Effect of Quinldine and Pronethalol on Acetylstrophanthidin-lnduced Ventricular Arrhythmia in Cats Treated with Reserpine

With pronethalol, quinidine, and reserpine it was necessary to increase the dose of acetylstrophanthidin which produced arrhythmia in combination with vagal stimulation. However, in reserpine-treated animals, quinidine and pro-nethalol were ineffective. The capability of large doses of acetylstrophan-thidin to produce ventricular arrhythmia was not diminished by quinidine, pronethalol, or reserpine. While pronethalol decreased the S-A nodal rate in normal animals, it failed to produce an effect on rate after reserpine pre-treatment. Since after catecholamine depletion by reserpine, pronethalol and quinidine did not affect acetylstrophanthidin-induced ventricular arrhythmia, it is suggested that the antidigitalis effect of these agents is related to their actions to diminish adrenergic nervous activity. ADDITIONAL KEY WORDS digitalis toxicity antiarrhythmic agents antiadrenergic agents adrenergic innervation beta receptor blockade • A relationship between adrenergic nervous activity and digitalis-induced ventricular ar-rhythmia has been suggested in previous re-ports.1 ' 2 Roberts et al.1 demonstrated that ventricular arrhythmias produced by small doses of acetylstrophanthidin could be pre-vented by treatment with reserpine, whereas those produced by large doses were not affected. Erlij and Mendez2 reported that reserpine as well as sympathectomy and adrenalectomy caused an increase in the dose of digitoxin necessary to produce death. Pro-nethalol, which blocks the effects of catechola-mines on the heart,"'4 has also been reporte