Transmitter substances of retinal neurons

有关突触传递的知识对于理解神经系统是必不可少的。本研究的目的是了解突触递质在脊椎动物视网膜中的作用。我们用膜片钳技术在全细胞形态上记录了孤立神经元的膜电流。从金鱼、乌龟和小鼠的视网膜中分离出细胞。以下是主要发现的清单1.光感受器对L-谷氨酸的摄取现在人们普遍认为L-谷氨酸是从光感受器释放出来的。L-谷氨酸被光感受器通过运输系统摄取。Na~(++)的电化学梯度是转运的能量来源，3个Na~(++)与每个谷氨酸模块共转运。因此，这个系统是产生电的，在所有亚型的光感受器中引起去极化。这一机制可能参与了异种光感受器之间的兴奋性相互作用。2.氨基丁酸对…的抑制作用更多的e细胞转变为双极细胞。GABA通过开放GABA受体介导的氯离子通道诱导金鱼双极细胞超极化。小鼠双极细胞的瞬时钙电流。小鼠双极细胞钙电流呈T型，表现为快速失活。I_&lt；Ca&gt；流经轴突终末和胞体。假设从双极单元终端释放的发射机也是瞬时的。因此，小鼠双极细胞的i&lt；ca&gt；可能在形成无长突细胞和神经节细胞的瞬时光诱发反应中起作用。海龟视网膜中光感受器和水平细胞之间的连接。海龟锥体的亚型很容易通过它们彩色的油滴在形态上识别出来。利用这一指标，我们分析了光感受器和水平细胞的连接性。与普遍认为的相反，红敏视锥与H_2和H_3水平细胞有直接联系。基于这一新发现，对颜色视觉模型进行了讨论。较少

Knowledge on the synapic transmission is essential for the understanding of a nervous system. The aim of the present study was to understand the action of synaptic transmitter in the vertebrate retina. We recorded membrane currents of solitary neurons by using patch clamp technique in the whole cell configuration. Cells were dissociated from the retina of goldfish, turtle and mouse. The following is a list of major findings.1. Uptake of L-glutamate by photoreceptors. It is now generally accepted that L-glutamate is released from photoreceptors. L-Glutamate is taken up by photoreceptors by a transport system. Electrochemical gradient of Na^+ is the enegy source for transport; 3 Na^+ are co-transported with each glutamate modecule. Thus, this system is electrogenic, causing depolarization in all subtypes of photoreceptors. It is likely that this mechanism contribute in excitatory interaction among heterologous photoreceptors.2 Inhibition mediated by -aminobutyric acid (GABA) from amacrin … More e cell to bipolar cell. GABA induced hyper-polarization in goldfish bipolar cells by opening chloride channels mediated by GABAalpha receptor.3. Transient calcium current of mouse bipolar cells. Calcium current (I_<ca>) in mouse bipolar cells is T-type showing rapid inactivation. I_<ca> flowed through the axon terminal as well as the soma. It is hypothesized that the transmitter release from bipolar cell terminal is also transient. Thus, I_<ca> of mouse bipolar cells may contribute in shaping transient light evoked responses in amacrine and ganglion cells.4. Connectivity between photoreceptors and horizontal cells in the turtle retina. Subtypes of turtle cones are readily identified morphologically by their colored oil droplets. Using this index, we analyzed connectivity of photoreceptors and horizontal cells. Contrary to the general belief, red-sensitive cones were found to make direct connection to H_2 and H_3 horizontal cells. Color vision models are discussed based on this new finding. Less