L17 - receptor antagonists and modulators Flashcards

1
Q

ligand

A

something that binds to a receptor

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2
Q

agonist

A

ligand that binds to a receptor and activates it to cause a response

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3
Q

antagonist

A

ligand that binds but does not activate the receptor

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4
Q

competitive antagonists

A

compete with agonist for the same receptor binding site

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5
Q

reversible competitive antagonist

A

increasing the agonist concentration cause lead to agonist outcompeting the antagonist and binding to the receptor

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6
Q

irreversible receptor antagonist

A

permanently binds to receptor, no amount of agonist will change this

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7
Q

concentration response curve when there in a reversible antagonist

A
  • higher conc of agonist is needed to elicit same response
  • look at notes to see pictures
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8
Q

when you increase conc of reversible antagonist what happens to Emax and E50 of agonist?

A
  • Emax stays same
  • EC50 increases/ gets larger
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9
Q

concentration response curve when there in an irreversible antagonist

A
  • higher concentrations of agonist will not have an effect on
  • reduced response
  • so emax decreases
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10
Q

when you increase conc of irreversible antagonist what happens to Emax and E50 of agonist?

A
  • emax of agonist reduces
  • ec50 gets bigger
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11
Q

how to measure antagonism?

A

schild plot and pA2

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12
Q

what is a schild plot?

A

finds nature and potency of antagonist

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13
Q

y axis of schild plot

A

log (dose ratio - 1)

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14
Q

x axis of schild plot

A

log (concentration of antagonist)

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15
Q

how to calculate dose ratio?

A

EC50 agonist with antagonist/ EC50 agonist withOUT antagonist

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16
Q

what is the pA2 value determined from?

A
  • where the line intersects the x-axis
  • negative log value of concentration
17
Q

pA2 equation for measuring antagonism?

A

pA2 = log (dose ratio -1) - log (conc of antagonist)

18
Q

what does pA2 measure?

A

antagonist potency

19
Q

higher PA2 =

A

more potent antagonist

20
Q

if 2 antagonists have same pA2 value, what does this suggest?

A

they both act through same receptor

21
Q

if the shape of the schild plot is linear what does this indicate about the nature of antagonism?

A

competitive antagonism

22
Q

if the shape of the schild plot is curved what does this indicate about the nature of antagonism?

A

non competitive antagonism

23
Q

where do agonists + competitive antagonists bind on?

A

orthosteric site of receptor

24
Q

where do other drugs/ molecules (allosteric modulators) bind to on a receptor to modify affects of agonists?

A

allosteric site

25
affinity modulation
affects how agonist binds to orthosteric site of receptor (alter how well the agonist binds to the receptor)
26
efficacy modulation
affects how agonist activates the receptor
27
allosteric agonism
allosteric modulators that push the receptor into an active conformation
28
what do affinity allosteric modulators cause?
- alter how well agonist binds to receptor - so more or less of the agonist is needed for the same response - shifts concentration response curve to the left if it is positive affinity modualtion - right if it negative
29
what do efficacy allosteric modulators cause?
- alter how well agonist activates the receptor - full response of agonist is increased or decreased - positive modulation = curve goes up - negative modulation = curve goes down (non-comp antagonism)