title: Investigations differentiating the mechanism of specific bradycardic agents from that of calcium channel blockers.
abstract: The effects of two "specific bradycardic agents", falipamil (AQ-A 39) and the alinidine-congener STH 2148 (2-[N-(cyclopropylmethyl)-N-(2,6-dibromophenyl)amino]-2-imidazolin e), on the spontaneous electrical discharge rate of intact guinea-pig sinus node preparations were investigated in comparison to that of the "calcium channel blocker" verapamil. Addition of falipamil (10 micrograms/ml) to a maximally rate lowering concentration of STH 2148 (30 micrograms/ml) exerted no further bradycardic effect. In contrast, verapamil (0.1 microgram/ml) added to either STH 2148 (30 micrograms/ml) or a maximally effective concentration of falipamil (30 micrograms/ml) resulted in a further, significant reduction of sinus rate. The results are compatible with the idea of a common mechanism of the two specific bradycardic agents, different from that of calcium channel blockers.
mesh_terms: D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002316:Cardiotonic Agents / Q000494:pharmacology*; D003000:Clonidine / Q000031:analogs & derivatives / Q000494:pharmacology; D004594:Electrophysiology; D006168:Guinea Pigs; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D054833:Isoindoles; D009200:Myocardial Contraction / Q000187:drug effects; D010797:Phthalimides / Q000494:pharmacology; D012849:Sinoatrial Node / Q000502:physiology; D014700:Verapamil / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D002316:Cardiotonic Agents; D007093:Imidazoles; D054833:Isoindoles; D010797:Phthalimides; C052618:2-(N-(cyclopropylmethyl)-N-(2,6-dibromophenyl)amino)-2-imidazoline; D014700:Verapamil; C022192:alinidine; D003000:Clonidine; C030532:falipamil