胍丁胺对谷氨酸和高钾诱发海马神经元细胞内钙离子浓度升高的影响

Effect of Agmatine on Rat Hippocampal Neural Calcium Overload Evoked by Glutamate or KCl

目的 观察胍丁胺对原代培养的大鼠海马神经元细胞内钙离子浓度（[Ca^2＋]i）的影响及其对谷氨酸和高钾诱发[Ca^2＋]。升高的影响，探讨胍丁胺对N-甲基-D-天冬氨酸（NMDA）受体和电压依赖性钙通道（VDCC）的作用。方法 原代培养的新生大鼠海马神经元，在细胞外液中加入1、10、100、1000μmol·L^-1胍丁胺，再用300μmol·L^-1谷氨酸诱发NMDA受体通道的开放，或用50mmol·L^-1KCl诱发VDCC的开放，应用激光共聚焦扫描技术，动态观察胍丁胺对[Ca^2＋]i的影响。结果 1～1000μmol·L^-1胍丁胺对细胞内基础钙荧光强度无影响，1、10、100、1000μmol·L^-1胍丁胺使谷氨酸引起的[Ca^2＋]i升高最大变化率由对照组的372％分别降至349％、327％、297％、233％。其中100、1000μmol·L^-1胍丁胺对谷氨酸引起的[Ca^2＋]i升高的抑制作用与对照组相比有显著性差异（P〈0．01）。仅1000μmol·L^-1胍丁胺能抑制KCl诱发的[Ca^2＋]．升高（P〈0．01），低剂量组对KCl诱发的[Ca^2＋]i的变化无影响。结论 胍丁胺可以阻断NMDA受体耦联钙离子通道而抑制钙离子的内流．高浓度时也抑制VDCC。

Aim To investigate the effects of agmatine on basal intracellular Ca^2＋ concentration （ [ Ca^2＋ ] i ） level and hippocampal neural calcium overload evoked by glutamate or KCl so as to explore the effects of agmatine on N- methyl-D-aspartate （NMDA） receptor and voltage-dependent calcium ion channel （VDCC）. Methods Hippocampal neurons of neonatal rats were cultured in vitro for 10 days,then the culture medium was loaded with agmatine at concentrations of,1,10,100,1 000μmol · L^-1 ,and then the neurons were exposed to 300μ mol · L^-1 glutamate or 50mmol · L^-1 KCl. Fluo-3 ,a fluorescent probe ,was used for imaging intracellular calcium by laser scanning confocal microscope （LSCM） to measure the real-time changes of [ Ca^2＋ ]i evoked by glutamate or KCl and the effect of inhibited [ Ca^2＋ ] i elevation caused by glutamate, which is an agonist of the NMDA receptor. The maximal changing rates of fluorescence intensity were reduced from 372% to 349%, 327 %, 297 % ,233%, respectively. However, only 1 000μmol · L^-1 agmatine could inhibit calcium overload evoked by KCl ,which induced the opening of the VDCC. Conclusions Agmatine inhibits [ Ca^2＋ ] i overload in rat hippocampal neurons by blocking the NMDA receptor calcium ion channels but also inhibits VDCC when at high concentration.