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QUANTITATIVE ANALYSIS OF INFORMATION TRANSMISSION IN THE RETINAL RIBBON SYNAPSES

视网膜带突触信息传递的定量分析

基本信息

批准号：
11480245
负责人：
TACHIBANA Masao
金额：
$ 9.98万
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：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

Mechanisms of transmitter release from retinal bipolar cells were investigated electrophysiologically and morphologically. We obtained the following results.1. Axon terminals of goldfish bipolar cells were whole-cell clamped, and the membrane capacitance changes associated with exocytosis were measured. The released glutamate was simultaneously monitored electrophysiologically with a glutamate receptor rich neuron as a sensor. Prolonged depolarization of bipolar terminals resulted in a phasic release of glutamate (due to the first and second pools), which was followed by a small tonic release, suggesting the presence of the third pool.2. Activation of protein kinase C (PKC) in the presynaptic terminals of goldfish bipolar cells increased the amount of glutamate release. The double-pulse experiments revealed that the increase was ascribed to the increase in the pool size of the second pool. EM studies indicated that synaptic vesicles accumulated near the synaptic ribbons after the PKC activation.3. A pair of bipolar and ganglion cells was simultaneously whole-cell clamped in the slice preparation of the newt retina. Depolarization of a bipolar cell evoked an EPSC in the ganglion cell. Blockade of glutamate transporters resulted in the prolongation of the evoked EPSC.Glutamate transporters actually contribute to the shaping of the evoked EPSC and the light-induced responses.4. The function of GABA_c-receptors at bipolar terminals was examined in the slice preparation of the mouse retina. When GABA_c-receptors were intact, the light-induced current in amacrine cells composed mainly of the AMPA-receptor mediated current. After the blockage of GABA_c receptors, the light-induced current composed of the AMPA-receptor mediated current, which was followed by the NMDA-receptor mediated current. GABA_c-mediated feedback from amacrine cells regulate the amount of glutamate release from bipolar cells.

从电生理和形态学的角度研究了视网膜双极细胞递质释放的机制。我们得到了以下结果。1.采用全细胞钳夹法分离金鱼双极细胞轴突终末，测定胞吐过程中细胞膜电容的变化。释放的谷氨酸同时监测电生理与谷氨酸受体丰富的神经元作为传感器。双极终末去极化延长导致谷氨酸的阶段性释放（由于第一池和第二池），随后是小的强直性释放，表明存在第三池.在金鱼双极细胞突触前末梢蛋白激酶C（PKC）的激活增加谷氨酸的释放量。双脉冲实验表明，增加归因于第二池的池大小的增加。电镜研究表明，PKC激活后，突触带附近有突触小泡聚集.一对双极和神经节细胞同时全细胞夹在蝾螈视网膜的切片制备。双极细胞的去极化在神经节细胞中诱发EPSC。阻断谷氨酸转运体可延长诱发的EPSC，谷氨酸转运体参与了诱发的EPSC的形成和光诱导反应.在小鼠视网膜切片制备中，研究了双极末梢GABA_c受体的功能。当GABA_c受体完整时，无长突细胞的光诱导电流主要由AMPA受体介导的电流组成。阻断GABA_c受体后，光诱导电流由AMPA受体介导的电流和NMDA受体介导的电流组成。GABA_c介导的无长突细胞反馈调节双极细胞谷氨酸释放量。