Which receptor is associated with vasoconstriction of vascular smooth muscle causing increased blood pressure?

• A. Beta 1 receptors
• B. Dopaminergic receptors
• C. Alpha 1 receptors
• D. V2 receptors

Answer: (C)

The key idea is how different receptors affect vascular smooth muscle. Alpha-1 adrenergic receptors on vascular smooth muscle trigger a Gq signaling cascade that raises intracellular calcium, causing the muscle to contract. That contraction narrows the vessels (vasoconstriction) and raises systemic vascular resistance, which in turn increases blood pressure.

Beta-1 receptors mainly increase heart rate and the force of cardiac contraction, boosting cardiac output rather than causing direct vasoconstriction of vessels. Dopaminergic receptors can cause vasodilation in some vascular beds at certain doses, not the primary vasoconstrictive effect described. Vasopressin acts via V1 receptors to constrict vessels, but V2 receptors regulate water reabsorption in the kidneys, not vascular smooth muscle constriction.