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背景:电磁脉冲是一种高能非电离辐射,它涵盖的频谱极宽,对电子仪器具有极强的破坏力,并具有一定的生物损伤效应。本课题组前期实验发现,电磁脉冲可造成实验大鼠学习记忆能力的显著下降,并且影响其海马长时程增强效应的形成。目的:观察电磁脉冲照射对大鼠海马组织中氨基酸类神经递质含量和N-甲基-D-天冬氨酸受体的影响。设计:随机对照的实验,方差分析。单位:军事医学科学院放射与辐射医学研究所。材料:实验于2004-01/03在军事医学科学院放射与辐射医学研究所完成。实验选用雄性Wistar大鼠32只,随机分为电磁脉冲组26只和对照组6只。方法:电磁脉冲组大鼠经电磁脉冲照射(6×104V/m,脉冲上升时间20ns,脉宽30μs,频率2.5脉冲/min,作用2min)后即刻,3,6,24,48h麻醉状态下断头取脑,剥离海马;用高效液相色谱法测定氨基酸含量,并以3H标记的谷氨酸为配基进行放射性配基-受体结合实验。对照组麻醉处死前不做任何处理。主要观察指标:①各组大鼠海马组织兴奋性氨基酸和抑制性氨基酸含量的变化。②各组大鼠海马N-甲基-D-天冬氨酸受体的最大结合量和平衡解离常数的变化。结果:32只大鼠全部进入结果分析。①电磁脉冲照射后即刻、3h、6h可见天冬氨酸的含量显著升高[峰值(17.25±1.63)μmol/L],明显高于对照组[(10.56±1.5)μmol/L,P<0.05],谷氨酸含量也于上述3个时间点升高[峰值(13.67±0.95)μmol/L],显著高于对照组[(6.94±1.1)μmol/L,P<0.05],两者含量均于照射后24h渐趋恢复,48h接近正常水平。3种抑制性氨基酸(甘氨酸、牛磺酸、γ-氨基丁酸)的含量也于电磁脉冲照射后不同时间点升高,并于48h恢复。谷氨酸/γ-氨基丁酸比值于照后即刻明显升高(P<0.05),照后24h明显下降,48h恢复至接近对照组。②电磁脉冲照射后即刻大鼠海马中N-甲基-D-天冬氨酸受体的平衡解离常数开始下降,照后3h下降最显著(P<0.05),6h渐有恢复,48h恢复至正常水平;受照大鼠海马中N-甲基-D-天冬氨酸受体的最大结合量于照后3h和6h显著下降(P<0.05),24h渐有恢复,照后48h明显升高,超过正常组水平(P<0.05)。结论:电磁脉冲照射导致大鼠海马组织中兴奋性氨基酸含量及谷氨酸/γ-氨基丁酸比值升高;同时N-甲基-D-天冬氨酸受体的亲和力升高及受体密度下降。提示实验动物认知障碍可能与兴奋性氨基酸的过度释放和N-甲基-D-天冬氨酸受体功能改变有关。
Background: Electromagnetic pulses are a type of high-energy, non-ionizing radiation that covers a very wide frequency spectrum and is extremely destructive to electronic equipment and has some biological damage effects. Our previous study found that electromagnetic pulse can cause significant decline in learning and memory ability of experimental rats, and affect the formation of hippocampal long-term potentiation effect. OBJECTIVE: To observe the effects of electromagnetic pulse irradiation on the contents of amino acid neurotransmitters and N-methyl-D-aspartate receptors in hippocampus of rats. Design: Randomized controlled trials, analysis of variance. Unit: Institute of Radiation Medicine and Radiation Medicine, Academy of Military Medical Sciences. Materials: The experiment was performed at Institute of Radiation Medicine and Radiation Medicine, Academy of Military Medical Sciences from January to March 2004. Thirty-two male Wistar rats were randomly divided into two groups: 26 rats in the electromagnetic pulse group and 6 rats in the control group. Methods: Rats in electromagnetic pulse group were anesthetized by electromagnetic pulse irradiation (6 × 104V / m, pulse rise time 20ns, pulse width 30μs, frequency 2.5 pulses / min for 2min) The brain was taken out and the hippocampus was dissected. The contents of amino acids were determined by high performance liquid chromatography (HPLC), and the 3H - labeled glutamate was used as the ligand for radioligand - receptor binding experiments. Control group anesthesia before death without any treatment. MAIN OUTCOME MEASURES: ①The changes of excitatory amino acids and inhibitory amino acids in hippocampus of rats in each group. ② The maximum binding capacity and equilibrium dissociation constant of N-methyl-D-aspartate receptors in hippocampus of rats in each group. Results: All 32 rats entered the result analysis. ① The content of aspartic acid was significantly increased at 3h and 6h after irradiation with electromagnetic pulse [17.25 ± 1.63 μmol / L], significantly higher than that in the control group [(10.56 ± 1.5) μmol / L, P <0.05 ], Glutamate content also increased at the above three time points [peak (13.67 ± 0.95) μmol / L], significantly higher than that in the control group [(6.94 ± 1.1) μmol / L, P <0.05] 24h after irradiation were gradually restored, 48h close to normal levels. The content of three kinds of inhibitory amino acids (glycine, taurine, γ-aminobutyric acid) also increased at different time points after electromagnetic pulse irradiation and recovered at 48h. The ratio of glutamate / γ-aminobutyric acid was significantly increased immediately after irradiation (P <0.05), significantly decreased 24 h after irradiation, and returned to control at 48 h. (2) The equilibrium dissociation constant of N-methyl-D-aspartate receptor in the hippocampus of rats began to decrease immediately after irradiation with electromagnetic pulse, the most significant decrease was seen at 3h after irradiation (P <0.05), gradually recovered at 6h, restored at 48h (P <0.05). The maximum binding of N-methyl-D-aspartate receptor in the hippocampus of irradiated rats decreased significantly at 3h and 6h after irradiation Increased more than normal group (P <0.05). CONCLUSION: Electromagnetic pulse irradiation causes the excitatory amino acid content and the ratio of glutamate / γ-aminobutyric acid to increase in the hippocampus of rats. At the same time, the affinity of N-methyl-D-aspartate receptor increases and the receptor Decreased density. It suggests that cognitive impairment in experimental animals may be related to the excessive release of excitatory amino acids and the changes of N-methyl-D-aspartate receptor function.