Nebivolol's vasodilatory action that distinguishes it from other beta-1 selective blockers is mediated through which mechanism?

• A Direct activation of beta-2 receptors in vascular smooth muscle
• B Stimulation of endothelial nitric oxide synthase via beta-3 receptor agonism ✓
• C Blockade of alpha-1 adrenoceptors on arteriolar smooth muscle
• D Activation of prostacyclin synthesis in endothelium

Explanation

Nebivolol, unlike other beta-1 selective blockers, produces vasodilation through agonism at beta-3 receptors on the vascular endothelium, stimulating eNOS and increasing nitric oxide production. This property accounts for its favourable haemodynamic profile and the absence of the peripheral vasoconstriction seen with older beta-blockers. Options A, C, and D are not the mechanism — direct beta-2 agonism, alpha-1 blockade, and prostacyclin are not involved.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

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