Plasticity and Function of the Rod/Cone Gap Junction

棒/锥耦合是二级棒路径的入口点。我们的总体假设是， 光诱导的视杆/视锥耦合调制改变视网膜功能， 视觉系统根据一天中的时间。电突触，也称为缝隙连接， 将神经元连接成耦合网络的构建块。虽然电突触显示出高度的 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根本性的差距。 我们预计，学习如何控制电耦合可能具有有用的临床潜力。我们有 开发了（1）从相邻小鼠光感受器对记录以直接测量跨连接电导的能力;（2）视杆特异性和视锥特异性连接蛋白36（Cx 36）敲除（XO）小鼠系。在 这些小鼠没有视杆细胞/视锥细胞耦合，模仿白天或明亮的光线。(3)一个磷酸化模拟突变体Cx 36 条件敲入（Cx 36-DEDD）线，显示饱和的杆/锥耦合，相当于夜间;以及 (4)一个同源的B6小鼠系，我们在其中拯救了褪黑激素的合成-一个重要的生物钟信号， 在大多数小鼠品系中缺失。来自同源系的视网膜显示多巴胺的昼夜节律变化 release. 在目标1中，我们将借由记录棒/锥对，来量测棒间的差距结电导 和锥体来检验棒/锥耦合跨度从~ 0到1，000 + pS的假设，反映了集体 褪黑激素、多巴胺和环境光的作用。我们已经证明Cx 36中没有杆/锥耦合 XO（模拟白天），我们预计在Cx 36-DEDD（模拟夜间）的最大耦合。我们将确定 视杆/视锥间隙连接电导如何随时间变化（同源B6线）。 在aim 2中，我们将记录来自视锥细胞和神经节细胞的信号，以检验视杆细胞中存在信号的假设。 次级视杆细胞通路随时间变化。我们希望我们的突变株系能以最少的投入设定极限 在Cx 36 XO中的最大输入（模拟白天）和在Cx 36-DEDD线中的最大输入（模拟夜间）。 在目标3中，我们将检查完整小鼠的视觉行为，以测量非活性（Cx 36）的影响。 XO，模拟白天）和饱和的视杆/视锥通路（Cx 36-DEDD，模拟夜间）。我们将测试 假设视杆细胞/视锥细胞耦合可塑性有助于对比敏感度和视觉的日常调节， 引导行为。 我们的工作将提供一个很好的例子，说明单个电突触如何改变视网膜功能， 视觉感知这项研究将有助于确定生物钟作用的一般原则， 与脑功能和行为相关的神经回路的日常变化中的电突触可塑性。

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.