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Dopamine is a catechol: a benzene ring carrying two neighbouring hydroxyl groups, with an ethylamine side chain. The ring is aromatic, flat with six delocalised π electrons, so its six carbon–carbon bonds come out essentially the same length. At physiological pH the amine is protonated, so dopamine carries a positive charge.

Aromatic C–C

1.395 Å

Ring C–O

1.362 Å

C–N

1.459 Å

Measured from PubChem’s computed 3D conformer of dopamine (CID 681).

Neurons build dopamine from the amino acid tyrosine in two steps. Tyrosine hydroxylase adds a second hydroxyl group to the ring, giving L-DOPA, and it is the rate-limiting step. Aromatic L-amino acid decarboxylase then removes the carboxyl group as carbon dioxide.

Dopamine neurons in the ventral tegmental area project to the nucleus accumbens. This mesolimbic pathway is central to reward, motivation and reinforcement learning. A second projection, the mesocortical pathway, reaches the prefrontal cortex.