TRAPPING OF GLUTAMATE AND GLYCINE DURING OPEN-CHANNEL BLOCK OF RAT HIPPOCAMPAL NEURON NMDA RECEPTORS BY 9-AMINOACRIDINE
TRAPPING OF GLUTAMATE AND GLYCINE DURING OPEN-CHANNEL BLOCK OF RAT HIPPOCAMPAL NEURON NMDA RECEPTORS BY 9-AMINOACRIDINE
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DOI：
10.1113/jphysiol.1995.sp020591
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发表时间：
1995-03-01
影响因子：
5.5
通讯作者：
MAYER, ML
中科院分区：
文献类型：
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作者：
BENVENISTE, M;MAYER, ML
1.用全细胞、外向和有核膜片记录技术记录了分离培养的大鼠海马神经元N-甲基-D-天冬氨酸（NMDA）受体反应。采用快速灌流法研究9-氨基吖啶（9-AA）和Mg ~（2+）对NMDA受体的电压依赖性阻断作用.在施加-100 mV的NMDA和9-AA而不是NMDA和Mg 2+后，在去极化至+60 mV时诱发大幅度尾电流。这些尾电流对NMDA受体上谷氨酸和甘氨酸结合位点的竞争性拮抗剂的阻断具有抵抗力，并且当单独应用NMDA或9-AA时不会诱发这些尾电流。3.尾电流的衰减动力学依赖于激动剂的亲和力; 80%的电荷转移所需的时间是10倍briefer为NMDA比谷氨酸和7倍briefer为L-丙氨酸比甘氨酸。这些结果与9-AA阻断NMDA受体的序贯模型雅阁，即谷氨酸和甘氨酸均不能从受体的开放-阻断状态解离.尾电流响应的幅度比对最大有效浓度的谷氨酸和甘氨酸的响应大2至4倍，表明NMDA受体通道在激动剂和9-AA的共同应用期间以开放-阻断状态积累。尾电流响应的上升时间和衰减动力学比对最大有效浓度的谷氨酸的简短应用的响应更快。总之，这些结果表明，在+60 mV时，从9-AA阻断中恢复的速度比响应谷氨酸的NMDA受体开放的速度更快。我们的实验表明，NMDA受体的开放通道阻断可以提供一种新的方法来测量开放的概率和第一个潜伏期分布的离子通道开放响应于激动剂的结合，并提供额外的证据表明，延迟开放的NMDA受体通道的基础缓慢激活和失活的响应谷氨酸。
1. N-methyl-D-aspartate (NMDA) receptor responses were recorded from rat hippocampal neurons grown in dissociated culture, using whole-cell, outside-out and nucleated patch recording techniques. Rapid perfusion was used to study voltage-dependent block of NMDA receptors by 9-aminoacridine (9-AA) and by Mg2+.2. Large amplitude tail currents were evoked on depolarization to +60 mV after application at -100 mV of NMDA and 9-AA but not NMDA and Mg2+. These tail currents were resistant to block by competitive antagonists to the glutamate and glycine binding sites on NMDA receptors and were not evoked when either NMDA or 9-AA were applied alone.3. The decay kinetics of the tail current were dependent on agonist affinity; the time required for 80% charge transfer was 10-fold briefer for NMDA than for glutamate and 7-fold briefer for L-alanine than for glycine. These results are in accord with a sequential model for block of NMDA receptors by 9-AA, in which neither glutamate nor glycine can dissociate from the open-blocked state of the receptor.4. Tail current responses had amplitudes 2- to 4-fold larger than responses to maximally effective concentrations of glutamate and glycine, indicating that NMDA receptor channels accumulate in the open-blocked state during co-application of agonist and 9-AA. The rise time and decay kinetics of tail current responses were faster than the response to brief applications of a maximally effective concentration of glutamate. Together, these results suggest that at +60 mV recovery from block by 9-AA occurs faster than the rate of opening of NMDA receptors in response to glutamate.5. Our experiments suggest that open channel block of NMDA receptors can provide a novel approach for measurement of both open probability and the first latency distribution for ion channel opening in response to the binding of agonists, and provide additional evidence suggesting that the delayed opening of NMDA receptor channels underlies slow activation and deactivation of responses to glutamate.