Huh, I'm surprised I missed these two papers...
www.ncbi.nlm.nih.gov/pubmed/15188158www.nature.com/ctg/journal/v3/n4/full/ctg20128a.htmlThe second one being really interesting especially this to me:
Short-chain fatty acids, produced by bacteria in the colon, can also stimulate 5-HT release.29 The complex interaction of the microbiota, diet, and the cells of the intestine all have an influence on 5-HT synthesis, release, and degradation, and therefore all may be responsible for the altered 5-HT function seen in many GI diseases.
And these papers: (which have been posted before elsewhere)
www.ncbi.nlm.nih.gov/pmc/articles/PMC2861806/www.ncbi.nlm.nih.gov/pmc/articles/PMC3540639/pdf/tacca123000268.pdfwww.erowid.org/references/refs_view.php?A=ShowDocPartFrame&id=6164&DocPartid=5790