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Molecular Mechanism of Neurotransmission Studied by Ultra-High Power Light Microscopy

超高功率光学显微镜研究神经传递的分子机制

基本信息

批准号：
03454566
负责人：
TERAKAWA Susumu
金额：
$ 3.39万
依托单位：
Okazaki National Research Institutes
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

项目摘要

Physiological activities in nerve terminals are vital for humoral control and brain function. Therefore, analyses of these activities are very important for understanding biological functions of the higher order. In this study, we aim at elucidation of molecular mechanisms of nerve terminals by observing them under a video-enhanced DIC light microscope. In cultured bovine chromaffin cells, terminals of the processes made synapselike contacts with neighboring cells. Electrical stimulation of the presynaptic terminal induced many popping responses of granules in the terminal. These responses were [Ca^<2+>]o dependent and suppressed by Cd^<2+> or La^<3+>. The smallest granule responded was 0.1 mum in diameter. The frequency of such responses were very high especially at areas which were in contact with the neighboring cell. Repetitive stimulation induced facilitation. Stimulation with many pulses induced fatigue characterized by a lack of granules in the terminals. These finding indicated that popping responses bear properties common to synaptic responses. Therefore, we concluded that these popping responses are exocytosis of granules in the terminal. Simultaneous Ca-imaging and DIC-imaging demonstrated a signal transmission from one cell to the other in the synapse-like contact, providing evidence for direct visualization of exocytosis in the synapse. Neither the swelling hypothesis nor the collision hypothesis is confirmed for initiation of exocytosis. Probably, membrane fusion at the final step of exocytosis is initiated by some Ca-dependent key molecules in the plasma membrane. In addition to this, we also found rapid sprouting of filopodia induced by electrical stimulation in nerve terminals. This sprouting may be deeply involved in the synaptic plasticity.

神经末梢的生理活动对于体液控制和大脑功能至关重要。因此，对这些活动的分析对于理解高级生物功能非常重要。在这项研究中，我们旨在通过在视频增强 DIC 光学显微镜下观察神经末梢的分子机制来阐明它们。在培养的牛嗜铬细胞中，突起的末端与邻近细胞形成突触状接触。突触前末梢的电刺激引起末梢颗粒的许多爆裂反应。这些反应是[Ca^2+]o依赖性的并且被Cd^2+或La^3+抑制。响应的最小颗粒直径为0.1微米。这种反应的频率非常高，尤其是在与相邻细胞接触的区域。重复刺激诱导促进。许多脉冲的刺激会引起疲劳，其特征是末端缺乏颗粒。这些发现表明爆裂反应具有突触反应所共有的特性。因此，我们得出结论，这些爆裂反应是末端颗粒的胞吐作用。同时 Ca 成像和 DIC 成像证明了突触样接触中从一个细胞到另一个细胞的信号传输，为突触中胞吐作用的直接可视化提供了证据。对于胞吐作用的启动，膨胀假说和碰撞假说均未得到证实。胞吐作用最后一步的膜融合可能是由质膜中一些依赖 Ca 的关键分子引发的。除此之外，我们还发现电刺激神经末梢会引起丝状伪足的快速萌芽。这种发芽可能与突触可塑性密切相关。