A-type potassium current in myenteric neurons from guinea-pig small intestine.
A-type potassium current in myenteric neurons from guinea-pig small intestine.
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豚鼠小肠肌间神经元中的 A 型钾电流。
DOI：
10.1016/s0306-4522(00)00196-2
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发表时间：
2000
期刊：
影响因子：
3.3
通讯作者：
Wood,JD
中科院分区：
文献类型：
--
作者：
Starodub,AM;Wood,JD
研究了豚鼠小肠肌间神经元A型钾电流（IA）的生物物理特性。IA存在于AH型和S型肌间神经元。减少外部Ca ~（2+）不影响电流。68个AH型神经元的电流密度为13.5±10.2pA/pF，31个S型神经元的电流密度为23.4±8.2pA/pF。S-型神经元似乎是一个均匀的组基于IA的密度。AH型神经元分为两组，电流密度分别为9.4±4.3和25.4±4.3pA/pF，AH型和S型神经元电流的其他生物物理特性无统计学差异。稳态激活和失活曲线显示半激活电位为− 7 mV（k=15.0mV）和− 86 mV（k=11.5mV）。曲线在接近静息电位约-55mV处重叠。在-20和50 mV之间的测试电位下，激活的时间常数范围为3.6至0.52 ms。在-20至50 mV的测试电位下，失活时间常数在41.5至11 ms之间。失活恢复的时间常数符合双指数曲线，快速和缓慢恢复时间分别为11和550 ms。4-当预脉冲至-110mV后，氨基吡啶在-20mV被激活时，可抑制IA。在外部溶液中加入Zn 2+导致激活和失活曲线在去极化方向上的浓度依赖性移动。在很宽的电位范围内，Zn ~（2+）使IA的活化和失活动力学减慢了3.3倍和1.2倍。外部H+的升高抑制了Zn 2+的作用，pK为7.3-7.4。Zn ~（2+）的影响被解释为不是由于表面电荷屏蔽，因为Zn ~（2+）对其在A通道上的结合位点的亲和力估计在170和312μM之间，而Mg ~（2+）的背景浓度为10 mM。肠神经系统被认为是一个独立的整合神经系统（脑在肠道），负责肠道行为的运动和分泌模式的局部组织控制。AH型和S型神经元通过突触相互连接，形成肠神经系统的微回路。结果表明，IA是神经元兴奋性的一个重要决定因素，无论是神经冲动的放电还是两种类型神经元中的各种突触事件。
Biophysical properties of A-type K+currents (IA) in myenteric neurons from guinea-pig small intestine were studied. IAwas present in both AH- and S-type myenteric neurons. Reduction of external Ca2+did not affect the current. Current density was 13.5±10.2pA/pF in 68 AH-type neurons and 23.4±8.2pA/pF in 31 S-type neurons. S-type neurons appeared to be a homogeneous group based on density of IA. AH-type neurons were subdivided into two groups with current densities of 9.4±4.3 and 25.4±4.3pA/pF. All other biophysical properties of the current were not statistically different for AH- and S-type neurons. Steady-state activation and inactivation curves showed half-activation potentials at −7mV (k=15.0mV) and −86mV (k=11.5mV). The curves overlapped at potentials near the resting potential of approximately −55mV. Time constants for activation ranged from 3.6 to 0.52ms at test potentials between −20 and 50mV. Inactivation time constants fell between 41.5 and 11ms at test potentials between −20 and 50mV. Time constants for recovery from inactivation fit a double-exponential curve with fast and slow recovery times of 11 and 550ms. 4-Aminopyridine suppressed IAwhen it was activated at −20mV following a pre-pulse to −110mV. Addition of Zn2+in the external solution resulted in a concentration-dependent shift of the activation and inactivation curves in the depolarized direction. Zn2+slowed the activation and inactivation kinetics of IAby factors of 3.3- and 1.2-fold over a wide range of potentials. Elevation of external H+suppressed the effect of Zn2+with a pK of 7.3–7.4. The effects of Zn2+were interpreted as not being due to surface charge screening, because the affinity of Zn2+for its binding site on the A-channel was estimated to be between 170 and 312μM, while the background concentration of Mg2+was 10mM. The enteric nervous system is perceived as an independent integrative nervous system (brain-in-the-gut) that is responsible for local organizational control of motility and secretory patterns of gut behavior. AH- and S-type neurons are synaptically interconnected to form the microcircuits of the enteric nervous system. The results suggest that IAis a significant determinant of neuronal excitability for both the firing of nerve impulses and the various synaptic events in the two types of neurons.