Synaptic Function and Organization of the Mammalian Retina

描述（由申请人提供）：本提案的目标是了解成熟哺乳动物视网膜中复杂视觉处理的突触机制和神经回路，重点研究方向选择回路中单个突触的功能和组织。提出的研究是基于最近的发现，确定了关键的突触相互作用的产生方向选择性。这些发现表明，在潜在的神经元回路中，突触复杂性的水平是以前未被认识到的。他们揭示了在微电路层面上理解定向计算机制的重要性和可能性。为了直接了解方向选择微电路的功能和组织，本文提出了一种新的实验方法，该方法集成了双光子成像、双膜片钳记录、斑点紫外线释放和转基因技术，从而可以在完整的视网膜网络中测量单个突触位点的神经元连接和相互作用，并在同一实验中与细胞的形态和功能特性相关联。本实验旨在了解(1)成熟视网膜中胆碱能传递的突触机制，(2)星爆无突细胞与定向选择神经节细胞之间单个胆碱能突触和gaba能突触的功能组织，(3)星爆无突细胞之间gaba能突触的功能组织，以及(4)双极细胞轴突末端的突触相互作用。这些实验的结果有望在突触水平和完整视网膜回路中为树突和轴突计算的本质提供新的见解。这种方法也可能为研究其他中枢神经系统回路中单个突触的功能和连通性提供一种新的实验范式。

DESCRIPTION (provided by applicant): The goal of this proposal is to understand the synaptic mechanism and neuronal circuitry underlying complex visual processing in the mature mammalian retina, with a focus on the function and organization of individual synapses in the direction selective circuit. The proposed study is based on recent findings that identified critica synaptic interactions underlying the generation of direction selectivity. These findings suggested a previously unappreciated level of synaptic intricacy in the underlying neuronal circuit. They revealed the importance, as well as the possibility, to understand the mechanism of directional computation at a microcircuit level. In order to gain direct knowledge of the function and organization of the direction-selective microcircuits, a novel experimental approach is proposed here, which integrates two-photon imaging, dual patch-clamp recording, spot UV uncaging, and transgenic technology, so that neuronal connectivity and interactions at individual synaptic sites can be measured in an intact retinal network and correlated with the morphological and functional properties of the cells in the same experiment. The proposed experiments are designed to understand (1) the synaptic mechanism of cholinergic transmission in the mature retina, (2) the functional organization of individual cholinergic and GABAergic synapses between starburst amacrine and direction-selective ganglion cells, (3) the functional organization of GABAergic synapses between starburst amacrine cells, and (4) the synaptic interactions at bipolar cell axon terminals. Results from these experiments are expected to provide novel insights into the nature of dendritic and axonal computation at a synaptic level and in an intact retinal circuit. This approach may also provide a novel experimental paradigm for studying the function and connectivity at individual synapses in other CNS circuits.