Nebivolol differs from other β1-selective blockers in its additional vasodilatory mechanism. This is due to:

• A Direct activation of guanylate cyclase independent of nitric oxide
• B Stimulation of endothelial β3-adrenoceptors, increasing endothelial nitric oxide synthase (eNOS) activity ✓
• C Partial agonism at α2-adrenoceptors in vascular smooth muscle
• D Blockade of voltage-gated L-type calcium channels in addition to β1-blockade

Explanation

Nebivolol's unique vasodilation is mediated through stimulation of β3-adrenoceptors on vascular endothelium, which activates eNOS and increases nitric oxide production, causing smooth muscle relaxation. This distinguishes it from carvedilol (which has α1-blocking vasodilatory action) and from standard β-blockers that cause vasoconstriction or no vasodilation. The β3 pathway is Gi-coupled, increasing eNOS via Akt phosphorylation.

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

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