Characterization of three types of potassium current in cultured neurones of rat supraoptic nucleus area.
Characterization of three types of potassium current in cultured neurones of rat supraoptic nucleus area.
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大鼠视上核区培养神经元三种钾电流的表征。
DOI：
10.1113/jphysiol.1989.sp017543
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
W. Mason
中科院分区：
文献类型：
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作者：
P. Cobbett;P. Legendre;W. Mason
1. 在分离细胞培养中获得了新生大鼠视上区神经元的全细胞电压钳记录。这些神经元的形态与抗利尿激素或催产素免疫反应的神经元相同。2. 根据其动力学、电压敏感性、Ca2+依赖性和药理学鉴定了三种电压激活K+电流。这些电流对应于延迟整流电流（IK）、A电流（IA）和其他神经元中描述的Ca2+依赖电流（IK(Ca)）。3. IK的阈值为‐40 mV，激活时间呈s型曲线，并且在持续时间小于300 ms的电压阶跃期间持续。底层电导与电压相关，在+30 mV时达到最大值（平均最大电导4.09 nS）。激活时间常数也与电压有关，从‐30 mV时的4.5 ms呈指数下降到+50 mV时的1.8 ms。IA是瞬态的，从保持负电位到‐70 mV被激活；在+10 mV时获得了电流下的最大电导（平均5.9 nS）。激活和失活时间常数与电压有关：激活时间常数在‐40 mV （2.2 ms）和+40 mV （0.65 ms）之间呈指数下降。5. K+通道阻滞剂四乙基铵（TEA）和4 -氨基吡啶（4 - AP）可减弱IK和IA。TEA阻断了IK的电导，但似乎改变了IA的动力学。相反，4‐AP阻断了IA的电导，并在较小程度上阻断了IK。6. IK和IA的激活独立于外部Ca2+和Ca2+通道的电压激活，因为这些电流是在Ca2+通道阻滞剂Co2+存在的情况下记录的。7. 只有当Ca2+ (2 mM)存在于外介质时，才记录IK（Ca）。在‐30 mV的保持电位下，IK（Ca）的阈值为‐20 mV，在+20 mV左右达到最大值，在更正的电位下下降。该电流在持续100 ms的电压阶跃期间持续，并通过向介质中添加Co2+ (2 mM)而消除。8. 讨论了三种K+电流在调节视上神经元在体内和体外记录的特征放电行为中的可能作用。
1. Whole‐cell, voltage‐clamp recordings were obtained from neurones of the supraoptic area of neonatal rats in dissociated cell culture. Recordings were made from neurones having the same morphology as those which were vasopressin or oxytocin immunoreactive. 2. Three types of voltage‐activated K+ current were identified on the basis of their kinetics, voltage sensitivities, Ca2+ dependence and pharmacology. The currents corresponded to the delayed rectifier current (IK), the A‐current (IA), and the Ca2+‐dependent current (IK(Ca] described in other neurones. 3. IK had a threshold of ‐40 mV, a sigmoidal time course of activation, and was sustained during voltage steps lasting less than 300 ms. The underlying conductance was voltage dependent reaching a maximum at +30 mV (mean maximum conductance 4.09 nS). The activation time constant was also voltage dependent declining exponentially from 4.5 ms at ‐30 mV to 1.8 ms at +50 mV. 4. IA was transient, and was activated from holding potentials negative to ‐70 mV; the maximum conductance (mean 5.9 nS) underlying the current was obtained at +10 mV. The activation and inactivation time constants were voltage dependent: the activation time constant declined exponentially between ‐40 mV (2.2 ms) and +40 mV (0.65 ms). 5. IK and IA were attenuated by the K+ channel blockers tetraethylammonium (TEA) and 4‐aminopyridine (4‐AP). TEA blocked the conductance underlying IK but appeared to alter the kinetics of IA. In contrast, 4‐AP blocked the conductance underlying IA and, to a lesser extent, IK. 6. IK and IA were activated independently of external Ca2+ and the voltage activation of Ca2+ channels since these currents were recorded in the presence of Co2+, a Ca2+ channel blocker. 7. IK(Ca) was recorded only when Ca2+ (2 mM) was present in the external medium. From a holding potential of ‐30 mV, IK(Ca) had a threshold of ‐20 mV, was maximal at about +20 mV and declined at more positive potentials. This current was sustained during voltage steps lasting 100 ms and was abolished by addition of Co2+ (2 mM) to the medium. 8. The possible roles of the three K+ currents in regulating the characteristic firing behaviour of supraoptic neurones previously recorded in vivo and in vitro are discussed.