title: Use-dependent effects of amiodarone on Vmax in cardiac Purkinje and ventricular muscle fibers.
abstract: Superfusion with 5 micrograms/ml amiodarone for 3-4 h induced use-dependent Vmax block in dog Purkinje and guinea pig ventricular muscle fibers. The recovery from block was exponential with tau of 289 +/- 30 ms in Purkinje (n = 7) and 282 +/- 47 ms in muscle (n = 6) fibers. The onset of frequency-dependent Vmax block was rapid, i.e. reached steady state after 4.2 +/- 0.5 beats (n = 5). The combination of rapid interaction with sodium channel and the reported action potential lengthening make amiodarone unique among Class I antiarrhythmic drugs.
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000638:Amiodarone / Q000494:pharmacology*; D000818:Animals; D001572:Benzofurans / Q000494:pharmacology*; D004285:Dogs; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects*; D006329:Heart Conduction System / Q000187:drug effects*; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000187:drug effects*; D010210:Papillary Muscles / Q000187:drug effects; D011690:Purkinje Fibers / Q000187:drug effects*
chemical_list: D001572:Benzofurans; D000638:Amiodarone