Receptor theory

Question 1

What is receptor theory?

Answer 1

That most drugs act by binding to receptors

Question 2

Does RT explain all drug actions?

Answer 2

No, chemical action or other properties

Example: Antacids - alkaline ions that chemically neutralize gastric acid in the stomach

Question 3

Drug definintion

Answer 3

A chemical compound that is administered to produce a desirable physiological or psychological effect

Question 4

What is a side effect?

Answer 4

Undesirable changes caused by a drug

Question 5

What is a receptor?

Answer 5

A molecule a drug can bind to which will cause a physiological change

Question 6

How does a drug bind its receptor?

Answer 6

Weakly and reverisibly

Question 7

Weak binding is

Answer 7

van der Waals force, H-bonds, ionic interactions

Question 8

Reversibly binding is

Answer 8

Enzyme-substrate binding

Question 9

Four main types of receptors

Answer 9

ion channels, G-protein coupled receptors, enzymatic, intracellular

Question 10

What is the equation for receptor theory?

Answer 10

D + R > [DR] > effect

Question 11

What are the properties of receptors?

Answer 11

Recognition and transduction

Question 12

Explain what the conformation of the receptors must allow

Answer 12

Must allow saturability, reversibility, stereoselectivity, agonist specificity and tissue specificity

Question 13

What is the transduction in receptors?

Answer 13

The spreading of the signal which leads to a physiological output

Question 14

What is an agonist?

Answer 14

A drug that binds to a receptor eliciting a cellular response

Question 15

What is an antagonist?

Answer 15

Prevents the action of an agonist

Question 16

What makes a drug an agonist?

Answer 16

Must have an affinity for the receptor and it must have an effect

Question 17

What are natural agonists?

Answer 17

Naturally occurring molecules that cause an effect, an example would be endorphins

Question 18

What is dose response?

Answer 18

The systemic relationship between the drug concentration and the magnitude of the response obtained

Question 19

Law of mass action

Answer 19

The rate of a chemical reaction is proportional to the product of the concentration of the reactants

Question 20

Do all receptors need to be occupied to give the max effect?

Answer 20

No

Question 21

what is the rate that the drug receptor complex disassembles?

Answer 21

Kd = K1/K2 = [D][R]/[DR

Question 22

What is the rate that the drug receptor complex assembles?

Answer 22

Ka = 1/Kd = K2/1=[DR]/[D][R]

Question 23

Limitations of the law of mass action

Answer 23

• assume that all receptors and ligands are equally available to each other
• Binding of drug and receptor is reversible
• The binding of drug and receptor leaves them unaltered
• There are no ambiguous partial states

Question 24

Occupancy theory

Answer 24

The effect is proportional to the number of receptors that are occupied

Question 25

Occupancy theory equation

Answer 25

Response = number of occupied receptors/ total number of receptors

Question 26

What does logging the x axis actually do on a dose response curve?

Answer 26

Helps you understand whats happening at the different concentrations

Question 27

What is the S shaped log dose curve called?

Answer 27

Sigmoid curve

Question 28

What way will the log dose curve shift if it is a less potent agonist?

Answer 28

Right

Question 29

What will a partial agonist do to the log dose response curve?

Answer 29

move it down

Question 30

What will positive cooperativity do to the curve?

Answer 30

steepen it

Question 31

What will negative cooperativity do to the log dose curve?

Answer 31

flatten the curve

Question 32

What are the 4 key parameters of the dose response curve?

Answer 32

- base line - slope - EC50 - maximal response

Question 33

What is a competitive antagonist?

Answer 33

a drug which interacts reversibly with the receptors

Question 34

A non competitive antagonist

Answer 34

a drug that binds with the receptors irreversibly

Question 35

What is a pA2 value?

Answer 35

An estimate of the concentration of agonist that is needed to double the concentration of agonist necessary to elicit the original response

Question 36

How does a competitive antagonist shift the curve?

Answer 36

to the right

Question 37

How does a non-competitive antagonist shift the curve?

Answer 37

moves it down

Question 38

What are the 2 properties of drugs?

Answer 38

Affinity and efficacy

Question 39

What is affinity?

Answer 39

a measure of the concentration range over which a drug binds to its receptor

Question 40

what is efficacy?

Answer 40

The ability of the drug to generate/ intiate a response once bound to the receptor

Question 41

what is the efficacy of an antagonist?

Answer 41

0

Question 42

How do you end the response?

Answer 42

receptors can be - desensitized - Internalised - downregulated