OFF bipolar cells express distinct types of dendritic glutamate receptors in the mouse retina
OFF bipolar cells express distinct types of dendritic glutamate receptors in the mouse retina
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DOI：
10.1016/j.neuroscience.2013.03.054
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发表时间：
2013-07
期刊：
影响因子：
3.3
通讯作者：
C. Puller;E. Ivanova;Thomas Euler;S. Haverkamp;T. Schubert
中科院分区：
文献类型：
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作者：
C. Puller;E. Ivanova;Thomas Euler;S. Haverkamp;T. Schubert
视觉世界的平行表征已经在视觉系统的第一个突触中建立起来。视锥光感受器对光反应过度，将视觉信号转发到不同类型的ON和OFF视锥双极细胞（BC）上。在OFF BCs的情况下，突触能视锥输入被离子型谷氨酸受体整合，产生突触传递的符号保留模式。谷氨酸受体（GluR）亚单位，即AMPA或红藻氨酸亚单位的组合，重要地有助于形成OFF双极细胞的独特的响应特性。小鼠是为数不多的哺乳动物之一，其中（最有可能）完整的一套（五）视网膜OFF BC类型被确定。然而，目前尚不清楚哪些GluR亚型由不同的小鼠OFF BC类型表达。我们通过结合免疫标记，电全细胞记录和药理学来解决这个问题，并提出证据表明不同类型的OFF BC表达不同类型的谷氨酸受体：1型BC仅表达AMPA受体，而2型和3a型BC表达不同亚基组成的红藻氨酸受体。此外，我们发现两种OFF BC类型（3b和4）很可能同时表达AMPA和红藻氨酸受体，但有趣的是，这两种受体亚基并不共定位于同一树突部位。我们在这里描述的复杂的，BC类型特异性的GluRs表达模式支持其在建立小鼠视觉系统的第一突触的平行通路中的重要作用。
Parallel representations of the visual world are already established at the very first synapse of the visual system. Cone photoreceptors, which hyperpolarize in response to light, forward the visual signal onto distinct types of ON and OFF cone bipolar cells (BCs). In the case of OFF BCs, the glutamatergic cone input is integrated by ionotropic glutamate receptors, giving rise to a sign-preserving mode of synaptic transmission. The combination of glutamate receptor (GluR) subunits, i.e. AMPA or kainate subunits, importantly contributes to shaping the OFF bipolar cells’ distinct response properties. The mouse is one of the few mammals in which the (most likely) complete set of (five) retinal OFF BC types is identified. However, it is not clear which GluR subtypes are expressed by the different mouse OFF BC types. We addressed this question by combining immunolabeling, electrical whole-cell recordings and pharmacology, and present evidence that the different types of OFF BCs express distinct types of glutamate receptors: Type 1 BCs exclusively expressed AMPA receptors, whereas type 2 and type 3a BCs expressed kainate receptors of different subunit compositions. Additionally, we found that two OFF BC types (3b and 4) very likely express both AMPA and kainate receptors but, interestingly, the two receptor subunits were not co-localized at the same dendritic site. The complex, BC type-specific expression pattern of GluRs we describe here supports their essential role in establishing parallel pathways at the first synapse of the mouse visual system.