Resting membrane potential and potassium currents in cultured parasympathetic neurones from rat intracardiac ganglia.
Resting membrane potential and potassium currents in cultured parasympathetic neurones from rat intracardiac ganglia.
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大鼠心内神经节培养的副交感神经元的静息膜电位和钾电流。
DOI：
10.1113/jphysiol.1992.sp019343
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发表时间：
1992
期刊：
影响因子：
--
通讯作者：
Adams,DJ
中科院分区：
文献类型：
--
作者：
Xu,ZJ;Adams,DJ
1.在从新生大鼠心内神经节分离并保持在组织培养中的电压钳位副交感神经元中研究了有助于静息膜电位和动作电位复极化的全细胞K+电流。2.大鼠心内神经元的平均静息膜电位为-52 mV，平均输入电阻为850 M Ω。在缓慢电压斜坡期间记录的电流-电压关系表明存在泄漏和电压依赖性电流。检查Na+、K+和Cl-对静息膜电位的贡献，并使用Goldman-Hodgkin-Katz电压方程计算相对离子渗透率PNa/PK = 0.12和PCl/PK < 0.001。钾通道阻滞剂，四乙基铵离子（TEA; 1 mM）或Ba 2+（1 mM）的浴中应用使神经元去极化约10 mV。通过暴露于无K（+）培养基或向浴液中加入0.1 mM哇巴因抑制Na（+）-K+泵，使神经元去极化3 - 5 mV。3.在大多数神经元中，去极化电流脉冲（0.5 - 1 s持续时间）引起85 - 100 mV的单个动作电位，随后是200 - 500 ms的后超极化。在10 - 15%的神经元中，持续电流注入产生最大频率为5 - 8 Hz的重复放电。4.河豚毒素（TTX; 300 nM）减少，但未能消除，动作电位。TTX不敏感动作电位的幅度和持续时间随着细胞外Ca 2+浓度的增加而增加，并且被0.1 mM Cd 2+的浴应用抑制。TTX不敏感动作电位的复极化率降低，并且在Cs+取代内部K+后，后超极化被后去极化取代。通过浴中应用Cd 2+（0.1 mM）降低动作电位的后超极化，并通过添加Cd 2+和TEA（10 mM）消除。5.通过向外部溶液中加入300 nM TTX和0.1 mM Cd 2+分离去极化激活的外向K+电流。阶跃去极化诱发的外向电流增加至稳态平台，并维持> 5 s。在不同的外部K+浓度下检查的瞬时电流-电压关系是线性的，并且反转（零电流）电位根据K（+）选择性电极的能斯特方程预测而移动。尾电流的反转电位随细胞外K+浓度的变化而变化，延迟外向K+通道的相对渗透性PNa/PK = 0.02。（摘要截短至400字）
1. Whole‐cell K+ currents contributing to the resting membrane potential and repolarization of the action potential were studied in voltage‐clamped parasympathetic neurones dissociated from neonatal rat intracardiac ganglia and maintained in tissue culture. 2. Rat intracardiac neurones had a mean resting membrane potential of ‐52 mV and mean input resistance of 850 M omega. The current‐voltage relationship recorded during slow voltage ramps indicated the presence of both leakage and voltage‐dependent currents. The contribution of Na+, K+ and Cl‐ to the resting membrane potential was examined and relative ionic permeabilities PNa/PK = 0.12 and PCl/PK < 0.001 were calculated using the Goldman‐Hodgkin‐Katz voltage equation. Bath application of the potassium channel blockers, tetraethylammonium ions (TEA; 1 mM) or Ba2+ (1 mM) depolarized the neurone by approximately 10 mV. Inhibition of the Na(+)‐K+ pump by exposure to K(+)‐free medium or by the addition of 0.1 mM ouabain to the bath solution depolarized the neurone by 3‐5 mV. 3. In most neurones, depolarizing current pulses (0.5‐1 s duration) elicited a single action potential of 85‐100 mV, followed by an after‐hyperpolarization of 200‐500 ms. In 10‐15% of the neurones, sustained current injection produced repetitive firing at maximal frequency of 5‐8 Hz. 4. Tetrodotoxin (TTX; 300 nM) reduced, but failed to abolish, the action potential. The magnitude and duration of the TTX‐insensitive action potential increased with the extracellular Ca2+ concentration, and was inhibited by bath application of 0.1 mM Cd2+. The repolarization rate of the TTX‐insensitive action potential was reduced, and after‐hyperpolarization was replaced by after‐depolarization upon substitution of internal K+ by Cs+. The after‐hyperpolarization of the action potential was reduced by bath application of Cd2+ (0.1 mM) and abolished by the addition of Cd2+ and TEA (10 mM). 5. Depolarization‐activated outward K+ currents were isolated by adding 300 nM TTX and 0.1 mM Cd2+ to the external solution. The outward currents evoked by step depolarizations increased to a steady‐state plateau which was maintained for > 5 s. The instantaneous current‐voltage relationship, examined under varying external K+ concentrations, was linear, and the reversal (zero current) potential shifted in accordance with that predicted by the Nernst equation for a K(+)‐selective electrode. The shift in reversal potential of the tail currents as a function of the extracellular K+ concentration gave a relative permeability, PNa/PK = 0.02 for the delayed outward K+ channel(s).(ABSTRACT TRUNCATED AT 400 WORDS)