COMPUTATIONAL AND PHYSIOLOGICAL STUDY OF RETINAL NEURONS

本研究方案旨在提高我们对脊椎动物视网膜神经节细胞和无突细胞兴奋性调控的生理机制的认识。我们将在本研究中使用的方法是建模和计算机模拟分析以及生理和形态学实验的独特结合。这项联合研究的主要目标之一将是扩展和完善神经节细胞中脉冲产生的详细多通道模型，特别强调树突在这些细胞的脉冲编码特性中所起的作用。在这个项目中，我们将使用贴片电极技术来研究单个、已识别的、解离的神经节细胞的树突，以识别和表征树突中电压门控离子通道的类型。这些研究的数据将用于完善我们的神经节细胞模型，以更准确地反映树突对冲动产生的贡献。类似的模型研究将在产生脉冲活动的无分泌细胞中进行。本研究的第二阶段是研究双极细胞末端的递质释放机制，特别强调带状突触，它似乎是谷氨酸胞外释放的放大装置。该方法还将包括AMPA和NMDA受体连接到不同细胞区域的模型，使用现实细胞形态的室室模型。AMPA和NMDA谷氨酸受体产生的突触电流的时间过程模型将基于我们将使用快速灌注技术进行的动力学研究。我们还将生成一个多离子通道模型来模拟哺乳动物神经节细胞中的脉冲编码，该模型基于猫神经节细胞全细胞记录的真实形态和脉冲序列记录。本研究的目的是制定将协同工作的模型，以指导和加强我们的实验工作，以破译对三阶视网膜神经元功能至关重要的机制。

This research proposal is designed to improve our understanding of the physiological mechanisms which regulate the excitability of ganglion and amacrine cells in the vertebrate retina. The methods we will use in this study represent a unique combination of modeling and computer simulation analysis together with physiological and morphological experiments. One of the major objectives of this combined study will be to expand and refine a detailed, multichannel model of impulse generation in ganglion cells with special emphasis on the role which dendrites play in contributing to the impulse encoding properties of these cells. For this project we will use patch-electrode techniques directed to studies of the dendrites of single, identified, dissociated ganglion cells to identify and characterize the types of voltage-gated ion channels in dendrites. Data from these studies will be used to refine our ganglion cell model to more accurately reflect the contribution which dendrites make to impulse generation. Similar modeling studies will be carried out in amacrine cells which generate impulse activity. A second phase of this research is to examine the mechanisms of transmitter release from bipolar cell terminals with special emphasis on the ribbon synapses which appear to serve as an amplification device for exocytotic release of glutamate. This approach will also include models of AMPA and NMDA receptors connected to different cellular regions using compartmental models of realistic cell morphologies. Models of the time course of synaptic currents generated by AMPA and NMDA glutamate receptors will be based on kinetic studies we will carry out using rapid perfusion techniques. We will also generate a multiple ion channel model to simulate impulse encoding in mammalian ganglion cells, based on realistic morphologies and impulse train records from whole-cell recordings of cat ganglion cells. The purpose of this research is to formulate models which will work in synergy to guide and enhance our experimental efforts to decipher to mechanisms that are critical for function among third-order retinal neurons.