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Pharmacology 1 > Pharmacodynamics And Drug Receptors > Flashcards

Pharmacodynamics And Drug Receptors Flashcards

1
Q

What does the drug receptor complex do

A

The drug-receptor complex initiates alterations in biochemical
and/or molecular activity of a cell by a process called signal transduction

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2
Q

How do Receptors signal their recognition of a
bound ligand?

A

by initiating a series of reactions that
ultimately result in a specific intracellular
response

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3
Q

What are second messagers

A

are
part of the cascade of events that translates
agonist binding into a cellular response.

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4
Q

What are the different type of receptors do cardiac cells have

A
  1. p-adrenergic receptors that bind and respond to epinephrine or norepinephrine.

2.Cardiac cells also
contain muscarinic receptors that bind and respond to acetylcholine.

These two receptor populations dynamically interact to control the
heart’s vital functions.

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5
Q

What is the relationship between The magnitude of the response
to the number of drug–receptor complexes?

A

The magnitude of the cellular response is proportional to the number of drug-receptor complexes

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6
Q

How are Most receptors named

A

Depending on the compounds that connects to them

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7
Q

Do all drugs exert their effects by interacting with a receptor.
Examples?

A

No
Antacids, for
instance, chemically neutralize excess gastric acid, thereby reducing
stomach upset.

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8
Q

What are the receptors states

A

inactive (R) and active (R*),
that are in reversible equilibrium with one another, usually favoring the
inactive state

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9
Q

How do agonists affect the receptors

A

Fully shift the equilibrium to R*

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10
Q

How do partial agonists affect the equilibrium

A

shift the equilibrium
from R to R* , but the fraction of R* is less than that caused by an
agonist.

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11
Q

How do fully inverted agonists effect the equilibrium

A

Shift it all to R

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12
Q

How do antagonists affect the equilibrium

A

Antagonists are drugs that bind to
the receptor but do not increase the fraction of R*

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13
Q

What are the different definitions for a receptor

A

any biologic molecule to which a drug binds and produces a measurable response.

Protein molecules whose function is to recognize and
respond to chemical signals.

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14
Q

What is the richest source for pharmacologic receptors

A

proteins that transduce extracellular signals into
intracellular responses

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15
Q

What are the different receptors

A

1) ligand-gated ion channels, 2) G protein-coupled receptors, 3)
enzyme-linked receptors, and 4) intracellular receptors

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16
Q

What are lingard-gatee ion channels responsible for

A

Responsible for regulation of the flow of ions across cell
membranes.

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17
Q

The ligand gated channel is usually
closed until the receptor is activated by an agonist

A

True

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18
Q

What’s the duration of response of ligand gated channels

A

a few milliseconds

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19
Q

What do linfand gated channels meditate

A

these receptors mediate diverse
functions, including neurotransmission and muscle contraction.
For example, stimulation of the nicotinic receptor by acetylcholine opens a channel that allows sodium influx and potassium
outflux across the cell membranes of neurons or muscle cells

(GABA) receptor increases
chloride influx, resulting in hyperpolarization of neurons and less
chance of generating an action potentia

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20
Q

Give examples for drugs that bind on voltage gated channels

A

local anesthetics bind to
the voltage-gated sodium channel, inhibiting sodium influx and
decreasing neuronal conduction

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21
Q

What are the 3 subunits for proteins

A

The a subunit
binds guanosine triphosphate (GTP), and the B and y subunits
anchor the G protein in the cell membrane

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22
Q

What are the changes that happens to the G protein when an angonist binds to the receptor

A

Binding of
an agonist to the receptor increases GTP binding to the a subunit,
causing dissociation of the a-GTP complex from the Itt complex.
The a and Itt subunits are then free to interact with specific cellular
effectors, usually an enzyme or an ion channel, that cause further
actions within the cell

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23
Q

What’s the duration of response for g protein

A

last several seconds to minutes

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24
Q

•What is a common effector, activated by Gs, and the second messenger ?

A

is adenylyl cyclase (enzyme) , which produces the second messenger cyclic
adenosine monophosphate (cAMP).

(activated by Gs. and inhibited by Gi)

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25
What's enzyme does the Gq active
phospholipase C,
26
What does phospholipaseC, generate
two other second messengers ip3 and DAG
27
What are enzyme linked receptors
•These consists of a protein that may form dimers or multi-subunit complexes.When activated, these receptors undergo conformational changes, resulting in increased cytosolic enzyme activity
28
What's the duration for enzyme like receptors
minutes to hours
29
•What is the most common enzyme linked to the enzyme linked receptors?
growth factors and insulin
30
What happens after activating enzyme linked receptors
•The activated receptor autophosphorylates, • and then phosphorylates tyrosine residues on specific proteins. •Phosphorylation can modify the structure of the target protein, thereby acting as a molecular switch.
31
How do intracellular receptors differ from other classes
the receptor is entirely intracellular, and, therefore, the ligand (for example, steroid hormones) must have sufficient lipid solubility to diffuse into the cell
32
How long is the response
hours to days
33
•What is the primary targets of these ligand- receptor complexes in intracellular receptors
ranscription factors in the cell nucleus that regulate gene expression
34
How do intercellular receptors work
The activation or inactivation of transcription factors alters the transcription of DNA into RNA and subsequently translation of RNA into proteins.
35
What are the characteristics of signal transduction
Signal amplification and Desensitization and down-regulation of receptors
36
How does signal amplification works
A characteristic of G protein-linked and enzyme-linked receptors is the ability to amplify signal intensity and duration via the signal cascade effect,activated G proteins persist for a longer duration than does the original agoist-receptor complex. The binding of albuterol, for example, may only exist for a few milliseconds, but the subsequent activated G proteins may last for hundreds of milliseconds.
37
What are spare receptors
n, only a fraction of the total receptors for a specific ligand may need to be occupied to elicit a maximal response
38
•Compare between the % of Spare receptors exhibited : •by insulin receptors, •To the human heart β-adrenoceptors
About 99% of insulin receptors are "spare;• providing an immense functional reserve that ensures that ade￾quate amounts of glucose enter the cell. about 5% to 1 0% of the total b-adrenoceptors in the heart are spare. Therefore, little functional reserve exists in the failing heart, because most receptors must be occupied to obtain maximum contractility.
39
What is down regulation?
The receptor may become desensitized due to too much agonist stimulation
40
What is the fate of down regulated receptors
receptors may be internalized within the cell, making them unavailable for further agonist interaction
41
The magnitude of the drug effect depends on the drug concentration at the receptor site, which in turn is determined by:
• 1) the dose of drug administered • 2) and by the drug’s pharmacokinetic profile.
42
what is a graded response
the response is continuous and gradual.
43
what is a quantal response
describes an all-or-nothing response.
44
what is the potency
A measure of the amount of drug necessary to produce an effect of a given magnitude.
45
what is EC50
The concentration of drug producing 50% of the maximum effect
46
Therapeutic preparations of drugs reflect their potency. ❑E.g., candesartan (4 to 32 mg) and irbesartan (75 to 300 mg )are used to treat hypertension.
true
47
what is the efficacy
The magnitude of response a drug causes when it interacts with a receptor.
48
what does efficacy depends on
1) the number of drug–receptor complexes formed 2) and the intrinsic activity of the drug.
49
what is the maximal efficacy of the drug [E max]
the max response that a drug gives after occuping all of the receptors [no change after increasing the conc]
50
whats the difference between the E max of the following 1. full agonist 2. partial agonsit 3. antagonist
1. full agonist --- 100% effect 2. partial agonist --- 0
51
Efficacy is a more clinically useful characteristic than drug potency.
true
52
what is the Effect of drug concentration on receptor bindin
quantitative relationship between drug concentration and receptor occupancy
53
what is the Kd
the equilibrium dissociation constant for the drug from the receptor. determines the affinity
54
what is the affinity
describes the strength of the interaction (binding) between a ligand and its receptor
55
whats the relationship between the affinity and the Kd
• The higher the Kd value, the weaker the interaction and the lower the affinity.
56
The affinity of an agonist for binding to receptors should be related to the potency of that drug for causing that physiological effect.
true
57
Many drugs and most neurotransmitters can bind to more than one type of receptor, thereby causing both desired therapeutic effects and undesirable side effects.
norephedrine and alpha and beta receptors
58
what is inrinsic activity
The intrinsic activity of a drug determines its ability to fully or partially activate the receptors.
59
what are full agonists
a drug binds to a receptor and produces a maximal biologic response that mimics the response to the endogenous ligand,
60
what is the intrinsic activity for full agonists
1
61
what are partial agonists
a drug that cant preduce the same E max as the full agonist even if it has a higher affinity
62
what is the intrinsic activity for partial agonits
0
63
When a receptor is exposed to a partial agonist and a full agonist, how does the partial agonist behave?
it behaves as an partial antagonist
64
What would happen to the Emax of a receptor saturated with an agonist in the presence of increasing concentrations of a partial agonist.
As the number of receptors occupied by the partial agonist increases, the Emax would decrease until it reached the Emax of the partial agonist
65
aripiprazole (for schizophrenia) is a partial agonist at dopamine receptors.
true
66
what is an inverse agonist
it turns all R* to R in spontaneous receptors
67
what is the intrinsic activity of inverse agonists
less than zero
68
what is the effect of inverse agonists
reverse the activation state of receptors, and exert the opposite pharmacological effect of agonists.
69
what are antagonists
Antagonists bind to a receptor with high affinity but possess zero intrinsic activity. An antagonist has no effect on biological function in the absence of an agonist,but can decrease the effect of an agonist when present by blocking it from binding
70
what are competitive antagonists
If both the antagonist and the agonist bind to the same site on the receptor (reversible), they are “competitive.”
71
Competitive antagonists shift the agonist dose–response curve to the right (increased EC50) without affecting Emax
true
72
what are irreversible antagonists
irreversible antagonist bind covalently to the active site of the receptor, thereby reducing the number of receptors available to the agonist.
73
what does irreversible antagonest
An irreversible antagonist causes a downward shift of the Emax, with no shift of EC50 value.
74
whats the difference between competitive antagonists and irreversable ones
• Irreversible antagonists cannot be overcome by adding more agonist.
75
whats is allosteric antagonists
binds to a site (allosteric site) other than the agonist-binding site and prevents receptor activation by the agonist.
76
whats the effect of allosteric antagonists
Similar to non-competitive effect on the Emax, and EC50 value.
77
whats functional antagonism
An antagonist may act at a completely separate receptor, initiating effects that are functionally opposite those of the agonist. A classic example is the functional antago- nism by epinephrine to histamine-induced bronchoconstriction
78
what is Quantal Dose–Response Relationships
The influence of the magnitude of the dose on the proportion of a population that responds. [all or nothing]
79
what is the therapeutic index
TI = TD50/ED50. TI is a measure of a drug's safety, because a larger value indicates a wide margin between doses that are effective and doses that are toxic.
80
What is the Clinical usefulness of the therapeutic index?
These usually reveal a range of effective doses and a different range of toxic doses.

Pharmacology 1 (10 decks)

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