Jain Varsha, Hanson Laura, Sethuramanujam Santhosh, Michaels Tracy, Gawley Jerram, Gregg Ronald G, Pyle Ian, Zhang Chi, Smith Robert G, Berson David, McCall Maureen A, Awatramani Gautam B
Department of Biology, University of Victoria, Victoria, BC V8W 3N5 Canada.
Department of Ophthalmology & Visual Sciences, University of Louisville, Louisville, KY 40202, USA.
Cell Rep. 2022 Feb 22;38(8):110410. doi: 10.1016/j.celrep.2022.110410.
In the retina, ON starburst amacrine cells (SACs) play a crucial role in the direction-selective circuit, but the sources of inhibition that shape their response properties remain unclear. Previous studies demonstrate that ∼95% of their inhibitory synapses are GABAergic, yet we find that the light-evoked inhibitory currents measured in SACs are predominantly glycinergic. Glycinergic inhibition is extremely slow, relying on non-canonical glycine receptors containing α4 subunits, and is driven by both the ON and OFF retinal pathways. These attributes enable glycine inputs to summate and effectively control the output gain of SACs, expanding the range over which they compute direction. Serial electron microscopic reconstructions reveal three specific types of ON and OFF narrow-field amacrine cells as the presumptive sources of glycinergic inhibition. Together, these results establish an unexpected role for specific glycinergic amacrine cells in the retinal computation of stimulus direction by SACs.
在视网膜中，ON型星爆无长突细胞（SACs）在方向选择性回路中起着关键作用，但其塑造反应特性的抑制来源仍不清楚。先前的研究表明，它们约95%的抑制性突触是γ-氨基丁酸（GABA）能的，但我们发现，在SACs中测量到的光诱发抑制电流主要是甘氨酸能的。甘氨酸能抑制极其缓慢，依赖于含有α4亚基的非典型甘氨酸受体，并由ON和OFF视网膜通路驱动。这些特性使甘氨酸输入能够累加并有效控制SACs的输出增益，扩大了它们计算方向的范围。连续电子显微镜重建揭示了三种特定类型的ON和OFF窄场无长突细胞作为甘氨酸能抑制的假定来源。总之，这些结果确定了特定甘氨酸能无长突细胞在SACs对刺激方向的视网膜计算中的意外作用。
