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

The stereoselectivity of central alpha 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 (S10089). 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 alpha 2-adrenoceptors which mediate sedation are stereoselective for alpha 2-antagonists.