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Pharm 507 > Receptor Pharm II > Flashcards

Receptor Pharm II Flashcards

1
Q

Competitive Antagonist

A

Bind to receptor at SAME site as agonist

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2
Q

E/Emax of competitive antagonists

A

0

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3
Q

Agonist and antagonist binding sites may not be identical, but they are…

A

Mutually exclusive

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4
Q

Drug + Antagonist-Receptor Binding Equation

A

R + A + B RA + RB

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5
Q

KA equation

A

KA = [R][A]/[RA]

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6
Q

KB equation

A

KB = [R][B]/[RB]

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7
Q

Binding and effect equation for antagonist

A

(E/Emax) = [A]/(EC50(1+[B]/KB) +[A])

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8
Q

Antagonists shift the agonist curve to the _____, making the agonist _____ potent

A

Right, less

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9
Q

Magnitude of the shift caused by antagonist

A

1 + [B]/KB

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10
Q

When [B] = KB, agonist curve shifts by a factor of

A

2

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11
Q

Half-maximal inhibitory concentration of antagonist (IC50) is used to…

A

Compare potency of antagonist drugs

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12
Q

What does intrinsic efficacy (e) of agonists determine?

A

How well drug activates receptor when bound

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13
Q

Full agonist

A

Produces max (100%) response

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14
Q

Intrinsic efficacy of full agonists

A

High

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15
Q

Partial agonists

A

Do not produce max response even when occupying ALL receptor sites

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16
Q

Intrinsic efficacy of partial agonists

A

Low

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17
Q

Intrinsic efficacy equation

A

(E/Emax) ~ e • ([D]/(EC50 + [D])

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18
Q

Partial agonist is also known as _____. Why?

A

Partial antagonist; they block the remaining efficacy of the full agonist

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19
Q

Why are some ligands agonists whereas others are antagonists?

A

Full agonists make all contact points on receptor
Partial agonists make some contact points on receptor
Antagonists don’t make any of the contact points, but occupy the pocket

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20
Q

Therapeutic implications of partial agonists

A

Agonist or antagonist action depends on receptor activation
Some response will always be present
Antagonist action prevents response from being over-activated by other endogenous ligands

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21
Q

Examples of partial agonists

A

Beta blocker with partial activator activity to ensure adequate resting HR… but prevents HR from increasing too much with exercise/stress

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22
Q

Non-Competitive Antagonists

A

Cannot be surmounted by any concentration of agonist

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23
Q

Types of non-competitive antagonists

A

Irreversible - permanent covalently bound

Allosteric - reversible, prevents receptor activation when agonist is bound, but does not impact agonist binding

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24
Q

Therapeutic effect of non-competitive antagonists

A

Reduces agonist effect potency (EC50)
Shift curve right
KA is unchanged

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25
Q

What happens when all the spare receptors are depleted?

A

Curve shifts down

26
Q

Action duration for irreversible inhibitors. Why?

A

Days to weeks; cell has to synthesize new receptors

27
Q

Allosteric modulators

A

Bind to secondary (Allosteric) binding site

28
Q

What do Allosteric modulators need to have action?

A

Endogenous ligands present

29
Q

Impact of binding at Allosteric site

A

Alters agonist binding at orthosteric/primary site

30
Q

Positive modulators

A

Increase actions/effects at primary site

31
Q

Negative modulators

A

Decease actions/effects at orthosteric/primary site

32
Q

Example of Allosteric modulators

A

Benzos

33
Q

Functional Antagonists/Physiological Antagonism

A

Agonist with opposing functional effect appears to act like antagonist of each other even though they bind to different receptors

34
Q

Functional Antagonist/Physiological Antagonism Example

A

ACh on muscarinic receptor causes vasodilation as a result of vasoconstriction caused by norepi acting on alpha-1 adrenergic receptor

35
Q

Ligand-Gated Ion Channel Receptor prototype

A

Nicotinic acetylcholine receptor

36
Q

Ligand-Gated Ion Channel Receptor: endogenous ligand and agonist drug

A

Endogenous ligand - acetylcholine

Agonist drug - nicotine

37
Q

Ligand-Gated Ion Channel Receptor: effect of agonist binding and response

A

Channel opens and sodium enters cell, causing depolarization
Response - muscle contraction

38
Q

Ligand-Gated Ion Channel Receptor: Time frame

A

Milliseconds

39
Q

GPRC: prototype and endogenous ligands

A

Beta-adrenergic receptor

Endogenous ligands - epi and norepi

40
Q

GPCR: agonist drug

A

Isoproterenol (cardiac stimulant)

41
Q

GPCR: effect of agonist binding and response

A

Binding - activated GTP-binding proteins that regulate enzymes in turn to generate 2nd messenger molecules
Response - metabolism, secretion, smooth muscle contraction/relaxation, cell migration, etc.

42
Q

GPCR: time frame

A

Seconds to minutes

43
Q

Receptors with Intrinsic Enzyme Activity: prototype

A

Insulin receptor

44
Q

Receptors with Intrinsic Enzyme Activity: endogenous ligand and agonist drug

A

Endogenous ligand & agonist drug: insulin

45
Q

Receptors with Intrinsic Enzyme Activity: effect of binding and response

A

Binding - activates enzymatic activity (tyrosine kinase) of intracellular domain
Response - gene expression, cell growth and differentiation, cancer cell growth

46
Q

Receptors with Intrinsic Enzyme Activity: time frame

A

Minutes to hours (long-lasting)

47
Q

Intracellular Transcription Factor Receptors: prototype

A

Estrogen receptor

48
Q

Intracellular Transcription Factor Receptors: endogenous ligand & agonist drug

A

Estradiol

49
Q

Intracellular Transcription Factor Receptors: effect of binding and response

A

Binding - causes receptor to trans locate and bind to DNA response elements, regulating gene transcription
Response - gene expression, cell growth and differentiation, cancer cell growth

50
Q

Receptor Subtypes

A

Different receptor proteins for the same endogenous ligand
Typically numbered to differentiate
Endogenous ligands act on multiple receptor subtypes

51
Q

Endogenous ligands are ________ agonists because they activate multiple subtypes

A

Non-selective

52
Q

Which drug tends to have fewer side effects?

A

Selective drugs

53
Q

Key differences among Subtypes

A

Expressed differently in various tissues

Coupled to different signaling pathways that mediate different effects

54
Q

Beta agonist/antagonist example

A

Beta 2: agonist for asthma but not HR/BP

Beta 1: antagonist for angina but not airway constriction

55
Q

G proteins signaling pathway examples

A

Beta-adrenergic couples to Gs and increases cAMP

Alpha-1 adrenergic couples to Gq and regulates Ca

56
Q

Repeated exposure to agonists lead to…

A

Modifying/phosphorylating receptor so it is removed and degraded

57
Q

Down-regulation

A

Removal of receptors so they no longer interact with agonists

58
Q

Tolerance/tachyphylaxis

A

Loss of responsiveness to drug effects

59
Q

What happens to ligand-gated ion channels if agonist occupancy is too long?

A

Desensitized/blocked

60
Q

What does repeated exposure to antagonists cause? What is this called?

A

Increased # of receptors to interact with agonists

Up-regulation

61
Q

Clinical implication of down-regulation

A

Increased agonist dose May be needed to maintain therapeutic effect

62
Q

Clinical implication of up-regulation

A

Abrupt discontinuation of antagonist may cause life threatening rebound effect when agonist action is restored

Pharm 507 (6 decks)

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