Posted by tensor on January 9, 2008, at 14:23:42
In reply to Re: FYI: Articles On Basic Neurology » tensor, posted by Phillipa on January 9, 2008, at 13:14:40
Maybe this is the answer you are looking for, I copy and paste directly from https://www.neurorelief.com/index.php?option=com_content&task=view&id=234&Itemid=48
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Serotonin is normally synthesized from the amino acid tryptophan. In order for this to occur in the brain, tryptophan must be shuttled across the blood-brain barrier (BBB) by the Large Neutral Amino Acid Transporter (LNAAT). This transporter is a transmembrane molecule and performs the crucial service of shuttling tryptophan and other Large Neutral Amino Acids (LNAAs) across the BBB. (The LNAAs include tryptophan, phenylalanine, tyrosine, histidine, arginine, leucine, isoleucine, threonine, methionine, and valine.)Without this mechanism, the BBB would exclude amino acids vital to the brain. Because this shuttle is not specific and will transport any of the LNAAs, it is important to consider the ratio of the amino acids and not the absolute level when considering how much of an amino acid will enter the brain.
This fact has been utilized in clinical trials to both enhance and inhibit the uptake of a particular amino acid into the brain. If a patient ingests an isolated large neutral amino acid, it's ratio relative to the other amino acids will increase, resulting in an increased concentration of the amino acid in the brain via the LNAAT.
In contrast, if an amino acid cocktail devoid of a particular amino acid is ingested the ratio of a particular amino acid can be decreased and this will deplete the level within the brain. Amino acid cocktails devoid of tryptophan have been widely used to study the effects of serotonin depletion. Of particular interest are studies demonstrating the ability of serotonin depletion to reduce the effectiveness of serotonin-acting antidepressants.
-------------I.e. if a too high intake of a certain amino acid is taken, it will decrease the amount of the other amonio acids (e.g. tryptophan) that the LNAAT can transport into the brain and cause e.g. serotonin depletion.
/Mattias
poster:tensor
thread:805340
URL: http://www.dr-bob.org/babble/20080105/msgs/805349.html