has role 4-[1-hydroxy-2-(methylamino)ethyl]benzene-1,2-diol hormone (R)-adrenaline The R-enantiomer of adrenaline. It is a hormone secreted by the adrenal glands resulting in the 'fight-or-flight' response. beta-adrenergic agonist bronchodilator agent sympathomimetic agent alpha-adrenergic agonist vasodilator agent (S)-adrenaline mydriatic agent vasoconstrictor agent (R)-adrenaline(1+) mouse metabolite