TRIGGERED ACTIVITIES IN CAT HEART INDUCED BY COMBINED ADMINISTRATION OF OUABAIN AND CALCIUM GLUCONATE

The pharmacological effects of iv a mixture of ouabain (Oua) (50 mug . kg-1) and calcium gluconate (Ca2+) (100 mg . kg-1) on the electric ac tivities of the cat hearts (n = 19) were studied by using a contact el ectrode and a contact electrode catheter to record both epicardial and endocardial monophasic action potentials (MAP). The results showed th at the 2 drugs together reduced the MAP amplitude, decreased V(max), a nd lengthened the MAP duration. Ouabain induced triggered activites, e g, early afterdepolarization, early afterhyperpolarization, delayed af terdepolarization including oscillatory afterpotentials, and triggered arrhythmias, which were enhanced by calcium gluconate. Endocardium is more sensitive than epicardium to ouabain.