Question

1. Recall the sites (effectors) of alpha₁-, beta₁-, and beta₂-adrenergic receptors and state the expected responses from their activation by a suitable agonist.
2. Classify the following agonists in terms of the adrenergic receptors they activate and the responses they cause as a result of direct receptor activation: (1) epinephrine, (2) norepinephrine, (3) phenylephrine, (4) isoproterenol, (5) terbutaline, and (6) dobutamine.
3. Explain the difference between direct cardiac (beta₁) effects of adrenergic agonists and reflex (baroreceptor reflex–mediated) effects of those same drugs, using norepinephrine, phenylephrine, and isoproterenol as examples.
4. Explain how each of the following affects structures controlled by the sympathetic nervous system, comparing how they work with how a direct-acting agonist such as epinephrine works, and state one or more clinical uses for each: (1) ephedrine, (2) amphetamines, (3) cocaine, and (4) monoamine oxidase (MAO) inhibitors.
5. Identify the desired effects when a therapeutic dose of epinephrine is given for anaphylaxis and explain the actions of the drug that earn it the label “drug of choice” for anaphylaxis.

Answer 1

Classify the following agonists in terms of the adrenergic receptors they activate and the responses they cause as a result of direct receptor activation: (1) epinephrine, (2) norepinephrine, (3) phenylephrine, (4) isoproterenol, (5) terbutaline, and (6) dobutamine.

epinephrine	Agonist	alpha receptor.
norepinephrine	Agonist	a1 receptor
Phenylephrine	Antagonist	a1 receptor
Isoproterenol	Agonist	b1 receptors
terbutaline	Agonist	b2 receptor
dobutamine	Agonist	b1 receptor

Explain how each of the following affects structures controlled by the sympathetic nervous system, comparing how they work with how a direct-acting agonist such as epinephrine works, and state one or more clinical uses for each: (1) ephedrine, (2) amphetamines, (3) cocaine, and (4) monoamine oxidase (MAO) inhibitors.

(1). Ephedrine: It acts on the alpha-adrenergic agonist and causes vasoconstriction which results in vascular resistance and an increase in blood pressure. It is used in asthma and shock.

(2). Amphetamines: It inhibits the reuptake of monoamine oxidase and thereby terminate the nerve signals. It is used in ADHD, cardiac arrest.

(3). Cocaine: It produces an anesthetic effect by blocking of nerve endings. It has vasoconstrictive effects. It is used for topical or local anesthesia.

(4). MAO inhibitors: Monoamine oxidase inhibitor inhibits the activities of Monoamine Oxidase A and monoamine oxidase B. It makes changes on the chemicals of the brain. It is used in panic disorders, depression.