Catecholaminergic

Catecholaminergic refers to neurons, tissues, or signaling systems that use catecholamines as transmitters or hormones. The principal catecholamines in humans are dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline). They are synthesized from the amino acid tyrosine through a defined enzymatic sequence: tyrosine hydroxylase produces L-DOPA; aromatic L-amino acid decarboxylase converts L-DOPA to dopamine; dopamine beta-hydroxylase forms norepinephrine; and phenylethanolamine N-methyltransferase converts norepinephrine to epinephrine in specialized cells, notably the adrenal medulla. Catecholaminergic signaling is widespread in the brain and peripheral nervous system and influences motor control, mood, attention, arousal, cardiovascular function, and stress responses.

Transmission begins with storage of catecholamines in vesicles by the vesicular monoamine transporter VMAT2, followed by activity-dependent release into the synaptic cleft. Termination occurs mainly through reuptake by transporters: DAT reuptakes dopamine, NET reuptakes norepinephrine, with epinephrine clearance partly via these and other pathways. Once inside the neuron, catecholamines can be metabolized by monoamine oxidases (MAO-A and MAO-B) and catechol-O-methyltransferase (COMT) to inactive metabolites that are excreted.

Physiologically, catecholaminergic signaling modulates autonomic and central processes. Dopamine pathways regulate movement and reward; norepinephrine and epinephrine modulate attention, vigilance, and sympathetic arousal. Dysregulation is implicated in several disorders, including Parkinson disease (dopaminergic neuron loss), mood disorders, ADHD, and anxiety. Pharmacologic approaches target catecholamines with L-DOPA or dopamine agonists for Parkinson disease, MAO or COMT inhibitors to prolong catecholamine action, adrenergic receptor antagonists or agonists, and various stimulants that increase catecholaminergic transmission.