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“Silent” NMDA Synapses Enhance Motion Sensitivity in a Mature Retinal Circuit
Neuron ( IF 16.2 ) Pub Date : 2017-10-26 00:00:00 , DOI: 10.1016/j.neuron.2017.09.058
Santhosh Sethuramanujam,Xiaoyang Yao,Geoff deRosenroll,Kevin L. Briggman,Greg D. Field,Gautam B. Awatramani

Retinal direction-selective ganglion cells (DSGCs) have the remarkable ability to encode motion over a wide range of contrasts, relying on well-coordinated excitation and inhibition (E/I). E/I is orchestrated by a diverse set of glutamatergic bipolar cells that drive DSGCs directly, as well as indirectly through feedforward GABAergic/cholinergic signals mediated by starburst amacrine cells. Determining how direction-selective responses are generated across varied stimulus conditions requires understanding how glutamate, acetylcholine, and GABA signals are precisely coordinated. Here, we use a combination of paired patch-clamp recordings, serial EM, and large-scale multi-electrode array recordings to show that a single high-sensitivity source of glutamate is processed differentially by starbursts via AMPA receptors and DSGCs via NMDA receptors. We further demonstrate how this novel synaptic arrangement enables DSGCs to encode direction robustly near threshold contrasts. Together, these results reveal a space-efficient synaptic circuit model for direction computations, in which “silent” NMDA receptors play critical roles.

中文翻译:

“静音” NMDA突触可增强成熟视网膜回路中的运动敏感性

视网膜方向选择性神经节细胞(DSGC)依靠出色协调的激发和抑制(E / I),具有在广泛的对比度范围内编码运动的出色能力。E / I由多种直接驱动DSGC的谷氨酸能双极细胞组成,并通过星爆无长突细胞介导的前馈GABA能/胆碱能信号间接驱动。要确定在各种刺激条件下如何生成方向选择响应,需要了解如何精确地协调谷氨酸,乙酰胆碱和GABA信号。在这里,我们结合使用了成对的钳形记录,串行EM和大规模多电极阵列记录,来显示单个高灵敏度的谷氨酸盐源通过AMPA受体的星爆和通过NMDA受体的DSGC进行了差分处理。我们进一步证明了这种新颖的突触安排如何使DSGCs在阈值对比度附近稳健地编码方向。总之,这些结果揭示了一种用于方向计算的节省空间的突触电路模型,其中“沉默的” NMDA受体起着至关重要的作用。
更新日期:2017-10-27
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