Increased myocardial α1adrenoceptor density in rats chronically treated with propranolol

Abstract Chronic treatment with propranolol for 6 weeks resulted in a 16.6% increase, over the level in control rats, in myocardial α 1 -adrenoceptor density as measured by [ 3 H]prazosin binding. The apparent affinity remained unaffected. No changes were observed in β-adrenoceptor density and apparent affinity as measured by [ 3 H]dihydroalprenolol binding. It is concluded that myocardial α 1 -adrenoceptors might have a compensatory role under conditions where β-adrenergic effects are attenuated.