BIOM20002 Lecture Notes - Lecture 31: Isoprenaline, Muscarinic Acetylcholine Receptor, Partial Agonist
Document Summary
Contraction of guinea pig ileum in response to 3 muscarinic receptor agonists. Structure-activity relationships: 3 drug analogues (differ by one chemical group)show varying properties - different potencies at the same (and at different) receptors. Not all agonists are equally efficacious (effective at activating the receptor once bound) Efficacious agonists (full agonists) may be able to maximally activate a cell (cause maximal response) by binding to only a few receptors. Less efficacious agonists (partial agonists) may elicit weak activation even when occupying all of the receptors. Antagonist: binds to receptor, does not induce response or can even decrease it. 50% occupation does not mean 50% response - binding is not equivalent to stimulating. Note there is no correlation between pka and potency. Pink circles are most potent pka is a measure of occupancy. Intrinsic efficacy - the stimulus generated upon receptor binding property of the drug. Different drugs can bind on same site of same receptor but can have varying effects.
