Nyitrai G, Kovács I, Szárics E, Skuban N, Juhász G, Kardos J
Department of Neurochemistry, Chemical Institute, Chemical Research Center, Hungarian Academy of Sciences, Budapest, Hungary.
J Neurosci Res. 1999 Sep 15;57(6):906-15.
The role of intracellular Ca(2+) stores in the control of brain activity was investigated in microdialysis experiments by monitoring changes in the extracellular concentration of amino acids (AA) in the hippocampus of the rat after intracerebroventricular (icv) administration of the intracellular Ca(2+) release blocker, dantrolene in vivo, as well as in D-aspartate release and transmembrane Ca(2+) flux measurements in dantrolene-treated (50 microM) hippocampal homogenates containing resealed plasmalemma fragments and nerve endings in vitro. Microdialysis data demonstrate that icv injection of 0.6 mM dantrolene significantly decreases ( approximately 20%) the background (Glu) in the hippocampus. Both the (Glu; approximately 300%) and the inhibitory effect of dantrolene thereupon ( approximately 50%) was significantly increased when 0.5 mM of the Glu uptake inhibitor, L-trans-pyrrolidine-2,4-dicarboxylic acid, was dialysed into the hippocampus. NMDA and (S)-AMPA induced [(3)H]-D-aspartate release in hippocampal homogenates. Preincubation of these homogenates with 50 microM dantrolene was found to reduce the response to NMDA, but not to (S)-AMPA, in a NMDA-dependent manner. Increased rates of transmembrane influx and efflux of Ca(2+) in hippocampal homogenates with half-times of 4 ms and 200 ms, respectively, can be observed by the addition of 100 microM NMDA as recorded using a stopped-flow UV/fluorescence spectrometer in combination with the Ca(2+) indicator dye, bisfura-2. Both the Ca(2+) influx and efflux rates of the NMDA response were reduced (25-fold and >5-fold, respectively) in homogenates preloaded with 50 microM dantrolene. These results suggest a role for NMDA-inducible intracellular Ca(2+) stores in the control of normal brain activity in vivo.
在微透析实验中，通过监测大鼠脑室内（icv）注射细胞内Ca(2+)释放阻滞剂丹曲林后海马中氨基酸（AA）细胞外浓度的变化，以及在体外对含有重封质膜片段和神经末梢的丹曲林处理（50 microM）海马匀浆进行D-天冬氨酸释放和跨膜Ca(2+)通量测量，研究了细胞内Ca(2+)储存对脑活动的控制作用。微透析数据表明，icv注射0.6 mM丹曲林可显著降低（约20%）海马中的背景（Glu）。当0.5 mM的Glu摄取抑制剂L-反式吡咯烷-2,4-二羧酸透析入海马时，Glu（约300%）及其上的丹曲林抑制作用（约50%）均显著增加。NMDA和（S）-AMPA诱导海马匀浆中[3H]-D-天冬氨酸释放。发现用50 microM丹曲林预孵育这些匀浆可降低对NMDA的反应，但不降低对（S）-AMPA的反应，且呈NMDA依赖性。通过使用停流紫外/荧光光谱仪结合Ca(2+)指示剂染料双苯甲酰亚胺-2记录，加入100 microM NMDA可观察到海马匀浆中Ca(2+)跨膜流入和流出速率增加，其半衰期分别为4毫秒和200毫秒。在预加载50 microM丹曲林的匀浆中，NMDA反应的Ca(2+)流入和流出速率均降低（分别降低25倍和>5倍）。这些结果表明NMDA诱导的细胞内Ca(2+)储存在体内正常脑活动的控制中起作用。
