L-(-)-Norepinephrine is a natural neurotransmitter and hormone that is biosynthesized from dopamine by dopamine β-hydroxylase. It is an agonist of adrenergic receptors (Ki values are 330, 56, and 740 nM for α1, α2, and β1 adrenoceptors, respectively). Through these receptors, L-(-)-norepinephrine regulates diverse processes, including those in neurological, immunological, and vascular systems.