Amacrine Cell Function in the Retina

描述（由申请人提供）：与其他 CNS 基因座一样，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，通过间隙连接的电突触传递形成了视网膜中神经元相互作用的第二种重要模式。现在很清楚，间隙连接在整个视网膜中无处不在，发生在五种主要细胞类别的细胞之间。此外，视网膜间隙连接已被证明可以通过环境照明和昼夜节律的变化进行动态调节，这些变化通过光激活的神经调节剂（例如多巴胺和一氧化氮）发挥作用。这些数据表明间隙连接在光适应中发挥着关键作用。因此，由电耦合的视网膜神经元形成的网络为视觉信号的流动提供了可塑的、可重构的电路。总体而言，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多样化的作用。这项研究的长期目标是明确哺乳动物视网膜间隙连接的分布、功能和调节，以了解它们在视觉信息传递中的作用。因此，该提案的具体目标包括：（1）确定在不同杆通路中形成关键元件的不同间隙连接的作用； (2)确定神经节与神经节细胞和神经节与无长突细胞电耦合在邻近α神经节细胞的尖峰活动同步中的作用以及这是否受光调节； （3）阐明在近端哺乳动物视网膜中形成独特且刻板的耦合网络的无长突细胞和神经节细胞的不同亚型。最终目标是定义无长突细胞类型的结构和功能，这也是我们实验室长期以来的工作重点，以提供一个框架来理解其电连接的作用。间隙连接的功能将通过在间隙连接被药物破坏或在 connexin36 敲除小鼠模型中被破坏的条件下从视网膜神经元记录来进行电生理学分析。此外，可以通过间隙连接的生物素化示踪剂Neurobiotin将用于形态学分析耦合程度的变化，以确定其在实验模型中如何受光调节或破坏。间隙连接与许多神经系统疾病有关，包括 X 连锁夏科-马里-图思病、非综合征性常染色体耳聋，以及在中风或创伤后的神经保护和细胞损失中发挥作用。尽管重点关注哺乳动物视网膜间隙连接的功能和调节，但拟议的工作仍然应该为整个大脑间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.