Orientation selectivity in rabbit retinal ganglion cells is mediated by presynaptic inhibition.
Orientation selectivity in rabbit retinal ganglion cells is mediated by presynaptic inhibition.
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DOI：
10.1523/jneurosci.2081-10.2010
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发表时间：
2010-11-17
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影响因子：
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通讯作者：
Taylor WR
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作者：
Venkataramani S;Taylor WR
对边缘方向敏感的细胞在视觉系统中普遍存在，并且已在脊椎动物视网膜中有所描述，然而在视网膜中产生方向选择性的突触机制在很大程度上是未知的。在此，我们分析了在兔视网膜神经节细胞中对垂直和水平方向刺激产生选择性反应的突触机制。数据表明，对方向选择性神经节细胞的兴奋性和抑制性输入在突触前回路中就具有了方向选择性。与先前的细胞外记录一致，突触前的γ -氨基丁酸（GABA）能抑制对于产生方向选择性至关重要，并且我们表明它包括对谷氨酸能双极细胞的侧向抑制以及γ -氨基丁酸能和甘氨酸能无长突细胞之间的串联抑制连接。尽管放电特性非常相似，但垂直和水平选择性神经节细胞（分别为VS - GCs和HS - GCs）在其潜在的突触机制上表现出显著差异。两种细胞类型都通过非N - 甲基 - D - 天冬氨酸（AMPA/红藻氨酸）和N - 甲基 - D - 天冬氨酸（NMDA）受体接收谷氨酸能输入，而VS - GCs还接收由甘氨酸能去抑制介导的额外兴奋。这些细胞之间的一个显著差异是，在非偏好刺激期间，HS - GCs中的兴奋被抑制且直接的甘氨酸能抑制增加，而对于VS - GCs，兴奋性和抑制性输入均被抑制。因此，方向选择性是通过双极细胞输出的调节以及无长突细胞之间的串联抑制连接在突触前产生的。我们提出了最小电路模型来解释这些观察结果。
Cells sensitive to the orientation of edges are ubiquitous in visual systems, and have been described in the vertebrate retina, yet the synaptic mechanisms that generate orientation selectivity in the retina are largely unknown. Here, we analyze the synaptic mechanisms that generate selective responses to vertically and horizontally oriented stimuli in rabbit retinal ganglion cells. The data indicate that the excitatory and inhibitory inputs to orientation-selective ganglion cells are rendered orientation selective within the presynaptic circuitry. In accordance with previous extracellular recordings, presynaptic GABAergic inhibition is critical to generate orientation selectivity, and we show that it includes lateral inhibition of glutamatergic bipolar cells and serial inhibitory connections between GABAergic and glycinergic amacrine cells. Despite very similar spiking properties, vertically and horizontally selective ganglion cells (VS-GCs and HS-GCs, respectively) show marked differences in their underlying synaptic mechanisms. Both cell types receive glutamatergic inputs via non-NMDA (AMPA/kainate) and NMDA receptors, while VS-GCs receive additional excitation mediated by glycinergic disinhibition. A striking difference between these cells is that during nonpreferred simulation, excitation is suppressed and direct glycinergic inhibition is increased in HS-GCs, whereas for VS-GCs, both excitatory and inhibitory inputs are suppressed. Thus, orientation selectivity is generated presynaptically both by modulation of bipolar cell output and by serial inhibitory connections between amacrine cells. Minimal circuit models are proposed that account for these observations.