Developmental changes in action potential prolongation by K +-channel blockers in chick myocardium

The effects of k+-channel blockers on the action potential duration of the myocardium were examined in isolated right ventricles from the 7-10-day-old,11-13-day-old,and 14-20-day-old embryo and 1-7-day-old hatched chicks. e-4031 significantly prolonged action potential duration at all developmental stages examined; the prolongation was largest in the 11-13-day-old embryo and was accompanied by early after-depolarizations. chromanol 293b showed smaller prolongation at all stages examined. terfenadine prolonged action potential duration in the 11-13-day-old embryo,but not in other stages. thus,the chick ventricular myocardium changes its repolarization properties during development. © the japanese pharmacological society.