Norepinephrine primarily acts on which receptor subtypes?

Norepinephrine primarily acts on which receptor subtypes?

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

Answer: (A)

Norepinephrine primarily engages alpha-1 and beta-1 receptors, with notable alpha-2 activity, and has little effect on beta-2 receptors. The strong alpha-1 effect explains its potent vasoconstriction and rise in systemic vascular resistance, which elevates mean arterial pressure. Its beta-1 action increases cardiac contractility (inotropy) and, via reflex mechanisms, can influence heart rate. Alpha-2 receptors provide a presynaptic feedback dampening norepinephrine release. Because beta-2 receptors mediate vasodilation and bronchodilation, norepinephrine’s pharmacology shows minimal beta-2 activity, making alpha-1 and beta-1 (plus some alpha-2) the best match.

Norepinephrine primarily engages alpha-1 and beta-1 receptors, with notable alpha-2 activity, and has little effect on beta-2 receptors. The strong alpha-1 effect explains its potent vasoconstriction and rise in systemic vascular resistance, which elevates mean arterial pressure. Its beta-1 action increases cardiac contractility (inotropy) and, via reflex mechanisms, can influence heart rate. Alpha-2 receptors provide a presynaptic feedback dampening norepinephrine release. Because beta-2 receptors mediate vasodilation and bronchodilation, norepinephrine’s pharmacology shows minimal beta-2 activity, making alpha-1 and beta-1 (plus some alpha-2) the best match.