The spontaneous diastolic depolarization in bullfrog cardiac pacemaker cells is generated by the interaction of a decaying delayed rectifier K+ current and an activating Ca2+ current, without an inwardly rectifying background K+ current.
This study identifies the specific interaction between the decay of a delayed rectifier K+ current and the activation of a Ca2+ current in generating spontaneous diastolic depolarization in cardiac pacemaker cells.
An enzymatic dispersion procedure has been developed to obtain viable, spontaneously active single myocytes from cardiac pacemaker tissue: the bullfrog (Rana catesbeiana) sinus venosus. Recordings of time- and voltage-dependent Ca2+ and K+ currents have been made by using a single suction-microelectrode technique. The results show that two time- and voltage-dependent currents interact to modulate the slope of the pacemaker potential. These are: (i) the decay of a delayed rectifier K+ current and (ii) the activation of a Ca2+ current. In addition, the data strongly suggest that cardiac pacemaker tissue does not have an inwardly rectifying background K+ current.
Shibata et al. (Fri,) reported a other. Whole-cell voltage-clamp was evaluated on Ionic currents generating spontaneous diastolic depolarization. The spontaneous diastolic depolarization in bullfrog cardiac pacemaker cells is generated by the interaction of a decaying delayed rectifier K+ current and an activating Ca2+ current, without an inwardly rectifying background K+ current.