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Pharmacology - Fall > Lecture 1 - Drug-receptor interaction > Flashcards

Lecture 1 - Drug-receptor interaction Flashcards

1
Q

What is a drug?

A
  • A substance used as a medicine to treat, prevent, or diagnose a disease
  • A substance used with intent of producing a change within the body
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2
Q

What are pharmacokinetic processes?

A
  • Absorption, distribution, metabolism, and elimination

- The actions of the body on the drug

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3
Q

What are pharmacodynamic processes?

A
  • Receptor and signal transduction

- The actions of the drug on the body

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4
Q

What is a receptor?

A

A protein molecule in a cell that interacts with drugs and initiates a chain of events causing some form of cellular response

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5
Q

Where are receptors located?

A
  • Cell membrane
  • Cytoplasm
  • Nucleus
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6
Q

What is the structure of receptors made from?

A

Proteins

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7
Q

What is the function of receptors?

A

Bind to ligands to activate or inhibit post-receptor signaling, which triggers a biological response

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8
Q

What is the main significance of receptors?

A

They transduce signals from outside a cell to inside a cell

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9
Q

What are the 4 receptor families?

A

1) G protein-coupled receptors
2) Ligand-gated ion channels
3) Enzyme-linked receptors
4) Intracellular receptors

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10
Q

What is the biggest family of receptors?

A

G-protein coupled receptors

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11
Q

Which receptors are the most common site of drug action?

A

GPCRs

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12
Q

What are the 2 subunits of a G protein?

A

1 alpha-subunit and 1 beta gamma-subunit

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13
Q

What does the alpha subunit of a G protein do?

A

Binds GTP and GDP

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14
Q

What does the beta gamma subunit of a G protein do?

A

Inhibits the alpha subunit

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15
Q

What are some second messengers?

A
  • cAMP
  • Ca2+
  • IP3
  • DAG
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16
Q

What happens when GPCRs are activated?

A

They either increase or decrease production of second messengers, depending on which G protein is activated

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17
Q

What are 5 examples of GPCRs?

A

1) Muscarinic receptors
2) Adrenergic receptors
3) Dopamine receptors
4) Serotonin (5-HT) receptors
5) Opioid receptors

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18
Q

What are drug examples of muscarinic receptors?

A
  • Acetylcholine

- Drugs for parasympathetic NS

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19
Q

What are drug examples of adrenergic receptors?

A
  • Alpha, beta receptors
  • Norepinephrine, epinephrine
  • Drugs for sympathetic NS
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20
Q

What are drug examples of dopamine receptors?

A
  • Dopamine

- Antipsychotics

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21
Q

What are drug examples of serotonin (5-HT) receptors?

A
  • Serotonin

- Antipsychotics

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22
Q

What are drug examples of opioid receptors?

A
  • Endorphins

- Morphine and other analgesics

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23
Q

Which ions are more abundant on the INSIDE of a cell?

A
  • K+
  • H+ (equal on both sides)
  • A- protein
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24
Q

Which ions are more abundant on the OUTSIDE of a cell?

A
  • Na+
  • Ca2+
  • Cl-
  • H+ (equal on both sides)
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25
Q

What does ligand binding trigger?

A

A conformational change in the receptor

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26
Q

What determines the direction of movement through an ion channel?

A

The electrochemical gradient

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27
Q

What are examples of ligand-gated ion channels?

A
  • Nicotinic acetylcholine receptor
  • Glutamate N-methyl-D-aspartate receptor
  • Gamma-aminobutyric acid receptor
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28
Q

Which ion does the nicotinic acetylcholine receptor transfer?

A

Na+

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29
Q

Which ion does the glutamate N-methyl-D-aspartate receptor transfer?

A

Ca2+

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30
Q

Which ion does the gamma-aminobutyric acid receptor transfer?

A

Cl-

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31
Q

What is a drug example of a nicotinic acetylcholine receptor?

A

Succinylcholine

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32
Q

What is the function of a nicotinic acetylcholine receptor?

A

Muscle contraction

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33
Q

What is the function of a glutamate N-methyl-D-aspartate receptor?

A

Long-term potentiation

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34
Q

What are drug examples of a glutamate N-methyl-D-aspartate receptor?

A
  • Memantine

- Ketamine

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35
Q

What is the function of a gamma-aminobutyric acid receptor?

A

CNS depression

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36
Q

What is a drug example of a gamma-aminobutyric acid receptor?

A

Benzodiazepines

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37
Q

What occurs in ion pumps?

A

Ions move across a membrane against their concentration gradient, using ATP

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38
Q

What occurs in ion channels?

A

Ions move down their concentration gradients

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39
Q

What is another name for cell membrane enzyme-linked receptors?

A

Tyrosine kinase receptors

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40
Q

Which receptors can form dimers?

A

Enzyme-linked receptors

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41
Q

What are functions of enzyme-linked receptors?

A
  • Induce tyrosine phosphorylation
  • Convert kinases from inactive to active form
  • Metabolism, growth, and differentiation
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42
Q

What are drug examples of tyrosine kinase receptors and what do they treat?

A
  • Imatinib (gleevec) - chronic myeloid leukemia

- Interleukin-2 (proleukin) - cancers

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43
Q

What is the most common intracellular enzyme-linked receptor?

A

Soluble guanylyl cyclase

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44
Q

Where is guanylyl cyclase located?

A

Cytoplasm

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45
Q

What is the structure of guanylyl cyclase?

A
  • Forms a heterodimer composed of an alpha and a beta-subunit
  • Contains a regulatory domain, a coiled-coil domain, and a cyclase domain
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46
Q

What activates guanylyl cyclase?

A

Nitric oxide

47
Q

How are guanylyl cyclase and adenylyl cyclase different?

A

Adenylyl cyclase is activated by a G-protein; guanylyl cyclase is activated by nitric oxide

48
Q

What are 2 drug examples of guanylyl cyclase and what do they treat?

A
  • Nitroglycerin (glyceryl trinitrate) - angina

- Sildenafil (viagra) - hypertension and erectile dysfunction

49
Q

Describe the structure of intracellular receptors

A

Ligand binding domain and DNA binding domain

50
Q

Where are intracellular receptors generally located?

A

Nucleus

51
Q

Receptor ligands for intracellular receptors are ____ soluble

A

Lipid

52
Q

How are intracellular receptors regulated?

A

The ligand must diffuse into the cell to interact with nuclear receptor

53
Q

What is the function of intracellular receptors?

A

Regulate gene expression

54
Q

What are 2 examples of intracellular receptors?

A
  • Steroid receptors

- Non-steroid nuclear receptors

55
Q

What are drug examples of steroid receptors?

A
  • Cortisone
  • Estrogen
  • Progesterone
  • Testosterone
56
Q

What are drug examples of non-steroid nuclear receptors?

A
  • Retinoic acid
  • Vitamin D
  • Thyroid hormone
57
Q

List the 4 families of receptors from shortest to longest duration of action

A

1) Ion channels (milliseconds)
2) GPCRs (seconds to minutes)
3) Enzyme-linked receptors (seconds to minutes, or minutes to hours)
4) Intracellular nuclear receptors (hours to days)

58
Q

What are the 3 isoforms of the alpha subunit of a G protein and what does each do?

A
  • G alpha s -> stimulatory -> adenylyl cyclase -> cAMP
  • G alpha i -> inhibitory -> inhibits adenylyl cyclase -> inhibits cAMP
  • Gq -> activates phospholipid-regulated signaling -> phospholipase C -> second messengers
59
Q

Which ion has the greatest difference between intracellular and extracellular levels?

A

Ca2+

60
Q

Where are ion channels abundant?

A

On excitable cells

61
Q

What is Bmax?

A

The maximal specific binding of a ligand to a receptor

62
Q

What does Bmax indicate?

A

The total concentration of receptor sites

63
Q

What is Kd?

A

The equilibrium dissociation constant between ligand and receptor

64
Q

What does Kd represent?

A

The concentration of drug at which half-maximal binding is observed

65
Q

What is affinity?

A

The ability of a drug to bind to a receptor

66
Q

What does affinity describe?

A

The strength of binding between a ligand and its receptor (how attractive a receptor is to its drug)

67
Q

How are Kd and affinity related?

A
  • Kd determines the affinity of a drug for its receptor

- Lower Kd means higher affinity

68
Q

What is selectivity?

A

The degree to which a drug acts on a given site relative to other sites

69
Q

What does selectivity describe?

A

Preference for one receptor over another

70
Q

What is Emax?

A

The maximal effect induced by a drug (full agonist)

71
Q

What is EC50?

A

The concentration of drug producing an effect that is 50% of the maximum

72
Q

What is potency?

A

A measure of the amount of drug required to produce an effect of given magnitude

73
Q

What is the relationship between EC50 and potency?

A
  • EC50 determines potency

- Higher EC50 means a lower potency

74
Q

What is efficacy?

A

A measure of the ability of a drug to elicit a biological response by agonist

75
Q

What is the relationship between efficacy and Emax?

A
  • Emax determines efficacy

- Higher Emax means higher efficacy

76
Q

When selecting a drug, is efficacy or potency more important?

A

Efficacy (usually)

77
Q

What are agonists?

A

Agents that can bind to a receptor and elicit a biologic response

78
Q

What is a full agonist?

A

A drug binds to a receptor and produces a maximal biologic response that mimics the response of the endogenous ligand

79
Q

Do full agonists have good or bad efficacy?

A

Good

80
Q

What are some characteristics of partial agonists?

A
  • Have affinity for the receptor but have low efficacy

- Binding site is the same as full agonist

81
Q

What occurs when a partial agonist is administered alone?

A

It activates the receptor

82
Q

What occurs when a partial agonist is administered in the presence of a full agonist?

A

The partial agonist reduces the effects of the full agonist

83
Q

What are some characteristics of inverse agonists?

A
  • Have affinity for the receptor but have negative effect

- Reverse the constitutive activity of receptors

84
Q

What are some characteristics of antagonists?

A
  • Drug has affinity for the receptor, but has no efficacy
  • Can bind to a receptor but fails to produce a response
  • Can decrease actions of agonist or endogenous ligands
85
Q

What happens when an antagonist is used alone?

A

No biological effect is produced

86
Q

What happens when a partial agonist is used alone?

A

Produces less of a biological effect

87
Q

What happens when an antagonist is used with a full agonist?

A

Antagonist will reduce biological effect

88
Q

What happens when a partial agonist is used with a full agonist?

A

Biological effect will be reduced

89
Q

What happens when an antagonist is used with a partial agonist?

A

Antagonist will block partial agonist

90
Q

What is the mechanism of competitive antagonists?

A

Bind to the same site on the receptor with the agonist

91
Q

What is the function of a competitive antagonist?

A

Prevent an agonist from binding to its receptor

92
Q

How can competitive antagonists be overcome?

A

By increasing the concentration of the agonist to the receptor

93
Q

What happens to the dose-response curve of the agonist when a competitive antagonist is added?

A

The curve shifts to the right

94
Q

What happens to the EC50 of the agonist when a competitive antagonist is added?

A

Increases

95
Q

What is the mechanism of irreversible antagonists?

A
  • Bind covalently or with very high affinity to the active site of the receptor
  • Bind to an allosteric site
96
Q

What happens to Emax of the agonist when an irreversible antagonist is added?

A

Decreases

97
Q

What happens to the potency of the agonist when a competitive antagonist is added?

A

Decreases

98
Q

What is an adverse effect?

A

An undesired harmful effect resulting from a medication

99
Q

What are 4 examples of adverse effects?

A

1) Too much therapeutic effect
2) Poor tissue selectivity
3) Poor receptor selectivity
4) Drug interactions

100
Q

What is TD50?

A

The drug dose that produces a toxic effect or adverse effect in 50% of patients taking the drug

101
Q

What is ED50?

A

The drug dose that produces a therapeutic response in 50% of patients taking the drug

102
Q

How can you determine therapeutic index (TI)?

A

TD50/ED50

103
Q

What does a high TI mean?

A

A wide therapeutic window and a high safety

104
Q

What will the therapeutic index be of a drug that has a high affinity and high selectivity?

A

High TI

105
Q

What is hyporeactive?

A

Lower response to a drug than is usual

106
Q

What is hyperreactive?

A

Higher response to a drug than usual

107
Q

What is idiosyncratic?

A

Individuals exhibit an unusual drug response

108
Q

What is tachyphylaxis?

A

An acute rapid loss of response to a drug

109
Q

What is tolerance?

A

A decreased response to a drug when the drug is taken repeatedly

110
Q

What is receptor desensitization?

A

A mechanism that reduces the receptor response to an agonist

111
Q

What occurs in phase 1 of clinical trials?

A
  • Screening for safety

- Find the maximum tolerated dose

112
Q

What occurs in phase 2 of clinical trials?

A

Identify the therapeutic dose and study the efficacy

113
Q

What occurs in phase 3 of clinical trials?

A

Further establish and confirm safety and efficacy

114
Q

What occurs in phase 4 of clinical trials?

A

Monitor the safety of the new drug under actual conditions of use

Pharmacology - Fall (15 decks)

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