Receptor theory 3 Flashcards Preview

Physioloogy and pharmacology > Receptor theory 3 > Flashcards

Flashcards in Receptor theory 3 Deck (13)
Loading flashcards...

What is suggested if a saturation point is not reached in a ligand binding assay

Non specific binding is occurring


What shape does specific binding show on a logarithmically scaled ligand binding assay graph

Sigmoidal curve - non specific remains level until very high concentrations where it rises exponentially


What is the drug concentration that occupies 50% of the receptors equal to?



What is on the Y axis of the scatchard plot

Bound radioligand/ free radioligand


What is on the X axis of the scatchard plot

Bound radioligand


What does the X intercept define

Bmax - Maximum amount of drug


What is the slope of the line equal to



What happens to the occupancy - concentration graph if the affinity is high

Shifted to the right


Give two examples example for when measuring affinity can indicate differences between receptors for the same ligand

Morphine side effect of constipation - Gut opiate receptors that control motility- Opiate receptors in the brain and spinal cord for pain - Different receptors due to different affinity for morphine

Muscarinic receptors - The differing affinity of sympathetic ganglia and sublinguinal gland mAchRs have differing affinities to pirenzepine - pirenzepine shows selectivity for sympathetic ganglion receptors


What is EC50

The concentration of drug needed to give 50% of the maximal response


How is possible to get an EC50 at a lower drug concentration than needed to occupy 50% of the receptors

Because there is a receptor reserve - more receptors present than needed to produce a maximal response
Common in the gut - need to occupy 5% to elicit maximum response


How is potency used to compare agonists

Concentration response graphs show the drug with the curve furthest to the left has the highest potency


What is suggested if an agonist has the same EC50 as another but cannot elicit a maximal response

It is a partial agonist - they have a lower efficacy than a full agonist