α-Adrenoceptor-effector coupling: affinity states or heterogeneity of the α2-adrenoceptor?

Receptor-effector coupling At the present time there is substantial evidence supporting the concept of at least two major groups of α-adrenoceptors, which have been termed α1 and α2 [1]. Whereas α1 and β2 adrenoceptors are linked positively to adenylate cyclase, it seems likely that α1- and α2-adrenoceptors possess different mechanisms for signal transduction.