Which receptor causes vaso-constriction leading to increased blood pressure?

• A. Beta 1 receptors
• B. Beta 2 receptors
• C. Dopaminergic receptors
• D. Alpha 1 receptors

Answer: (D)

Vascular tone is governed by sympathetic receptors on vascular smooth muscle. Alpha-1 receptors, when stimulated (by norepinephrine), trigger a cascade that increases intracellular calcium and causes smooth muscle contraction, leading to vasoconstriction. This constriction raises systemic vascular resistance, which raises blood pressure.

Beta-1 receptors are mainly in the heart and increase heart rate and contractility, boosting cardiac output rather than directly constricting vessels. Beta-2 receptors promote vasodilation in certain beds (like skeletal muscle) via a cAMP pathway, which can lower resistance. Dopaminergic receptors (D1) tend to cause vasodilation in renal and mesenteric vessels, with higher-dose effects being more variable and not the primary driver of systemic vasoconstriction. Therefore, alpha-1 receptors are the ones that cause vasoconstriction leading to increased blood pressure.