Increased myocardial alpha 1 adrenoceptor density in rats chronically treated with propranolol

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