M-Chapter 6: Adrenergic Agonists

Question 1

Which of the following is correct regarding adrenergic
neurotransmission?
A. Epinephrine is the major neurotransmitter released
from sympathetic nerve terminals.
B. Norepinephrine is mainly released from the adrenal glands.
C. Tricyclic antidepressants and cocaine prevent reuptake of norepinephrine into the nerve terminals.
D. Monoamine oxidase (MAO) converts dopamine to
norepinephrine in the nerve terminal.

Answer 1

C. Tricyclic antidepressants (TCAs) and
cocaine inhibit the transporter protein that prevents the
reuptake of norepinephrine into the sympathetic nerve ter
minals. Norepinephrine, not epinephrine, is the major neu
rotransmitter released from sympathetic nerve terminals.
Epinephrine, not norepinephrine, is mainly released from
the adrenal glands. Dopamine is converted to norepineph
rine by dopamine β-hydroxylase, not by MAO.

Question 2

All of the following are correct regarding adrenergic
receptors, except:
A. α1
Receptors are primarily located on the
postsynaptic membrane in the effector organs.
B. α2
Receptors are primarily located on the
presynaptic sympathetic nerve terminals.
C. β1
Receptors are found mainly in the heart.
D. β2
Receptors are found mainly in adipose tissue.

Answer 2

D. α1
Receptors are located on the post
synaptic membrane in the effector organs such as blood
vessels. α2 Receptors are mainly found on the presynaptic
sympathetic nerve terminals, where they inhibit the release of norepinephrine when activated. β1Receptors are found in the heart,in addition to some other tissues, and cause increase in heart rate and contractility when activated. β2receptors are found in the lungs, in addition to some other tissues, and cause relaxation of bronchial smooth muscles when activated. β3 Receptors are found in adipose tissue and are involved in lipolysis.

Question 3

A hypertensive patient was accidentally given an α2

agonist instead of an α1
blocker. Which of the following
is correct in this situation?
A. α2 Agonists can increase the release of
norepinephrine from sympathetic nerve terminals.
B. α2 Agonists can reduce blood pressure in this patient.
C. α2 Agonists can increase blood pressure in this
patient.
D. α2 Agonists will not affect blood pressure in this
patient.

Answer 3

B. α2 Agonists activate α2 receptors located in the presynaptic terminal of sympathetic neurons and cause a reduction in the release of norepinephrine from sympathetic nerve terminals. This leads to a reduction in blood pressure. α2Agonists such as clonidine and methyldopa are therefore used as antihypertensive agents.

Question 4

Which of the following is correct regarding responses
mediated by adrenergic receptors?
A. Stimulation of α1receptors increases blood pressure.
B. Stimulation of α1 receptors reduces blood pressure.
C. Stimulation of sympathetic presynaptic α2receptors
increases norepinephrine release.
D. Stimulation of β2 receptors increases heart rate (tachycardia).
E. Stimulation of β2receptors causes bronchoconstriction.

Answer 4

A. Stimulation of α1receptors, mostly found in the blood vessels, causes vasoconstriction and increase in blood pressure. Stimulation of α2receptors on the sympathetic presynaptic terminal reduces the release of norepinephrine. β2receptors are not found in the heart,so activation of β2receptors does not affect heart rate. Stimulation of β2 receptors found in the bronchial tissues causes bronchodilation, not bronchoconstriction.

Question 5

An asthma patient was given a nonselective β agonist
to relieve bronchoconstriction. Which of the following
adverse effects would you expect to see in this patient?
A. Bradycardia.
B. Tachycardia.
C. Hypotension (reduction in blood pressure).
D. Worsening bronchoconstriction.

Answer 5

B. A nonselective β agonist activates both β1as well as β2receptors. β1activation causes an increase in heart rate (tachycardia), contractility, and subsequent increase in blood pressure. It relieves bronchoconstriction because of the β2receptor activation.

Question 6

Which of the following adrenergic agonists is most
likely to cause CNS side effects when administered
systemically?
A. Epinephrine.
B. Norepinephrine.
C. Isoproterenol.
D. Dopamine.
E. Ephedrine.

Answer 6

E. Ephedrine is more lipophilic compared
to the other drugs listed and therefore is more likely to
cross the blood–brain barrier when administered systemi
cally. Therefore, ephedrine is more likely to cause CNS side
effects compared to other listed drugs.

Question 7

A 12-year-old boy who is allergic to peanuts was brought
to the emergency room after accidentally consuming
peanuts contained in fast food. He is in anaphylactic
shock. Which of the following drugs would be most
appropriate to treat this patient?
A. Norepinephrine.
B. Phenylephrine.
C. Dobutamine.
D. Epinephrine.

Answer 7

D. Norepinephrine has more α agonis
tic effects and activates mainly α1, α2, and β1receptors.
of choice in anaphylactic shock that can both stimulate the heart (β1
activation) and dilate bronchioles (β2activation).Epinephrine has more β agonistic effects and activates mainly α1, α2, β1, and β2 receptors. Phenylephrine has predominantly α effects and activates mainly α1receptors. Dobutamine mainly activates β1receptors and has no significant effects on β2receptors. Thus, epinephrine is the drug

Question 8

A 70-year-old patient was brought to the emergency
room with a blood pressure of 76/60 mm Hg,
tachycardia, and low cardiac output. He was diagnosed
with acute heart failure. Which of the following drugs
would be the most appropriate to improve his cardiac
function?
A. Epinephrine.
B. Fenoldopam.
C. Dobutamine.
D. Isoproterenol.

Answer 8

C. Among the choices, the ideal drug to
increase contractility of the heart in acute heart failure is
dobutamine, since it is a selective β1-adrenergic agonist.
Fenoldopam is a dopamine agonist used to treat severe
hypertension. Other drugs are nonselective adrenergic
agonists that could cause unwanted side effects.

Question 9

Which of the following adrenergic agonists is commonly
present in nasal sprays available over-the-counter
(OTC) to treat nasal congestion?
A. Clonidine.
B. Albuterol.
C. Oxymetazoline.
D. Dobutamine.
E. Norepinephrine.

Answer 9

C. Drugs with selective α1agonistic activity are commonly used as nasal decongestants because of their ability to cause vasoconstriction in the nasal vessels. Oxymetazoline is an α1agonist and therefore the preferred drug among the choices as a nasal decongestant. Clonidine is an α2agonist, albuterol is a β2agonist, dobutamine is a
β1agonist, and norepinephrine is a nonselective adrenergic agonist.

Question 10

One of your patients who is hypertensive and gets mild
asthma attacks occasionally bought an herbal remedy
online to help with his asthma. He is not on any asthma
medications currently but is receiving a β1-selective
blocker for his hypertension. The herbal remedy seems
to relieve his asthma attacks, but his blood pressure
seems to increase despite the β-blocker therapy. Which
of the following drugs is most likely present in the herbal
remedy he is taking?
A. Phenylephrine.
B. Norepinephrine.
C. Dobutamine.
D. Ephedrine.
E. Salmeterol.

Answer 10

D. Two drugs among the choices that
could relieve asthma are ephedrine and salmeterol, as they
activate β2 receptors in the bronchioles and cause broncho
dilation. However, salmeterol is a selective β2agonist and
should not cause an increase in blood pressure. Ephedrine
on the other hand stimulates the release of norepinephrine
and acts as a direct agonist at α- and β-adrenergic receptors,
thus causing an increase in blood pressure. Phenylephrine
(a nonselective α agonist) does not cause bronchodilation.
Norepinephrine is a nonselective adrenergic agonist that
does not have any stimulatory effects on β2 receptors. Also, norepinephrine is not active when given orally.