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Pharmacology FINAL > Adrenoceptor Agonists (Sympathomimetics) > Flashcards

Adrenoceptor Agonists (Sympathomimetics) Flashcards

1
Q

drugs that mimic the actions of epinephrine or norepinephrine have been termed….

A

sympathomimetic drugs

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2
Q

adrenergic agonists can be direct acting, mixed acting, or indirect acting.

what are epinephrine and norepinephrine? also explain their selectivity**

A

DIRECT ACTING adrenergic agonists

they are nonselective

epinephrine binds a1,a2,b1,b2

norepinephrine binds a1,a2,b1

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3
Q

name 2 adrenergic agonist that is mixed acting

A

ephedrine, pseudoephedrine

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4
Q

name 4 types of indirect acting adrenergic agonists

A

releasing agents
uptake inhibitor
MOA inhibitor
COMT inhibitors

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5
Q

why does a beta blocker used for hypertension have to be selective?

A

blocking b1 only is the goal.

blocking b1 binding will prevent vasoconstriction and thus lower hypertension

however, if b2 is blocked as well, the lungs cannot relax and they will constrict - preventing breathing

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6
Q

name 3 INDIRECT acting adrenergic agonists

A

amphetamine
cocaine
tyrosine

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7
Q

albuterol is a ____ acting adrenrgic agonist

A

direct acting

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8
Q

Name 6 direct acting adrenergic agonists, aside from epinephrine and norepinephrine

A

albuterol
dobutamine
dopamine
isoproteronol
terbutaline
salmeterol

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9
Q

recap: name the 4 things that can block something in the synthesis of norepineprhine

A

metyrosine blocks tyrosine hydroxylase and dopamine cannot be formed from tyrosine

reserpine stops the packaging of NE/dopamine into vesicles

cocaine and tricyclic antidepressants prevent the reuptake of NE through NET and it thus stays in the synaptic cleft for longer

bretylium and guanethidine prevent the release of NE by blocking SNAPs and VAMPS

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10
Q

what is a direct acting adrenergic agonist

A

binds and activates adrenergic receptors.
true agonist

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11
Q

explain the mechanism of Tyramine

A

indirect acting adrenergic agonist

it displaces the stored catecholamines from the adrenergic nerve ending

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12
Q

what has the same MOA as tyramine?

A

amphetamine

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13
Q

mechanism of cocaine
what else has this same mechanism?

A

cocaine + tricyclic antidepressants

prevent the reuptake of catecholamines that have already been released

indirect acting adrenergic agonist

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14
Q

what prevents the enzymatic metabolism of norepineprhine?

A

MAO inhibitors
monoamine oxidase

COMT inhibitors
catechol-o-methyltransferase

INDIRECT ACTING adrenergic agonists

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15
Q

what enzyme(s) is responsible for catecholamine metabolism in the brain

A

COMT and MAO

drugs that prevent them from metabolizing NE and E are indirect acting adrenergic agonists

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16
Q

true or false

COMT is a phase 2 biotransformation enzyme

A

true

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17
Q

** rank the following according to their affinity for the alpha adrenoceptor:

norepinephrine, isoproterenol, and epinephrine

A

highest affinity or equal: epinephrine
norepinephrine is either equal or less than epinephrine

lowest affinity by far is isoproterenol

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18
Q

rank the following according to their affinity for the beta adrenoceptor

norepineprhine
isoproterenol
epinephrine

A

isoproterenol has the highest affinity
epinephrine
norepinephrine is less than or equal to epinephrine

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19
Q

name a factor that can contorl the response of an indirect acting adrenergic agonist

A

the underlying sympathetic activity

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20
Q

true or false

the route of administration of adrenergic agonists does not control the response

A

false - it does

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21
Q

adrenoreceptors are what kinf of receptors?

A

GPCRs

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22
Q

the alpha 1 receptor uses what class of g protein?
also explain the mechanism

A

Gq

agonist binds to a1 receptor, alpha subunit of gq protein dissocitates and binds GTP (instead of GDP) and binds phospholipase c

phospholipase c increases DAG and IP3

DAG activates PKC

IP3 releases stored calcium to become FREE CALCIUM which activates calcium dependent protein kinase and second messengers (IP3,PKC, DAG ETC)

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23
Q

in alpha 1 receptors, what releases the stored calcium?

A

IP3

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24
Q

in alpha1 receptors, what activates PKC (protein kinase c)

A

DAG

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25
Q

What g protein does alpha 2 adrenoceptors work through

A

gi

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26
Q

what g protein do Beta receptors work through

A

Gs

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27
Q

explain the mechanism of agonist binding to alpha 2 receptors

A

agonist binds, alpha i(nhibitory) subunit binds GTP and disociates from b and y subunits

alpha subunit bound to GTP does NOT bind adenylyl cyclase and cAMP is not produced

cAMP levels decrease

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28
Q

explain the mechanism of agonist binding to beta receptor

A

as subunit binds GTP and dissociates from by subunits

as binds Adenylyl cyclase which causes ATP to increase cAMP

29
Q

name an alpha1 agonist
what will it cause when binds to alpha 1?

A

phenylephrine
vasoconstriction

30
Q

alpha 1 antagonist
what will be the effect when binding to alpha1?

A

prazosin
will block vasoconstriction and cause vasodilation

31
Q

name an alpha 2 agonist
what will happen upon binding to alpha 2 receptor?

A

clonidine
will cause vasodilation

32
Q

name an alpha 2 antagonist

A

yohimbine - not used clinically anymore

33
Q

true or false

when an alpha 2 agonist binds to it, IP3 and DAG will increase

A

FALSE

this is alpha 1 mechanism

alpha 2 will decrease camp levels

34
Q

true or false

a1 receptor works through Gq

A

true

35
Q

name a nonselective beta agonist
what happens upon binding?

A

isoproterenol
increased cAMP levels - works through Gs
increased heart rate and relaxes bronchial smooth muscle

36
Q

name a nonselective beta antagonist

what happens upon binding?

A

propanolol

decreased heart rate and possible bronchoconstriction

37
Q

general effect of beta receptor binding

A

works through Gs, so increased cAMP levels

38
Q

explain what receptor selectivity means

A

the drug preferentially binds to a certain subgroup of receptors

however, only at low concentrations. selectivity is not absolute because at higher concentrations the drug also interacts with related classes of receptors

39
Q

the effects of a drug depend on the selectivity for certain subtypes and also….

A

the expression of these receptor subtypes in a given tissue

40
Q

where is the B3 receptor

A

adipose tissue

41
Q

name 2 alpha agonists that are most selective for alpha 1

A

phenylephrine and methoxamine

a1>a2»»»»»B

42
Q

name 2 alpha agonists that are most selective for A2

A

clonidine and methylnorepinephrine

a2>a1»»»»>B

43
Q

name 2 mixed alpha and beta agonists

A

epinephrine and norepinephrine

44
Q

explain the selectivity of both epinephrine and norepinephrine

A

both have equal affinity for alpha1 and alpha2

epinephrine has equal affinty B1=B2 also

norepinephrine has more affinity for B1 than B2
B1»B2

45
Q

isoproterenol selectivity

A

B1=B2&raquo_space;»»»»»»a

46
Q

albuterol/terbutaline/metaproterenol/ritodrine selectivity

A

B2»B1»»»a

47
Q

dobutamine selectivity

A

B1>B2»»>A

48
Q

What happens if a potent drug continually binds to a receptor?

A

desensitization

49
Q

what is heterologous desensitization?
how can it happen?

A

the desensitization of receptors that were NOT exposed to the agonist

2nd messengers like PKC and PKA phosphorylate different receptors and decrease their activity

ex: PKA phosphorylates the b2 receptor and changes its preference from Gs to Gi

50
Q

what does biased agonists mean?
give an example

A

a receptor can have many effects

for example, binding to B1 incresed the heart rate and cardiac workload through the GPCR mechanism BUT also has non-GPCR arrestin-mediated efects

biased agonists for heart attack work through non-GPCR pathway

51
Q

NET reuptakes norepinephrine

breakdown where it takes the NE

A

reuptakes 90% NE into heart synapses and about 60% into other synapses

there, it enters vesicles and undergoes metabolism by MAO and COMT

52
Q

explain how amphetamine works

A

an indirect acting adrenergic agonist

instead of NET reuptaking the NE in the cleft, the transporter is reversed and more NE comes out into the cleft

53
Q

explain how cocaine works

A

indirect acting adrenergic agonist

blocks the reuptake of NE by NET so it stays in the synaptic cleft longer

54
Q

effect of alpha 1 binding on most vascular smooth muscle

A

contraction

55
Q

effect of alpha1 binding on the eye

A

contracts the pupillary dilator muscle (which dilates the eye)

56
Q

effect of alpha1 binding on pilomotor smooth muscle

A

hair gets erected

57
Q

effect of alpha 1 on prostate

A

contraction

58
Q

effect of alpha 1 on heart

A

increased force of contraction

59
Q

effect of alpha 2 binding on fat cells

A

inhibitis lipolysis

60
Q

effect of alpha 2 on platelets

A

causes them to aggregate

61
Q

effect of alpha 2 on adrenergic/cholinergic nerve terminals

A

inhibits the release of neurotransmitter

62
Q

effect of B1 on the heart and on juxaglomerular cells

A

increased force and rate of contraction of the heart

increases release of renin (body retains fluid, increased BP)

63
Q

effect of B2 on smooth muscle

A

smooth muscle relaxation

64
Q

true or false

b2 binding causes bronchodilation and vasodilation

A

true

65
Q

effect of b3 binding on fat cells

A

activates lipolysis

66
Q

true or false

alpha 2 agonists cause lipolysis

A

FALSE inhibits lipolysis

B3 agonists cause lipolysis

67
Q

explain how the cardiovascular effects of adrenergic agonists can vary

A

there is a widespread distribution of alpha and beta receptors in heart/blood vessels/neural/hormonal systems that are all involved in BP regulation

thus, the effects depend on whether the agonist acts on alpha, beta, or both

68
Q
A

Pharmacology FINAL (11 decks)

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