Norepinephrine, epinephrine, and dopamine are catecholamines that are synthesized from the dietary amino acid tyrosine. Tyrosine is hydroxylated to form L-Dopa that is then decarboxylated to form dopamine. Dopamine is a neurotransmitter in the central nervous system. In the peripheral and central nervous systems, the dopamine is then hydroxylated to form Norepinephrine. In tissues that make epinephrine, the Norepinephrine is further metabolized to epinephrine via addition of a methyl group.