What is the effect of norepinephrine on vascular tone and blood pressure?

• A. Norepinephrine causes vasoconstriction via α1 receptors increasing peripheral resistance; β1 increases heart rate and contractility, increasing BP
• B. Norepinephrine causes vasodilation via β2 receptors
• C. Norepinephrine has no effect on vascular tone
• D. Norepinephrine decreases heart rate via vagal reflex

Answer: (A)

Norepinephrine raises vascular tone and blood pressure mainly by activating α1 receptors on vascular smooth muscle, causing vasoconstriction that increases peripheral resistance. It also stimulates β1 receptors in the heart, increasing heart rate and contractility, which boosts cardiac output. The combined effect is a rise in blood pressure. It doesn’t cause vasodilation through β2 receptors, and while a reflex vagal response can occur if blood pressure rises, the direct actions of norepinephrine are to increase heart rate and force of contraction rather than decrease it.