Functional Roles of Retinal Gap Junctions in Visual Processing

经缝隙连接的电突触传递是脑内神经元传递的一种重要方式 中枢神经系统。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通过 GJS。广泛的分布，不同的连接蛋白亚单位结构，以及视网膜GJS的调节表明 视觉处理中功能角色的多样性；阐明这些角色是我们的长期目标 实验计划。在这里，我们建议研究小鼠视网膜内的GJS，它补充了丰富的和 复杂多样的电路。这项建议的第一个目标是确定细胞到细胞与 产生视网膜神经节细胞表现出的强健、相关活动的神经元集合相互作用 (RGCs)。相关的RGC活动被认为具有许多功能，包括增强信号 突出和编码有关视觉刺激的特定信息，如强度、大小和运动。虽然它是 现在清楚的是，GJS对于在研资局邻居之间建立强有力的协调活动至关重要， 确切的机制尚不清楚。虽然已经假设耦合的研资局之间的相互驱动 邻居可以产生协同射击，我们的初步数据表明这种情况并没有发生。相反，它 似乎神经元群中的一致活动对于招募更多的视网膜节细胞和产生 他们连贯的活动。我们提出了一种多学科的方法，将电生理、 药理学和光遗传学技术应用于转基因和基因敲除小鼠品系的分化 负责相关RGC活动的回路。第二个目标将集中在RGC之间的耦合 和无长突细胞(ACS)。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 由于缺乏实验平台，对神经元活动的影响还没有得到全面的研究 视觉化和目标化RGC-AC对以用于记录。我们将使用两个RGC-AC对作为目标 技术：(1)用GJ-Permenat染料Po-Pro-1标记细胞；(2)使用转基因Grik4小鼠 在α-RGC和偶联的AC上表达荧光标记的品系。对于这两种情况，我们都将从Couble录制 RGC和AC的配对，以确定这种电相互作用对INTERNAL反应活动的作用 视网膜神经元。在第三个目标中，我们将研究RGC可以通过信号改变视网膜内活动的新想法 通过互联GJS返回交流。我们假设RGC可以改变偶联的AC的活动，在 转而，通过常规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因此 创造了一种提供一种新形式的侧抑制的电路。GJ沟通缺陷已被牵连 在许多脑神经疾病中，包括与视网膜色素变性、青光眼相关的视觉障碍 以及缺血性视网膜病变。这里提出的实验计划将扩大我们对 GJS的分布和生理作用是决定GJS如何发挥作用的重要前提 功能障碍会影响神经功能，从而为人类疾病的治疗提供新的靶点。

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.