Exam 2 - Alpha/Beta Agonists

Question 1

Recall the basic structure of catecholamines, and how substitutions affect degradation.

Answer 1

Catecholamine structure (benzene ring, two hydroxyl groups).

Substitutions affect receptor specificity and COMT/MAO degradation

Question 2

Describe the MOA of direct and indirect acting catecholamines.

Answer 2

Direct: Bind directly to adrenergic receptors (e.g., epinephrine).

Indirect: Increase NE release or inhibit reuptake (e.g., amphetamines)

Question 3

List the major types and subtypes of adrenergic receptors, including their downstream signaling.

Answer 3

Alpha Receptors:

α1 (Gq): Activates phospholipase C (PLC), which increases IP3 and DAG, leading to calcium release and smooth muscle contraction.

α2 (Gi): Inhibits adenylyl cyclase, reducing cAMP, which decreases neurotransmitter release and promotes smooth muscle relaxation

Beta: β1 (Gs): Stimulates adenylyl cyclase, increasing cAMP levels, which enhances heart rate and contractility.

β2 (Gs): Increases cAMP via adenylyl cyclase, leading to smooth muscle relaxation (e.g., bronchodilation).

β3 (Gs): Also increases cAMP, primarily involved in lipolysis in adipose tissue

Question 4

Define a pressor agent.

Answer 4

Increases blood pressure by vasoconstriction or increasing cardiac output (e.g., norepinephrine)​

Question 5

Describe what happens in the cardiovascular system after the administration of an alpha-
agonist, a beta-agonist, or a mixed agonist.

Answer 5

α-agonist: Vasoconstriction, increased BP.
β-agonist: Increased heart rate, bronchodilation.
Mixed: Combination of effects​

Question 6

List tissues that contain significant numbers of β1 or β2 receptors.

Answer 6

β1: Heart, kidney.
β2: Lungs, skeletal muscle vasculature

Question 6

Name a typical nonselective α agonist, a selective α2 agonist, a nonselective β agonist, a
selective β1 agonist, selective β2 agonists.

Answer 6

Nonselective α: Phentolamine.
Selective α2: Clonidine.
Nonselective β: Isoproterenol.
Selective β1: Dobutamine.
Selective β2: Albuterol​

Question 7

List tissues that contain significant numbers of α1 or α2 receptors.

Answer 7

α1: Vascular smooth muscle, prostate.
α2: Presynaptic nerve terminals​

Question 8

List the major clinical applications of the adrenoceptor agonists.

Answer 8

Epinephrine: Anaphylaxis.
Norepinephrine: Hypotension.
Albuterol: Asthma​

Question 9

Define the triphasic effects of dopamine.

Answer 9

Low dose: Vasodilation (D1).
Moderate dose: Increased heart rate (β1).
High dose: Vasoconstriction (α1)

Question 10

Delineate the decision in selecting a specific adrenergic agonist

Answer 10

Based on receptor specificity, clinical indication (e.g., albuterol for β2 in asthma)

Question 11

List the most common toxicities associated with sympathomimetics

Answer 11

Tachycardia, hypertension, arrhythmias, CNS effects (nervousness, insomnia)​