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Intro to Med > Receptor basic, agonists antagonistic > Flashcards

Receptor basic, agonists antagonistic Flashcards

1
Q

What are the effects of adrenaline?

A

-Many effects on the body including increasing heart rate and contraction

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2
Q

What is bisoprolol and and what is it prescribed for?

A

-Synthetic drug
-Prescribed to reduce heart rate and contraction

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3
Q

What is the bisoprolol used to treat?

A

-Used to treat cardiovascular conditions such as angina and heart failure when we want to reduce the effort of the heart

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4
Q

What does bisoprolol reduce the effect of?

A

-Bisoprolol reduces the effect of adrenaline

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5
Q

What does adrenaline do to the heart?

A

-Increase heart rate and contraction strength

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6
Q

What does adrenaline do to the lungs?

A

-Dilates airways

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7
Q

What does adrenaline do to the liver?

A

-Increases breakdown of glycogen, increasing plasma glucose

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8
Q

What is the importance of enantiomers for adrenaline

A

-The (+) enantiomer of adrenaline has about 100 fold greater biological than (-) adrenaline

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9
Q

Potency of adrenaline?

A

-Very high. Adrenaline acts at very low concentrations (bc they act act receptors)
e.g. 10-9M - 10-15M ranges can produce significant increases in heart rate

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10
Q

What are receptors?

A

-Target molecules with endogenous substances or ‘given’ drugs bind to produce a cellular response

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11
Q

What receptors in the heart does adrenaline stimulate?

A

-Adrenaline is a physiological hormone, which stimulates the beta-adrenoceptors

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12
Q

Where does bisoprolol act in the heart?

A

Bisoprolol is a synthetic drug which acts at beta adrenoceptors to prevent the action of adrenaline

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13
Q

What are the general properties of receptors?

A

-Expressed in different tissues
-High selective targets: Only specific drug structures bind to receptors
-Amplify signals: Small number of drug/receptor interactions initiate significant biological effects

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14
Q

What is the general structure of beta-adrenoceptor?

A

-Is a large complex protein molecule consisting of transmembrnae domains

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15
Q

What do the transmembrane regions contain in beta-adrenoceptor and what does this allow for?

A

-Transmembrane regions with hydrophilic and lipophilic amino acids
-Allows the folding of membrane hence creates binding sites

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16
Q

Where else can beta-adrenoreceptors be found?

A

-liver
-lungs

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17
Q

What are the 4 different types of receptors?

A

Receptors
-Adrenaline and Bisoprolol act at beta adrenoreceptor
Enzymes
-Ibuprofen acting on cyclooxygenase
Carrier molecules
-Fluoxetine(anti-depressant) acting at serotonin uptake carrier
Ion channels
-Lignocaine (local anaesthetic) acting at Na+ channels

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18
Q

What is an agonist

A

A drug which binds to a receptor to produce a biological cellular response
-e.g. adrenaline is an agonist that increases heart rate

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19
Q

What is an antagonist?

A

A drug which binds to a receptor but does NOT produce a biological cellular response
-e.g. Bisoprolol is an antagonist that blocks adrenaline-mediated increases in heart rate

20
Q

What are drugs classified according to?

A

Clinical use
- e.g. bisoprolol is used to treat angina hence “anti-anginal drug”
Target receptor
-e.g. bisoprolol binds to beta-adrenoreceptors hence “beta-adrenoreceptor antagonist (beta-blocker)”

21
Q

What are receptors often classified according to?

A

-Receptors are often classified according to the agonists and antagonists that act upon them e.g. adrenoceptors: These drugs bind to adrenoceptors, but their differential actions define whether an alpha or beta adrenoceptor is involved

22
Q

What receptors do blood vessels express?

A

Alpha adrenoceptors

23
Q

What is most to least potent on alpha adrenoceptors in blood vessels? What do they do?

A

Noradrenaline>Adrenaline>Isoprenaline
-Increase constriction

24
Q

What drugs acts as an antagonist on alpha adrenoceptors?

A

-Alpha adrenoceptors on blood vessels are blocked by prazosin(not bisoprolol)

25
Q

What is most to least potent on alpha adrenoceptors in the heart? What do they do?

A

Isoprenaline>Adrenaline>Noradrenaline
-Increase heart rate

26
Q

What is the occupation of receptor governed by?

A

-Occupations of receptor is governed by affinity

27
Q

What is activation of receptor goverend by?

A

-Activation governed by efficacy

28
Q

What is binding of agonist and antagonist assessed by?

A

Both agonists and antagonists bind to receptors
-How well they bind is assessed by equilibrium constant(KA, Kant)

29
Q

How is the quality of action produced by an agonist assessed?

A

How well they produce an action is assessed by effective concentration producing 50% of maximal response(EC50)
- only agonists

30
Q

In what fashion do agonists and antagonists bind to receptors?

A

Reversibly -Adrenaline and bisoprolol bind to beta adrenoceptor-then dissociate- this is a continuous ‘off and on’ process

31
Q

What are the types of binding that occur between receptor and agonist/antagonist?

A

Hydrogen bonding, Ionic bonding, van der waal’s forces
-Relatively weak therefore reversible binding and good dissociation

Covalent binding
-Stable strong bonds therefore irreversible binding and poor dissociation hence “conformational change”

32
Q

What governs the reversible binding of agonist to receptor? What is this dependant on?

A

-Rate of reversible binding of agonist to receptor is governed by law of mass action
-Dependent on concentration of the reactants involved

33
Q

What does the law of mass predict?

A
  1. Low concentration of A and lots of Rfree results in a low rate of AR interactions
  2. Increase the concentration of A and you increase rate of AR interactions-shifts reaction to right
  3. Continue increasing concentration of A results in few Rfree, which results in a low rate of AR interaction
34
Q

When is the equilibrium constant (KA or KANT) reached?

A

When 50% of receptors are free and 50% are bound by drug

35
Q

What is KA or KANT for the drug and what does this mean?

A

-KA or KANT is the concentration of the drug at equilibrium:
-This means that a KA of 50nM means that at this concentration 50% of receptors will be occupied by agonist

36
Q

What does a small KA or KANT value mean?

A

Smaller KA or KANT means agonist or antagonist has a greater affinity for receptor(binds more) than an agonist or antagonist with a higher KA or KANT

37
Q

What does efficacy measure?

A

-Efficacy measures biological effect like increase in heart rate by adrenaline

38
Q

What is EC50?

A

Effective concentration giving 50% biological response

39
Q

Are affinity and efficacy equal? Why?

A

Affinity and Efficacy of an agonist are not equal
-You do not need full occupancy to give a maximum response
-The reason why drugs can work at low concentration is because receptors amplify signals, so only a small number of drug-receptor interactions provide biological effects

40
Q

What happens to response against log(agonist) curve in the presence of a competitive antagonist?

A

-Presence of a competitive antagonist shift agonist curve to the right
-Same maximal response

41
Q

What needs to be done to overcome/surmount competitive antagonism?

A

-Increasing concentration of agonist will out compete or surmount antagonism

42
Q

What happens to response against log(agonist) curve in the presence of a non competitive antagonist?

A

-reduce slope and depress maximum

43
Q

How does non-competitive antagonism work?

A

-Antagonist binds to a different site than agonist

44
Q

How does irreversible antagonism work?

A

-Antagonists binds irreversibly to either agonist or non-agonist binding sites on the receptor through covalent bonds

45
Q

What impact do both non-competitive/irreversible antagonists have?

A

-Both non competitive/irreversible antagonists reduce number of receptors

Intro to Med (46 decks)

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