[Autonomic regulation of pacemaker activity in the sinoatrial node]

Recent technical advances have made it possible to investigate quantitatively the ionic events underlying pacemaker activity in the sinoatrial node. Various time-dependent currents through ion channels such as the delayed rectifier K current, two types of Ca currents and the hyperpolarization-activated current have been found to play an important role in the generation of the pacemaker activity of sinoatrial node cells. Time-independent background currents, transporter-mediated current and pump current also contribute to pacemaker activity. In this article, the physiological significance of these currents for the pacemaker depolarization and their modulation by autonomic nerves and humoral factors are discussed.