Inhibition of the myocardial Ca2+ inward current by the class 1 antiarrhythmic agent, cibenzoline.
Cibenzoline, a class 1 (local anaesthetic-type) antiarrhythmic drug, was investigated for possible effects upon the myocardial Ca2+ inward current. In voltage-clamp experiments with isolated cardiac myocytes of guinea-pig, cibenzoline caused a concentration-dependent inhibition of the Ca2+ current, with an IC50 of 14 microM. Inhibition of the Ca2+ current by cibenzoline (2 microM) was dependent upon stimulation frequency, with a greater block occurring at 2 Hz (approximately 50%) than at 0.2 Hz (approximately 15%). The magnitude of Ca2+ current block was also potential-dependent. A markedly greater inhibition by cibenzoline (20 microM) was recorded when myocytes were depolarized (to +20 mV) from a holding potential of -35 mV than of -80 mV. At the less negative potential, cibenzoline also caused a reduction in the level of the holding current, which suggests a decrease in the inwardly rectifying K+ current. Cibenzoline also caused a concentration-dependent inhibition of KCl-induced contractures of isolated aortic strips of the rat (IC50 = 55 microM) and a reduction in contractile force of isolated, electrically-stimulated papillary muscles of the guinea-pig (IC50 = 35 microM). Thus, cibenzoline possesses Ca2+ channel blocking (class 4) properties in addition to its local anaesthetic actions.
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Holck
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Osterrieder
D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D001013:Aorta, Thoracic / Q000187:drug effects; D001692:Biological Transport / Q000187:drug effects; D002121:Calcium Channel Blockers; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects; D007093:Imidazoles / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D010210:Papillary Muscles / Q000187:drug effects; D011189:Potassium Chloride / Q000494:pharmacology
D000889:Anti-Arrhythmia Agents; D002121:Calcium Channel Blockers; D007093:Imidazoles; D011189:Potassium Chloride; C032151:cifenline