Imidazoline ReceptorsIdazoxanReceptors, DrugAgmatineImidazolesBenzofuransReceptors, Adrenergic, alpha-2Adrenergic alpha-2 Receptor AgonistsClonidineAdrenergic alpha-AntagonistsDioxanesAdrenergic alpha-AgonistsYohimbineOxazolesAdrenergic alpha-2 Receptor AntagonistsMedetomidineImidazolinesIsoindolesAntihypertensive AgentsRadioligand AssayBinding, CompetitiveChromatography, AffinityBinding SitesLigandsDose-Response Relationship, DrugRats, Sprague-DawleyAffinity LabelsProtein BindingKineticsHeart AtriaMedulla OblongataAntibody AffinityAtrial FunctionPC12 Cells