Effect of higenamine on action potential of Purkinje and ventricular myocardial cells.
Action potentials of isolated Purkinje cells of dogs and the electrophysiological actions of higenamine on the dog's Purkinje cells were studied by glass microelectrodes. The actions of higenamine on the action potential of Purkinje cells were: (1) increase of amplitude of the plateau phase, (2) enhancement of repolarization of phase 3 and shortening of action potential duration (APD), (3) lower concentration of higenamine (10(-7) g/ml) causing shortening of APD without any significant change of the effective refractory period (ERP), and higher concentration (10(-6) g/ml) of it causing shortening of both APD and ERP, (4) higher concentration (10(-6) g/ml) of higenamine increasing the slope of phase 4, decreasing the threshold of depolarization, and increasing the automaticity of the Purkinje cells, (5) action of higenamine on the Purkinje cells only partially blocked by tetrodotoxin (TTX) and verapamil. The above facts suggest that: (1) higher concentration of higenamine may induce tachyarrhythmias, while lower concentration may prevent arrhythmias; (2) in low concentration of higenamine, there is a relative increase of ERP. Thus, higenamine seems to be safer than isoproterenol in the treatment of bradyarrhythmias.
D000200:Action Potentials / Q000187:drug effects*; D000470:Alkaloids / Q000494:pharmacology*; D000818:Animals; D002316:Cardiotonic Agents / Q000494:pharmacology*; D004285:Dogs; D006321:Heart / Q000187:drug effects*; D006329:Heart Conduction System / Q000187:drug effects*; D066298:In Vitro Techniques; D009206:Myocardium / Q000166:cytology; D011690:Purkinje Fibers / Q000166:cytology / Q000187:drug effects*; D044005:Tetrahydroisoquinolines
D000470:Alkaloids; D002316:Cardiotonic Agents; D044005:Tetrahydroisoquinolines; C012348:higenamine