F8.2- concentration response curves Flashcards
what is Rmax?
the maximal response to the agonist drug
what is EC50?
Effective agonist Concentration to generate 50 % of that agonist’s maximal response. A measure of agonist potency
comparing agonists on a concentration response curve?
one note
what is a full agonist?
a drug that binds to and activates a receptor, producing the maximum biological effect possible- high efficacy and affinity
what is a partial agonist?
A partial agonist binds to a receptor but only partially activates it- high affinity, partial efficacy
what do concentration response curves depend on?
-the potency (EC50) of a receptor agonist is determined by affinity, efficacy and properties of the functional response e.g amplication
Describe an amplified system
In an amplified system, maximum response to a drug can be obtained without all the receptors occupied (and EC50 < KD)
- If so, the assay has “receptor reserve” for that drug
Describe antagonists
many receptor antagonists are competitive (compete with agonist drug) and reversible (binds non-covalently and can dissociate from the receptor)
What happens to the agonist concentration response curve in the presence of a competitive reversible antagonist?
-Agonist potency (EC50) is reduced in the presence of antagonist, but not its maximum response (Rmax)
-Surmountable antagonism with increasing agonist concentration
ONE NOTE
what is surmountable antagonism?
a type of antagonism where the effects of an antagonist can be overcome by increasing the concentration of an agonist
what is non-surmountable antagonism?
In non-surmountable antagonism, the presence of the antagonist reduces the maximal agonist response (Rmax)
non-surmountable antagonism can occur if the antagonist is:
-Irreversible – forming a covalent bond with the receptor protein, so cannot dissociate from the binding site
Or
-Non-competitive – binding at a different (allosteric) site on the receptor from the agonist drug
ONE NOTE
