[Experimental findings on tyramine-dependent release of noradrenaline in various parts of the heart under the influence of practolol].

Determinations of Noradrenaline-concentrations (NA) in the myocardium of the atria and ventricles of rats were performed and the influences of Practolol and Tyramine were controlled. Following Tyramine, NA was decreased significantly in all specimens. After preinjection of Practolol, NA depletion was considerably less in the right and left atria compared to control values. By these results, the clinical observation of a preferential antiarrhythmic action of Practolol on atrial extrasystoles and tachycardias may be supported.