THE CAPACITY OF DIFFERENT DIGITALIS MATERIALS TO INDUCE VENTRICULAR RHYTHM DISTURBANCES IN THE RESERPINE-PRETREATED CAT

¹ Department of Pharmacology, Cornell University Medical College, 1300 York Avenue, New York

Differences in the capacity of digitalis materials to produce rhythm disturbances appeared after pretreatment with reserpine. The rhythm disturbances induced by intermittent i.v. injection of acetylstrophanthidin, ouabain, deslanoside, digoxin and digitoxin were studied in anesthetized, vagotomized cats. The dose of each material required to induce ventricular rhythm disturbance in combination with vagal stimulation (VSA), independent of vagal stimulation (A) and to produce death by ventricular fibrillation or asystole (D) was determined. After 5 mg/kg of reserpine, the dose of all digitalis materials, except digoxin, needed to induce VSA was increased. With the exception of acetylstrophanthidin and digoxin, the dose needed to induce A and D was also increased. Although reserpine failed to influence the dose of acetyistrophanthidin and digoxin needed to produce A, the rate of A was slower in reserpine-pretreated animals. Consequently, the action of reserpine to prevent digitalis-induced arrhythmia may be different from its action to influence the rate of the arrhythmia.