SF - Drug receptor interaction Flashcards
What is an agonist?
Activates a receptor.
What is an antagonist?
Reduces the response of an agonist.
What is the EC50?
The concentration of the drug that gives 50% of the maximal response.
What is the Kd?
Dissociation constant. The concentration of the drug that occupies 50% of the receptors.
What is the efficacy?
The difference in the percentage of the response to the percentage of receptors occupied.
What does it mean if there is a high efficacy?
Less receptors need to be occupied to produce a response.
What is affinity?
A measure of the binding of a drug to a receptor.
What is the receptor occupancy equation?
P = [D]/([D]+Kd)
P - proportion of receptors occupied.
[D] - drug concentration
Kd - dissociation constant
What is the function of a partial agonist?
Drugs which have a maximum response that is less than the full response that the tissue is capable of. Useful therapeutically if a full response is not required.
What is the potency of a drug?
How much drug is required to produce a particular response.
Why do weak agonists have an EC50 close to Kd?
- Not all DR complexes will be in their active form.
- EC50~Kd (At a given drug concentration)
- A lot of receptors are occupied to produce this response.
Why do strong agonists have an EC50
- More DR complexes are active.
- At a low drug concentration, there is a high response.
What is the effect on EC50 if you lower the efficacy?
EC50 gets larger.
The receptor reserve is reduced.
The concentration response curve moves to the right.
What affects the relative position of the agonist when testing different agonists with the same preparation?
Affinity and efficacy of the drug.
What affects the relative position of the agonist when testing the same agonist on different preparations?
Number of receptors
What are the 4 types of drug antagonism? Describe each type.
Competitive - binds at the agonist recognition site preventing access of a normal ligand.
Non-competitive - binds to an allosteric binding site.
Un-competitive - Can block receptors within a transduction pathway.
Physiological - one drug may antagonise the actions of another via an action on an independent molecular target.
What is constitutive activity?
The basal level of activity at a receptor.
What is an inverse agonist?
Causes activity of the receptor to completely switch off.
What is tolerance?
Repeated drug administration may lead to adaptive down regulation of receptors. This can be vital for a therapeutic use - antidepressants.
