Amacrine Cell Function in the Retina

描述（由申请人提供）：与其他中枢神经系统位点一样，哺乳动物视网膜中细胞通讯的主要模式是通过化学介导的突触传递。然而，过去十年的研究表明，通过间隙连接的突触电传递在视网膜中形成了神经元相互作用的第二种重要模式。现在我们很清楚，间隙连接在视网膜中无处不在，发生在五种主要细胞类别中的每一种细胞之间。此外，视网膜间隙连接已被证明受环境光照和昼夜节律变化的动态调节，这些变化通过光激活的神经调节剂（如多巴胺和一氧化氮）起作用。这些数据表明，缝隙连接在光适应中起着关键作用。由电耦合的视网膜神经元形成的网络因此为视觉信号流提供了可塑的、可重构的电路。总的来说，通过电耦合的直接细胞间通信在每个视网膜水平的视觉信息的传输和整合中发挥着关键和不同的作用。本研究的长期目标是明确哺乳动物视网膜间隙连接的分布、功能和调控，从而了解它们在视觉信息传递中的作用。因此，本提案的具体目标包括：(1)确定在不同的杆通路中形成关键元素的不同间隙连接的作用；(2)确定神经节-神经节细胞和神经节-无突细胞电偶联在同步邻近α神经节细胞尖峰活动中的作用，以及这是否受到光的调节；(3)阐明在哺乳动物视网膜近端形成独特而刻板的偶联网络的无突细胞和神经节细胞的不同亚型。最终目标是定义无毛细胞类型的结构和功能，这是我们实验室长期工作的重点，为理解它们的电连接的作用提供一个框架。在间隙连接被破坏的条件下，或在connexin36敲除小鼠模型中，通过记录视网膜神经元的电生理功能来分析间隙连接的功能。此外，生物素化的示踪剂神经生物素可以通过间隙连接，将用于对偶联程度的变化进行形态学分析，以确定在实验模型中它是如何被光调节或破坏的。间隙连接与许多神经系统疾病有关，包括x连锁沙科-玛丽-图斯病、非综合征性常染色体耳聋，并在中风或创伤后的神经保护和细胞损失中发挥作用。虽然研究重点是哺乳动物视网膜缝隙连接的功能和调节，但这项工作应该为了解整个大脑缝隙连接的作用和可塑性提供重要的见解。

DESCRIPTION (provided by applicant): Like other CNS loci, the major mode of cellular communication in the mammalian retina is via chemically-mediated synaptic transmission. However, work over the last decade indicates that electrical synaptic transmission, via gap junctions, forms a second significant mode of neuronal interaction in the retina. It is now clear that gap junctions are ubiquitous throughout the retina, occurring between cells within each of the five major cell classes. In addition, retinal gap junctions have been shown to be dynamically regulated by changes in ambient illumination and circadian rhythms acting through light-activated neuromodulators such as dopamine and nitric oxide. These data suggest that gap junctions play a key role in light adaptation. The networks formed by electrically coupled retinal neurons thus provide plastic, reconfigurable circuits for the flow of visual signals. Overall, direct intercellular communication via electrical coupling is positioned to play key and diverse roles in the transmission and integration of visual information at every retinal level. The long-term goal of this research is to define the distribution, function and regulation of the gap junctions in the mammalian retina so as to understand their roles in the transmission of visual information. Accordingly, the specific aims of this proposal include: (1) to determine the roles of the different gap junctions that form crucial elements in the different rod pathways; (2) to determine the roles of ganglion-to-ganglion cell and ganglion-to-amacrine cell electrical coupling in the synchronization of the spike activity of neighboring alpha ganglion cells and whether this is regulated by light; and (3) to elucidate the different subtypes of amacrine and ganglion cells that form distinct and stereotypic coupled networks in the proximal mammalian retina. A final aim is to define the structure and function of amacrine cell types, long a focus of the work in our lab, to provide a framework to understand the role of their electrical junctions. The functions of gap junctions will be assayed electrophysiologically by recording from retinal neurons under conditions in which gap junctions are disrupted either pharamcologically or in a connexin36 knockout mouse model. In addition, the biotinylated tracer Neurobiotin, which can pass through gap junctions, will be used to morphologically assay changes in the extent of coupling so as to determine how it is regulated by light or disrupted in the experimental models. Gap junctions have been implicated in a number of neurological diseases including X-linked Charcot-Marie-Tooth disease, nonsyndromic autosomal deafness as well as having a role in neuroprotection and cell loss following stroke or trauma. Although focused on the function and regulation of gap junctions in the mammalian retina, the proposed work should nevertheless provide important insights into the roles and plasticity of gap junctions throughout the brain.