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Regulation of transmitter release from retinal neurons with synaptic ribbons

突触带对视网膜神经元递质释放的调节

基本信息

批准号：
09480238
负责人：
TACHIBANA Masao
金额：
$ 7.3万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09480238/
关键词：
retina synapse chemical transmitter glutamate calcium current glutamate receptors protein kinase synaptic vesicles プロテインキナーゼC 興奮性シナプス後電位

项目摘要

Bipolar cells, the second order neurons in the retina, respond to light stimulation with graded potentials. In their axon terminals there are synaptic ribbons, to which synaptic vesicles are attached. To elucidate the regulatory mechanisms of transmitter (glutamate) release, the patch-clamp technique was applied to the axon terminals of Mb1 bipolar cells that were enzymatically isolated from the goldfish retina. We measured simultaneously the Ca current and membrane capacitance changes associated with fusion of synaptic vesicles. At the same time, the released glutamate was monitored electrophysiologically with glutamate receptor-rich neurons. The following conclusions were obtained. 1) Glutamate is released with a minimal delay of-1 ms after the onset of the Ca current. 2) Transmitter release is stopped within 300 ms after the termination of the Ca current. 3) There are at least two kinds of synaptic vesicle pools ; an immediately releasable pool and a reserve pool. 4) Activation of protein kinase C in bipolar cells potentiates transmitter release by increasing the size of the reserve pool. 5) The immediately releasable pool and the reservoir pool may correspond to synaptic vesicles attached to the bottom row of the synaptic ribbons and those to the upper rows, respectively. Furthermore, we investigated properties of glutamatergic synaptic transmission by simultaneously voltage-clamping a pair of connected bipolar cells and their post-synaptic neurons (amacrine or ganglion cells) in the newt retinal slice preparation. The following conclusions were obtained. 6) Only non-NMDA receptors may be expressed in the postsynaptic regions immediately beneath the release sites of bipolar cells, whereas NMDA receptors slightly away from the release sites. 7) Both non-NMDA and NMDA receptors cooperate to transfer the graded photoresponses of bipolar cells proportionally to post-synaptic neurons.

双极细胞是视网膜中的二级神经元，对光刺激的反应具有渐变电位。在轴突终末有突触带，突触小泡附着在突触带上。为了阐明递质(谷氨酸)释放的调节机制，将膜片钳技术应用于酶法分离的金鱼视网膜Mb1双极细胞的轴突终末。我们同时测量了与突触小泡融合相关的钙电流和膜电容的变化。同时，用富含谷氨酸受体的神经元对释放的谷氨酸进行电生理监测。得到了以下结论。1)钙电流开始后，谷氨酸以-1ms的最小延迟释放。2)在钙电流终止后300ms内停止变送器释放。3)突触小泡池至少有两种：可立即释放池和备用池。4)双极细胞中蛋白激酶C的激活通过增加储备池的大小来增强递质的释放。5)可立即释放池和储存池可能分别对应于附着在突触带底部的突触小泡和附着在突触顶端的突触小泡。此外，在Newt视网膜切片制备中，我们通过同时电压钳制一对相连的双极细胞及其突触后神经元(无长突细胞或神经节细胞)来研究谷氨酸能突触传递的特性。得到了以下结论。6)在双极细胞释放部位正下方的突触后区域可能只有非NMDA受体表达，而NMDA受体仅在距离释放部位稍远的部位表达。7)非NMDA受体和NMDA受体协同作用，将双极细胞的渐变光反应按比例传递给突触后神经元。