Which drug–process pair is incorrect?

• A. Metyrosine — Transmitter synthesis
• B. Nicotine — Receptor activation
• C. Cocaine — Transmitter release
• D. Vesamicol — Transmitter storage

Answer: (C)

Understanding how these drugs affect neurotransmission helps you see why one pair doesn’t fit. The test looks at four steps: transmitter synthesis, receptor activation, transmitter release, and transmitter storage.

Metyrosine works by inhibiting tyrosine hydroxylase, the enzyme that starts catecholamine synthesis. By blocking this step, it reduces the amount of transmitter produced, so the pairing with transmitter synthesis is correct.

Nicotine binds to and activates nicotinic acetylcholine receptors, directly triggering receptor-mediated signaling. That makes this pairing correct as well.

Vesamicol blocks the vesicular acetylcholine transporter, preventing acetylcholine from being packaged into vesicles for storage and eventual release. This correctly maps to transmitter storage.

Cocaine, however, does not primarily cause transmitter release. Its main action is to block the reuptake of monoamines (like dopamine, norepinephrine, and serotonin) by inhibiting their transporters. This increases the amount of transmitter remaining in the synaptic cleft but is not a direct action on transmitter release itself. That’s why this pair is the incorrect one.