dopamin

Dopamin, known in English as dopamine, is a catecholamine neurotransmitter and neurohormone. In German and several other languages it is spelled Dopamin. It is produced in specialized neurons and released into synapses where it modulates neuronal signaling. In the periphery it also serves as a precursor to other catecholamines.

Biosynthesis and handling occur in a few steps. Tyrosine is hydroxylated by tyrosine hydroxylase to produce L-DOPA, which is decarboxylated to dopamine by aromatic L-amino acid decarboxylase. In the brain, dopaminergic neurons in regions such as the substantia nigra and the ventral tegmental area generate and store dopamine in vesicles. After release, dopamine is cleared from the synapse by reuptake through the dopamine transporter (DAT) and is metabolized by monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT).

Dopamine acts on five known receptor subtypes (D1 through D5), grouped into D1-like and D2-like families. Receptors are distributed postsynaptically and presynaptically, with diverse signaling mechanisms that influence cAMP levels, ion channels, and other intracellular pathways. Dopamine signaling participates in multiple brain functions, including movement control, motivation, reward processing, and reinforcement learning, as well as the regulation of prolactin release from the pituitary.

Clinical relevance is substantial. Degeneration of dopaminergic neurons in Parkinson’s disease leads to motor symptoms that are treated with L-DOPA or dopamine agonists. Altered dopaminergic signaling is also implicated in schizophrenia and in addictive behaviors. Peripheral dopamine has roles in renal blood flow and modulates cardiovascular and gastrointestinal functions.