A patient with septic shock has a MAP of 52 mmHg despite adequate fluid resuscitation and norepinephrine infusion at 0.5 mcg/kg/min. Vasopressin is added. Which receptor subtype on vascular smooth muscle mediates the vasoconstrictive effect of vasopressin in this setting?

• A Oxytocin receptor
• B V2 receptor
• C V3 receptor
• D V1 receptor ✓

Explanation

V1 receptors on vascular smooth muscle mediate vasoconstriction via Gq-coupled phospholipase C activation and intracellular calcium release. V2 receptors are located in the renal collecting duct and mediate water reabsorption. V3 receptors are pituitary receptors. Vasopressin acts as a catecholamine-sparing agent in vasodilatory shock.

Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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