Dopamine

Dopamine is a chemical messenger of the catecholamine family, a group of biogenic amines made from the amino acid tyrosine. Neurons turn tyrosine into L-DOPA and then into dopamine, and some cells go on to convert dopamine into norepinephrine and epinephrine. Dopamine acts through a family of dopamine receptors: D1-type receptors tend to excite target cells, while D2-type receptors tend to inhibit them. After release it is cleared from the synapse mainly by transporter proteins that carry it back into the neuron.

Dopamine neurons in the substantia nigra, a small region deep in the brain, send their axons to the basal ganglia and help produce smooth, controlled movement. Other dopamine pathways form part of the brain's reward circuit, where dopamine works less as a pleasure signal than as a teaching signal that reinforces behaviors and makes people want to repeat them.

The loss of dopamine neurons in the substantia nigra causes the movement problems of Parkinson disease, which is commonly treated with L-DOPA (levodopa). Addictive drugs such as cocaine and amphetamine flood synapses with far more dopamine than natural rewards do, and many antipsychotic medicines work by blocking dopamine receptors.