Mon, 22 Jun 1998 23:03:31 EDT Nancy Anderson <[log in to unmask]> wrote:
<<<<
Simply put.....a Dopamine Agonist makes the Dopamine receptors that make
Dopamine do what it does best.. work better. An "antagonist" will make the
receptor stop doing what it is doing. This works well in the case of
something that needs to be stopped. >>>>
Hello Nancy,
You are near and I hope the next explanation helps you to get there!
The next explanation is a simplified model of how dopamine(-agonists) and
antagonists work in the brain.
The two big oct-angles are motoric braincells, reacting on chemical
stimulation by transporting an electrical signal from the cell to its
nerve-ends.
A chain of motoric (brain)cells leads the signal finally to a muscle.
Dopamine is the agonist. Acetylcholine the antagonist.
The dopamine-producing cells produce dopamine, that gets stored in the
DOP-depots. The acetylcholine gets stored in the CHO-depots.
// and \\ and || are receptors
|||||||||||||||| are nerves (tracks)
/
/
K are nerve-ends, splitting up around the next cell
\
\
___ _
|DOP| are dopamine-depots |D| are dopamine-producing cells
~~~ ~
___ _
|CHO| are acetylcholine-depots |C| are acetylcholine-prod. cells
~~~ ~
_ _
|D| |C| _
_ ~ ___ ___~ |C|
|D| |DOP||CHO| ~
______ ~ ~~~ ~~~______
/ \ / / \ /
// \ / // \ /
/ \ / / \ /
| | / | | /
|| 1 ||||||||||||||K || 2 ||||||||||K
| | \ | | \
\ / \ \ / \
\\ / \ \\ / \
\______/ \ \______/ \
___ ___
|DOP||CHO|
~~~ ~~~
How does it work in a "healthy" person:
cell 1 gets stimulated, makes an electrical signal and sends the signal
through the nerve to the nerve-ends. The nerve-end stimulates the
dopamine-depots to release dopamine into the space (=synaps) between the
nerve-ends of cell 1 and the "body" of cell 2. When enough dopamine is
released, this chemically stimulates the receptors of cell 2, thus
stimulating cell 2 to make an electrical signal and send it to cell 3, etc.
After the signal is given to the next cell, the amount of dopamine in the
synaps is also a stimulation for the acetylcholine-depots to release
acetylcholine to neutralise the dopamine in the synaps.
In PWP there are four ways this system can be blocked:
1) dopamine-producing cells are not making (enough) dopamine.
2) the DOP-depots are not working correctly.
3) the receptors are not working correctly.
4) a combination of 1 and/or 2 and/ or 3.
Solutions:
To problem 1):
a) L-dopa
b) anti-cholinergics
c) dopa-agonists
To problem 2):
dopa-agonists. They don't need the depots and can act directly.
(L-dopa is here no solution, because L-dopa has to be transformed into
dopamine first and then stored in the depots).
To problem 3):
No solution. An example is MSA (Multiple System Atrophy), one of the
Parkinsonism's. Giving meds won't help, because the receptors won't pick up
the chemical stimulation.
To problem 4):
A combination of meds. That's why a combined therapy sometimes helps better
than increasing one med's dose. A combination fights the battle at all fronts.
Any questions? Just ask!
Hope this helps,
Greetings, Hans.
