Effect of propranolol on beta-adrenoceptors in rat hearts.

The question of whether the chronic administration of propranolol modifies the numbers or properties of cardiac beta-adrenoceptors was examined because of many reports suggestive of cardiac hypersensitivity following the withdrawal of beta-antagonists. In three studies, rats were given (+/-)-propranolol, 30 mg/day, orally or intraperitoneally, for 1 to 7 weeks. The numbers and affinities of specific binding sites for radioactive dihydroalprenolol in whole hearts from 60 control and 75 test animals were found to be the same. Thus catecholamine deprivation does not exert an important regulatory effect on most beta-receptors in the heart, as it does in the brain.