Epinephrine and norepinephrine are agonists at which receptor subtypes?

Epinephrine and norepinephrine are agonists at which receptor subtypes?

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

Answer: (B)

Adrenergic receptor subtypes and where common endogenous agonists act is the idea here. Epinephrine and norepinephrine both activate Alpha-1 and Beta-1 receptors. Activation of Alpha-1 causes blood vessels to constrict, increasing vascular resistance and blood pressure. Activation of Beta-1 increases heart rate and the force of contraction, boosting cardiac output. While epinephrine also engages Beta-2 (and Alpha-2) and norepinephrine has little Beta-2 activity, the receptors they share action on are Alpha-1 and Beta-1, making those the best common targets. This overlap explains why both can raise blood pressure and influence cardiac contractility, with epinephrine providing additional Beta-2–related effects (like bronchodilation) that norepinephrine does not.

Adrenergic receptor subtypes and where common endogenous agonists act is the idea here. Epinephrine and norepinephrine both activate Alpha-1 and Beta-1 receptors. Activation of Alpha-1 causes blood vessels to constrict, increasing vascular resistance and blood pressure. Activation of Beta-1 increases heart rate and the force of contraction, boosting cardiac output. While epinephrine also engages Beta-2 (and Alpha-2) and norepinephrine has little Beta-2 activity, the receptors they share action on are Alpha-1 and Beta-1, making those the best common targets. This overlap explains why both can raise blood pressure and influence cardiac contractility, with epinephrine providing additional Beta-2–related effects (like bronchodilation) that norepinephrine does not.