Desensitization to acetylcholine in single sinoatrial node cells isolated from rabbit hearts.
Desensitization to acetylcholine in single sinoatrial node cells isolated from rabbit hearts.
复制标题
从兔心脏分离的单个窦房结细胞对乙酰胆碱的脱敏。
DOI：
10.1152/ajpheart.1992.263.6.h1779
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发表时间：
1992
期刊：
影响因子：
--
通讯作者：
M. Boyett
中科院分区：
文献类型：
--
作者：
H. Honjo;I. Kodama;W. Zang;M. Boyett
乙酰胆碱（ACh）对窦房结的负变时作用在ACh持续存在时由于脱敏而减弱。我们利用全细胞膜片钳技术研究了兔单窦房结细胞脱敏的机制。注入恒定的超极化电流所产生的负变时效应逐渐消失。乙酰胆碱激活了一个向内整流钾电流（iK,ACh），该电流在乙酰胆碱的持续存在下逐渐消失。乙酰胆碱对“基础”l型钙电流（iCa）没有影响，但乙酰胆碱降低了iCa，异丙肾上腺素增强了这一作用。这种效果在暴露于乙酰胆碱2分钟后没有减弱。乙酰胆碱降低了超极化激活电流（i(f)）。这种效果也没有消退。这些结果表明，乙酰胆碱负变时反应的脱敏部分是膜超极化的结果，部分是乙酰胆碱和乙酰胆碱褪色的结果。这些结果还表明，虽然乙酰胆碱对钾电流的激活迅速消退，但抑制腺苷酸环化酶的作用却不会。
The negative chronotropic effect of acetylcholine (ACh) on the sinoatrial node fades in the continuous presence of ACh as a result of desensitization. We have investigated the mechanism underlying desensitization in single rabbit sinoatrial node cells using the whole cell patch clamp technique. The negative chronotropic effect resulting from the injection of a constant hyperpolarizing current faded. ACh activated an inwardly rectifying potassium current (iK,ACh), which faded in the continuous presence of ACh. ACh had no effect on "basal" L-type calcium current (iCa), but ACh decreased iCa, which had been potentiated by isoprenaline. This effect did not fade during a 2-min exposure to ACh. ACh decreased the hyperpolarization-activated current (i(f)). This effect again did not fade. These results suggest that desensitization of the negative chronotropic response to ACh is, in part, the result of the membrane hyperpolarization and, in part, the result of the fade of iK,ACh. These results also suggest that, whereas the activation of potassium current by ACh rapidly fades, the effects resulting from the inhibition of adenylate cyclase do not.