title: On the characteristics of the inward tail current induced by calcium overload.
abstract: The characterization of an inward tail current (Iex) induced by calcium overload and often associated with the oscillatory current (Ios) was studied by means of a two-microelectrode voltage clamp method in sheep cardiac Purkinje fibers. It was found that: (1) the inward tail current requires a prior depolarization to about -25 mV (or less negative values) in order to appear; (2) after depolarization to those values, the membrane needs to be repolarized to about -45 mV (or to more negative values) for the inward tail current to be initiated; (3) the inward tail current becomes larger after larger or longer clamp steps and increases progressively at more negative potentials; (4) the inward tail current can be separated from other known currents, notably from the pacemaker current; (5) the inward tail current is reduced by quinacrine, a blocker of Na-Ca exchange; (6) the inward tail current does not reverse at less negative potentials; (7) the membrane conductance does not increase during the inward tail current. Thus, the inward tail current shows similarities and dissimilarities with the oscillatory current, probably in relation to a common final pathway and to a different mode of onset of the two currents, respectively.
authors.affiliation: Department of Physiology, State University of New York, Brooklyn 11203.
authors.forename: H
authors.initials: H
authors.lastname: Satoh
authors.forename: J
authors.initials: J
authors.lastname: Hasegawa
authors.forename: M
authors.initials: M
authors.lastname: Vassalle
mesh_terms: D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D004553:Electric Conductivity; D004594:Electrophysiology; D006329:Heart Conduction System / Q000502:physiology*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D011690:Purkinje Fibers / Q000187:drug effects / Q000502:physiology*; D011796:Quinacrine / Q000494:pharmacology; D012756:Sheep; D013327:Strophanthidin / Q000494:pharmacology
chemical_list: D002110:Caffeine; D013327:Strophanthidin; D011796:Quinacrine; D002118:Calcium