Receptors as drug targets I Flashcards
What is competitive antagonism?
The mechanism by which one drug can REDUCE the effect of another.
What happens in irreversible competitive antagonism?
Increasing agonist concentration DOES NOT overcome the antagonism.
What does efficacy mean?
Parameter which describes the ‘strength’ of the agonist - receptor complex.
How can antagonist potency be expressed?
pA2 value is used. It is essentially the negative logarithm of the molar concentration of the antagonist.
What indicates a higher potency on a Schild plot?
A higher Pa2 value.
What is irreversible competitive antagonism?
Antagonist binds to same site on receptor as the antagonist but dissociates VERY slowly.
Thus, there is no change in the antagonist occupancy when the agonist is applied.
What happens to the graph in reversible competitive antagonism?
When the antagonist is present, the curve on the graph is shifted to the right without change in slope or maximum.
What is an orthosteric site?
Direct interception and direct binding to the receptor site.
What is an allosteric site?
This site allows the activity of binding to be turned on or off.
Explain the two forms of desensitisation (KNOWN AS TACHYPHYLAXIS).
- Uncoupling of receptor from its transduction mechanism.
- Translocation or internalisation of receptor.
Why does uncoupling of the receptor occur?
This is due to the receptors being exposed to continuous presence of agonist.
