无能细胞是构成哺乳动物视网膜中最多样化的细胞类别的中间神经元。它们通过介导内丛状层(IPL)中输入(即双极)和输出(即神经节)神经元之间的兴奋性和抑制性相互作用来帮助编码视觉特征,例如边缘或定向运动。像其他大脑区域一样,视网膜还含有促进神经递质摄取的神经胶质细胞,代谢调节和神经血管控制。这里,我们报告说,在小鼠视网膜(任何性别),丰富的,尽管以前未研究过的抑制性无长突细胞直接与Müller胶质细胞偶联。这种无长碱类型的电子显微镜重建显示化学突触与已知的视网膜细胞类型以及与Müller神经胶质的广泛关联,其过程通常完全覆盖该无长突细胞的神经突。将小示踪剂分子微注射到这些无长突细胞的体细胞中,导致附近Müller胶质细胞的选择性标记,导致我们建议“Müller胶质细胞偶联无长突细胞”的名称,\"或MAC。我们的数据还表明,MAC在常规化学突触释放甘氨酸,和来自背侧外侧膝状核(dLGN)的病毒逆行跨突触示踪显示MAC与RGC类型亚群之间的选择性连接。视觉诱发的反应显示出对光增量的强烈偏好;这些“ON”响应主要是由兴奋性化学突触输入和与其他细胞的直接电耦合介导的。MAC的这种初始表征提供了哺乳动物视网膜中神经元-神经胶质偶联的第一个证据,并将MAC鉴定为抑制性加工和神经胶质功能之间的潜在联系。意义陈述:神经元或神经胶质细胞对之间的间隙连接常见于整个神经系统,并发挥多种作用,包括电耦合和代谢交换。相比之下,神经元和神经胶质细胞之间的缝隙连接很少被报道,也很少被理解。在这里,我们报道了哺乳动物视网膜中神经元-神经胶质细胞偶联的第一个证据,特别是在丰富的(但以前未研究的)抑制性中间神经元和穆勒神经胶质之间。此外,病毒追踪,光遗传学和系列电子显微术提供了有关神经元的突触伙伴和生理反应的新信息。
Amacrine cells are interneurons composing the most diverse cell class in the mammalian retina. They help encode visual features, such as edges or directed motion, by mediating excitatory and inhibitory interactions between input (i.e., bipolar) and output (i.e., ganglion) neurons in the inner plexiform layer (IPL). Like other brain regions, the retina also contains glial cells that contribute to neurotransmitter uptake, metabolic regulation, and neurovascular control. Here, we report that, in mouse retina (of either sex), an abundant, though previously unstudied inhibitory
amacrine cell is coupled directly to Müller glia. Electron microscopic reconstructions of this
amacrine type revealed chemical synapses with known retinal cell types and extensive associations with Müller glia, the processes of which often completely ensheathe the neurites of this amacrine cell. Microinjecting small tracer molecules into the somas of these
amacrine cells led to selective labeling of nearby Müller glia, leading us to suggest the name \"Müller glia-coupled
amacrine cell,\" or MAC. Our data also indicate that MACs release glycine at conventional chemical synapses, and viral retrograde transsynaptic tracing from the dorsal lateral geniculate nucleus showed selective connections between MACs and a subpopulation of retinal ganglion cell types. Visually evoked responses revealed a strong preference for light increments; these \"ON\" responses were primarily mediated by excitatory chemical synaptic input and direct electrical coupling with other cells. This initial characterization of the MAC provides the first evidence for neuron-glia coupling in the mammalian retina and identifies the MAC as a potential link between inhibitory processing and glial function.SIGNIFICANCE STATEMENT Gap junctions between pairs of neurons or glial cells are commonly found throughout the nervous system and play multiple roles, including electrical coupling and metabolic exchange. In contrast, gap junctions between neurons and glia cells have rarely been reported and are poorly understood. Here we report the first evidence for neuron-glia coupling in the mammalian retina, specifically between an abundant (but previously unstudied) inhibitory interneuron and Müller glia. Moreover, viral tracing, optogenetics, and serial electron microscopy provide new information about the neuron\'s synaptic partners and physiological responses.