Stereoselectivity of central α-adrenoceptors involved in sleep induced by clonidine in chickens

The stereoselectivity of central α 2-adrenoceptors involved in sleep induced in chicks by clonidine, suggested by the results observed with the stereoisomers of idazoxan, was further investigated with the stereoisomers of(imidazolinyl-2)-2-dihydro-2,3-benzofurane (S9871) and those of (imidazolinyl-2)-2-benzocyclobutane (S 10089). As for the stereoisomers of idazoxan, there was not a good separation between the effects of the stereoisomers of S10089. In contrast, there was a clearcut separation between the effects of(+)S9871 (antagonist) and (−)S9871 (no effect against the action of clonidine). Therefore, these results strongly support the view that central α 2-adrenoceptors which mediate sedation are stereoselective for α 2-antagonists.