On Fri 28 Feb, Ron Reiner wrote:
> Here is something I've been wondering about. My doctor tells me that the
> substantia nigra (SN) produces dopamine which is a neurotransmitter for
> controlling many important bodily functions.
>
> Does a healthy SN produce dopa at a constant rate all the time like a faucet
> turned on at one flow level? Or does it sometimes turn off, slow down or
> increase the flow? Does the SN simply try to keep a fixed concentration of
> dopa in the brain? If it isn't a constant flow, what determines the amount
> of dopa to be generated at any given time?
>
> Anyone have an explanation that I could understand?
>
> Ron Reiner
>
>
Hello Ron, This is the Dopamine story as I understand it: The Dopamine
production system is one which is dedicated to providing Dopamine where it is
needed, when it is needed, and in the right quantities. It is a constantly
flowing system because when the Dopamine has done its work as a neuro
transmitter, it decomposes and is transported out of the way by the brain's
clean-up system. So it is a self-regulating system with apparently quite a
fast reaction time. The best proof that I know is to consider what happens
to a person with a normal healthy brain if you give them a large dose of
Sinemet - one that would drive a PWP into wild Dyskinesias. The answer is that
virtually nothing happens! The reason is that a healthy brain can sense the
invasion of the tablet, and immediately cut-back productionto compensate.
The brain of a PWP simply doesn't have enough Dopamine -producing cells to
shut down to compensate for the large intruder, and so an overdose condition
exists, causing what we know as dyskinesias.
This model (because that is all it is) has worked pretty well for me: it
explains:
Why it gets progressively more difficult to achieve the ideal dosage of
levodopa.
Why a newly-diagnosed PWP can tolerate a large input of Sinemet, although
he doesn't need it.
Why a long-term PWP has to take small doses of levodopa, when ideally he
needs large doses.
Interested ?
Regards,
--
Brian Collins <[log in to unmask]>
