Recently, mouse OFF-α transient (OFF-α T) retinal ganglion cells (RGCs) were shown to display a gradient of light responses as a function of position along the dorsal-ventral axis; response differences were correlated to differences in the level of excitatory presynaptic input. Here, we show that postsynaptic differences between cells also make a strong contribution to response differences. Cells in the dorsal retina had longer axon initial segments (AISs)—the greater number of Na_v1.6 channels in longer AISs directly mediates higher rates of spiking and helps avoid depolarization block that terminates spiking in ventral cells with shorter AISs. The pre- and postsynaptic specializations that shape the output of OFF-α T RGCs interact in different ways: In dorsal cells, strong inputs and the long AISs are both necessary to generate their strong, sustained spiking outputs, while in ventral cells, weak inputs or the short AISs are both sufficient to limit the spiking signal.

最近，小鼠 OFF-α 瞬态 (OFF-α T) 视网膜神经节细胞 (RGC) 显示出光响应梯度作为沿背腹轴位置的函数。反应差异与兴奋性突触前输入水平的差异相关。在这里，我们表明细胞之间的突触后差异也对反应差异做出了很大贡献。背侧视网膜中的细胞具有更长的轴突初始节段 (AIS)——Na _{v的数量越多}较长 AIS 中的 1.6 个通道直接介导更高的尖峰率，并有助于避免去极化阻滞终止具有较短 AIS 的腹侧细胞的尖峰。塑造 OFF-α T RGC 输出的突触前和突触后特化以不同的方式相互作用：在背侧细胞中，强输入和长 AIS 都是产生其强大、持续的尖峰输出所必需的，而在腹侧细胞中，弱输入或者短的 AIS 都足以限制尖峰信号。