Norepinephrine receptors activated include which subtypes?

Norepinephrine receptors activated include which subtypes?

• A. Only alpha1
• B. Direct alpha1, alpha2 and beta1 agonism
• C. Only alpha2
• D. Beta1 and Beta2

Answer: (B)

Norepinephrine acts on several adrenergic receptors, with its principal actions coming from alpha-1, alpha-2, and beta-1 stimulation. Alpha-1 receptors on vascular smooth muscle cause vasoconstriction, raising systemic vascular resistance and blood pressure. Beta-1 receptors in the heart increase contractility and, to a lesser extent, heart rate, boosting cardiac output. Alpha-2 receptors, mainly presynaptic, provide a feedback mechanism that reduces further norepinephrine release. Norepinephrine has little direct effect on beta-2 receptors, so it doesn’t produce beta-2–mediated bronchodilation or vasodilation. So the receptors activated by norepinephrine are alpha-1, alpha-2, and beta-1.

Norepinephrine acts on several adrenergic receptors, with its principal actions coming from alpha-1, alpha-2, and beta-1 stimulation. Alpha-1 receptors on vascular smooth muscle cause vasoconstriction, raising systemic vascular resistance and blood pressure. Beta-1 receptors in the heart increase contractility and, to a lesser extent, heart rate, boosting cardiac output. Alpha-2 receptors, mainly presynaptic, provide a feedback mechanism that reduces further norepinephrine release. Norepinephrine has little direct effect on beta-2 receptors, so it doesn’t produce beta-2–mediated bronchodilation or vasodilation. So the receptors activated by norepinephrine are alpha-1, alpha-2, and beta-1.