Thank you everyone who replied to my problem understanding what a
dopamine agonist really meant . I am especially grateful to Rager for
researching medical dictionaries online to produce definitions .
> To help a few members who have questions about medical terms, try the =
> "Medical Dictionary" on the web at:http://www.graylab.ac.uk/omd/
> For example: this is what it says about some of the terms in question:
>
There seems to be a view that an agonist can be best understood as
the opposite of antagonist . Rager produces the two definitions below
> antagonistic effect
> This is the consequence of one chemical (or group of chemicals) =
> counteracting the effects of another chemical, the opposing chemicals =
> cancel out each other's effects.
The opposite of this inthe case of dopamine would be to define the
agonist effect as " the consequence of one chemical ( or group of
chemicals ) increasing ( ? ) the effect of another chemical ( ? )" .
Is this " another chemical " confined to dopamine in the term "
dopamine agonist " or can it be extended to include chemicals like
levodopa that boost dopamine availabilty ?
In the first case the definiyion of a dopamine agonist would be "
a chemical or group of chemicals that increases the effect of dopamine
. Since most PD medication increases the amount of dopamine in the
brain and not the effect . It would seem to excluded most medications
for PD . The only things that could come under this definition of "
dopamine agonist " are all those medications that help PD but not
directly increasing the dopamine in the brain . The definition is
meaningless since it does not add to our understanding . If we
include in the definition all the substances that boost the dopamine
in the brain then the term " dopamine agonist " is to general to be
useful .
>
> antagonist
> <pharmacology> A substance that tends to nullify the action of another, =
> as a drug that binds to a cell receptor without eliciting a biological =
> response.=20
Here we have a useful precise definition in that an agonist can be
described as a substance that unbinds the antagonist or prevents the
antagonist binding . My reservation is that I am far from sure that
the term " dopamine agonist " is used in this exclusive way or that
anybody can really be sure that any substance described as " dopamine
agonist " really behaves in this way . Further this definition
requires an antagonist which is ???
>
>
>
> agonist
> 1. <anatomy> A prime mover.=
Aristotelean philosophy ?
>
> 2. <pharmacology> A drug that has affinity for and stimulates =
> physiologic activity at cell receptors normally stimulated by naturally =
> occurring substances, thus triggering a biochemical response.=20
This definition would mean that a " dopamine agonist " has an affinity
for and stimulates the dopamine receptors . Sounds good but what does
it mean in practice ?? Has there been any description of any so
called dopamine agonist's method of stimulating the dopamine receptor
?? The only method that I know of is that that " dopamine agonist "
mimics the dopamine . In other words it becomes a replacement
neurotransmitter .
If the term " dopamine agonist " is confined to a replacement
neurotransmitter for dopamine then it has meaning . But I suspect it
is used more widely than this with no clear understanding of meaning
.
I certainly am guilty of this in my posting on Gabapentin I used the
term GABA agonist with no clear idea what I was talking about . Of
course I was merely trying to convey information to list members from
other sources and was repeating their words . I hoped maybe it would
mean more to others than it did to me .
I dont want to go into the philosophical questions about reality,
understanding and language . But I would like to give an analogy of
why I made the original posting .
The original posting concerned the term " dyskinesia " . I feel
knowledge is like an ice skater skating on the ice of language . As
more and more people use the word "dyskinesia " in the same way the
ice gets thicker and one can skate more confidently over it . But in
Judith's posting some medical people were redefining the term "
dyskinesia " . This is the equivalent of taking hammer and smashing
the ice . I was no longer skating over what I thought was thick ice
but was floundering around questioning everything . The term "
dopamine agonist " has me similarly floundering as I am having
difficulty in finding a precise and consistant use of the term .
peace
Alastair ( [log in to unmask] )
