On Mon 02 Aug, John I Quist wrote:
> Hi Brian!
>
> Bo Johnels, the neurology-professor at my hospital, believes that
> involuntary movements (paraphrased by me, I've forgotten the wording) is
> the result of dopamine receptors detecting a decrease of dopamine
> levels, cranking up their sensitivity to dopamine, and then producing
> way too powerful signals to the muscles when dopamine comes into the system.
>
> How about that as an explanation? It sounds believable to me...
>
> /John.
>
>
>
> On Mon, 2 Aug 1999, Brian Collins wrote:
> >
> > I ask every Neurologist the same question: What is Dyskinesia? I don't
> > mean the outward physical manifestations of dyskinesia - we all know
> > those, but what is really going on?
> >
> > The answer so far has been "We don't know"
>
>
>
Hello John, It's good to see that your neurologist is prepared to give you
an answer - it was by pestering my local neurologist that I learned what
little I now know.
Some points strike me which do not match with my understanding - see what
you think...
1/ If we consider a scenario where a PWP is 'off'; takes a tablet which
contains a bit too much levodopa for his requirement and thus finds
himself with dyskinesias- (This is a typical situation, I think), then
2/ I don't see where the production capacity comes from to produce this
large signal, because our problem is lack of dopamine. Actually, on a
more fundamemtal level, I think you will find that Dopamine's function
is to bathe the synapses which occur at intervals along the nerves
so that the electrical signal, which follows a few millisecs later may
continue its journey. It is the content of that electrical signal which
tells the body what to do, not the dopamine. To corroborate that, I have
a paper which finds that vigorous excercise does not result in an
increase in Dopamine demand.
3/ If the off signal which I describe in item 1 is the point where you
describe the dopamine receptors clamouring for Dopamine, then the
introduction of the tablet will immediately produce your dyskinesia,
ie on the rise of dopamine, and the size of the tablet is not relevant.
In fact, my observation is that dyskiesias occur as the tablet output
rounds off at the top of its curve. Also, if I take a slightly smaller
tablet, i don't get the dyskinesia, i get the perfect match of tablet
content and dopamine shortfall which i wanted.
I would be delighted if you could persuade your Prof. to read my version,
which is based on rates of flow of dopamine. It is based on Simon Coles
web site which is at
< http://james.parkinsons.org.uk >
Look for my name and the article is called "A Model to describe the effect
of levodopa on a PWP" or something like that.
Thanks for your input.
Regards,
--
Brian Collins <[log in to unmask]>
