The Cardiac Pacemaker Current if

摘要: Pacemaker Current if. Since the hyperpolarization-activated current, if, was originally associated with diastolic depolarization phase of action potential in sinoatrial (SA) node 1979, its central role generation and control pacemaker activity has become increasingly clear through a series experimental findings, some which have substantially modified pre-existing theories cardiac pacemaking modulation by autonomic transmitters. Thus, current Purkinje fibers, formerly described as deactivating pure potassium (K) found to be fact, like nodal inward activating on hyperpolarization. Furthermore, SA cells, well mediating rhythm acceleration induced catecholamines, if underlie slowing effect low acetylcholine (ACh) concentrations, contrast generally accepted hypothesis that activation K conductance is main process responsible for slowing. A final, atypical property recently demonstrated concerns exerted intracellular cAMP. Unlike other voltage-gated, cAMP-modulated channels, this independent phosphorylation involves direct binding cAMP channels. (J Cardiovasc Electrophysiol, Vol. 3, pp. 334–344, August 1992)