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.

神经末端的生理活性对于体液控制和脑功能至关重要。因此，对这些活动的分析对于理解高阶的生物学功能非常重要。在这项研究中，我们旨在通过在视频增强的DIC光学显微镜下观察神经末端的分子机制。在培养的牛铬蛋白细胞中，该过程的末端与相邻细胞建立了类似的接触。突触前末端的电刺激引起了末端中颗粒的许多弹出反应。这些响应是[Ca^<2+>] o依赖性的，并由CD^<2+>或La^<3+>抑制。响应最小的颗粒直径为0.1妈妈。这种反应的频率很高，尤其是在与相邻细胞接触的区域。重复刺激引起促进。刺激许多脉冲引起的疲劳，其特征是末端缺乏颗粒。这些发现表明弹出响应具有突触反应常见的特性。因此，我们得出的结论是，这些弹出反应是末端中颗粒的胞吐作用。同时的CA形成和DIC成像表明在突触样接触中从一个细胞到另一个细胞的信号传递，提供了直接可视化突触中胞吐作用的证据。尚未证实肿胀假说和碰撞假设以开始胞吐作用。可能是在胞吞作用的最后一步处的膜融合是由质膜中的某些CA依赖性钥匙分子引发的。除此之外，我们还发现了神经末端电刺激引起的丝状疾病的快速发芽。这种发芽可能与突触可塑性深深相关。