Hi Robert,
There is a weak chronological connection between starting taking tyrosine,(Aug), and suffering terrible offs after meds wore off.(late Sept).
Dopamine does regulate heart rate, in his book, "The Parkinson's Handbook", Dr D. McGoon says dopamine is a body hormone with this effect, often administered during an operation to boost a flagging heart.
I can't find where I said dopamine and dopa share a transport, but I may have inadvertently have implied it.
I have stopped taking the tyrosine, and will let you know what happens.
Ron
Quote:
Originally Posted by RLSmi
Your comment about taking additional tyrosine is very interesting. It could well be that the added tyrosine is indeed creating a "traffic jam" which is preventing sufficient dopa entry to provide sx relief. Is there a chronological connection between beginning the use of supplementary tyrosine and the "super offs" you have experienced? The rate-limiting step in neuronal production of dopa is tyrosine hydroxylation, so our limited remaining dopaminergic neurons need pre-formed dopa to provide for the more rapid step of decarboxylation in which dopamine is the product.
Regarding your statement about dopamine and dopa sharing a transport system, the amino acid transport systems are very specific for amino acids only. Since dopamine is missing its carboxylate group, it is not a substrate for this system.
Also, I am unaware that dopamine is used to regulate heart rate. I think that is one of the roles for epinephrine, or adrenaline, a different catecholamine. Cardiac muscle tissue is very responsive to that hormone, which is provided by the adrenal medulla in the "fight or flight" response.
Robert
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