Dendritic Ih ensures high-fidelity dendritic spike responses of motion-sensitive neurons in rat superior colliculus
Dendritic Ih ensures high-fidelity dendritic spike responses of motion-sensitive neurons in rat superior colliculus
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DOI：
10.1152/jn.00556.2007
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发表时间：
2008-05-01
影响因子：
2.5
通讯作者：
Isa, Tadashi
中科院分区：
文献类型：
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作者：
Endo, Toshiaki;Tarusawa, Etsuko;Isa, Tadashi
超极化激活的环核苷酸门控（HCN）通道产生I-h电流，广泛分布于大脑中，并已被证明有助于各种神经元功能。在本研究中，我们研究了I-h在上级丘运动敏感投射神经元[宽场垂直（WFV）细胞]中的功能，上丘是检测和定位显著物体的关键视觉中心。结合全细胞记录和免疫组化研究表明，HCN通道占主导地位，有助于在WFV细胞中的I-h的HCN亚型表达在浅上级丘，主要位于其膨胀的树突状树。我们发现，阻断I-h抑制了短潜伏期和固定潜伏期的树突锋电位反应的启动，而是导致了对光纤刺激的长潜伏期和波动性的体细胞锋电位反应。这些结果表明，树突状I-h有利于树突状细胞的启动和/或传播的动作电位，并确保WFV细胞产生的尖峰反应，远端突触输入在一个敏感的和强大的时间锁定的方式，可能是作为连续的去极化驱动器和固定树突状细胞膜电位接近尖峰阈值。这些功能是不同的已知功能的树突状I-H在海马和新皮质锥体细胞，在那里他们时空限制传播的突触输入沿着顶端树突，通过减少树突膜电阻。因此，我们揭示了新的功能方面的I-H，这些树突状特性可能是至关重要的视觉运动处理在这些神经元。
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels that generate I-h currents are widely distributed in the brain and have been shown to contribute to various neuronal functions. In the present study, we investigated the functions of I-h in the motion-sensitive projection neurons [wide field vertical (WFV) cells] of the superior colliculus, a pivotal visual center for detection of and orientating to salient objects. Combination of whole cell recordings and immunohistochemical investigations suggested that HCN1 channels dominantly contribute to the I-h in WFV cells among HCN isoforms expressed in the superficial superior colliculus and mainly located on their expansive dendritic trees. We found that blocking I-h suppressed the initiation of short- and fixed-latency dendritic spike responses and led instead to long- and fluctuating-latency somatic spike responses to optic fiber stimulations. These results suggest that the dendritic I-h facilitates the dendritic initiation and/or propagation of action potentials and ensures that WFV cells generate spike responses to distal synaptic inputs in a sensitive and robustly time-locked manner, probably by acting as continuous depolarizing drive and fixing dendritic membrane potentials close to the spike threshold. These functions are different from known functions of dendritic I-h revealed in hippocampal and neocortical pyramidal cells, where they spatiotemporally limit the propagations of synaptic inputs along the apical dendrites by reducing dendritic membrane resistance. Thus we have revealed new functional aspects of I-h, and these dendritic properties are likely critical for visual motion processing in these neurons.