Adrenoceptor Agonists

Question 1

Drugs that mimic the actions of epinephrine or norepinephrine have traditionally been termed

Answer 1

sympathomimetic drugs

Question 2

indirect agonists because their actions are dependent on their ability to enhance the actions of endogenous catecholamines by:

Answer 2

1. inducing the release of catecholamines by displacing them from adrenergic nerve endings
2. decreasing the clearance of catecholamines by inhibiting their neuronal reuptake
3. preventing the enzymatic metabolism of norepinephrine

Question 3

Adrenoceptors are typical ___ receptors

Answer 3

G protein-coupled

Question 4

Alpha1 receptors are coupled via G proteins in the G_ family to
phospholipase C.

Answer 4

q

Question 5

Alpha2 receptors are coupled to the inhibitory regulatory protein G_ that inhibits adenylyl cyclase activity and causes intracellular cyclic adenosine monophosphate (cAMP) levels to decrease

Answer 5

i

Question 6

Activation of all three receptor subtypes (β1, β2, and β3) results in:

Answer 6

stimulation of adenylyl cyclase and increased cAMP

Question 7

a selective β3 agonist, is approved for the treatment of symptoms
of overactive bladder

Answer 7

Mirabegron

Question 8

means that a drug may preferentially bind to one subgroup of
receptors at concentrations too low to interact extensively with
another subgroup.

Answer 8

Selectivity

Question 9

After a cell or tissue has been exposed for a period
of time to an agonist, that tissue often becomes less responsive to
further stimulation by that agent

Answer 9

desensitization

Question 10

refers to loss of responsiveness exclusively of the receptors
that have been exposed to repeated or sustained activation by an
agonist

Answer 10

Homologous

Question 11

refers to the process by
which desensitization of one receptor by its agonists also results
in desensitization of another receptor that has not been directly
activated by the agonist in question

Answer 11

Heterologous

Question 12

A major mechanism of desensitization that occurs rapidly involves phosphorylation of receptors by members of the
__

Answer 12

G protein-coupled receptor kinase (GRK) family

Question 13

Recognition that G protein-coupled receptors can signal through both G protein-coupled and G protein-independent pathways has raised the concept of developing ___that selectively activate these arrestin-coupled signaling pathways

Answer 13

biased agonists

Question 14

distinct polymorphisms occur in specific combinations termed

Answer 14

haplotypes

Question 15

90% of released norepinephrine is removed by the

Answer 15

NET

Question 16

may be considered the parent compound from
which sympathomimetic drugs are derived

Answer 16

Phenylethylamine

Question 17

Alpha1 receptors are widely expressed in vascular beds, and their
activation leads to ___

Answer 17

arterial and venous vasoconstriction.

Question 18

Intravenous administration of dopamine promotes ___ of renal, splanchnic, coronary, cerebral, and perhaps other
resistance vessels, via activation of D1 receptors

Answer 18

vasodilation

Question 19

Activation of β2 receptors in bronchial smooth muscle leads
to __

Answer 19

bronchodilation

Question 20

In the eye, the radial pupillary dilator muscle of the iris
contains α receptors; activation by drugs such as phenylephrine causes ___

Answer 20

mydriasis

Question 21

___ increase
the outflow of aqueous humor from the eye and can be used
clinically to reduce intraocular pressure.

Answer 21

Alpha2 agonists

Question 22

___ antagonists decrease the production of
aqueous humor and are used in the treatment of glaucoma

Answer 22

β

Question 23

Activation of β adrenoceptors in fat cells leads
to

Answer 23

increased lipolysis

Question 24

the immediate precursor in the synthesis of
norepinephrine

Answer 24

Dopamine

Question 25

It
is an important neurotransmitter in the CNS and is involved in
the reward stimulus relevant to addiction.

Answer 25

Dopamine

Question 26

The primary indication for midodrine is the
treatment of

Answer 26

hypotension

Question 27

used as a centrally
acting muscle relaxant.

Answer 27

tizanidine

Question 28

is a direct-acting α agonist used as a topical
decongestant because of its ability to promote constriction of the
vessels in the nasal mucosa and conjunctiva

Answer 28

Oxymetazoline