Lectures 3 and 4 Flashcards Preview

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Flashcards in Lectures 3 and 4 Deck (23):
1

Agonist

Drug that binds to and activates receptor

Can be full, partial or inverse

2

Allosteric modulator

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.

3

Antagonist

A drug that attenuates the effect of an agonist

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

4

Bmax

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

5

Cheng-Prusoff equation

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

6

Desensitisation

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

7

EC50

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

8

ED50

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

9

Efficacy

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

10

Half life

Important pharmacokinetic measurement

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

11

IC50

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

12

ID50

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

13

Kd

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

14

Ki

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

15

Non-specific binding

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

16

pA2

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

p before abbreviation

Negative logarithm

18

Specific binding

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

19

LGIC

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

20

Structure of LGIC

Homo or hetero
3-5 subunits around central pore

21

Families of LGIC

Cys loop type- pentamers eg nAchR

NMDA type- tetramers

P2X type- trainers
Eg P2XR

22

Why is the gut useful in pharmacology?

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

23

Propanalol is an example of

Reversible competitive antagonist
Competes with isoprenaline