dopamiin

Dopamine is a neurotransmitter and neuromodulator in the catecholamine family that plays a central role in motor control, motivation, reward, and several cognitive functions. It is produced in dopaminergic neurons and released into synapses and neural circuits throughout the brain.

Biosynthesis and pathways: Dopamine is synthesized from the amino acid tyrosine via the enzymes tyrosine hydroxylase and DOPA decarboxylase, producing dopamine. Major dopaminergic pathways include the mesolimbic and mesocortical systems (involved in reward, motivation, and learning), the nigrostriatal tract (involved in movement), and the tuberoinfundibular pathway (inhibiting prolactin release from the pituitary).

Receptors and signaling: Dopamine acts on five receptor types, D1 through D5, which are G protein–coupled receptors. D1-like receptors (D1 and D5) typically stimulate adenylyl cyclase and increase cAMP, whereas D2-like receptors (D2, D3, D4) often inhibit it. Receptor distribution varies across brain regions, contributing to diverse effects on behavior, cognition, and autonomic regulation.

Termination and metabolism: In the synapse, dopamine is cleared primarily by the dopamine transporter (DAT). It is metabolized by enzymes such as monoamine oxidase and catechol-O-methyltransferase, which regulate the duration and intensity of dopaminergic signaling.

Clinical significance: Dopamine dysfunction is implicated in several disorders. Parkinson’s disease involves degeneration of nigrostriatal neurons, and treatment frequently uses L-DOPA or other dopaminergic drugs. Hyperdopaminergia in the mesolimbic pathway is associated with schizophrenia, while dopaminergic dysregulation is explored in ADHD and substance use disorders. Dopamine dynamics are studied with imaging techniques and neurochemical assays to understand its role in health and disease.