Locke R E, Nerbonne J M
Department of Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
J Neurophysiol. 1997 Nov;78(5):2321-35. doi: 10.1152/jn.1997.78.5.2321.
Role of voltage-gated K+ currents in mediating the regular-spiking phenotype of callosal-projecting rat visual cortical neurons. J. Neurophysiol. 78: 2321-2335, 1997. Whole cell current- and voltage-clamp recordings were combined to examine action potential waveforms, repetitive firing patterns, and the functional roles of voltage-gated K+ currents (IA, ID, and IK) in identified callosal-projecting (CP) neurons from postnatal (day 7-13) rat primary visual cortex. Brief (1 ms) depolarizing current injections evoke single action potentials in CP neurons with mean +/- SD (n = 60) durations at 50 and 90% repolarization of 1.9 +/- 0.5 and 5.5 +/- 2.0 ms, respectively; action potential durations in individual cells are correlated inversely with peak outward current density. During prolonged threshold depolarizing current injections, CP neurons fire repetitively, and two distinct, noninterconverting "regular-spiking" firing patterns are evident: weakly adapting CP cells fire continuously, whereas strongly adapting CP cells cease firing during maintained depolarizing current injections. Action potential repolarization is faster and afterhyperpolarizations are more pronounced in strongly than in weakly adapting CP cells. In addition, input resistances are lower and plateau K+ current densities are higher in strongly than in weakly adapting CP cells. Functional studies reveal that blockade of ID reduces the latency to firing an action potential, and increases action potential durations at 50 and 90% repolarization. Blockade of ID also increases firing rates in weakly adapting cells and results in continuous firing of strongly adapting cells. After applications of millimolar concentrations of 4-aminopyridine to suppress IA (as well as block ID), action potential durations at 50 and 90% repolarization are further increased, and firing rates are accelerated over those observed when only ID is blocked. Using VClamp/CClamp and the voltage-clamp data in the preceding paper, mathematical descriptions of IA, ID, and IK are generated and a model of the electrophysiological properties of rat visual cortical CP neurons is developed. The model is used to simulate the firing properties of strongly adapting and weakly adapting CP cells and to explore the functional roles of IA, ID, and IK in shaping the waveforms of individual action potentials and controlling the repetitive firing properties of these cells.
电压门控钾电流在介导大鼠胼胝体投射视皮层神经元规则放电表型中的作用。《神经生理学杂志》78: 2321 - 2335, 1997年。采用全细胞电流钳和电压钳记录相结合的方法，研究了出生后（第7 - 13天）大鼠初级视皮层中已鉴定的胼胝体投射（CP）神经元的动作电位波形、重复放电模式以及电压门控钾电流（IA、ID和IK）的功能作用。短暂（1毫秒）的去极化电流注入可在CP神经元中诱发单个动作电位，在复极化50%和90%时，其平均±标准差（n = 60）持续时间分别为1.9±0.5毫秒和5.5±2.0毫秒；单个细胞的动作电位持续时间与外向电流峰值密度呈负相关。在长时间的阈下去极化电流注入过程中，CP神经元重复放电，出现两种不同的、不可相互转换的“规则放电”模式：弱适应性CP细胞持续放电，而强适应性CP细胞在持续去极化电流注入期间停止放电。强适应性CP细胞的动作电位复极化更快，超极化后电位更明显。此外，强适应性CP细胞的输入电阻更低，平台期钾电流密度更高。功能研究表明，阻断ID可缩短动作电位发放潜伏期，并增加复极化50%和90%时的动作电位持续时间。阻断ID还可增加弱适应性细胞的放电频率，并导致强适应性细胞持续放电。在应用毫摩尔浓度的4 - 氨基吡啶抑制IA（以及阻断ID）后，复极化50%和90%时的动作电位持续时间进一步增加，放电频率比仅阻断ID时更快。利用VClamp/CClamp和前文的电压钳数据，生成了IA、ID和IK的数学描述，并建立了大鼠视皮层CP神经元电生理特性的模型。该模型用于模拟强适应性和弱适应性CP细胞的放电特性，并探讨IA、ID和IK在塑造单个动作电位波形以及控制这些细胞的重复放电特性中的功能作用。
