Amacrine Cell Function in the Retina

描述(申请人提供)：与其他中枢神经系统基因座一样，哺乳动物视网膜的主要细胞通讯方式是通过化学介导的突触传递。然而，过去十年的研究表明，通过缝隙连接进行的电突触传递，在视网膜中形成了第二种重要的神经元相互作用模式。现在很清楚，缝隙连接在整个视网膜中无处不在，发生在五个主要细胞类别中的每一个细胞之间。此外，视网膜缝隙连接已被证明受到环境照明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来发挥作用。这些数据表明，缝隙连接在光适应中起着关键作用。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性、可重新配置的电路。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扮演着关键的和不同的角色。本研究的长期目标是确定哺乳动物视网膜中缝隙连接的分布、功能和调控，以了解它们在视觉信息传递中的作用。因此，该建议的具体目标包括：(1)确定在不同的视杆细胞通路中构成关键元件的不同缝隙连接的作用；(2)确定神经节到神经节细胞和神经节到无长突细胞的电耦合在相邻α神经节细胞的峰活动同步中的作用以及这是否受光的调节；(3)阐明在哺乳动物近端视网膜形成不同类型的无长突细胞和神经节细胞的不同亚型，这些细胞形成了不同的和定型的耦合网络。最终的目标是定义无长突细胞类型的结构和功能，这一直是我们实验室工作的重点，以提供一个框架来理解它们的电连接的作用。缝隙连接的功能将通过记录视网膜神经元在缝隙连接被药理学或在连接蛋白36基因敲除的小鼠模型中被破坏的条件下进行电生理学测试。此外，可以通过缝隙连接的生物素化示踪剂神经生物素将被用于从形态上分析偶联程度的变化，以确定在实验模型中它是如何受光调节或被破坏的。缝隙连接与许多神经系统疾病有关，包括X连锁的Charcot-Marie-Tooth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丢失中发挥作用。虽然这项工作的重点是哺乳动物视网膜中缝隙连接的功能和调节，但这项拟议的工作应该会为了解缝隙连接在整个大脑中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.