Electrical Synapses of Horizontal Cells

描述(申请人提供)：由视网膜电突触或缝隙连接形成的神经元网络对视觉信息处理具有重要的生理意义。水平细胞是二级中间神经元，通过缝隙连接电耦合形成致密的神经元网络，介导双极细胞和神经节细胞感受野的中心-周围拮抗组织。HC缝隙连接的调制是视网膜神经网络功能对不同光照水平适应性变化的基础。多巴胺是缝隙连接神经调节剂之一，在光适应过程中显著改变HC网络。总体而言，HCS是研究电耦合和神经网络可塑性功能方面的一个很好的模型系统。我研究的长期目标是了解HC电突触在视网膜可塑性和视觉信息处理中的作用。缺乏视杆和视锥的视网膜变性(RD)小鼠是研究哺乳动物HC电突触电生理特性的有利模型。平板式RD视网膜的使用使得可以很容易地接近HC以进行记录。我将这项技术与双全细胞膜片钳技术相结合，以证明通过HC缝隙连接获得电流电生理记录的可行性。这些技术可用于实现以下特定目标：特定目标1：表征HC电突触的电生理特性。具体地说，我将(1)测量缝隙连接电导和HC电耦合的耦合系数；(2)确定甘草甜素和细胞内H+是否影响HC电突触；(3)测试HC电突触是否起低通滤波器的作用。特定目标2：多巴胺对HC电突触的调节。具体地说，我将(1)表征外源性和内源性多巴胺对HC缝隙连接的调节；(2)确定多巴胺对HC电突触的细胞机制。这些研究将极大地促进我们对视网膜神经元网络在明/暗适应过程中的功能和可塑性的理解，以及对光感受器退变过程中视网膜功能改变的理解。

DESCRIPTION (provided by applicant): Neuronal networks formed by retinal electrical synapses, or gap junctions, are of physiological importance for visual information processing. Horizontal cells (HCs), second-order interneurons, are electrically coupled through gap junctions to form a dense neuronal network that mediates the antagonistic center-surround organization of bipolar and ganglion cell receptive fields. Modulation of HC gap junctions underlies adaptive changes in the function of retinal neuronal networks to different levels of illumination. Dopamine is one of the gap junction neuromodulators that significantly alters HC networks during light adaptation. Overall, HCs are an excellent model system to study the functional aspects of electrical coupling and neuronal network plasticity. The long-term goal of my research is to understand the role of HC electrical synapses in retinal plasticity and visual information processing. The retinal degeneration (rd) mouse that lacks rods and cones is an advantageous model for investigation of electrophysiological properties of mammalian HC electrical synapses. The use of flat-mount rd retinas permits HCs to be readily approached for recording. I have combined this technique with the dual whole-cell patch-clamp technique to demonstrate the feasibility of obtaining electrophysiological recordings of currents through HC gap junctions. These techniques can be utilized to achieve the following specific aims: Specific Aim 1: Characterization of electrophysiological properties of HC electrical synapses. Specifically, I will (1) measure gap junction conductance and coupling coefficient of HC electrical coupling; (2) determine whether carbenoxolone and intracellular H+ affect HC electrical synapses; (3) test whether HC electrical synapses function as a low-pass filter. Specific Aim 2: Modulation of HC electrical synapses by dopamine. Specifically, I will (1) characterize regulation of HC gap junctions by exogenous and endogenous dopamine; (2) determine the cellular mechanism of dopamine on HC electrical, synapses. These studies will greatly advance our understanding of the function and plasticity of retinal neuronal networks during light/dark adaptation and our understanding of retinal functional modification during photoreceptor degeneration.