Multiple components of synaptosomal [3H]-gamma-aminobutyric acid release resolved by a rapid superfusion system.
Multiple components of synaptosomal [3H]-gamma-aminobutyric acid release resolved by a rapid superfusion system.
复制标题
通过快速灌注系统解析突触体 [3H]-γ-氨基丁酸释放的多种成分。
DOI：
10.1021/bi00428a026
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发表时间：
1989
期刊：
影响因子：
2.9
通讯作者：
Goldin,SM
中科院分区：
文献类型：
--
作者：
Turner,TJ;Goldin,SM
摘要：采用一种新的快速灌流方法，以60 ms的时间分辨率研究了大鼠脑突触体释放[3 H]-氨基丁酸（[3 H] GABA）。通过相关的GABA摄取系统，用[3 H] GABA预标记突触体。KCl去极化刺激GABA释放的至少三种不同组分：（1）阶段性Ca依赖性组分，其快速发展并以至多60 ms的时间常数衰减;（2）紧张性Ca依赖性组分，其在KCl去极化结束后持续存在;（3）Ca非依赖性组分。GABA释放的三个组分是截然不同的。50 µ Cd 2+选择性阻断相位成分，而100 µ Ni 2+选择性阻断强直成分。钙非依赖性成分被哌啶甲酸（IC 50 = 21 µ）选择性阻断，哌啶甲酸是一种已知的Na+依赖性GABA摄取抑制剂。Ca ~（2+）离子载体A23187诱发的Ca依赖性GABA释放的时程和幅度与去极化诱发的Ca依赖性GABA释放的时程和幅度基本一致。这一结果表明，钙依赖性GABA的释放主要取决于Ca 2+进入神经末梢，而不是去极化，本身。相成分的性质表明，它通常是由一个电压敏感的钙离子通道，这是功能和药理学不同于先前描述的。GABA释放的Ca-独立成分可能是由Na-依赖性的、产电的GABA摄取系统的逆转介导的。在生理相关的时间尺度上识别GABA释放的多个组分的能力可以提供被认为影响大脑神经传递的药物的作用机制的更精确的定义。氨基丁酸（GABA）是中枢神经系统中主要的抑制性神经递质，在大脑的大部分区域都有大量发现。由于GABA的重要性以及通过改变对GABA的突触后反应而起作用的药物的可用性，如苯二氮卓类和巴比妥类，对GABA能传递的兴趣一直很强烈。对GABA的突触后反应的动力学以及负责药物和毒素作用的机制已被详细研究（Barker & Owen，1986）。然而，GABA的突触前释放的类似研究有限，因此突触前释放的突触后事件的时间过程的贡献是不确定的。使用突触前神经末梢或脑切片的制备物进行的GABA释放的研究受到不确定的时间分辨率的影响，释放通常以秒至分钟的时间尺度测量（Cotman等人，1976; Levi等人，1981年）。
Revised Manuscript Received September 7, 1988 abstract: Release of [3H]--aminobutyric acid ([3H] GABA) from rat brain synaptosomes was studied with 60-ms time resolution, using a novel rapid superfusion method. Synaptosomes were prelabeled with [3H] GABA via an associated GABA uptake system. KC1 depolarization stimulated at least three distinct components of GABA release:(1) a phasic Ca-dependent component, which develops rapidly and decays with a time constant of at most 60 ms;(2) a tonic Ca-dependent component that persists after KC1 de-polarization is ended;(3) a Ca-independent component. The three components of GABA release are pharmacologically distinct. The phasic component was selectively blocked by 50 µ Cd2+, while the tonic component was selectively blocked by 100 µ Ni2+. The Ca-independent component was selectively blocked by nipecotic acid (IC50= 21 µ), a known inhibitor of Na+-dependent GABA uptake. The time course and amplitude of Ca-dependent GABA release evoked by the Ca2+ ionophoreA23187 were nearly identical with Ca-dependent release evoked by depolarization. This result indicates that Ca-dependent GABA release depends primarily on Ca2+ entry into the nerve terminal, and not depolarization, per se. The properties of the phasic component suggest that it is normally initiated by a voltage-sensitive Ca2+ channel that is functionally and pharmacologicallydistinct from those previously described. The Ca-independent component of GABA release is probably mediated by reversal of the Na-dependent, electrogenic GABA uptake system. The ability to identify multiple components of GABA release on a physiologically relevant time scale may afford a more precise definition of the mechanism of action of drugs thought to affect neurotransmission in the brain.-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the central nervous system and is found in abundance in most regions of the brain. Interest in GAB-Aergic transmission has been intense due tothe importance of GABA and to the availability of drugs that act by modifying the postsynaptic response to GABA, such as benzodiazepines and barbiturates. The kinetics of the postsynaptic response to GABA and mechanisms responsible for the action of drugs and toxins have been studied in detail (Barker & Owen, 1986). However, similar studies of the presynaptic release of GABA have been limited, and therefore the contribution of presynaptic release to the time course of postsynaptic events is uncertain. Studies of GABA release using preparations of presynaptic nerve terminals or brain slices have sufferedfrom undefined temporal resolution, with release generally measured on a second to minute time scale (Cotman et al., 1976; Levi et al., 1981).