银杏叶提取物改善学习记忆障碍老龄大鼠痴呆模型的作用途径

背景近年研究显示,银杏叶提取物是一种天然的自由基清除剂,可保护机体免受自由基引起的损害,改善脑循环障碍和神经元的功能,而关于银杏叶提取物对认知功能等高级神经功能活动影响的实验或临床研究相对滞后.目的探讨银杏叶提取物对中枢神经系统高级功能活动的作用,为临床应用银杏叶提取物治疗认知功能障碍提供实验依据.设计随机对照实验.单位华中科技大学同济医学院附属精神病医院老年科,华中科技大学同济医学院病理生理教研室,华中科技大学同济医学院附属协和医院神经内科.材料实验于2002-06在华中科技大学同济医学院基础部完成.选择Wistar大鼠40只,随机分为5组正常老龄对照组、模型组、银杏叶提取物75 mg/kg组、银杏叶提取物150 m/kg组,银杏叶提取物500 mg/kg组,每组8只.方法采用东莨菪碱致老龄大鼠学习记忆障碍的拟老年性痴呆动物模型,其中正常老龄对照组和模型组以相同体积的生理盐水灌胃,银杏叶提取物各组分别按75,150,500 mg/kg银杏叶提取物灌胃,50～400g/次,单次连续给药5 d,于第6天测试水迷宫及避暗试验,测试期间停止灌药,以水迷宫和避暗实验等学习记忆行为训练及生化检测方法,观察用药前后动物学习记忆行为和脑海马区乙酰胆碱及蛋白质含量的变化.主要观察指标①各组大鼠游迷宫所需时间.②各组大鼠游迷宫错误次数.③各组大鼠避暗试验所需时间及错误次数.④各组大鼠脑海马区乙酰胆碱及蛋白质含量.结果银杏叶提取物150 mg/kg组中除1只大鼠不明原因死亡外,银杏叶提取物75,500 mg/kg组各有1只大鼠在灌胃时逃走,最终进入结果分析大鼠为37只.①银杏叶提取物各剂量组造模大鼠游迷宫所需时间和途中错误次数均明显少于模型组(P＜0.05或P＜0.01),模型组大鼠游迷宫所需时间和途中错误次数明显高于正常老龄对照组(P＜0.01).②银杏叶提取物500,150,75 mg/kg组大鼠为达到暗环境被动回避试验内容,学习过程明显短于模型组(156.78±25.97),(172.66±13.56),(198.54±17.12),(208.34±28.56)s,P＜0.05或P＜0.01].模型组学习时间较正常老年对照组显著延长(208.46±28.56),(127.46±11.03)s,P＜0.01];银杏叶提取物500,150,75 m/kg组发生电击的错误次数也明显少于模型组(3.41±0.26),(6.97±0.35),(7.23±0.62),(8.38±0.92)次,P＜0.01],银杏叶提取物500mg/kg组电击次数显著少于150mg/kg组(P＜0.01),150mg/kg组明显少于75mg/kg组(P＜0.05).③银杏叶提取物500,150,75 mg/kg组造模大鼠海马乙酰胆碱含量明显高于模型组(421.89±36.32),(387.45±32.76),(380.17±41.25),(36528±11.42)mg/g,P＜0.05或P＜0.01],而银杏叶提取物500 mg/kg组的海马乙酰胆碱含量显著高于银杏叶提取物150,75 mg/kg组(P＜0.01).另外,与正常老龄对照组比较,东莨菪碱致学习记忆障碍模型组大鼠海马脑区的蛋白质含量显著降低(41.75±3.82),(95.13±6.34)mg/kg,P＜0.01],在给予银杏叶提取物后,造模后的实验大鼠海马脑区蛋白质含量虽有所增加,但差异无显著性意义(P＞0.05).结论银杏叶提取物呈剂量依赖性显著改善实验动物的学习记忆能力,并显著增加海马脑区乙酰胆碱含量.

Functional approach of gingko biloba extract to the improvement of learning and memory disturbance in dementia models of aged rats

BACKGROUND: It is indicated in the study of recent years that gingko biloba extract (EGB) is a kind of natural cleaner of free radical and it protects the body from the damage induced by free radical and improves cerebral circulatory disturbance and neuronal function. But the experimental or clinical study on the effects of EGB on high neural functional activity, like cognition, is relatively lagged.OBJECTIVE: To probe into the function of EGB on high functional activity in central neural system so as to provide the experimental evidence on clinical application of EGB in treatment of cognitive disturbance.DESIGN: Randomized controlled experiment was designed.SETTING: Department of Geriatrics of Psychiatric Hospital affiliated to Tongji Medical College of Huazhong University of Science and Technology,Department of Pathophysiology in Tongji Medical College of Huazhong University of Science and Technology and Department of Neurology in Union Hospital affiliated to Jinan Medical College of Huazhong University of Science and Technology.MATERIALS: The experiment was performed in Basic Department of Tongji Medical College of Huazhong University of Science and Technology in June 2002. Forty Wistar rats were employed and randomized into 5groups, named as normal control of aged rats (normal group), model group,EGB 75 mg/kg group, EGB 150 mg/kg group and EGB 500 mg/kg group, 8 rats in each one.METHODS: Scopolamine was used to induce disturbance of learning and memory in aged rats to simulate the model of senile dementia animals. In normal and model groups, physiological saline of same volume was used for gastric perfusion and in every EGB group, EGB of 75, 150 and 500 mg/kg was used for gastric perfusion successively, 50-400 g/time, continuously for 5 days. On the 6th day, water maze and evading-dark-room tests were performed. During the testing, the medical perfusion stopped. The assay methods of behavioral training of learning and memory, such as experiment with water maze and evading-dark-room test, and biochemical assay were used to observe the changes in learning and memory and in acetylcholine (Ach) and protein contents in cerebral hippocampus before and after medication.MAIN OUTCOME MEASURES: ① Time required in maze test of rats in each group. ② Mistakes in maze test of rats in each group. ③ Time required and mistakes in evading-dark-room test of rats in each group. ④Contents of Ach and protein in cerebral hippocampus of rats in each group.RFSULTS: Except that 1 rat was died without definite reason in EGB 150 mg/kg group and 1 rat was escaped in either EGB 75 mg/kg or 500 mg/kg group during gastric perfusion, terminally, 37 rats entered result analysis.① The time required and mistakes in maze test in every EGB group were less remarkably than model group (P＜0.05 or P＜0.01). The time required and mistakes in maze test in model group were higher remarkably than normal group (P＜0.01). ② In learning of passive escaping in evading-darkroom test, the duration of learning for the rats in EGB 500, 150, 75 mg/kg groups was shorter remarkably than that in model group (156.78±25.97),(172.66±13.56), (198.54±17.12), (208.34±28.56) s, P ＜ 0.05 or P＜0.01].The mistakes of electric shock in EGB 500, 150, 75 mg/kg groups were less remarkably than model group (3.41±0.26), (6.97±0.35), (7.23±0.62),(8.38±0.92) times, P＜0.01]. The times of electric shock in EGB 500 mg/kg group was less significantly than 150 mg/kg group (P＜0.01) and that in 150 mg/kg was less remarkably than 75 mg/kg group (P＜0.05). ③ Hippocampal Ach content in modeled rats in EGB 500, 150, 75 mg/kg groups was higher than that in model group (421.89±36.32), (387.45±32.76),(380.17±41.25), (365.28±11.42) μg/g, P＜0.05 or P＜0.01]. Hippocampal Ach content in 500 mg/kg group was higher significantly than 150 and 75 mg/kg groups (P＜0.01). In addition, compared with normal group,protein content in hippocampus in rats with disturbance of learning and memory induced by scopolamine in model group was reduced significantly (41.75±3.82), (95.13±6.34) mg/kg, P ＜ 0.01]. After administrated with EGB,even though the protein content in hippocampus was increased in experimental rats after modeling, the difference was not significant (P＞0.05).CONCLUSION: EGB improves significantly learning and memory in experimental animal in dose-dependence and increases significantly Ach content in hippocampus.