Posted by Larry Hoover on March 30, 2007, at 9:57:51
In reply to Re: Glutamic acid.....?, posted by Meri-Tuuli on March 30, 2007, at 9:33:53
> Thanks, Lar.
>
> >GABA also antagonizes glutamate. It's just one of the yin/yang things in the brain. Balancing acts going on all the time.
>
> I don't suppose you could explain this bit? I've never quite got to grips with antagonists, but thats partly due to brain laziness. I'm never quite sure whats the diff between agonists and antagonists.
>
> Kind regards
>
> MeriFrom the Greek, for contest, and later the Latin meaning contender, agonism in the biochemical sense is the activation of a receptor. It can be a term applied to the natural ligand (binding substance(s)), or to an artificial one. Anything that interferes with or completely blocks an agonist is an antagonist. There are numerous mechanisms of both agonism and antagonism. Mother Nature is devious. For example, the same substance can be an antagonist or agonist, at the same receptor, based only on concentration. We determine this by interpreting the signal given off by the receptor/ligand complex. An activation/up-regulating effect is due to agonism. A substance that blocks the effect of an agonist is an antagonist. Well, originally, those definitions held. But now we've discovered inverse agonists, substances that produce a negative signal. So, antagonists can also block negative signalling.
Here's a nice graph to consider: http://en.wikipedia.org/wiki/Inverse_agonist
An antagonist would tend to keep the receptor response at what they label "baseline receptor" response, *despite* increasing concentrations of either a positive or negative agonist.
Of course, outcomes could lie anywhere between the two extremes.
Lar
poster:Larry Hoover
thread:745397
URL: http://www.dr-bob.org/babble/alter/20070320/msgs/745420.html