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PA10315 > Receptors 2 > Flashcards

Receptors 2 Flashcards

1
Q

What is neurotransmission?

A

Chemical communication and therefore has a central role in almost every regulatory mechanism in our body.

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2
Q

Who was the receptor concept found by?

A

John Newport Langley in 1905.

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3
Q

How was the receptor concept found?

A

Nicotine was applied to frog skeletal muscle and it was found that the muscle only contracted when placed at the joint between the nerve and the muscle (motor end plate).
When it was applied to the nerve itself it had no effect

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4
Q

Who originated the quantitative receptor theory?

A

Alfred J Clark - it applied chemical laws to biological ideas.

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5
Q

What is a receptor?

A

A macromolecule that combines with a drug in order to produce effects.

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6
Q

How do drugs modify the function of different organ systems?

A

A pharmacodynamic interaction between the drug and the recognition system for that drug.

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7
Q

How can the response of muscle to a drug be measured?

A

A Kymograph (made by Matteucci) can record variations in muscular and physiological processes. It was based on a rotating drum that was smoked with benzene and a scribe scratched a recording of the experiment.

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8
Q

What is an agonist response?

A

A response in which the drug produces a response.

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9
Q

Why is a graph of concentration against response not useful for pharmacologists?

A

Only the lower concentrations of the drug are useful - hard to see from this type of graph.

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10
Q

What graph is more useful?

A

A log scale of concentration - a sigmoid graph is produced and the EC50 can be calculated by drawing a line at the 50% reponse.
The log concentration transforms curve from rectangular parabola to sigmoid curve

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11
Q

What can EC50s be used for?

A

They can be compared to work out how much more potent a certain drug is compared to another.

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12
Q

What is pEC50?

A

-log(EC50), measures drug potency.

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13
Q

What is intrinsic efficacy?

A

The ability of a drug to stimulate tissue - the ability of a molecule to force a receptor into its active state, which is the state leading to cellular response.

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14
Q

What are antagonists?

A

Drugs that bind to receptors that don’t cause an effect themselves but block responses produced by agonists.
receptor antagonists have affinity for the receptor but no intrinsic efficacy (ability to produce reponse)

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15
Q

What do antagnonists do the potency of agonists?

A

They reduce the potency so larger doses are required for the same effects.

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16
Q

What is a competitive antagonist?

A

When the antagonist competes for the same site of the agnonist.

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17
Q

What are partial agonists?

A

Ligands that show some agonist activity but do not produce full responses and block responses produced by full agonists at the receptor.

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18
Q

Simplify the term for a strong partial agonist.

A

A strong agonist and a weak antagonist.

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19
Q

Simpify the term for a weak partial agonist.

A

A weak agonist and a strong antagonist.

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20
Q

What is affinity?

A

The ability of a drug to bind to a receptor.

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21
Q

What is potency?

A

A measure of drug activity expressed in terms of the amount required to produce an effect of given intensity.

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22
Q

What gives potency?

A

The combined effects of affinity and efficacy.

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23
Q

What forces control affinity?

A

Thermodynamic and chemical (vary depending on distance between drug and receptor - electrostatic, hydrogen, van der Waals, hydrophobic).

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24
Q

come back and do that long equation please

A

please

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25
Q

What is the law of mass action?

A

The rate of reaction is proportional to the product of the concentrations of the reactants.

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26
Q

What is receptor occupancy?

A

The portion of receptors bound to the ligand.

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27
Q

What is kd?

A

The ligand concentration that gives 50% of receptor occupancy.

28
Q

finish again pls

A

pls

29
Q

what did langley conclude from his experiments

A

Ach was combining with a ‘receptive’ substance in the motor end plate region (receptor!)

30
Q

4 kinds of drug targets

A

enzymes, carrier molecules, ion channels and receptors

31
Q

without a stimulus

A

no response, but still formation of drug-receptor complex

32
Q

how can the result of a drug-receptor interaction be measured?

A

drugs labelled with one or more radioactive atoms- incubate samples of tissues with various concentrations of radioactive drug
biological response can be plotted as concentration-response curve

33
Q

What is EC50

A

concentration of a drug required to elicit 50% maximal response

34
Q

what can’t concentration-effect graphs show

A

affinity of agonists, because response is not directly proportional to receptor occupancy
Arises because max response produced when occupancy not 100%
in this circumstance tissue said to possess ‘spare receptors’

35
Q

when is a drug less potent

A

when it requires a higher concentration to elicit 50% maximal response

36
Q

in the presence of a antagonist what happens to concentration-effect curve

A

shifts right, no change in slope or maximum

37
Q

area available for binding

A

1- θ1

38
Q

Rate of diffusion of molecules towards a surface

A

condensation,α

39
Q

Rate of dissociation away

A

evaporation, V1

40
Q

rate of adsorption

A

α x µ x (1- θ1)

where µ= drug concentration

41
Q

rate of evaporation

A

V1 x θ1

42
Q

At equilibrium..

A

adsorption = evaporation

43
Q

equation rearranged

A

θ1 = αµ/(αµ + V1)

44
Q

p

A

fraction of maximal binding

45
Q

[AR]

A

amount of drug receptor complex

46
Q

[R1]

A

total number of receptor sites

47
Q

[A]

A

conc of drug

48
Q

Ka

A

dissociation constant

49
Q

drugs of high potency

A

have high affinity for receptors so have high receptor occupancy even at low concentration

50
Q

where α=

A

intrinsic activity

51
Q

what does this equation assume

A

that relationship between receptor occupancy and tissue response is linear

52
Q

what does our model of receptor-agonist activation suggest

A

stimulation of receptor leads to response, so implies receptor only activates when agonist binds

53
Q

constitutive activation

A

basal level of activation when no ligand is bound

54
Q

Inverse agonsits

A

ligands that can reduce level of constitutive activation

55
Q

what can an antagonist do here

A

only in the presence of agonists/inverse agonists, can restore system towards constitutional level

56
Q

Inverse agonists

A

ligands that can reduce level of constitutive activation

57
Q

what can an antagonist do here

A

only in the presence of agonists/inverse agonists, can restore system towards constitutional level

58
Q

constitutively active receptors

A

higher proportion of receptors occupy R* conformation in the absence of any ligand

59
Q

What is affinity?

A

The property of a molecule being closely associated with a receptor protein.

60
Q

What are some of the forces that control the strength of interaction between a drug and a receptor?

A

Electrostatic, hydrogen bonding, Van der Waals and hydrophobic bonds.

61
Q

What is condensation?

A

The rate of diffusion to a surface.

62
Q

What is evaporation?

A

The rate of dissociation from a surface.

63
Q

What is Ka?

A

The concentration of a drug required to occupy 50% of the total receptor population.

64
Q

What can be used to measure receptor occupancy?

A

Binding experiments.

65
Q

What can Kd values be used for?

A

Compare the affinity of ligands.

PA10315 (47 decks)

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