On 2017 Feb 21, Simon Young commented:

This paper reports a concentration of tryptamine in human cerebrospinal fluid (CSF) of 60 nmol/L. A concentration that high seems unlikely. The concentration in human CSF of the related compound 5-hydroxytryptamine (serotonin) is very much lower. Although levels of serotonin in human CSF reported in the literature vary over several orders of magnitude, most of the results reported are probably false due to lack of rigorous methodology and analytical inaccuracy Young SN, 2010. In a study with rigorous methodology, measurements were performed in two different laboratories using different HPLC columns and eluting buffers Anderson GM, 2002. One lab used an electrochemical detector (detection limit 7 – 8 pg/ml for serotonin) and the other a fluorometric detector (detection limit 7 – 15 pg/ml). In both labs, N-methylserotonin was used as an internal standard and a sample was injected directly into the HPLC after removal of proteins. Neither system could detect serotonin in any CSF sample. The conclusion was that the real value was less than 10 pg/ml (0.057 nmol/L, about three orders of magnitude less than the level reported for tryptamine). Anderson et al Anderson GM, 2002 suggest that the higher values for serotonin reported in the literature can be attributed to a failure to carry out rigorous validation steps needed to ensure that a peak in HPLC is in fact the analyte of interest and not another compound with a similar retention time and fluorescent or electrochemical properties.

The concentration of tryptamine in rat brain is very much lower than the concentration of serotonin Juorio AV, 1985, and levels of the tryptamine metabolite, indoleacetic acid, in human CSF are lower than the levels of the serotonin metabolite, 5-hydroyindoleactic acid Young SN, 1980. Thus, the finding that the concentration of tryptamine in human CSF is about a thousand times greater than the concentration of serotonin does not seem plausible. There are three possible explanations for this finding. First, there may be some unknown biochemical or physiological factor that explains the finding. Second, the result may be due to the use of CSF obtained postmortem instead of from a live human. Levels of some neuroactive compounds change rapidly after death. For example, levels of acetylcholine decrease rapidly after death due to the continued action of acetylcholinesterase, the enzyme that breaks down acetylcholine Schmidt DE, 1972. Serotonin can be measured in postmortem samples because the rate limiting enzyme in the conversion of tryptophan to serotonin, tryptophan hydroxylase, and the main enzyme metabolizing serotonin, monoamine oxidase, both require oxygen. The brain becomes anoxic quickly after death thereby preventing synthesis or catabolism of serotonin. Tryptamine is synthesized by the action of aromatic amino acid decarboxylase, which does not require oxygen, but is metabolized by monoamine oxidase, which does require oxygen. Autopsies usually occur many hours after death, and therefore the high levels of tryptamine reported in this study may reflect continued synthesis, and the absence of catabolism, of tryptamine after death. Third, there may be problems with the HPLC and fluorometric detection of tryptamine in this paper, in the same way that there have been many papers reporting inaccurate measurements of serotonin in human CSF, as outlined above. The method reported in this paper would have greater credibility if the same results were obtained with two different methods, as for serotonin Anderson GM, 2002.

In conclusion, more work needs to be done to establish a reliable method for measuring tryptamine in CSF obtained from living humans. Levels in human CSF obtained postmortem may have no physiological relevance.

On 2017 Feb 21, Simon Young commented:

This paper reports a concentration of tryptamine in human cerebrospinal fluid (CSF) of 60 nmol/L. A concentration that high seems unlikely. The concentration in human CSF of the related compound 5-hydroxytryptamine (serotonin) is very much lower. Although levels of serotonin in human CSF reported in the literature vary over several orders of magnitude, most of the results reported are probably false due to lack of rigorous methodology and analytical inaccuracy Young SN, 2010. In a study with rigorous methodology, measurements were performed in two different laboratories using different HPLC columns and eluting buffers Anderson GM, 2002. One lab used an electrochemical detector (detection limit 7 – 8 pg/ml for serotonin) and the other a fluorometric detector (detection limit 7 – 15 pg/ml). In both labs, N-methylserotonin was used as an internal standard and a sample was injected directly into the HPLC after removal of proteins. Neither system could detect serotonin in any CSF sample. The conclusion was that the real value was less than 10 pg/ml (0.057 nmol/L, about three orders of magnitude less than the level reported for tryptamine). Anderson et al Anderson GM, 2002 suggest that the higher values for serotonin reported in the literature can be attributed to a failure to carry out rigorous validation steps needed to ensure that a peak in HPLC is in fact the analyte of interest and not another compound with a similar retention time and fluorescent or electrochemical properties.

The concentration of tryptamine in rat brain is very much lower than the concentration of serotonin Juorio AV, 1985, and levels of the tryptamine metabolite, indoleacetic acid, in human CSF are lower than the levels of the serotonin metabolite, 5-hydroyindoleactic acid Young SN, 1980. Thus, the finding that the concentration of tryptamine in human CSF is about a thousand times greater than the concentration of serotonin does not seem plausible. There are three possible explanations for this finding. First, there may be some unknown biochemical or physiological factor that explains the finding. Second, the result may be due to the use of CSF obtained postmortem instead of from a live human. Levels of some neuroactive compounds change rapidly after death. For example, levels of acetylcholine decrease rapidly after death due to the continued action of acetylcholinesterase, the enzyme that breaks down acetylcholine Schmidt DE, 1972. Serotonin can be measured in postmortem samples because the rate limiting enzyme in the conversion of tryptophan to serotonin, tryptophan hydroxylase, and the main enzyme metabolizing serotonin, monoamine oxidase, both require oxygen. The brain becomes anoxic quickly after death thereby preventing synthesis or catabolism of serotonin. Tryptamine is synthesized by the action of aromatic amino acid decarboxylase, which does not require oxygen, but is metabolized by monoamine oxidase, which does require oxygen. Autopsies usually occur many hours after death, and therefore the high levels of tryptamine reported in this study may reflect continued synthesis, and the absence of catabolism, of tryptamine after death. Third, there may be problems with the HPLC and fluorometric detection of tryptamine in this paper, in the same way that there have been many papers reporting inaccurate measurements of serotonin in human CSF, as outlined above. The method reported in this paper would have greater credibility if the same results were obtained with two different methods, as for serotonin Anderson GM, 2002.

In conclusion, more work needs to be done to establish a reliable method for measuring tryptamine in CSF obtained from living humans. Levels in human CSF obtained postmortem may have no physiological relevance.