Inhibition by cinnarizine of heart ionic changes induced by isoprenaline

Cinnarizine, a specific blocker of Ca entry in depolarized smooth muscles, exerts a protection upon cardiac lesions induced by isoprenaline. Its action has been studied on ionic changes induced in hearts of rats injected with 30 mg/kg isoprenaline subcutaneously. Cinnarizine (20 mg/kg) was administered intraperitoneally 2 hours before isoprenaline. Ionic contents (Na,K,C,Mg) were measured over an observation period of 3 days following drug treatment. Isoprenaline induced changes in the content of the various ions studied. Changes occurring in the atria were reversible. The following observations were made in the apex: Mg, transient increase in the first hour followed by a long-lasting decrease; Ca, progressive increase up to 6 hours followed by a progressive restoration; Na, increase up to 24 hours followed by restoration. These ionic changes were significantly reduced by cinnarizine.