Lecture 4 alpha Adrenergic agonists

Question 1

g-protein; second messenger pathway

alpha-1
alpha-2
beta-1
beta-2

Answer 1

alpha 1- Gq - IP3/DAG
alpha 2 - Gi - decreased cAMP
beta 1 - Gs - increased cAMP –> Ca
beta 2 - Gs - increased cAMP –> PKA

Question 2

in addition to inhibiting cAMP formation, alpha 2 agonists cause opening of ___ channels, causing an ___ of the substance and ___polarization

Answer 2

K+, efflux, hyper

Question 3

As you increase the dose of adrenergic receptor agonists, you ___ the selectivity

Answer 3

decrease

Question 4

Of phenylephrine, Epinephrine, NE, and isoproterenol (PENI), which has the highest alpha 1 adrenergic receptor activation? Which has very little alpha 1 activity?

Answer 4

phenylephrine;

isoproterenol

Question 5

Of PENI, which has the highest beta 1 receptor activation? Which has very little activation?

Answer 5

isoproterenol;

phenylephrine

Question 6

of PENI, which has the highest B2 receptor activation? Which have lower activation?

Answer 6

Iso and EPI = high

NE and phenylepi = low

Question 7

The baroreceptor reflex is initiated due to changes in ___ ___

Answer 7

blood pressure

Question 8

Of NE, Epi, and isoprterenol. which causes reflex tachy? Which causes reflex brady?

Answer 8

tachy = isoproterenol

brady = NE

Question 9

NE acts on alpha 1 receptors, causing vasoconstriction and an ____ in bp. Although it also activates ___ receptors, the heart rate actually _____ due to _____ in vagal tone

Answer 9

increase; B1

decreases, increase

Question 10

Epi causes vasoconstriction via ___ receptors. It also binds ___ receptors, causing vasodilation. What is its overall effect on blood pressure? Is there a baro-receptor effect?

Answer 10

alpha 1, beta 2

no change;

no baro-receptor effect

Question 11

Epinephrin acts on ____ receptors, causing an overall ___ in heart rate

Answer 11

B1, increase

no baro-receptor reflex!

Question 12

Isoproterenol acts on ___ receptors causing vasodilation and a drop in blood pressure. This induces the baro-receptor reflex causing an ____ in heart rate. Isoproterenol also acts on ___ receptors, causing a ___ in heart rate directly

Answer 12

B2; increase;

B1, increase

Question 13

how does phenylephrine effect HR and BP?

Answer 13

alpha 1 agonist–> increase in bp–>reflex brady –> decrease in HR

Question 14

Because NE is a substrate for __ and ___, it is short acting. NE is used mostly as a ___. What is added in preparations of it and Epi to increase half life?

Answer 14

COMT, MAO;
pressor;

sodium bisuflite

Question 15

sodium bisulfie prevents ___ in EPI and NE

Answer 15

oxidation

Question 16

at low doses, the ___ effects of epinpehrine predominate–>so we see vaso____, ____ in heart rate

Answer 16

beta;

dilation (beta 2), increase (beta 1)

Question 17

at high doses of epi, the ____ effects predominate–> se we see a ___ in blood pressure

Answer 17

alpha;

increase

Question 18

Main uses of epinephrine?

Answer 18

anaphylaxis, open-angle glaucoma, asthma

Question 19

phenylephrine acts mainly on __ receptors. it causes ____ without ____; it is also a nasal _____

Answer 19

alpha 1;
myrdriasis without cycloplegia;

decongestant

Question 20

tetrahydrozoline, naphazoline, and oxymetazoline (visine) are partial ____ receptor agonists. They are administered ____ to promote vasoconstriction. Thus, they are ____

Answer 20

alpha 1;
locally/topically;
decongestants

Question 21

visine and other a1 agonists contain a ___ ring that causes compounds to exist in an ___ form at physiologic pH, limiting systemic effects

Answer 21

imidazole; ionized

Question 22

What is the main issue with visine and other alpha 1 receptor agonists?

Answer 22

tachyplaxis/desensitization after a few uses –> stopping can cause a rebound effect

Question 23

clonidine is a selective __ receptor agonist. Its clinical effect is linked to activation of receptors in the _____. Overall, this causes a ____ in sympathetic tone

Answer 23

alpha 2;
nucleus tractus solitarious
decrease

Question 24

alpha 2 agonists act in the brain ____ to decrease sympathetic tone. this causes a decrease in heart rate, contractility, and release of ____

Answer 24

stem;

renin

Question 25

guanabenz and guanfacine are special alpha 2 agonists in that they can do what?

what are they used for?

Answer 25

cross the BBB;

ADHD, hypertension

Question 26

what precursor of a natural NT is an alpha 2 receptor agonist? what is it used for, according to FA?

Answer 26

alpha methyldopa;

hypertension in pregnancy

Question 27

tizanidine is a ___ receptor agonist. it is used for what?

Answer 27

alpha 2;

muscle relaxant

Question 28

_____ is a alpha 2 receptor agonist used to treat glaucoma

Answer 28

apraclonidine

Question 29

adverse effects of alpha 2 agonists:

CNS ____; __ and ___ retention, dry mouth

Answer 29

sedation/depression, Na, water