慢性应激对大鼠海马长时程增强和氨基酸神经递质的影响

背景:严重或持久的应激是很多身心疾病的诱发因素,明显损害机体的认知功能。目的:观察应激状态下海马氨基酸的变化及慢性应激对大鼠海马长时程增强的影响。设计:完全随机对照动物实验。单位:汕头大学精神卫生中心。材料:实验于2000-12在汕头大学医学院完成。实验动物为SD成年雄性大鼠16只,随机分为对照组和应激组,每组8只。方法:应激组强迫游泳4周建立慢性应激模型,采用离体海马脑片(500μm)结合电生理的方法观测海马CA1区长时程增强的变化。在海马CA3区Schaffer侧支施加高频刺激后,观察CA1区锥体神经元群体峰电位幅值和场兴奋性突触后电位斜率的改变。应用高效液相色谱紫外检测法对海马氨基酸神经递质进行定量分析。主要观察指标:①以群体峰电位的幅值和场兴奋性突触后电位的斜率作为观察长时程增强变化的指标。②海马氨基酸含量变化。结果:实验第2周应激组大鼠溺水死亡1只,给予补充,其余全部进入结果分析。①对照组的群体峰电位幅值和场兴奋性突触后电位斜率在高频刺激后增大的幅度明显高于应激组(P<0.05)。②对照组天冬氨酸和谷氨酸的水平明显低于应激组,[(2.425±0.211),(4.746±0.609)μmol/g,P<0.01];[(6.016±0.677)(8.094±1.035)μmol/g,P<0.01],而两组间γ-氨基丁酸的含量接近,差异无显著性[(4.229±0.449),(4.249±0.463)μmol/g,P>0.05]。结论:慢性应激抑制海马CA1区长时程增强的形成,提高海马组织天冬氨酸和谷氨酸的水平,而对γ-氨基丁酸的含量没有影响。慢性应激所引起的海马兴奋性氨基酸的堆积可能是学习和记忆能力损害的神经生化基础。

Effect of chronic stress on long-term potentiation of hippocampus and neurotransmitter of amino acid in rats

BACKGROUND: Severe or prolonged stress is harmful to health and even induces many mental and physical disorders and then impairs cognitire functions of the organism.OBJECTIVE: To investigate the effects of stress on the changes in amino acid and chronic stress on long-term potentiation (LTP) of hippocampus of rats.DESIGN: Completely randomized controlled experiment.SETTING: Mental Health Center of Shantou University.MATERIALS: The experiment was completed in the Medical College of Shantou University in December 2000. Totally 16 adult male SD rats were divided randomly into control group and stress group with 8 in each group.METHODS: Mice in stress group were swum compulsively for 4 weeds.Chronic stress model was established, and isolated hippocampal slice(500 μm) combined with electrophysiological technique was used to observe the changes of LTP in hippocampal CA1 field. High-frequency stimulation (HFS) was applied to Schaffer collaterals in hippocampus CA3, then the changes of PS amplitude and fEPSPs slope in CA1 pyramidal neurons were observed. High performance liquid chromatography (HPLC) coupled with UV detection was used for the quantificative analysis of hippocampal amino-acid neurotransmitters.MAIN OUTCOME MEASURES: ① Population spike (PS) amplitude and field excitatory postsynaptic potentials (fEPSPs) slope were used to indicate the changes of LTP. ② Changes of amino acid of hippocampus.RESULTS: One rat in stress group died because of drowning in the second week of experiment was supplied, and others entered the final analysis. ① The increases of PS amplitude and fEPSPs slope after HFS in control group were significantly higher than those in stress group (P＜ 0.05). ② The levels of aspartate and glutamate in control group were significantly lower than those in stress group [(2.425±0.211) μmol/g,(6.016±0.677) μmol/g. P＜ 0.01; (4.746±0.609) μmol/g. (8.094±1.035) μmol/g.P ＜ 0.01]; but there was no significant difference of γ-aminobutyric acid between control and stress groups [(4.229±0.449) μmol/g, (4.249± 0.463) μmol/g, P ＞ 0.05].CONCLUSION: It is suggested that chronic stress can inhibit the development of LTP in hippocampal CA1 field and increase the levels of hippocampal aspartate and glutamate, but does not affect the level of γ-aminobutyric acid. The accumulation of hippocampal excitatory amino acids induced by chronic stress may be the neurobiochemical basis of impairments in learning and memory abilities.