On the reversal by (+) and (-)-propranolol of irreversible α-adrenoceptor blockade in rabbit aorta

(+)- and (-)-Propranolol were equally effective in producing an apparent reversal of α-adrenoceptor blockade produced by a number of irreversible α-adrenoceptor antagonists in rabbit aortic strips: MJ 1999 was ineffective. Propranolol also partly relieved the apparent desensitization produced by high concentrations of norepinephrine. These results indicate that β-antagonist reversal of irreversible α-adrenoceptor antagonism is not attributable to a shift in the relative availability of α- and β-adrenoceptors or to displacement of antagonist from the α-adrenoceptor.