A researcher wants to block the storage of newly synthesised acetylcholine into presynaptic vesicles at the cholinergic nerve terminal, leaving choline uptake intact. Which experimental agent achieves exactly this site of action?

• A Hemicholinium
• B Trimetaphan
• C Botulinum toxin
• D Vesamicol ✓

Explanation

Vesamicol selectively blocks the vesicular acetylcholine transporter, preventing packaging of acetylcholine into synaptic vesicles, so transmitter stores run down with repetitive firing. Hemicholinium blocks the high-affinity choline uptake carrier, an upstream step, while botulinum toxin cleaves SNARE proteins to prevent vesicle fusion and release. Trimetaphan is a nicotinic ganglion blocker acting postsynaptically and has no effect on synthesis or storage steps.

Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 13th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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