DiFrancesco D
Nature. 1986;324(6096):470-3. doi: 10.1038/324470a0.
Normal pacemaking in the mammalian heart is driven by spontaneously active cells located in the sino-atrial (SA) node. The rate of firing of these cells and the modulation of this rate by catecholamines are controlled by if, an inward Na- and K-current that turns on at voltages more negative than -40 mV. The 'pacemaker' current if is also present in other types of cell where its ability to produce and modulate a depolarizing process may be useful. For example, in vertebrate photoreceptors if drives the depolarization that terminates the light-induced hyperpolarization. Currents similar to if are also found in hippocampal neurones and DRG neurones. The present report shows for the first time that the opening of single if-channels of low conductance (1 pS) can be resolved using a modification of the patch-clamp technique on isolated SA-node cells. Modulation of if by adrenaline is shown to be mediated by an increase in the probability of channel opening, whereas the single-channel amplitude remains unchanged.
哺乳动物心脏的正常起搏由位于窦房（SA）结的自发活动细胞驱动。这些细胞的放电频率以及儿茶酚胺对该频率的调节由If控制，If是一种内向钠钾电流，在电压低于 -40 mV时开启。“起搏”电流If也存在于其他类型的细胞中，其产生和调节去极化过程的能力可能是有用的。例如，在脊椎动物光感受器中，If驱动终止光诱导超极化的去极化。在海马神经元和背根神经节神经元中也发现了与If相似的电流。本报告首次表明，使用改良的膜片钳技术在分离的窦房结细胞上可以分辨出低电导（1 pS）的单个If通道的开放。结果表明，肾上腺素对If的调节是通过增加通道开放概率介导的，而单通道幅度保持不变。
