Comment · Sat, July 20, 2013 · Ceretropic
Levodopa: faster and better word learning in normal humans.
What they were answering
LegoOctopus · 3 points
Sounds like one of the likely causes for that is excess dopamine in the peripheral nervous system, in which case a DDC inhibitor like carbidopa would help to prevent it.
Syndopa is a mixture of carbidopa and l-dopa that is commonly used to improve (drastically) the action of the l-dopa while preventing it from turning to dopamine outside the brain. I haven't seen anyone using it for nootropic purposes, but I've got some on the way so I'll hopefully have some experience to report soon (not that I'll know if it's causing long-term harm of course).
u/MisterYouAreSoDumb · Ceretropic
It's the same reason I always tell people to use EGCG with their 5-HTP. Aromatic L-amino acid decarboxylase is present centrally and in the periphery. Since both L-DOPA and 5-HTP use that same enzyme, and the neurotransmitters dopamine and serotonin cannot pass the BBB, it leads to increased peripheral levels. EGCG is an aromatic L-amino acid decarboxylase inhibitor.
http://www.ncbi.nlm.nih.gov/pubmed/11374875
http://www.ncbi.nlm.nih.gov/pubmed/22107329
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Also, 90% or more of your EGCG dose does not pass the blood brain barrier.
http://n.b5z.net/i/u/10124624/f/Resveratrol_and_Polyphenols_-_The_Down_Side.pdf
>However even after continuous administration
of EGCG until 24 h, levels of the compound in brain tissue
reaches 5–10% of its blood levels. This suggests that a very high
plasma concentration is needed for EGCG to reach a reasonable
therapeutic level in brain
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http://www.aseanfood.info/Articles/11022865.pdf
>A study more relevant
for human exposure to epicatechins followed six subjects
(scheduled for lumbar puncture) after the ingestion of a 300
mL boiling water infusion of 7 g of green Kenyan tea (150).
The average intake of (-)-epicatechins was 53 μmol of
epicatechin, 149 μmol of epigallocatechin, 206 μmol of epigallocatechin-
3-O-gallate, and 97 μmol of epicatechin-3-Ogallate.
After 1 h, plasma levels of the epicatechins were readily
detectable with total epicatechin concentrations amounting to
about 1.6 μM; **however, nothing was found in cerebral spinal
fluid.**
So a majority of the aromatic L-amino acid decarboxylase will be inhibited in the periphery when using EGCG with your L-DOPA or 5-HTP.