NMJ workshop Flashcards
what is the EC50
concentration of agonist that elicits 50% of maximal response
why do we only use the 50% of the maximal response of an agonist when measuring potency
receptor desensitization and other factors have an effect
what happens to a concentration - response graph when there is a reversible competitive antagonist present
there is a shift to the right with no major change in the slope
why is the chick biventer cervicis a good model for testing the effects of antagonists and agonists ?
it has multiple end plate regions on a single muscle fiber that allows it respond to exogenous Ach and other agonists with being exposed to an electrical stimulation
define concentration ratio
factor by which the agonist concentration must be increased to restore a given response in the presence of an antagonist
how do you calculate concentration ratio
EC50 for agonist in the Prescence of an antagonist / EC50 for agonist alone
Define apparent PA2
affinity of antagonists to receptors ( potency of antagonist)
how do you calculate apparent PA2
log10((CR-1)/[concentration of antagonist])
what is the relationship between PA2 and how potent the antagonist is ?
the higher the PA2 the more potent the antagonist is
what method do you have to use to get the actual PA2 ( more accurate) ?
Schild plot
how do you calculate actual PA2
PA2= - log of Kb
( note: get Kb by calculating CR for multiple concentrations of atropine and plotting on a graph )
what are the characteristics of a concentration response graph when a non-competitive or irreversible antagonist
it won’t reach maximum response even with increasing agonist concentration
what does the correct drug dosage give us
the clinically relevant blood plasma concentration of the drug
define IC50
concentration of antagonist where the agonist evoked response is reduced by 50%
what is the IC50 used to estimate
the potency of irreversible competitive and non-competitive antagonists
how do you calculate % control response ?
amplitude in presence of antagonist / amplitude in absence of antagonist x 100
