Lecture 4 (Receptor Theory II Agonists) Flashcards
What are the number of complexes we form governed by?
Affinity
What model does an Agonist fit into but not Antagonist?
Lock and Key
What is EC50?
effective concentration giving 50% of maximal response
What does plateau show on response graph?
Maximum response
Why do some tissues have more receptors on surface that needed for response? ‘receptor reserve’
It means you can release less neurotransmitter as it is more sensitive
Is occupancy directly proportional to response?
No, some tissues can get to max response on 5% occupancy
How does amplification work in signalling? (e.g G-proteins)
(3)
G-protein activated which activates more than one enzyme molecule, each enzyme activates secondary messengers
What is the purpose of amplification?
Don’t need lots of receptors for signalling
What do square brackets mean?
Conecentration
What is Xa?
Concentration of agonist
What is n? (slope factor/hill slope)
(When calculating drug response)
Number of molecules that have to bind for receptor to activate it
Which drug has the highest potency?
The one that requires the lowest to produce a 50% maximum response (most left)
What are partial agonists?
Agonises with max response less than 100
What is the difference in efficacy of full agonist and partial agonist?
Partial agonist has lower efficacy (affinity could b high or low)
What happens if you mix equal amount of partial and full agonists? and why?
-Response curve shifts right
-Agonists compete for occupancy, proportion of full agonists reduced
What occupancy does partial agonist need for maximum response?
100%
What is the one situation where Kd and EC50 are equal?
Partial agonists
Where are partial agonist used often?
(lots of drugs are partial agonists, act as ‘safety valve’, drugs that inhibit important areas likely to use partial agonists)
What is efficacy?
Efficacy is a measure of a single agonist-receptor complex’s ability to generate a response
What 3 properties determine the effect of a drug in a living system? (3) and what are they?
Specificity - Interact with a structurally defined site / receptor chemical properties/ molecular structure
Affinity - (agonists and antagonists)
ability to bind to receptor
Efficacy - agonists (NOT antagonists)
ability to activate receptor
a full agonist has an efficacy of 1
antagonists have an efficacy of 0
What is the efficacy of a full agonist and an antagonist? (2)
A full agonist has an efficacy of 1
Antagonists have an efficacy of 0
