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Introduction to Psychopharmacology Quiz
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Which transporter is the primary target of an SSRI?
- A The vesicular monoamine transporter, VMAT You picked ✕
- B The serotonin transporter, SERT You picked ✓
- C The dopamine transporter, DAT You picked ✕
- D The noradrenaline transporter, NET You picked ✕
- E The presynaptic choline transporter You picked ✕
Correct!
Incorrect
The answer is B: The serotonin transporter, SERT
Explanation
Why B is correct
See Antidepressant Targets. Option B is correct: the serotonin transporter (SERT). A transporter is a carrier protein in a cell membrane that moves a substance across it. SERT sits in the outer membrane of the nerve cell that released the serotonin (the presynaptic neurone) and pulls serotonin back out of the gap between neurones (the synaptic cleft), which ends the signal and lets the transmitter be reused. An SSRI blocks this retrieval, so serotonin stays in the cleft for longer and keeps stimulating its receptors on the next cell. Sertraline and fluoxetine are examples. "Selective" means that SERT is blocked more strongly than NET at usual doses; it does not mean the drug has no other effects. A transporter is not the same as a receptor: a receptor is the protein that responds when the transmitter binds to it. The antidepressant effect takes weeks to build, because the receptors and circuits downstream keep adapting after the first rise in serotonin. Memory aid: the name gives the target away, since a serotonin reuptake inhibitor must block the serotonin reuptake transporter, SERT.
- Target: the serotonin transporter (SERT) in the membrane of the presynaptic neurone.
- Action: an SSRI blocks serotonin retrieval, so serotonin stays in the synaptic cleft for longer and keeps stimulating its receptors.
- Onset: the antidepressant effect takes weeks, because downstream receptors and circuits keep adapting.
Why the other options are incorrect
- A. The vesicular monoamine transporter, VMAT: VMAT sits on the membrane of storage vesicles inside the nerve terminal and loads monoamines into them. SSRIs act one step later, on the cell-surface retrieval of serotonin that has already been released. Your answer
- C. The dopamine transporter, DAT: DAT retrieves dopamine from the gap between neurones, not serotonin. SSRIs have little effect on it at usual doses, which is part of what makes them selective for serotonin. Your answer
- D. The noradrenaline transporter, NET: NET retrieves noradrenaline and is the second target of SNRIs and tricyclic antidepressants. At usual doses SSRIs inhibit SERT more strongly than NET, which is exactly what makes them selective. Your answer
- E. The presynaptic choline transporter: The high-affinity choline transporter takes up choline, the raw material for making acetylcholine. It belongs to acetylcholine-releasing neurones and plays no part in clearing serotonin. Your answer
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More questions from this set. Start the quiz to answer them and see each explanation.
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1
Which step in monoamine handling is mainly reduced by a monoamine oxidase inhibitor (MAOI)?
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2
A tricyclic antidepressant inhibits the noradrenaline transporter (NET) and also antagonises alpha-1 adrenoceptors. Which effect follows most directly from the alpha-1 action?
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