A monoamine NEUROTRANSMITTER and hormone with an adrenaline-like action. Dopamine is the principal neurotransmitter in the extrapyramidal system. It is formed in the brain from the amino acid tyrosine via dopa and the latter, in the form of levodopa is used to treat PARKINSON’S DISEASE. Dopamine is the precursor of noradrenaline. It is also concerned with mood, memory and food intake. Excess is associated with psychiatric disorders. Dopamine is converted into at least 30 other substances some of which are hallucinogenic.