Plasticity and Function of the Rod/Cone Gap Junction

杆/锥联轴器是二次杆通道的入口点。我们的总体假设是昼夜节律 视杆/视锥耦合的光诱导调制改变了视网膜功能，并在整个过程中产生了深远的影响 视觉系统根据一天中的不同时间。电突触，也被称为缝隙连接，是常见的 将神经元连接成耦合网络的积木。尽管电突触表现出高度的 关于可塑性，在理解这种可塑性如何改变电路活动和输出方面存在着根本的差距。 我们预计，学习如何控制电耦合可能会有有用的临床潜力。我们有 开发出(1)从相邻的小鼠光感受器对记录直接测量跨连接电导的能力；(2)杆状和锥体特异的连接蛋白36(Cx36)基因敲除(XO)小鼠品系。在……里面 这些老鼠，没有杆/锥耦合，模仿白天或明亮的光线。(3)拟磷突变体Cx36 有条件敲入(Cx36-DEDD)线，显示饱和的杆/锥耦合，相当于夜间；以及 (4)我们挽救了褪黑激素合成的同源B6小鼠系--一个重要的昼夜节律时钟信号 在大多数小鼠品系中缺失。来自同基因系的视网膜显示出强烈的多巴胺昼夜节律变化。 放手。 在目标1中，通过棒/锥对的记录，我们将测量棒与棒之间的间隙结电导 和锥体，以检验杆/锥体耦合跨度从~0到1,000+ps的假设，反映集体 褪黑素、多巴胺和周围光线的作用。我们已经证明，在Cx36中没有杆/锥联接 XOS(模拟白天)，我们预计Cx36-DEDD(模拟夜间)的耦合最大。我们将决定 杆/锥间隙结电导随时间的变化(同源B6线)。 在目标2中，我们将从视锥细胞和神经节细胞进行记录，以检验以下假设：视杆细胞中的信号 次要视杆通路随着时间的不同而改变。我们希望我们的突变系以最小的输入来设定限制 在Cx36 XO(模拟白天)和最大输入在Cx36-DEDD线路(模拟夜间)。 在目标3中，我们将检查完整小鼠的视觉行为，以测量不活动(Cx36)的影响 XO，模拟白天)和饱和视杆/锥体途径(Cx36-DEDD，模拟夜间)。我们将测试 假设杆/锥耦合可塑性有助于对比敏感度和视觉的日常调节- 引导性行为。 我们的工作将提供一个最好的例子，说明一个单一的电子突触如何改变视网膜功能，从而影响 视觉感知。这项研究将有助于确定生物钟作用的一般原则和 神经回路中突触可塑性的日常变化与大脑功能和行为有关。

Rod/cone coupling is the entry point to the secondary rod pathway. Our overall hypothesis is that the circadian and light-induced modulation of rod/cone coupling changes retinal function and has profound effects throughout the visual system according to the time of day. Electrical synapses, also known as gap junctions, are common building blocks that connect neurons into coupled networks. Although electrical synapses display a high degree of plasticity, there is a fundamental gap in understanding how this plasticity modifies circuit activity and output. We anticipate that learning how to control electrical coupling may have useful clinical potential. We have developed (1) the capability to record from pairs of adjacent mouse photoreceptors to directly measure the trans-junctional conductance; (2) rod-specific and cone-specific connexin36 (Cx36) knockout (XO) mouse lines. In these mice, there is no rod/cone coupling, mimicking daytime or bright light. (3) a phospho-mimetic mutant Cx36 conditional knock-in (Cx36-DEDD) line, which displays saturated rod/cone coupling, equivalent to night time; and (4) a congenic B6 mouse line in which we rescued melatonin synthesis—an important circadian clock signal that is missing in most mouse strains. Retinas from the congenic line show robust circadian variations in dopamine release. In aim 1, by recording from rod/cone pairs, we will measure the gap junction conductance between rods and cones to test the hypothesis that rod/cone coupling spans from ~ 0 to 1,000+ pS, reflecting the collective action of melatonin, dopamine, and ambient light. We have shown there is no rod/cone coupling in the Cx36 XOs (mimics daytime) and we expect maximal coupling in the Cx36-DEDD (mimics nighttime). We will determine how the rod/cone gap junction conductance changes by time of day (congenic B6 line). In aim 2, we will record from cones and from ganglion cells to test the hypothesis that rod signals in the secondary rod pathway change by time of day. We expect our mutant lines to set the limits, with minimal input in the Cx36 XOs (mimics daytime) and maximal input in the Cx36-DEDD line (mimics nighttime). In aim 3, we will examine visual behavior in the intact mouse to measure the effect of an inactive (Cx36 XO, mimics daytime) and of a saturated rod/cone pathway (Cx36-DEDD, mimics nighttime). We will test the hypothesis that rod/cone coupling plasticity contributes to the daily modulation of contrast sensitivity and visually- guided behavior. Our work will offer a prime example of how a single electrical synapse can change retinal function to influence visual perception. This research will help define general principles underlying the role of circadian clocks and electrical synaptic plasticity in the daily changes in neural circuits relevant to brain function and behavior.