Definitions

Question 1

Antagonist

Answer 1

A drug that binds to a receptor and prevents activation
affinity but no efficacy
several diff types; competitive, non competitive and uncompetitive

Question 2

Greater Emax =

Answer 2

Greater efficacy

Question 3

Smaller EC50

Answer 3

higher potency

Question 4

Bmax

Answer 4

The maximum binding obtained in a saturation assay

corresponds to the number of receptors in the system

Question 5

rectangular hyperbola

Answer 5

a curve that rises and then smoothly reaches a plateau.
characteristic of concentration-binding relationships.
predicted by Hill-Langmuir equation

Question 6

Ki

Answer 6

may mean 2 diff things
someties used to define the afffinity of a competitive antagonist
more often used to define the affinity of a ligand and derived from a concentration binding assay

Question 7

Conc ratio

Answer 7

ratio of agonist EC50 in the presence of antagonist to the Ec50 in the absence. for a competitive antagonist but it is more often used to define the degree of ‘right shift’ on the agonist concentration response curve

Question 8

Gaddum equation

Answer 8

An equation used to describe the actions of a competitive antagonist.

Question 9

EC50

Answer 9

The conc. of an agonist that gives 50%of the max response

Question 10

sigmoid curve

Answer 10

S shaped curve, seen with log conc. response relationships

Question 11

Receptor

Answer 11

A protein involved in cell signalling.
takes a signal, binds it, passes on info that signal conveys.
important drug binding sites

Question 12

Kd

Answer 12

equilibrium dissociation constant used to measure drug affinity
is the conc. of a ligand that occupies 50% of a receptor population and thus as Kd increases so affinity decreases

Question 13

Full agonist

Answer 13

a drug that gives the max response possible from a receptor

Question 14

Partial agonist

Answer 14

drug that activates a receptor, but not to the same degree as a full agonis.
It is ‘part way’ between a full agonist and an antagonist

Question 15

Affinity

Answer 15

tightness with which a drug binds to a receptor or other protein. It is usually measured by the equilibrium dissociation constant, Kd. As Kd increases, affinity decreases

Question 16

Agonist

Answer 16

A drug that binds to a receptor and activates it. It has both affinity and efficacy

Question 17

Potency

Answer 17

conc. of drug required to produce a defined effect.
ec50 is often used as a measure of agonist potency
for antagonists, PA2 is the most frequently used parameter

Question 18

PA2

Answer 18

Conc of competitive antagonist such that twice the concentration of agonist is required to restore the original response for a competitive antagonist, the PA2 is theoretically equal to -logKi

Question 19

Emax

Answer 19

maximal effectthat can be obtained from a functional assay. It may depend on both receptor and system factors

Question 20

ED50

Answer 20

dose that produces 50% of maximal response. This term should only be used when drug responses are measured in animals or mans

Question 21

PKd

Answer 21

-ve log of Kd. A drug with a Kd of 1e^-9M has a pKd of 9

Question 22

Hill Langmuir Equation

Answer 22

the basic equation relating the binding of a drug to its conc. It can be derived from the Laws of Mass Action

Question 23

Non-competitive antagonist

Answer 23

An antagonist that binds to a receptor at a site other than the agonist binding site. The EC50 for agonist is unchanged but the max response is decreased.
unsurmountable by agonist conc

Question 24

IC50

Answer 24

Conc of an agonist that reduces response to a particular conc. of agonist by 50%

Question 25

Efficacy

Answer 25

the degree to which an agonist can activate a receptor. A full agonist has the maximal possible efficacy. An antagonist has zero efficacy. A partial agonist has some efficacy, but less than that of a full agonist

Question 26

pEC50

Answer 26

negative log of the EC50

Question 27

competitive antagonist

Answer 27

a drug that binds to the same site as an agonist, but does not activate the receptor. The presence of a competitive antagonist will reduce occupancy by agonists. In a functional assay, a competitive antagonist will cause a parallel rightward shift in the agonist conc response curve

Question 28

Selectivity

Answer 28

the ability of a drug to bind more tightly (or activate more potently) one receptor type compared with another. A drug with an affinity of 1nM for receptor X and 10nM for receptor Y has 10 fold selectivity for receptor x

Question 29

Drugs acting on adrenergic transmission

Answer 29

Cardiovascular system (diverse)
Anti-asthma drugs
Decongestants
Aphrodisiacs 
Migraine
ADHD
Depression