Glutamatergic synaptic transmission in the vertebrate retina

脊椎动物视网膜中的谷氨酸突触传递

• 批准号: 07458218
• 负责人: TACHIBANA Masao
• 金额: $ 4.8万
• 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: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07458218/
• 关键词: retina; synapse; chemical transmitter; glutamate; glutamate receptor; calcium ion; calcium pump; sodium・calcium exchanger; エクソサイトーシス; カルシウムチャネル; カルシウム依存性カリウムチャネル; カルシウム依存性塩素チャネル

Glutamate plays a key role in retinal synaptic transmission. Firstly, we examined Ca^<2+> buffering system in the presynaptic terminals of bipolar cells. Bipolar cells with large presynaptic terminals were isolated from the goldfish retina. The presynaptic Ca current (I_<Ca>) was measured under the whole-cell voltage clamp, and at the same time, the cytoplasmic free Ca^<2+> concentration ([Ca^<2+>]_i) in the terminal was monitored with fura-2 fluorimetry. Activation of I_<Ca> by a depolarizing pulse evoked a Ca^<2+> transient. Its peak amplitude was determined mainly by Ca^<2+> -binding substances, while its recovery was due to the extrusion of Ca^<2+> by Ca^<2+> -ATPase and Na^+/Ca^<2+> exchanger in the plasma membrane. Submembrane [Ca^<2+>]_i, which was estimated using the Ca^<2+> -activated K^+ channel as a Ca^<2+> probe, increased to >10muM upon activation of Ca^<2+> channels. Secondly, we examined the relationship between I_<Ca> and glutamate release. Glutamate release was monitored with a NMDA-receptor rich neuron or as membrane capacitance changes associated with exocytosis. Glutamate release composed of two components ; the rapid component seemed to be due to the fusion of immediately releasable synaptic vesicles, while the delayd slow component seemed to reflect the mobilization of releasable synaptic vesicles. Thirdly, using retinal slice preparation, we examined the properties of glutamate receptors in ganglion cells. Analysis of EPSPs, which were evoked spontaneously, by the electrical stimulation of bipolar cells, or by light stimulation, demonstrated that glutamate released from bipolar cells activated both NMDA and non-NMDA receptors.

谷氨酸在视网膜突触传递中起关键作用。首先，我们研究了双极细胞突触前末梢的Ca^<2+>缓冲系统。从金鱼视网膜分离出具有大突触前终末的双极细胞。用全细胞电压钳技术测定突触前钙电流（I）<Ca>，同时用Fura-2荧光法测定突触终末胞浆游离Ca^2+浓度（[Ca^2+] i）。去<Ca>极化脉冲激活I_2引起Ca^&lt;2+&gt;瞬变.其峰值主要由Ca^2+结合物质决定，而其恢复则是由于质膜上Ca ^2+-ATPase和Na^+/Ca^2+交换体对Ca^2+的挤出。用Ca^&lt;2 +&gt;激活的K^+通道作为Ca^&lt;2 +&gt;探针测定的亚膜[Ca^&lt;2+&gt;]_i在Ca^&lt;2+&gt;通道激活后增加到&gt; 10 μ M。其次，我们研究了I_2和谷氨酸释放之间的关系<Ca>。谷氨酸释放监测与NMDA受体丰富的神经元或膜电容的变化与胞吐作用。谷氨酸的释放由两部分组成;快速的部分似乎是由于立即释放的突触囊泡的融合，而延迟的缓慢的部分似乎反映了可释放的突触囊泡的动员。第三，利用视网膜切片制备技术，研究了神经节细胞谷氨酸受体的特性。电刺激双极细胞或光刺激自发诱发的EPSP的分析表明，从双极细胞释放的谷氨酸激活NMDA和非NMDA受体。

项目成果

立花政夫: "中枢神経系における伝達物質放出機構研究のモデル:網膜双極細胞" 神経眼科. 14(印刷中). (1997)

Masao Tachibana：“研究中枢神经系统递质释放机制的模型：视网膜双极细胞”《神经眼科》14（出版中）。

Kobayashi,K.,et al.: "Ca^<2+> regulation in the presynaptic terminals of goldfish retinal bipcolar cells." Journal of Physiology. 483. 79-94 (1995)

Kobayashi,K.,et al.：“金鱼视网膜双角细胞突触前末梢的 Ca^2 调节”。