(Imidazolinyl-2)-2-Benzodioxane 1–4 (Idazoxan) and Its Stereoisomers, New α2-Antagonists

Since (-) idazoxan is well known as α2-antagonist, the present report described some results on the α-adrenoceptor blocking properties of the stereoisomers of idazoxan. At peripheral sites. (+) idazoxan revealed to be equipotent for blocking postsynaptic α1- and α2-adrenoceptors of the rat. On the other hand, it revealed to be a full antagonist of the inhibitory effects of cionidine on presynaptic α1-adrenoceptors of rats. However, in vitro investigations have shown (+) idazoxan to be less selective than (-) idazoxan for α2-adrenoceptors. (-) Idazoxan was selective for postsynaptic α2-adrenoceptors and antagonized presynaptic α2-adrenoceptors of the rat. Results obtained in central investigations revealed species differences between chickens and mice. The present results led to the conclusion that (+) idazoxan was equipotent on α1- and α2-adrenoceptors whereas (-) idazoxan was selective for α2-adrenoceptors. On the other hand, they suggested a stereoselectivity of peripheral and central α2-adrenoceptors for α-antagonists.