title: Comparison of the bradycardic effects of alinidine (St 567), AQ-A 39 and verapamil on guinea-pig sinoatrial node superfused with different Ca2+ and NaCl solutions.
abstract: Two new substances, alinidine (St 567) and AQ-A 39, previously described as 'specific bradycardic agents' were investigated with respect to their effects on the rate of electrical discharges from sinus nodes of isolated right guinea-pig atria. Both substances decreased the discharge rate concentration dependently within a wide range (3-100 micrograms/ml). Low external Ca2+ (0.18 mM) increased and low external NaCl (62 mM) decreased the rate lowering effect of alinidine as well as of AQ-A 39. In contrast, the reference compound verapamil (an inhibitor of slow inward current) was less effective in low Ca2+ and more effective in low NaCl. The similar reactions of alinidine and AQ-A 39 are discussed with respect to their different chemical structure and different electrophysiological action patterns as described so far.
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology; D003000:Clonidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004594:Electrophysiology; D005260:Female; D006168:Guinea Pigs; D006339:Heart Rate / Q000187:drug effects*; D066298:In Vitro Techniques; D054833:Isoindoles; D008297:Male; D010797:Phthalimides / Q000494:pharmacology*; D012849:Sinoatrial Node / Q000187:drug effects*; D012965:Sodium Chloride / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology*
chemical_list: D054833:Isoindoles; D010797:Phthalimides; D012965:Sodium Chloride; D014700:Verapamil; C022192:alinidine; D003000:Clonidine; C030532:falipamil; D002118:Calcium