Dopamine is metabolized by which pathways?

Dopamine is metabolized by which pathways?

• A. Glucuronidation in liver
• B. Excreted unchanged
• C. Uptake by nerve terminals and breakdown by MAO & COMT
• D. Metabolism by acetylcholinesterase

Answer: (C)

Dopamine's inactivation hinges on reuptake into the presynaptic nerve terminal followed by enzymatic breakdown by monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT). After release, dopamine is taken back up through the dopamine transporter, which serves to terminate its signaling and concentrate the transmitter for metabolism. Inside the neuron (and in nearby synaptic sites), MAO oxidizes dopamine to DOPAC, and COMT can further metabolize these catecholamines to additional metabolites, eventually yielding HO- and HVA-type end products. This pathway explains why dopamine is not typically excreted unchanged or metabolized primarily by a liver-specific step like glucuronidation, and why acetylcholinesterase is not involved (that enzyme targets acetylcholine, not dopamine).

Dopamine's inactivation hinges on reuptake into the presynaptic nerve terminal followed by enzymatic breakdown by monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT). After release, dopamine is taken back up through the dopamine transporter, which serves to terminate its signaling and concentrate the transmitter for metabolism. Inside the neuron (and in nearby synaptic sites), MAO oxidizes dopamine to DOPAC, and COMT can further metabolize these catecholamines to additional metabolites, eventually yielding HO- and HVA-type end products. This pathway explains why dopamine is not typically excreted unchanged or metabolized primarily by a liver-specific step like glucuronidation, and why acetylcholinesterase is not involved (that enzyme targets acetylcholine, not dopamine).