Hello Brian:
You wrote -
>>> Brian Collins <[log in to unmask]> 12/14/97
08:17pm >>>
>>>I also had a chuckle at the references to avoiding early
introduction of levodopa, and the total lack of understanding
of what goes on to produce increased sensitivity to levodopa.
Still, it is dated 1994 - is this what you mean about checking
the date of articles to make sure that they are up to date?
I know that you quoted that report as a source of references,
but we don't seem to have them. In any case, they must
pre-date the Koller report, so I would be very wary of the
provenance of those references.
Incidentally, let's try to stick to the essential point that I am
trying to get across which is: In PRACTICE, the experience
so far (such as it is) seems to indicate that all the agonists
are much the same in their ability to make-up for missing
dopamine, and avoid earlier onset of diskinesias.<<<
Brian:
I do not have anything to add to your conclusion about
the effectiveness of dopamine agonists . . . however, I do
wish to offer this aside:
Dr. Roger Duvoisin, M.D., in 1989 reported that
parkinsonism was not only marked by a depletion of
dopamine, but also a concomitant depletion of
norepinephrine stored in the synaptic vesicles. He
suggested that levodopa therapy may only partially correct
what he termed a norepinephrine deficiency.
Norepinephrine is described in the Merck Manual as the
predominant neurotransmitter in the central nervous system.
It can be found in most sympathetic post-ganglionic nerve
terminals. Dopamine is a precursor to norepinephrine in the
synthesis of the amino acid tyrosine - they are both
described as inhibitory of physiologic functions (sleep,
arousal, memory, temperature regulation, blood pressure and
food intake).
Since dopamine agonists do not activate the nerve
receptors for norepinephrine, they do not address the
problem that Dr. Duvoisin described, which in turn implicates
the point you are trying to advance about the lack of
difference in result among dopamine agonists.
I join you in wondering why there appears to be no
research in this area.
Stephan 53/7
