On Thu 11 Feb, [log in to unmask] wrote:
> Brian,
> Let me toss a few other tidbits into the stew--1) It is my understanding that
> during a typical meds cycle (focusing on sinemet, of course) we PWP's go from
> being undermedicated to overmedicated at peak dosage and back to
> undermedicated. 2)"Normals" have tens of thousands more dopamine producing
> neurons than we do, so why don't they become dyskinetic? the answer must lie
> in the pacing, or rate of absorption of dopamine by the cells in the
> substantia nigra. Strictly speaking, then, we PWP's are susceptible to
> dyskinesia not because we have more dopamine in our systems than "normals" but
> because we absorb dopamine at a faster, more uneven rate in the substantia
> nigra than "normals". I think we're both trying to say this same thing but
> with slightly different words. Another thing I find interesting about this
> theory is the implication that although "normals" have so much more dopamine
> producing capacity than we do, apparently they use only a fraction of it. abd
> possibly in other parts of the brain.
> MMMarty
>
>
>
hello Marty, I have to disagree with several of your statements:-
1/ If you are taking your tablets and routinely going through an overdose
phase, then you are taking too big a dose. It is as simple as that! (I
dont mean that you should change from 1 Sinemet to half a Sinemet, that
represents a gross change and would cause you to miss the target zone
altogether). If you need to know what your potential max. levodopa value
is, you need to back off maybe to half a tablet, and then explore the
region between half and one mg by progressively increasing the dose. I
use Madopar 62.5 dispersible because it only contains 50 mg levodopa,
giving more precision when you start breaking tablets. I believe Sinemet
do a similarly-sized tabled called Sinemet LS (meaning Low Start)
2/ We know that when we exhibit PD symptoms, we have lost 80% to 90% of
our dopamine-producing cells. 'Normals' will also have lost some, but we
don't know how many. Remember that all these cells are produced in the
localised area called the Substantia Nigra. There may be other sites, but
they do not supply the main Motor system.
3/ All of the cells which produce the dopamine (in the SN) can control
their output of dopamine. It is not clear whether this control is exercised
by a 'Main Control Centre' or by individual cells responding to their
local environment. I prefer the latter setup, but it is not important,
as the outcome is the same with either system.
4/ So we have a setup with the 'normals' coasting along with their dopamine
-producing cells throttled well back, and a newly-diagnosed PWP with all of
his remaining dopamine cells working flat out, and just failing to meet
the demand
5/ Items 2,3,and 4 are generally accepted and are non-controversial. What
follows is my theory
6/ I postulate that the rate of dopamine flow required for normal operation
is revealed when the symptoms become apparent, and for each PWP this rate
remains at the same level. Of course, as time progresses, it takes all the
cell's output Plus a contribution from the tablets to attain that target value.
7/ If you take too much Sinemet, then as the output reaches the 'critical
value' , the remaining dopamine-producing cells begin to abandon their
flat-out efforts, and switch off, and the existing dopamine is with-held
in the synaptic vesicles. It keeps on doing this until the tablet begins
to fade away, or the entire(!) output of the Substantia Nigra is is shut
down,and the vesicles can hold no more. At that point, the rate of flow
of dopamine into the system begins to exceed the dyskinesia threshold, and
the problems begin.
8/ I don't want to keep repeating myself when you can read my words just as
easily on our web site. ( I probably thought it out more carefully for that
entry as well.
Look for
http://james.parkinsons.org.uk/brian.htm
--
Brian Collins <[log in to unmask]>
