The slow calcium‐dependent potassium current in a myenteric neurone of the guinea‐pig ileum.
The slow calcium‐dependent potassium current in a myenteric neurone of the guinea‐pig ileum.
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豚鼠回肠肌间神经元中缓慢的钙依赖性钾电流。
DOI：
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发表时间：
1985
期刊：
影响因子：
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通讯作者：
D. V. van Helden
中科院分区：
文献类型：
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作者：
G. Hirst;S. Johnson;D. V. van Helden
在豚鼠肌间神经丛的电流钳位和电压钳位超极化后（AH）神经元中进行实验，以检查慢钙激活超极化后（VK，Ca）的钾电导（gK，Ca）特性。将四乙基氯化铵（TEA）与VK、Ca.结果与钙内流增强导致VK、Ca增加一致。4-氨基吡啶（4-AP）直接降低VK、Ca. gK、Ca的电压钳数据通过延迟（约等于60 ms）随后指数激活（时间常数约等于300 ms）和失活（时间常数约等于2 s）的过程拟合良好。注意到存在一个小的、慢得多的失活过程。时间常数的值与Morita，North & Tokimasa（1982）和North & Tokimasa（1983）报告的值相似，其中在动作电位刺激后的VK，Ca期间测量gK，Ca。比较了gK，Ca（或钙激活钾电流IK，Ca）与各种电压下引起的短持续时间钙电流引起的估计钙内流之间的关系。钙电流积分和gK，Ca均表现出类似的依赖性，除了gK，Ca曲线有约4 mV的正移。这种转变归因于需要钙离子来启动gK，Ca机制。在gK、Ca发生显着激活之前，需要向内离子电荷移动约8 pC。在“预激”条件建立后，静息电位下测定的gK、Ca对内向钙电流的敏感性约为500 pS/pC内向电荷。长时间钙电流所获得的大量钙内流使IK、Ca的峰幅饱和，并使电流达到峰幅的时间变慢，持续时间变长。增加钙浓度的外部解决提供比例较大的IK，Ca电流饱和前。IK、Ca（即gK、Ca）的饱和幅度相对不受影响。
Experiments were performed in current‐clamped and voltage‐clamped after‐hyperpolarizing (AH) neurones of the guinea‐pig myenteric plexus to examine the properties of the potassium conductance (gK, Ca) underlying the slow calcium‐activated after‐hyperpolarization (VK, Ca). The action potential plateau lengthened by the addition of tetraethylammonium chloride (TEA) to the bathing medium was compared to VK, Ca. Results were consistent with enhanced calcium entry causing an increase of VK, Ca. 4‐Aminopyridine (4‐AP) directly reduced VK, Ca. Voltage‐clamp data of gK, Ca were well fitted by a process with a delay (approximately equal to 60 ms) followed by exponential activation (time constant approximately equal to 300 ms) and inactivation (time constant approximately equal to 2 s). The presence of a small, much slower inactivating process was noted. Values for time constants were similar to those reported by Morita, North & Tokimasa (1982) and North & Tokimasa (1983) where gK, Ca was measured during VK, Ca subsequent to action potential stimulation. The relation between gK, Ca (or the calcium‐activated potassium current IK, Ca) and estimated calcium influx resulting from short‐duration calcium currents elicited at various voltages was compared. Both the integral of the calcium current and gK, Ca showed a similar dependence on the depolarizations used to elicit IK, Ca except there was a positive shift of about 4 mV for the gK, Ca curve. This shift was attributed to a requirement for calcium ions to prime the gK, Ca mechanism. An inward ion charge movement of about 8 pC was required before significant activation of gK, Ca occurred. After the 'priming' condition had been established, the sensitivity of gK, Ca to inward calcium current measured at the resting potential was about 500 pS/pC of inward charge. Large calcium entry obtained by prolonged calcium currents caused saturation of the peak amplitude of IK, Ca and initiated currents with slower time to peak amplitude and longer duration. Increasing the calcium concentration of the external solution provided proportionally larger IK, Ca currents before saturation. The saturation amplitude of IK, Ca (namely gK, Ca) was relatively unaffected.