Two transient potassium currents in layer V pyramidal neurones from cat sensorimotor cortex.
Two transient potassium currents in layer V pyramidal neurones from cat sensorimotor cortex.
复制标题
来自猫感觉运动皮层的第五层锥体神经元中的两个瞬时钾电流。
DOI：
10.1113/jphysiol.1991.sp018488
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发表时间：
1991
期刊：
影响因子：
--
通讯作者：
Crill,WE
中科院分区：
文献类型：
--
作者：
Spain,WJ;Schwindt,PC;Crill,WE
1.使用体外脑切片制备和单微电极电压钳，在猫感觉运动皮层V层的大锥体神经元（“Betz细胞”）中识别出两个瞬时外向电流。从电压钳测量推导出的电流特性反映在恒定电流刺激期间的神经元反应中。2.这两种瞬时外向电流在一步去极化后迅速上升，但它们随后的时程差异很大。快速瞬变电流在20 ms内衰减，而缓慢瞬变电流衰减时间超过10 s。升高的细胞外钾降低电流幅度。两种电流均存在于含镉或无钙灌注液中。3.四乙基铵在1 mM浓度下对慢瞬态电流几乎没有影响，但快速瞬态电流降低了60%。在20 μ M-2 mM范围内，4-氨基吡啶对快速瞬态电流的影响很小，但这些浓度降低了慢瞬态电流并改变了其时间过程。4.两种瞬时电流均由低于动作电位阈值的去极化诱发。快速瞬态电流由比缓慢瞬态电流小7 mV的去极化诱发，但其弦电导随去极化的增加不太陡峭。5.快速瞬变的电压依赖性失活比缓慢瞬变电流更陡（每e倍变化4与7 mV），半失活发生在较低的负电位（-59与-65 mV）。然而，每个电流的激活和失活特征重叠，这意味着存在一个稳定的“窗口电流”，其范围约为14 mV，开始负向于动作电位阈值。6.快速瞬态电流显示其激活和失活动力学的明显电压依赖性，而缓慢瞬态电流则没有。在接近-70 mV时，任一电流从失活中恢复约1 s。慢瞬态电流的恢复随着超极化而变得更快。7.根据药理学反应评估每个瞬时电流对动作电位复极化的贡献。阻断钙离子内流对动作电位复极的速率几乎没有影响，而选择性降低任一瞬时电流则导致复极显著减慢。8.我们的结论是，贝茨细胞具有至少两个瞬时钾电流，每个成员的迅速扩大家庭的电压门控钾电流已被确定在各种类型的细胞。（400字处删节）
1. Two transient outward currents were identified in large pyramidal neurones from layer V of cat sensorimotor cortex (‘Betz cells’) using an in vitro brain slice preparation and single‐microelectrode voltage clamp. Properties of the currents deduced from voltage‐clamp measurements were reflected in neuronal responses during constant current stimulation. 2. Both transient outward currents rose rapidly after a step depolarization, but their subsequent time course differed greatly. The fast‐transient current decayed within 20 ms, while the slow‐transient current took greater than 10 s to decay. Raised extracellular potassium reduced current amplitude. Both currents were present in cadmium‐containing or calcium‐free perfusate. 3. Tetraethylammonium had little effect on the slow‐transient current at a concentration of 1 mM, but the fast‐transient current was reduced by 60%. 4‐Aminopyridine had little effect on the fast‐transient current over the range 20 microM‐2 mM, but these concentrations reduced the slow‐transient current and altered its time course. 4. Both transient currents were evoked by depolarizations below action potential threshold. The fast‐transient current was evoked by a 7 mV smaller depolarization than the slow‐transient current, but its chord conductance increased less steeply with depolarization. 5. Voltage‐dependent inactivation of the fast‐transient was steeper than that of the slow‐transient current (4 vs. 7 mV per e‐fold change), and half‐inactivation occurred at a less negative potential (‐59 vs. ‐65 mV). The activation and inactivation characteristics of each current overlapped, however, implying the existence of a steady ‘window current’ extending over a range of approximately 14 mV beginning negative to action potential threshold. 6. The fast‐transient current displayed a clear voltage dependence of both its activation and inactivation kinetics, whereas the slow‐transient current did not. Recovery of either current from inactivation took about 1 s near ‐70 mV. The recovery of the slow‐transient current became faster with hyperpolarization. 7. The contribution of each transient current to repolarization of the action potential was assessed from pharmacological responses. Blockade of calcium influx had little or no effect on the rate of action potential repolarization, whereas the selective reduction of either transient current caused significant slowing of repolarization. 8. We conclude that Betz cells possess at least two transient potassium currents, each a member of the rapidly expanding family of voltage‐gated potassium currents that have been identified in various cell types.(ABSTRACT TRUNCATED AT 400 WORDS)