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Experimental and Monte Carlo studies of calcium channel function and fast transmitter release at presynaptic active zones of the frog neuromuscular junction.

机译：青蛙神经肌肉接头突触前活动区钙通道功能和快速递质释放的实验和蒙特卡洛研究。

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摘要

During fast chemical synaptic transmission, neurotransmitter release is triggered by calcium (Ca2+) influx through voltage-gated Ca2+ channels (VGCCs) opened by an action potential (AP) at the nerve terminal. The magnitude and time course of neurotransmitter release is critically determined by the coupling between Ca2+ channels and synaptic vesicles. Studies of the quantitative dependence of transmitter release on the number of VGCCs provide important information for our understanding of the mechanisms that underlie the control and modulation of presynaptic release probability and kinetics. Using high-resolution calcium imaging techniques and variance analysis, I have determined the number of functional VGCCs within individual active zones (AZs) of the adult frog neuromuscular junction (NMJ) and their opening probability in response to single AP stimulation. The results have shown that the average number of VGCCs within individual active zones was relatively small (∼28) and the average opening probability of individual Ca2+ channels during a presynaptic AP was very low (∼0.24). Therefore, it is predicted that an action potential induced opening of relatively few Ca2+ channels in a single active zone. Furthermore, by combining pharmacological channel block, calcium imaging, postsynaptic recording, and 3D Monte Carlo diffusion-reaction simulations, I have studied the coupling of single Ca2+ channel openings to the triggering of vesicle fusion. I have provided evidence that Ca2+ entry through single open Ca2+ channels at the nerve terminal can be imaged directly and that such Ca2+ flux is sufficient to trigger synaptic vesicle fusion. I have further shown that following a single AP, the Ca2+ influx through a single open channel plays the predominant role in evoking neurotransmitter release, while Ca2+ ions derived from a collection of open Ca2+ channels are rarely required for vesicle exocytosis at this synapse.
机译：在快速的化学突触传递过程中，神经递质的释放是由钙（Ca2 +）通过电压门控的Ca2 +通道（VGCC）流入而触发的，该通道由神经末梢的动作电位（AP）打开。神经递质释放的幅度和时间过程由Ca2 +通道与突触小泡之间的耦合决定。递质释放对VGCC数量的定量依赖性研究为我们理解突触前释放概率和动力学的控制和调节机理提供了重要信息。使用高分辨率钙成像技术和方差分析，我确定了成年青蛙神经肌肉接头（NMJ）各个活动区域（AZ）内功能性VGCC的数量及其对单个AP刺激的响应打开可能性。结果表明，单个活动区内的VGCC的平均数量相对较少（〜28），而突触前AP期间单个Ca2 +通道的平均打开概率非常低（〜0.24）。因此，据预测动作电位在单个活性区域中引起相对较少的Ca 2+通道的开放。此外，通过结合药理通道阻滞，钙成像，突触后记录和3D蒙特卡洛扩散反应模拟，我研究了单个Ca2 +通道开口与囊泡融合触发的耦合。我提供的证据表明，可以直接对通过神经末梢的单个开放Ca2 +通道进入的Ca2 +进行成像，并且此类Ca2 +通量足以触发突触小泡融合。我进一步表明，在单个AP后，通过单个开放通道的Ca2 +流入在引起神经递质释放中起主要作用，而在此突触中囊泡胞吐很少需要来自一系列开放Ca2 +通道的Ca2 +离子。

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  • 作者

    Luo, Fujun.;

  • 作者单位

    University of Pittsburgh.;

  • 授予单位 University of Pittsburgh.;
  • 学科 Biology Neuroscience.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 143 p.
  • 总页数 143
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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