Lecture 1 and 2 (Part 3) Flashcards

1
Q

What terminology is different between receptors and enzymes?

A

Receptors have ligands which can be agonists and antagonists while enzymes have substrates, products and inhibitors

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2
Q

What is the difference between a concentration-response curve and a dose-response curve

A

Concentration-response curve is used when there is an isolated system is immersed while a dose is the amount given to the whole organism

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3
Q

What is a saturation effect?

A

When increasing the concentration of the drug does not result in an increased effect, but does NOT require all agonists to be bound to receptors

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4
Q

What is Emax?

A

The maximum effect possible (saturation effect)

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5
Q

What is pD2?

A

A measure of agonist potency, a higher pD2 means a greater potency

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6
Q

What is EC50?

A

The effective concentration that produces 50% of the maximum effect, a lower EC50 means a greater potency

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7
Q

What is ED50?

A

The effective dose that produces the 50% of the maximum effect

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8
Q

What is the relationship between pD2 and EC50?

A

pD2=-logEC50

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9
Q

What shape is characteristic of concentration response curves?

A

Sigmoidal

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10
Q

What is IC50?

A

The concentration of an antagonist which inhibits half of the agonist response

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11
Q

What are the changes to an agonist concentration response curve in the presence of reversible and irreversible antagonists?

A

with a reversible antagonist the curve is right shifted (but not downwards shifted) with no effect on maximal responseWith an irreversible antagonist the curve is left shifted and will plateau out at a lower level

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12
Q

What is competitive reversible antagonism?

A

When the antagonist is reversible and competes directly with the agonist for the same binding site on the receptor resulting in a higher agonist concentration being required to produce the same effect

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13
Q

What is pA2?

A

-log (2*concentration that gives EC50), varies with different receptor and agonists is a measure of the potency of the antagonist

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14
Q

What is an example of a competitive reversible antagonist?

A

Propranolol at beta-2 receptors,Atropine at M

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15
Q

What is competitive irreversible antagonism?

A

An antagonist competes for the same binding site as the agonist but the antagonist has much greater affinity and can typically not be easily removed from the receptor and therefore not be overcome through increasing the amount of agonist

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16
Q

What is the potency measure for competitive irreversible antagonists and non-competitive antagonists?

A

pD2 DASH

17
Q

What is an example of a competitive irreversible antagonist?

A

Phenoxybenzamine at H1 receptors

18
Q

What occurs to the concentration response curve in the presence of low and high concentrations of competitive irreversible antagonists?

A

In low concentrations there would be a right shift in the curve with no change in the maximal response due to the spare receptor theory (this has never been practically proven)In high concentrations there would be a strong right shift and a large depression in the maximal response,this has been practically proven

19
Q

What is the spare receptor theory?

A

The theory that there are more receptors than required to create a maximal response in a tissue so some of these receptors can be occupied by competitive irreversible antagonists and there will still be enough free receptors present to induce a maximal response

20
Q

What is non-competitive antagonism?

A

Don not bind to the same receptor or binding site as the agonist and therefore can not be out competed by changing the concentration of agonistsIts actions occur occur through interfering with the cascade of events initiated by receptor-agonist binding

21
Q

What is the effect of a non-competitive antagonist on the concentration response curve?

A

A non-parallel rightwards shift with a depression in the max response

22
Q

What is an example of non-competitive antagonist?

A

Verapamil antagonism of histamine

23
Q

What is physiological antagonism?

A

Occurs when the actions of two agonists working at two different receptor types have opposing effects

24
Q

What is an example of physiological antagonism?

A

Histamine acting at H1 receptors to cause bronchoconstriction and adrenaline acting and beta-2 receptors to cause bronchodilation

25
Q

What is a partial agonist?

A

Agonists which do not elicit a maximal response, despite having full receptor occupancy

26
Q

What is an example of a partial agonist?

A

Methysergide at 5HT receptors

27
Q

What is the effect of partial agonists on full agonists?

A

Initially, at low concentrations the partial agonist will aid the agonist while at higher concentrations the partial agonist will act as an antagonist as it will get in the way of the full agonist and therefore reduce the effect that could have been gained

28
Q

What is an inverse agonist?

A

Some receptors are always on, ligands can bind to this resting state resulting in a change in state resulting in less constitutive activityInverse agonists is essentially the same as a competitive reversible antagonist

29
Q

Can a competitive reversible antagonist be distinguished from a competitive irreversible antagonist based only off a concentrations response curve?

A

No, this is theoretically possible due to the spare receptor theory but is not practically possible