Influence of acidic peptide on learning and memory of rats with Alzheimer disease / 中国组织工程研究

ABSTRACT

BACKGROUND: Acidic peptide is the tripeptide composed of 3 glutamic acids, which cannot bring excitatory nerve signal transmission into playlike single glutamic acid through presynaptic release and integration withpostsynaptic NMDA receptor directly as excitable neurotransmitter. It is quite possible that acidic peptide plays its actions by integrating with multiple metabolic glutamic acidic receptors so as to promote neuron proliferation or release nerve growth factor (NGF). OBJECTIVE: To probe into whether acidic peptide induces changes in learning and memory of model rats with Alzheimer disease (AD).DESIGN: Randomized controlled single experiment was designed.SETTING: Teaching-Research Room of Biochemistry and Molecular Biology of Basic Medical College of Zhengzhou University.MATERIALS: The experiment was performed in 2nd Research Room and Experimental Animal Room of Teaching-Research Room of Biochemistry and Molecular Biology of Basic Medical College of Zhengzhou University.Totally 100 SD male rats were selected and some of them were excluded due to retarded response in step down test. Totally 84 rats were included in the experiment and randomized into 7 groups, named normal control,model group, physiological saline group (PS group), piracetam group, acidic peptide groups of 60, 30 and 15 mg/kg, 12 rats in each group. Acidic peptide is a new small molecular peptide separated from bovine brain in this research team and is tripeptide composed of three glutamic acids.METHODS: Except normal control, in the rest groups, after 1 week routine breeding, cerebral stereotactic microinjection was used to inject 5 μg ibotenic acid in hippocampus of rats to destroy bilateral Meynert's basal ganglia to establish AD model. In normal control and model group, no medication was applied. In PS group, physiological saline was used for gastric perfusion. In piracetam group, piracetam of 0.3 g/kg was used for gastric perfusion and in acidic peptide groups of 15, 30 and 60 mg/kg,acidic peptide of 60, 30 and 15 mg/kg was applied for gastric perfusion successively, continuously for 20 days, once per day, 2 mL/time. On the expiration of gastric perfusion, learning and memory of rats were examined with step down test in every group. The animal was placed on the safe table on step down platform to adapt to the environment for 3 minutes, afterwards, 36 V electric current was given. Error response was recorded if the animal jumped to the copper railings after electric shock and correct response was recorded if the animal jumped back the safe area. Step-up latent phase and frequency of correct response were recorded in 3 minutes.MAIN OUTCOME MEASURES: Comparison of learning and memory of rats in every group. RESULTS: Totally 84 rats were all included in the result analysis. ①Comparison of learning in every group: Compared with model group, stepup latent phase was shortened remarkably in every acidic peptide group[(102.03±5.33), (71.77±4.38), (68.28±9.53), (69.13±8.79) s, P ＜ 0.01] and the frequency of correct response was improved remarkably [(12.92±2.91),(16.17±2.79), (15.83±3.27), (16.33±2.53) times, P ＜ 0.01]. ② Comparison of memory in every group: Compared with model group, step-up latent phase was shortened remarkably in every acidic peptide group [(43.17±4.66),(29.78±4.48), (26.20±3.28), (22.09±4.43) s, P ＜ 0.01] and the frequency of correct response was improved remarkably [(15.67±2.15), (20.92±2.68),(20.83±2.29), (20.25±2.05) times, P ＜ 0.01].CONCLUSION: Acidic peptide can shorten remarkably the step-up latent phase of AD rats in step down test and improve the frequency of correct response. It is indicated that acidic peptide provides good intervention on learning and memory of rat model of Alzheimer disease.