Anti-arrhythmic action of d-isocorydine hydrochloride

In anesthetized rats, d-isocorydine hydrochloride (ISOC) 5-20 mg/kg iv significantly counteracted the arrhythmias caused by BaCl2 3 mg/kg or aconitine 20 microg/kg iv, and decreased the incidence of ventricular fibrillation and mortality rate caused by CaCl2 120 mg/kg iv. In rabbits, ISOC 10 mg/kg iv abolished the arrhythmias induced by inhalation of chloroform and adrenaline iv. The doses of ouabain necessary to induce ventricular extrasystole, ventricular fibrillation and death were elevated by ISOC 10 mg/kg iv in anesthetized guinea pigs. The functional refractory period (FRP) of myocardial monophasic action potentials in rabbits was prolonged and the heart rate of rats decreased after ISOC 10 mg/kg iv. In vivo, ISOC decreased the contractility, excitability, and automaticity induced by adrenaline and FRP of guinea pig papillary muscle was prolonged, with weaker Ca2+ antagonistic effect.