Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile.
Physiology Institute I, Alberts Ludwig University, Freiburg, Germany.
Sci Rep. 2018 Feb 15;8(1):3123. doi: 10.1038/s41598-018-21119-0.
A17 amacrine cells are an important part of the scotopic pathway. Their synaptic varicosities receive glutamatergic inputs from rod bipolar cells (RBC) and release GABA onto the same RBC terminal, forming a reciprocal feedback that shapes RBC depolarization. Here, using patch-clamp recordings, we characterized electrical coupling between A17 cells of the rat retina and report the presence of strongly interconnected and non-coupled A17 cells. In coupled A17 cells, evoked currents preferentially flow out of the cell through GJs and cross-synchronization of presynaptic signals in a pair of A17 cells is correlated to their coupling degree. Moreover, we demonstrate that stimulation of one A17 cell can induce electrical and calcium transients in neighboring A17 cells, thus confirming a functional flow of information through electrical synapses in the A17 coupled network. Finally, blocking GJs caused a strong decrease in the amplitude of the inhibitory feedback onto RBCs. We therefore propose that electrical coupling between A17 cells enhances feedback onto RBCs by synchronizing and facilitating GABA release from inhibitory varicosities surrounding each RBC axon terminal. GJs between A17 cells are therefore critical in shaping the visual flow through the scotopic pathway.
A17 无长突细胞是暗视觉通路的重要组成部分。它们的突触小球接受来自视杆双极细胞 (RBC) 的谷氨酸能输入，并将 GABA 释放到同一 RBC 末梢上，形成一种互惠反馈，从而塑造 RBC 的去极化。在这里，我们使用膜片钳记录技术对大鼠视网膜 A17 细胞之间的电耦合进行了表征，并报告了存在强相互连接和未连接的 A17 细胞。在耦合的 A17 细胞中，诱发电流优先通过 GJ 流出细胞，一对 A17 细胞中突触前信号的交叉同步与其耦合程度相关。此外，我们证明刺激一个 A17 细胞可以在相邻的 A17 细胞中诱导电和钙瞬变，从而证实了通过 A17 耦合网络中的电突触传递信息的功能。最后，阻断 GJ 会导致 GABA 对 RBC 产生的抑制反馈的幅度显著降低。因此，我们提出 A17 细胞之间的电耦合通过同步和促进围绕每个 RBC 轴突末梢的抑制性小球释放 GABA，增强了对 RBC 的反馈。因此，A17 细胞之间的 GJ 在塑造暗视觉通路上的视觉流中起着至关重要的作用。
