Which of the following drugs lowers blood pressure by irreversibly blocking vesicular monoamine transporter (VMAT), thereby depleting norepinephrine stores in sympathetic nerve terminals?
- A Guanethidine
- B Reserpine ✓
- C Metyrosine
- D Bretylium
Correct answer: B. Reserpine
Explanation
Reserpine irreversibly binds VMAT2 in adrenergic storage vesicles and blocks amine uptake into them, so norepinephrine leaking into the axoplasm is degraded by mitochondrial MAO and transmitter stores are depleted for days until new vesicles are synthesized. Metyrosine also depletes catecholamines but does so by inhibiting tyrosine hydroxylase, the synthetic step, not vesicular storage. This distinction between synthesis inhibition and vesicular storage blockade is what separates metyrosine from reserpine.
Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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