(-)-Epinephrine is a natural neurotransmitter that is released from the adrenal medulla and activates adrenoceptors (Kis = 15, 735, and 3,970 nM for α1A-, β2-, and β1-adrenergic receptors, respectively). Through these receptors, (-)-epinephrine may induce either contraction or relaxation of vascular smooth muscle, depending on adrenoceptor subtype expression. Receptor-mediated actions of (-)-epinephrine are also relevant to blocking anaphylaxis, reversing cardiac arrest, and reducing bleeding in clinical trials.
