酸性肽对阿尔茨海默病鼠学习记忆能力的影响

背景:酸性肽是由3个谷氨酸连接而成的三肽,不可能像单个谷氨酸一样直接作为兴奋性神经递质而由突触前释放并与突触后的NMDA受体结合而发挥兴奋性神经信号传递作用,但通过与多种代谢性谷氨酸受体结合而促进神经细胞增殖或释放神经生长因子而发挥作用具有很大的可能性。目的:探讨酸性肽是否能够引起阿尔茨海默病模型大鼠学习记忆能力的变化。设计:随机对照单一实验。单位:郑州大学基础医学院生物化学与分子生物学教研室。材料:实验于2003-02/07在郑州大学基础医学院生物化学与分子生物学教研室的第二研究室和实验动物房完成。选取雄性SD大鼠100只,用跳台实验除去反应迟钝的动物,共84只大鼠纳入实验,随机分为7组:正常对照组,模型组,生理盐水组,吡拉西坦治疗组,酸性肽60,30,15mg/kg治疗组,12只/组。酸性肽为本课题组从牛脑中分离出的一个新的小分子肽,由三个谷氨酸连成的三肽。方法:除正常对照组外,其余各组大鼠常规饲养1周后,均采用大鼠脑组织立体定位微量注射技术,脑海马注射5μg鹅膏蕈氨酸,以损毁大鼠双侧迈纳特基底核建立阿尔茨海默病模型。正常对照组和模型组不给药,生理盐水组用生理盐水灌胃,吡拉西坦治疗组用0.3g/kg吡拉西坦灌胃,酸性肽60,30,15mg/kg治疗组分别用60,30,15mg/kg酸性肽灌胃,连续20d,1次/d,2mL/次。灌胃期满后通过跳台实验测定各组大鼠的学习和记忆能力。将动物放在跳台装置的安全台上,适应环境3min,然后通以36v电流,受到电击后动物跳至铜栅为错误反应,跳回安全区为正确反应,记录3min内的上台潜伏期与正确反应次数。主要观测指标:各组大鼠学习与记忆能力的比较。结果:纳入实验的84只大鼠全部进入结果分析。①各组大鼠学习能力的比较:与模型组比较,酸性肽15,30,60mg/kg治疗组的上台潜伏期均明显缩短[(102.03±5.33),(71.77±4.38),(68.28±9.53),(69.13±8.79)s,P<0.01];正确反应次数均明显提高[(12.92±2.91),(16.17土2.79),(15.83±3.27),(16.33±2.53)次,P<0.01]。②各组大鼠记忆能力的比较:与模型组比较,酸性肽15,30,60mg/kg治疗组的上台潜伏期均明显缩短[(43.17±4.66),(29.78土4.48),(26.20±3.28),(22.09±4.43)s,P<0.01];正确反应次数均明显提高[(15.67±2.15),(20.92土2.68),(20.83±2.29),(20.25±2.05)次,P<0.01]。结论:酸性肽能够明显缩短阿尔茨海默病鼠在跳台实验中的上台潜伏期,提高正确反应次数,表明酸性肽对阿尔茨海默病模型大鼠的学习记忆能力具有良好的干预作用。

Influence of acidic peptide on learning and memory of rats with Alzheimer disease

BACKGROUND: Acidic peptide is the tripeptide composed of 3 glutamic acids, which cannot bring excitatory nerve signal transmission into play like single glutamic acid through presynaptic release and integration with postsynaptic 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.