NAPLEX (North American Pharmacist Licensure Examination) Practice Exam

Norepinephrine acts primarily as what type of agonist?

1. A-1

2. B-1

3. B-2

4. DA-1

The correct answer is: A-1

Norepinephrine primarily acts as an A-1 agonist. A-1 refers to alpha-1 adrenergic receptors, which are primarily found in the blood vessels and cause vasoconstriction. This fits with the known effects of norepinephrine, which is a hormone and neurotransmitter responsible for increasing blood pressure by constricting blood vessels. Option B-1 is incorrect because B-1 refers to beta-1 adrenergic receptors, which primarily affect heart rate and contractility. Option B-2 is incorrect because B-2 refers to beta-2 adrenergic receptors, which primarily affect smooth muscle relaxation and dilation of blood vessels. Option DA-1 is incorrect because DA-1 refers to dopamine-1 receptors, which primarily play a role in the brain's reward and pleasure pathways. While norepinephrine does interact with dopamine receptors, its primary mechanism of action is through alpha-1 adrenergic receptors, making A-1 the correct answer.