Binding of yohimbine stereoisomers to α‐adrenoceptors in rat liver and human platelets

Abstract

Displacement of tritiated prazosin binding to rat liver plasma membranes and tritiated yohimbine human platelet membranes shows that (+)‐yohimbine, alloyohimbine and α‐yohimbine (rauwolscine) are selective α2‐adrenoceptor antagonists (KDα1/KDα2:635, 46.6 and 112 respectively) whereas corynanthine is more α1‐selective (KDα1/KDα2:0.036). 11‐Methoxy derivatives of α‐yohimbine and epi‐α‐yohimbine are very weak α‐adrenoceptor blockers. It is concluded that the aromatic A ring, the Nb atom, and the carboxymethyl moiety are important for the binding of yohimbine to the α‐adrenoceptor, the carboxymethyl group being important for the α1/α2 specificity of the molecule. 1983 British Pharmacological Society