats for a week.The learning and memory abilities of rats were tested with the Morris water maze again.Transmission electron microscope was used to observe synapse ultrastructrue in hippocampal CA1 area.The protein level of synaptophysin and AT4 in hippocampus were detected by immunohistochemical method.The mRNA level of AT4 in hippocampus were detected by RT-PCR.Result:In Morris water maze,compared with the normal group,diabetic model group showed the escaping latency prolonged(P<0.05)and the frequency of passing the original platform position decreased(P<0.05).Compared with diabetic model group,the AngⅣtreatment group showed a significant decrease in the mean time of escape latencies(P<0.05),and a increase in the number of passing the original platform position(P<0.05)after injecting.Under Electron microscope,in hippocampal CA1 area of diabetic model group,mitochondria swelled,the synapses degenerated,presynaptic membrane and postsynaptic membrane were unclear,the number of synaptic vesicles decreased,synaptic clefts were narrowed and chondriosomes were swell.Compared with diabetic model group,hippocampal synapse structure of AngⅣtreatment group improved little.The conclusion of immunohistochemical detection showed:compared with the normal group,the protein expression of synaptophysin in hippocampus were decreased(P<0.05).Compared with diabetic model group ,the protein expression of synaptophysin of AngⅣtreatment group were elevated(P<0.05).Compared with diabetic model group,the expression of AT4 receptor protein and mRNA in hippocampus were decreased significantly in AngⅣtreatment group(P<0.05).Conclusion:1.Twelve weeks later,compared with the normal group learning and memory ability of diabetic rat was dec reased significantly.After AngⅣinjecting,the learning results of diabetic rats was improved obviously.2.AngⅣcould make the expression of synapse in hippocampus increase.Maybe the changes of expression of synapse was related to the improvement of cognition by AngⅣ.3.The expression of AT4 receptor in hippocampus of diabetic rats decrease after AngⅣinjecting,maybe it related to the protective action of AngⅣon cognitive ability.
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