Serotonergic System — MRCPsych Paper B MCQ
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Correct answer: D — Serotonin transporter (SERT)
The correct answer is D, the serotonin transporter (SERT). Fluoxetine is a selective serotonin reuptake inhibitor: it inhibits serotonin reuptake through SERT, thereby increasing serotonin availability in the synaptic cleft. Its primary action is therefore on a transporter rather than directly at a serotonin receptor. The dopamine transporter and noradrenaline transporter are the principal reuptake targets of other drug classes and are not fluoxetine's primary target. GAT-1 mediates GABA reuptake, while EAAT2 clears glutamate; neither accounts for fluoxetine's antidepressant mechanism. The transporter-based wording is more pharmacologically precise than simply describing the target as the serotonergic neurotransmitter system.
Reference: Electronic Medicines Compendium, Fluoxetine 20 mg Capsules, Summary of Product Characteristics, section 5.1 Pharmacodynamic properties, revised 2026. https://www.medicines.org.uk/emc/product/11909/smpc