lecture 4 - Agonists

Question 1

Defintions of an agonist?

Answer 1

substance which initiates a response when bound to a receptor. Agonists have an efficacy of > 0.

Question 2

Partial Agonist definition?

Answer 2

partial agonists can bind to a receptor but only have partial efficacy so have a partial response.

Partial agonists are not able to produce the same maximum/full response as a full agonist. In the presence of a ‘full agonist’ a partial agonist behaves like an antagonist, causing a shift to the right in the concentration response curve

Question 3

What is a competitive antagonist?

Answer 3

Agonists and antagonists “compete” for the same binding site on the receptor. Once bound, an antagonist will block agonist binding and does not activate the receptor.

Question 4

what is the meaning of efficacy?

Answer 4

Efficacy is a measure of a single agonist-receptor complex’s ability to generate a response.

Question 5

what is the definition of Ec50?

Answer 5

effective concentration giving 50% of maximal response.

Question 6

What does pA2 measure?

Answer 6

meaures the potency of an antagonist.

Question 7

what is dose-ratio?

Answer 7

the fold increase of the agonist needed to achieve the same response at a given concentration of antagonist.

Question 8

what is an inverse agonist?

Answer 8

nverse agonist is a drug that binds to the same receptor as an agonist but induces a pharmacological response opposite to that of the agonist.

inverse agonits have negative efficacy.

Question 9

what does the potency of an agonist depend on?

Answer 9

Affinity and efficacy.