Phenylephrine mediates vasoconstriction primarily through which receptor to raise mean arterial pressure?

• A. Beta-2 receptor
• B. Dopamine receptor
• C. Alpha-1 receptor
• D. Alpha-2 receptor

Answer: (C)

Phenylephrine raises mean arterial pressure mainly by activating alpha-1 adrenergic receptors on vascular smooth muscle. This receptor is linked to a Gq pathway that increases intracellular calcium, causing vasoconstriction of arterioles. The resulting increase in systemic vascular resistance boosts blood pressure. Beta-2 receptors would cause vasodilation, not constriction, so they aren’t responsible for the rise in MAP here. Dopamine receptors aren’t involved in phenylephrine’s vasoconstrictive action, and while alpha-2 effects can influence NE release with complex outcomes, the dominant, clinically relevant mechanism is alpha-1–mediated vasoconstriction.