Conformationally defined adrenergic agents. 2. Catechol imidazoline derivatives: biological effects at .alpha.1 and .alpha.2 adrenergic receptors

Abstract

The synthesis and pharmacology of 2-(5,6-dihydroxy-1,2,3,4-tetrahydro-1-naphthyl)imidazoline (A-54741, 4), a very potent .alpha.-adrenergic agonist, are described. The change in biological activity resulting from variation of the carbocyclic ring size of 4 from four through seven members (2-5) is presented, as well as an explanation that accounts for this change in activity by considering the "exactness of fit" of these compounds to both the .alpha.1- and .alpha.2-adrenergic receptors. Compound 4 was found in vitro to be a full agonist with greater potency at the .alpha.2 receptor (ED50 norepinephrine (NE)/ED50 4 = 188 .+-. 22) than at the .alpha.1 receptor (ED50NE/ED50 4 = 13 .+-. 2).