Effect of α-adrenergic receptor blockers on the vulnerability of cat heart to ventricular fibrillation

Abstract

Recently, α-adrenergic receptors have been implicated in the precipitation of arrhythmias associated with myocardial ischemia and reperfusion. The present investigation has been undertaken to study the effect of α-adrenoceptor antagonists on electrically induced ventricular fibrillation. The effect of ventricular fibrillation on the α-adrenergic receptor population in myocardium and its modification by phentolamine pretreatment has also been investigated. Phentolamine and prazosin raised the ventricular fibrillation threshold significantly. However, yohimbine was protective at high doses only (3 and 5 mg/kg). There was no change in α-receptor population and affinity after ventricular fibrillation. Cyclic AMP levels increased in the fibrillating myocardium. Pretreatment with phentolamine did not prevent the decrease in blood flow observed after electrically induced ventricular fibrillation. It is concluded that α1-adrenergic receptor blockade is protective against ventricular fibrillation in cats.