THE ACTION OF DICHLOROISOPROTERENOL (DCI) AND SEVERAL OTHER PHARMACOLOGICAL AGENTS UPON THE ACONITINE-INDUCED VENTRICULAR ARRHYTHMIA IN THE ISOLATED RABBIT HEART

¹ Department of Pharmacology, University of Michigan, Ann Arbor, Michigan

The action of DCI upon the aconitine-induced arrhythmia was studied using the isolated perfused rabbit heart. It has been demonstrated that DCI does not inhibit the aconitine-induced ectopic focus. However, in the presence of DCI the rate of ectopic discharge is increased. This effect has been shown to be unrelated to the intrinsic sympathomimetic activity of DCI.

In addition to DCI, the effects of acetyicholine, acetylstrophanthidin, Ca⁺⁺ and K⁺ ions upon the aconitine arrhythmia have been investigated. The actions of these agents are discussed. It has been noted that the calcium and potassium ions have opposite effects upon the aconitine-induced pacemaker. In addition the activity of DCI appears to be dependent upon a suitable concentration of the potassium ion. It has been suggested that DCI may exert its effects by altering the ionic permeability of the myocardial cell.