Elevated beta-adrenergic receptor number after chronic propranolol treatment.

Treatment of rats with the beta-adrenergic antagonist propranolol for two weeks leads to a 100% increase in the number of beta-adrenergic receptors ((?) ³H]dihydroalprenolol binding sites) in cardiac particulate fractions. No change in receptor affinity was observed. These findings may l) represent the converse of agonist-induced desensitization which is associated with decreases in beta-receptor number, 2) provide a potential explanation for the clinically observed “propranolol withdrawal syndrome”.