Grimes William N, Seal Rebecca P, Oesch Nicholas, Edwards Robert H, Diamond Jeffrey S
Synaptic Physiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892-3701, USA.
Vis Neurosci. 2011 Sep;28(5):381-92. doi: 10.1017/S0952523811000290. Epub 2011 Aug 25.
Amacrine cells constitute a diverse class of interneurons that contribute to visual signal processing in the inner retina, but surprisingly, little is known about the physiology of most amacrine cell subtypes. Here, we have taken advantage of the sparse expression of vesicular glutamate transporter 3 (VGLUT3) in the mammalian retina to target the expression of yellow fluorescent protein (YFP) to a unique population of amacrine cells using a new transgenic mouse line. Electrophysiological recordings made from YFP-positive (VGLUT3+) amacrine cells provide the first functional data regarding the active membrane properties and synaptic connections of this recently identified cell type. We found that VGLUT3+ amacrine cells receive direct synaptic input from bipolar cells via both N-methyl-d-aspartate receptors (NMDARs) and non-NMDARs. Voltage-gated sodium channels amplified these excitatory inputs but repetitive spiking was never observed. VGLUT3+ amacrine cells responded transiently to both light increments (ON response) and decrements (OFF response); ON responses consisted exclusively of inhibitory inputs, while OFF responses comprised both excitatory and inhibitory components, although the inhibitory conductance was larger in amplitude and longer in time course. The physiological properties and anatomical features of the VGLUT3+ amacrine cells suggest that this bistratified interneuron may play a role in disinhibitory signaling and/or crossover inhibition between parallel pathways in the retina.
无长突细胞是一类多样的中间神经元，它们参与视网膜内层的视觉信号处理，但令人惊讶的是，对于大多数无长突细胞亚型的生理学特性知之甚少。在这里，我们利用了囊泡谷氨酸转运体3（VGLUT3）在哺乳动物视网膜中的稀疏表达，通过一种新的转基因小鼠品系，将黄色荧光蛋白（YFP）的表达靶向到一类独特的无长突细胞群体。从YFP阳性（VGLUT3+）无长突细胞进行的电生理记录提供了关于这种最近鉴定出的细胞类型的活性膜特性和突触连接的首批功能数据。我们发现，VGLUT3+无长突细胞通过N-甲基-D-天冬氨酸受体（NMDARs）和非NMDARs从双极细胞接收直接的突触输入。电压门控钠通道放大了这些兴奋性输入，但从未观察到重复放电。VGLUT3+无长突细胞对光增强（ON反应）和光减弱（OFF反应）均有瞬时反应；ON反应仅由抑制性输入组成，而OFF反应包括兴奋性和抑制性成分，尽管抑制性电导在幅度上更大且在时间进程上更长。VGLUT3+无长突细胞的生理学特性和解剖学特征表明，这种双分层中间神经元可能在视网膜平行通路之间的去抑制信号传导和/或交叉抑制中发挥作用。
