Functional Roles of Retinal Gap Junctions in Visual Processing

通过间隙连接（GJ）的电突触传递是脑中神经元通讯的一种重要模式 CNS。一个很好的例子是视网膜，其中五种主要神经元类型中的每一种都是通过 GJ广泛的分布，多样的连接蛋白亚基结构和视网膜GJ的调节表明， 视觉处理中功能角色的多样性;阐明这些角色形成了我们的长期目标 实验计划在这里，我们建议研究小鼠视网膜内层的GJs，这有助于丰富和 复杂多样的电路该建议的第一个目的是确定细胞对细胞的作用与 神经元整体相互作用在创建由视网膜神经节细胞显示的强大的相关活动中 （RGC）。相关的RGC活性被认为具有许多功能，包括增强信号传导， 显著性和编码有关视觉刺激的特定信息，如强度，大小和运动。虽然 现在很清楚，GJ对RGC邻国之间建立强大的协调活动至关重要， 确切的机制尚不清楚。虽然有人认为，耦合的研究资助机构之间的相互驱动 邻居可以产生协同射击，我们的初步数据表明，这不会发生。而是 似乎神经元集合内的连贯活动对于募集额外的RGC并产生 其连贯的活动。我们提出了一种多学科的方法， 药理学和光遗传学技术应用于转基因和敲除小鼠品系，以区分 负责相关RGC活动的回路。第二个目的将集中于各研资局之间的耦合 和无长突细胞（AC）。这种类型的电耦合广泛地发生在整个视网膜上，但这是如何发生的呢？ 由于缺乏实验平台， 可视化和靶向耦合的RGC-AC对以进行记录。我们将使用两个 技术：（1）用GJ-permenat染料Po-Pro-1标记细胞;和（2）使用转基因Grik 4小鼠 其中ON α-RGC和偶联AC表达荧光标记物的细胞系。对于这两个，我们将记录从耦合 对RGC和AC，以确定这种电相互作用对内分泌系统的反应活性的作用。 视网膜神经元在第三个目标中，我们将研究RGCs可以通过信号传导改变视网膜内活动的新想法， 通过互连的GJ回到AC。我们认为RGC可以改变偶联AC的活性， 反过来，通过传统的化学突触抑制其他神经节细胞。这种形式的视网膜内信号， 创造了一个提供新型侧抑制的回路。GJ通信的缺陷已经被牵连 在许多脑神经病中，包括与视网膜色素变性、青光眼 和缺血性视网膜病。这里提出的实验方案将扩展我们对 GJ的分布和生理作用，这是确定GJ如何发挥作用的重要前提。 功能障碍影响神经功能，从而为人类疾病的治疗指明了新的靶点。

Electrical synaptic transmission via gap junctions (GJs) is an important mode of neuronal communication in the CNS. An elegant example is the retina in which each of the five main neuronal types is electrically coupled via GJs. The broad distribution, diverse connexin subunit structure, and regulation of retinal GJs suggest a diversity of functional roles in visual processing; elucidating these roles forms the long-term goal of our experimental program. Here we propose to study the GJs in the inner mouse retina, which subserve a rich and complex variety of electrical circuits. The first aim of this proposal is to determine the role of cell-to-cell vs. neuron ensemble interactions in creating the robust, correlated activity displayed by retinal ganglion cells (RGCs). Correlated RGC activity is believed to have a number of functions, including enhancement of signal saliency and encoding of specific information about visual stimuli such as intensity, size, and motion. While it is now clear that GJs are critical to the creation of the robust concerted activity between RGC neighbors, the exact mechanism remains unclear. While it has been posited that reciprocal drive between coupled RGC neighbors can produce concerted firing, our preliminary data suggest that this does not occur. Rather, it appears that coherent activity within neuronal ensembles is necessary to recruit additional RGCs and produce their coherent activity. We propose a multidisciplinary approach combining electrophysiological, pharmacological, and optogenetic techniques applied to transgenic and knockout mouse lines to differentiate the circuits responsible for correlated RGC activity. The second aim will focus on the coupling between RGCs and amacrine cells (ACs). This type of electrical coupling occurs extensively across the retina, but how this affects neuronal activity has not been studied comprehensively due to a lack of an experimental platform to visualize and target coupled RGC-AC pairs for recording. We will target coupled RGC-AC pairs using two techniques: (1) labeling cells with the GJ-permenat dye Po-Pro-1; and (2) using the transgenic Grik4 mouse line in which ON α-RGCs and coupled ACs express fluorescent markers. For both, we will record from coupled pairs of RGCs and ACs to determine the role that this electrical interaction has on the response activity of inner retinal neurons. In the third aim we will study the novel idea that RGCs can alter intraretinal activity by signaling back to AC through interconnecting GJs. We posit that RGCs can alter the activity of coupled ACs, which, in turn, inhibit other ganglion cells via conventional chemical synapses. This form of intraretinal signaling thereby creates a circuit providing a novel form of lateral inhibition. Deficits in GJ communication have been implicated in a number of brain neuropathies, including visual impairments associated with retinitis pigmentosa, glaucoma and ischemic retinopathy. The experimental program proposed here will extend our understanding of the distribution and physiological roles of GJs, which forms an important prerequisite for determining how GJ dysfunction affects neural function so as to indicate novel targets for the treatment of human diseases.