Block of outward current in cardiac Purkinje fibers by injection of quaternary ammonium ions.
We have studied the effects of iontophoretic injection of the quaternary ammonium compounds tetraethylammonium (TEA) and tetrabutylammonium (TBA) in cardiac purkinje fibers. We find that TBA(+) is a more effective blocker than TEA(+), but injection of either compound reduces the time-dependent outward plateau currents, transient outward current (I(to)), and the delayed rectifier (I(x)). Our findings provide evidence that these outward cardiac currents are carried by channels that in some respects are pharmacologically similar to squid axon potassium channels. We demonstrate that this procedure is a new tool that can be useful in the analysis of membrane currents in the heart.
D000818:Animals; D002417:Cattle; D004553:Electric Conductivity / Q000187:drug effects; D006329:Heart Conduction System / Q000187:drug effects*; D007473:Ion Channels / Q000187:drug effects*; D007478:Iontophoresis; D009119:Muscle Contraction / Q000187:drug effects; D011690:Purkinje Fibers / Q000187:drug effects*; D000644:Quaternary Ammonium Compounds / Q000008:administration & dosage / Q000494:pharmacology*; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000008:administration & dosage / Q000494:pharmacology*; D013997:Time Factors
D007473:Ion Channels; D000644:Quaternary Ammonium Compounds; D013757:Tetraethylammonium Compounds; D019789:Tetraethylammonium; C009405:tetrabutylammonium