Note on the False Transmitter Effect From L-5-HTP

This is one article showing the false-transmitter effect of L-5-hydroxytryptophan (L-5-HTP) [Stamford et al., 1990: (http://www.ncbi.nlm.nih.gov/pubmed/2357555)]. That effect wouldn't occur with L-tryptophan (dopaminergic neurons don't express tryptophan hydroxylase, at least not in all but some few subsets that could conceivably co-express tyrosine hydroxylase and tryptophan hydroxylase). It's sort of interesting. A lot of articles showing neuroendocrine effects have used a peripheral decarboxylase inhibitor in combination with 5-HTP (i.e. benserazide or carbidopa). But that wouldn't prevent the false transmitter effect. It would potentiate it (taking a peripheral decarboxylase inhibitor with it, which one couldn't do without a prescription anyway), to the extent that the decarboxylase inhibitor would increase the entry of 5-HTP into the brain. But as far as interpreting research on 5-HTP, one has to see if the researchers used carbidopa or benserazide, etc. I don't know how much of a dose would be taken up by dopaminergic neurons, and I haven't read the full text of that article (in a long time, if at all).