title: Differential effects of Bay k 8644, a presumed calcium channel activator, on sinoatrial nodal and ventricular automaticity of the dog heart.
abstract: Bay k 8644 is suggested to increase calcium influx through the voltage-dependent calcium channel. In isolated, blood-perfused sinoatrial node preparations of the dog. Bay k 8644 injected intra-arterially increased sinus rate as isoprenaline did. In isolated, blood-perfused papillary muscle preparations of the dog isoprenaline injected intra-arterially increased both the force of contraction of the papillary muscle and its spontaneous beating rate. In these preparations, however, Bay k 8644 failed to increase the beating rate, although it increased the force of contraction. These results are consistent with the concept that the slow inward current plays a role in sinoatrial nodal automaticity but not in automaticity of Purkinje fibres which was reflected as ventricular automaticity of the papillary muscle preparations used here.
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D000818:Animals; D004285:Dogs; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects*; D007545:Isoproterenol / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects; D009543:Nifedipine / Q000031:analogs & derivatives* / Q000494:pharmacology; D010210:Papillary Muscles / Q000187:drug effects; D011690:Purkinje Fibers / Q000187:drug effects; D012849:Sinoatrial Node / Q000187:drug effects*
chemical_list: D007473:Ion Channels; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D009543:Nifedipine; D007545:Isoproterenol