六甲铵行动模式在青蛙骨骼肌乙酰胆碱受体通道。

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亚当斯DJ,贝文年代,Terrar哒

六甲铵行动模式在青蛙骨骼肌乙酰胆碱受体通道。

Br J杂志。1991年1月,102 (1):135 - 45。

PubMed ID
1710523 (在PubMed
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文摘

1。之间的对抗六甲铵和cholinoceptor受体激动剂在青蛙骨骼肌纤维与电压钳技术研究。六甲铵减少造成压敏终板电流的振幅。神经诱发终板电流,减少增加e-fold 38 mV膜超极化。2。六甲铵的作用的时间进程上终板电流很小,和最为明显,稍微延长衰减阶段的超极化电位负(超过-100 mV)。一个类似小延长单通道一生与波动分析技术检测。六甲铵生产压敏电阻器减少明显的单通道电导作为膜超极化。3所示。日志(量效)为全身的乙酰胆碱(ACh)电流曲线,确定从洋流陪同坡道膜电位的变化从稳态电流或电压波动实验,不浸泡在六甲铵的反应。 This reduction in slope became more pronounced at more negative membrane potentials. Observations at +50 mV suggested that the equilibrium constant for competitive antagonism was approximately 200 microM. 4. In voltage-jump experiments with a two-microelectrode voltage clamp, the current evoked by ACh in the presence of hexamethonium differed from that recorded with ACh alone. In the presence of hexamethonium, the expected 'instantaneous' ohmic increase in membrane current in response to a hyperpolarizing step was not detected; instead a decrease in current was observed. This problem was further investigated with a vaseline-gap voltage-clamp technique which provides improved temporal resolution. With this method a rapid decrease in the ACh-induced inward current was observed with step hyperpolarizations in the presence of hexamethonium. 5. When the membrane potential was stepped back to its resting level from a more hyperpolarized potential in the presence of hexamethonium, there was a surge of ACh-induced inward current that decayed with a time constant of less than 100 microseconds. 6. The slow relaxation in the ACh-induced current that followed a voltage step recorded in the presence of hexamethonium was slower than that recorded with ACh alone. In the presence of hexamethonium the time constant of this relaxation increased e-fold for a 67 mV hyperpolarization. 7. The results are consistent with a rapid voltage-dependent block of ACh-activated channels by hexamethonium with hyperpolarization, and voltage-dependent unblock with depolarization. The voltagedependent block is combined with competitive antagonism at the ACh receptors. However, not all observations appear to be compatible with a simple sequential block of open ion channels, but rather suggest that occupation of the channel by hexamethonium may not prevent channel closure.

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