Lect 5: adrenergic stimulants

Question 1

What is the rate limiting step in the conversion from tyrosine to NE

Answer 1

conversion of tyrosine to l-dopa

Question 2

Where is NE converted to epinephrine

Answer 2

adrenal medulla

Question 3

effect of tyramine and amphetamine on NE release

Answer 3

increase or cause the release of NE from the presynaptic terminal. Therefore these drugs have an effect only if noradrenergic innervation is intact.

Question 4

antidepressants and cocaine effect on NE

Answer 4

block the reuptake of NE into the presynaptic terminal

• This is the main mechanism for termination of the action of NE in the synaptic cleft.

Question 5

NE is metabolized by what two enzymes

Answer 5

monoamine oxidase (MAO) and catechol-O-methyl transferase (COMT).

Question 6

List the steps from tyrosine to NE

Answer 6

Tyrosine -> L-DOPA-> dopamine -> NE

Question 7

What are adrenergic receptors

Answer 7

alpha and beta receptors

Question 8

differentiate between direct and indirect drugs

Answer 8

• direct: act on receptors to mimic sympathetic stimulation
• indirect: increase synthesis, cause release, or inhibit re-uptake/breakdown

Question 9

what happens to effect of direct and indirect drugs with denervation

Answer 9

• abolish effect of indirect drugs
• may enhance effect of direct drugs

Question 10

NE, epinephrine, and isoproterenol: list order of effect on alpha receptors

Answer 10

• epi > NE > > isoproterenol

Question 11

what is phenylephrine

Answer 11

an alpha 1 agonist

Question 12

alpha 1 acts via what G protein

Answer 12

• Gq
• excitatory

Question 13

alpha 2 acts via what G protein

Answer 13

• Gi
• inhibitory

Question 14

what is clonidine

Answer 14

alpha 2 agonist

Question 15

which adrenergic receptor is responsible for constriction of blood vessels to skin, kidneym mucous membranes

Answer 15

alpha 1

Question 16

which adrenergic receptor is responsible for the relaxation of BV to skeletal muscle

Answer 16

beta 2

Question 17

which adrenergic receptor is responsible for relaxation of gut wall and bronchioles

Answer 17

beta 2

Question 18

which adrenergic receptor is responsible for cardiac excitatory

Answer 18

beta 1

Question 19

which adrenergic receptor is responsible for lipolysis in fat cells

Answer 19

beta 3

Question 20

which adrenergic receptor is responsible for modulation of insulin and renin

Answer 20

beta 1

Question 21

Which drug has a high affinity for all beta receptors

Answer 21

Isoproterenol

Question 22

NE does not have much of an effect on which beta receptor

Answer 22

Beta 2

Question 23

Epi and NE affinity for B1 receptors

Answer 23

same effect; but less than isoproterenol

Question 24

what is dobutamine

Answer 24

beta 1 agonist

Question 25

function of dobutamin on heart and renin secretion

Answer 25

* increase HR and contractility * increase renin secretion

Question 26

what is albuterol

Answer 26

a beta 2 agonist

Question 27

function of albuterol on bronchiol smooth muscle, skeletal muscle BV, uterus, bladder, and GI muscle?

Answer 27

Relax

Question 28

which adrenergic receptor is responsible for glycogenolysis/gluconeogenesis

Answer 28

beta 2

Question 29

function of dopamine 1 receptors

Answer 29

* _Dilate_ renal BV, increase renal blood flow

Question 30

alpha receptor stimulation by NE effect on cardiovascular function

Answer 30

1. **Skin and splanchnic blood vessels** have mainly α receptors * Smaller blood vessels are more densely innervated than larger ones, therefore the largest effect is on small blood vessels. 2. Net effect is to **increase blood pressure**. * Peripheral artery resistance is increased and venous capacity is decreased * Increased blood pressure will stimulate **baroreceptors**, which then increase vagal input to _slow the heart_

Question 31

what happens to cardiovascular response if atropine is given prior to norepinephrine

Answer 31

the vagal reflex is inhibited, the baroreceptor effect will not occur, and heart rate will increase

Question 32

NE must be injected; why is it used only rarely, for severe hypotensive crisis

Answer 32

NE can cause severe vasoconstriction at the infusion site and can cause necrosis

Question 33

NE has what strength of effect on alpha, beta 1 and beta 2 receptors?

Answer 33

stimulates α and β1 receptors, with little effect on β2 receptors (α = β1\>\> β2)

Question 34

epinephrine has what strength of effect on alpha, beta 1 and beta 2 receptors?

Answer 34

Epinephrine stimulates α, β1 and β2 receptors, which makes the effect complex \*\*\***the effect depends upon the dose administered**

Question 35

which receptors are most sensitive to epinephrine

Answer 35

* B2 receptors in blood vessels supplying skeletal muscle are more sensitive to epinephrine than alpha receptors

Question 36

what effect does low dose epinephrine stimulation have on alpha, beta 1 and beta 2 receptors

Answer 36

* **beta1 receptors** increase heart rate, conduction, contractility * (**inc systolic pressure**) * **alpha receptors** constrict blood vessels in the skin, mucosa and kidney * increased systolic * **beta2 receptors** relax blood vessels supplying skeletal muscle * **decrease in diastolic pressure** * pulse pressure increases * since **mean blood pressure is unchanged**, there is little reflex slowing of the heart rate -\> heart rate is increased

Question 37

what effect does high dose of epinephrine have on systolic, diastolic, and mean arterial pressure

Answer 37

* **alpha receptors** in blood vessels supplying skeletal muscle are stimulated * diastolic pressure increases * **increases blood pressure substantially** * both systolic and diastolic pressure will increase * **mean pressure increases** * **​**there is less increase in heart rate

Question 38

epinephrine has a short duration of action and must be administered via

Answer 38

injection

Question 39

Explain how an alpha block can be used to reverse the effect on high dose epinephrine and not norepinephrin

Answer 39

* taking out alpha receptors from high dose epinephrine leaves beta 2 receptor activation which causes vasodilation of BV to skeletal muscle and BP drops * NE has no effect on B2 receptors

Question 40

what are the primary uses of epinephrine

Answer 40

* **bronchodilation** in severe asthma attack via B2 * **vasoconstrictor**: decrease diffusion of injected drugs such as local anesthetics * **anaphylactic shock** to restore blood pressure, decrease bronchospasm, decrease congestion and angioedema, and reverse cardiovascular collapse

Question 41

what are some side effects of epinephrine

Answer 41

tremor, throbbing headache, increased blood pressure, tachycardia, angina

Question 42

why is epinephrine contraindicated in people taking beta-blocker

Answer 42

unopposed effects on α receptors may lead to severe hypertension!

Question 43

what is Ephedrine

Answer 43

* a drug that : stimulates α and β receptors similar to low-dose epinephrine, and also increases NE release * long duration of action * CNS stimulant * bronchodilator * taken off market due to deaths from high BP and stroke