Which receptor mediates vasoconstriction in vascular smooth muscle when activated by a vasopressor?

Which receptor mediates vasoconstriction in vascular smooth muscle when activated by a vasopressor?

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

Answer: (C)

The receptor responsible for vasoconstriction in vascular smooth muscle when a vasopressor is present is the alpha-1 adrenergic receptor. Activation of alpha-1 on vascular smooth muscle signals through Gq to raise intracellular calcium via the phospholipase C–IP3/DAG pathway, causing the muscle to contract and the vessel to constrict, increasing vascular resistance and blood pressure. Beta-1 receptors drive cardiac effects (increasing heart rate and contractility) rather than direct vascular constriction. Beta-2 receptors promote vasodilation in many beds (via cAMP and smooth muscle relaxation), and alpha-2 receptors mainly modulate neurotransmitter release with varying local effects. Thus alpha-1 mediates the vasopressor-induced vasoconstriction.

The receptor responsible for vasoconstriction in vascular smooth muscle when a vasopressor is present is the alpha-1 adrenergic receptor. Activation of alpha-1 on vascular smooth muscle signals through Gq to raise intracellular calcium via the phospholipase C–IP3/DAG pathway, causing the muscle to contract and the vessel to constrict, increasing vascular resistance and blood pressure. Beta-1 receptors drive cardiac effects (increasing heart rate and contractility) rather than direct vascular constriction. Beta-2 receptors promote vasodilation in many beds (via cAMP and smooth muscle relaxation), and alpha-2 receptors mainly modulate neurotransmitter release with varying local effects. Thus alpha-1 mediates the vasopressor-induced vasoconstriction.