Department of Ophthalmology, Casey Eye Institute, Oregon Health & Science University, Portland, Oregon.
Department of Neuroscience, University of Pennsylvania, Philadelphia, Pennsylvania.
J Comp Neurol. 2019 Jan 1;527(1):270-281. doi: 10.1002/cne.24207. Epub 2017 Mar 29.
Directional responses in retinal ganglion cells are generated in large part by direction-selective release of γ-aminobutyric acid from starburst amacrine cells onto direction-selective ganglion cells (DSGCs). The excitatory inputs to DSGCs are also widely reported to be direction-selective, however, recent evidence suggests that glutamate release from bipolar cells is not directional, and directional excitation seen in patch-clamp analyses may be an artifact resulting from incomplete voltage control. Here, we test this voltage-clamp-artifact hypothesis in recordings from 62 ON-OFF DSGCs in the rabbit retina. The strength of the directional excitatory signal varies considerably across the sample of cells, but is not correlated with the strength of directional inhibition, as required for a voltage-clamp artifact. These results implicate additional mechanisms in generating directional excitatory inputs to DSGCs.
视网膜神经节细胞的方向反应在很大程度上是由星状无长突细胞对方向选择性神经节细胞（DSGCs）的γ-氨基丁酸的方向选择性释放产生的。DSGCs 的兴奋性输入也被广泛报道为是方向选择性的，然而，最近的证据表明，双极细胞释放的谷氨酸不是定向的，在膜片钳分析中观察到的定向兴奋可能是由于不完全的电压控制而产生的假象。在这里，我们在兔视网膜的 62 个 ON-OFF DSGC 记录中测试了这个电压钳假象假说。定向兴奋性信号的强度在整个细胞样本中变化很大，但与方向抑制的强度无关，这是电压钳假象所必需的。这些结果表明，在产生 DSGCs 的定向兴奋性输入中存在其他机制。
