dopaminu

Dopamine is a catecholamine neurotransmitter and neurohormone that plays a central role in reward, motivation, movement, and a range of autonomic functions. It is synthesized from the amino acid tyrosine through the enzymes tyrosine hydroxylase and DOPA decarboxylase, yielding dopamine. In neurons, dopamine is packaged into synaptic vesicles, released upon stimulation, and acts on five known receptor subtypes (D1–D5), with activity terminated mainly by reuptake via the dopamine transporter or breakdown by monoamine oxidase and catechol-O-methyltransferase.

Major dopaminergic pathways include the nigrostriatal tract, from the substantia nigra to the striatum, which largely governs motor control; and the mesolimbic and mesocortical pathways, projecting to limbic regions and the prefrontal cortex, which underlie reward processing, motivation, and cognition. A separate tuberoinfundibular pathway influences prolactin secretion from the pituitary.

In addition to brain functions, dopaminergic signaling in the periphery influences renal sodium handling and vascular tone at certain receptors. In the brain, dopamine modulates learning, decision making, mood, and arousal. Dysfunctions of dopaminergic systems are implicated in several disorders, including Parkinson’s disease, schizophrenia, ADHD, and substance-use disorders.

Clinically, L-DOPA (levodopa) remains the most effective symptomatic treatment for Parkinson’s disease, often combined with a dopa decarboxylase inhibitor. Dopamine agonists, MAO-B inhibitors, and COMT inhibitors are used as adjuncts. Dopamine also serves as a drug in acute care to raise blood pressure and improve renal perfusion in shock, though its use depends on clinical context. Understanding dopamine pathways helps explain behavior, movement, and disease.