Effect of nine adrenergic drugs on experimental myocardial infarction in rats

Experimental myocardial infarction was made by ligating the left coronary artery (LCA) in rats. On d 4, myocardial infraction size (MIS) was measured by nitro-blue tetrazolium technique and histological examination. Neither beta2-receptor stimulant nor alpha-receptor blocking agents exerted significant effects on MIS and heart metabolism. All 7 beta-blocking agents diminished the MIS and elevated the myocardial glycogen and ATP contents. Among the beta blockers, atenolol and metoprolol showed the most beneficial effects. Propranolol and phentolamine given concomitantly showed better effects than either drug alone. Labetalol showed a better effect than that of propranolol too. It is suggested that blockade of beta1-receptor in myocardium is essential in limiting MIS and improving the myocardial metabolism, while blockade of alpha-receptor exerts a beneficial contributing effect.