Competitive receptor-ligand Binding

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Competitive receptor-ligand Binding

Post by someguy456345 » Thu Feb 24, 2011 7:48 pm

First let me apologize if I've selected the wrong sub-forum to post this in, this question is more pharmacological in nature but maybe a few cellular physioligists will have an answer for me.

My prof has posted a few statements in his lecture pertaining to what he calls 'receptorology' and I'm just trying to elaborate a bit on them in lieu of my exam.

"An agonist dose-response curve will be shifted to the right in the presence of a constant concentration of an antagonist that binds to the same receptor"

Would it be safe to say the agonist's dose-respone curve wold be shifted in the presence of a constant concentration of a partial agonist; my thought behind this is there will still be some receptor sequestration by the partial agonist (like an antagonist) and this group of receptors, although giving a response, would show lower efficacy then if those receptors were available to be bound by morphine.

One thing thats confusing me is trying to apply this to a practical approach. If one was to take a constant level of meperidine (a partial opioid agonist) in conjunction with morphine I would assume an increased level of pain relief rather than if morphine was given by itself (lets assume they both act on the same opioid receptor, my example seems to be getting more and more complicated).

Am I overthinking this or maybe getting caught up in the concept of therapeutic efficacy as opposed to intrinsic efficacy??

Any insight would be greatly appreciated.

Edit: Another quick question I had concerns another statement;
Heading: Basic characteristics of concentration-response curves
"Ideally, data at higher drug concentrations should taper off towards a clear maximal response (if not...)"
The only conclusion I could think of is that there could be another binding site (one of lower affinity) which would increase the maximal response, any thoughts?

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