Possible functional significance of a novel type of cardiac Ca channel.
Pacemaker activity of sino-atrial (SA) node cells is explained by reconstructing the pacemaker potentials using a Hodgkin-Huxley type model which based on voltage clamp data. The new point of the reconstruction is the consideration of kinetic data of a novel "transient" (T-type) Ca current. It is demonstrated that the diastolic depolarization is closely correlated to the activation of the T-type Ca current. Overshooting SA node action potentials, however, are evoked by activation of the conventional L-type Ca current triggered by a depolarization induced by the T-type Ca current.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D006168:Guinea Pigs; D006321:Heart / Q000502:physiology*; D007473:Ion Channels / Q000502:physiology*; D007700:Kinetics; D008433:Mathematics; D008564:Membrane Potentials; D008954:Models, Biological; D012849:Sinoatrial Node / Q000502:physiology*
D007473:Ion Channels; D002118:Calcium