Lectures 3 and 4 Flashcards

1
Q

Agonist

A

Drug that binds to and activates receptor

Can be full, partial or inverse

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2
Q

Allosteric modulator

A

Drug that binds to receptor at a site distinct from the active site. Induces a conformational change in the receptor, which alters the affinity of the receptor for the endogenous ligand.

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3
Q

Antagonist

A

A drug that attenuates the effect of an agonist

Can be competitive or non-competitive, each of which can be reversible or irreversible

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4
Q

Bmax

A

The maximum amount of drug or radioligand, usually expressed as picomoles per mg protein, which can specifically bind to receptors in a membrane preparation

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5
Q

Cheng-Prusoff equation

A

Used to determine the Ki value from an IC50 value measured in a competition radioligand binding assay

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6
Q

Desensitisation

A

A reduction in response to an agonist while it is continuously present at the receptor

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7
Q

EC50

A

The molecular concentration of an agonist that produces 50% of the maximum possible response for that agonist

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8
Q

ED50

A

Dose of drug that produces 50% of its maximum response or effect

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9
Q

Efficacy

A

The way that agonists vary in the response they produce when they occupy the same number of receptors

High efficacy agonists produce their maximal response while occupying a relatively low proportion of the total receptor population

Lower efficacy agonists do not activate receptors to the same degree and may not be able to produce the maximal response

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10
Q

Half life

A

Important pharmacokinetic measurement

Time taken for a drug’s concentration in plasma to decline to half its original level

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11
Q

IC50

A

Concentration of an agonist or antagonist which produces 50% of its maximum possible inhibition

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12
Q

ID50

A

Dose of a drug needed to cause 50% of the maximum possible inhibition of that drug

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13
Q

Kd

A

The dissociation constant for a radio labelled drug determined by saturation analysis

It is the molar concentration of radioligand which, at equilibrium, occupies 50% of the receptors

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14
Q

Ki

A

The inhibition constant for a ligand, which donates the affinity of the ligand for a receptor

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15
Q

Non-specific binding

A

The proportion of radioligand that is not displaced by other competitive ligands specific for the receptor

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16
Q

pA2

A

Measure of potency of antagonist

It is the negative logarithm of the molar concentration of an antagonist that would produce a 2-fold shift in the concentration response curve for an agonist

17
Q

p before abbreviation

A

Negative logarithm

18
Q

Specific binding

A

The proportion of radioligand that can be displaced by competitive ligands specific to the receptor

19
Q

LGIC

A

Ionotrophic
Typically at site where fast NTs act
Eg. GABA, nAchR, Glu

20
Q

Structure of LGIC

A

Homo or hetero

3-5 subunits around central pore

21
Q

Families of LGIC

A

Cys loop type- pentamers eg nAchR

NMDA type- tetramers

P2X type- trainers
Eg P2XR

22
Q

Why is the gut useful in pharmacology?

A

Contains many receptors that are the same as those in the brain

23
Q

Propanalol is an example of

A

Reversible competitive antagonist

Competes with isoprenaline