Ionic mechanisms of the cardiac pacemaker potential.

将膜片钳技术应用于分离的兔心窦房结细胞，研究了心脏起搏器动作电位的离子机制。(1)超极化激活电流主要由Na~(++)、K~(++)等一价阳离子携带。电流被锶以时间和电压依赖的方式阻断。当前的激活需要外部溶液中的Cl^-。不同浓度的K~(++)影响通道的表观选择性。发现去极化失活的时间过程依赖于一价阳离子浓度的变化。建立了一个数学模型来估计电流对舒张期去极化的贡献，约为1-4pA。(2)我们发现了一种新的内向电流，它在舒张期电位范围内被激活。其药理性质与L钙通道相似，但离子选择性不同。也就是说，电流由Na~(++)携带。该电流被β-肾上腺素能刺激所增加，并与这种持续的内向电流在驱动舒张期去极化中起主要作用的观点一致。

The ionic mechanisms of the cardiac pacemaker action potential were studied by the patch clamp technique applied to dissociated sinoatrial node myocytes of rabbit heart. (1) The hyperpolarization-activated current was shown to be carried by monovalent cations, such as Na^+ and K^+. The current was found to be blocked by Sr in a time-and voltage-dependent manner. The current activation required Cl^- in the external solution. Varying concentrations of K^+ affected the apparent selectivity of the channels. The time-course of deactivation on depolarization was found to be dependent on the variety in the monovalent cation concentrations. A mathematical model was developed to estimate the contribution of the current to the diastolic depolarization, which was around 1-4pA.(2) We found a new inward current which is activated over the diastolic potential range. The pharmacological properties were similar to those of the L-type Ca channel, but the ion selectivity was different. Namely the current was carried by Na^+. The current was increased by the beta-adrenergic stimulation, and is consistent with the idea that this sustained inward current takes a major role in driving the diastolic depolarization.