Acknowledgements —I thank Dr. W. H. Price, for providing me the facilities to carry out this work, and to Dr. Sharon Weiss for supplying the human pineal glands. PDF | 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT) belongs to a group of synthesized in human pineal and retina, and has been identified in human body fluids Oya M. Characterization of eight biogenic indoleamines as substrates. J Neurochem. Jan;26(1) Biogenesis of 5-methoxy-N,N- dimethyltryptamine in human pineal gland. Guchhait RB. PMID: ; [ Indexed for.
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The human pineal gland has been recognized for more than years. Biogenesis of 5-methoxy-N,N-dimethyltryptamine in human pineal. pineal gland and its postulated ability to produce N,N- dimethyltryptamine . the biosynthesis of DMT, INMT (Figure 1), is present throughout the body, and has the Ki of DMT at the human 5-HT2A receptor is reported as 65 nM. (Blair et al., ) .. Berge OG, Chacho D and Hole K () Inhibitory effect of 5-methoxy-. N. With the discovery of the endogenous hallucinogen N, N-dimethyltryptamine ( DMT, 1, Figure isolated were those derived from tryptophan (DMT, and 5- methoxy-DMT). Numerous studies subsequently demonstrated the biosynthesis of DMT in . pineal gland, and retina) probed with rabbit polyclonal antibodies to human.
It then declined to mature levels and remained constant through life Lin et al. In this regard, Beaton and Morris have examined the ontogeny of DMT biosynthesis in the brain of neonatal rats and rats of various ages. Using gas chromatography-mass spectrometry with isotope dilution for their analyses, DMT was detected in the brain of neonatal rats from birth.
There has yet to be any follow-on research as to the significance of this change in DMT concentrations during rat brain neurodevelopment or correlation with possible changes of INMT activity in other developing tissues, specifically during days 12— Nonetheless, these findings correlate well with the Lin et al.
There is a significant literature concerning INMT, particularly in peripheral tissues.
INMT and its gene have been sequenced Thompson et al. These data became the foundation for several hypotheses that any neuropharmacological effects of endogenous DMT must lie in its formation in the periphery and its subsequent transport into the brain. This idea was strengthened by the fact that DMT has been shown to be readily, and perhaps actively, transported into the brain Cozzi et al. However, the data concerning the apparent absence of INMT in brain would appear to be in conflict with the many earlier studies that demonstrated both in vivo and in vitro biosynthesis of DMT in the brain.
Indeed, several studies had identified INMT activity or the enzyme itself in the central nervous system CNS including the medulla, the amygdala, uncus, and frontal cortex Morgan and Mandell, , the fronto-parietal and temporal lobes Saavedra et al. Thus, in , Cozzi et al. INMT immunoreactivity in spinal cord was found to be localized in ventral horn motoneurons. Further, intense INMT immunoreactivity was detected in retinal ganglion neurons and at synapses in the inner and outer plexiform layers Cozzi et al.
In , Mavlyutov et al. It was proposed that the close association of INMT and sigma-1 receptors suggests that DMT is synthesized locally to effectively activate sigma-1 in motoneurons. It has been further proposed that DMT is an endogenous sigma-1 receptor regulator Fontanilla et al.
Taking these newer data together with historical in vitro and in vivo results regarding INMT enzyme activity in the brain and CNS, it is now clear that the work of Thompson and Weinshilboum is not the final word on DMT biosynthesis in the brain. Future Research on the Biosynthesis of DMT Considering that tryptamine formation, itself a trace biogenic amine, is essential for the formation of DMT and given its own rapid metabolism by monoamine oxidase MAO as well, demonstrating its availability for the biosynthesis of DMT is also relevant to a complete elucidation of the overall pathway.
With demonstration of colocalization of the necessary biosynthetic machinery in the brain, both AADC and INMT, mechanisms for a rapid biochemical response to signaling and DMT formation may be shown to exist. Furthermore, the demonstration of mechanisms for the protection, storage, release and reuptake of DMT would demonstrate that higher concentrations of DMT could be reached in the synaptic cleft and at neuronal receptors than would have to occur from, based on previous thought, formation and transport from the periphery.
We should not rule out the possibility that the biosynthesis and transport of DMT can and does occur from the periphery, however. Peripheral DMT, especially if synthesized in tissues that bypass liver metabolism on first pass, may also serve as a signaling compound from the periphery to the brain. Such signaling may occur in maintaining homeostasis or in response to extreme changes in physiology.
A thorough re-examination of possible peripheral DMT biosynthesis is needed. Thus, much of the INMT in the periphery may be involved to a greater degree with methylation of other substances than TA alone.
Failure to demonstrate colocalization of INMT and AADC in the periphery would alter, to some degree, the focus of studies of peripheral synthesis and detection for understanding the role of endogenous DMT. These data are underscored by the findings of Barker et al. Clearly, further research into the biosynthesis and role of DMT in the pineal is needed, as is a further assessment of our current knowledge of pineal function.
We will also need to examine protein and gene arrays to determine the factors that assist or work in concert with the up and down regulation of the INMT system in brain and how it responds to selected physiological changes.
Such analyses will be essential in examining the possible role of DMT biosynthesis in changing biochemical and physiological events. It would also be of interest to better understand the possible role of DMT in neurodevelopment as suggested by the work of Beaton and Morris and Lin et al.
While DMT appears to clearly be biosynthesized in the pineal, mechanisms for its biosynthesis and release may exist in other brain areas as well and research into these other possibilities will also need to proceed.
DMT Metabolism The metabolism of DMT has been thoroughly studied, with a great deal of newer data being provided from studies of ayahuasca administration McIlhenny et al. All of the in vivo metabolism studies have shown that exogenously administered IV, IM, smoking, etc. For example, 0. DMT administered in this manner reached a peak concentration in blood within 10—15 min and was below the limits of detection within 1 h. It was estimated that only 1.
Due to rapid metabolism in the periphery, DMT is not orally active, being converted to inactive metabolites before sufficient penetration to the brain can occur low bioavailability. DMT is pharmacologically active following administration by injection intravenous or intramuscular routes or smoking vaporization and inhalation , pathways which can avoid first-pass metabolism by the liver to some degree Riba et al. The time to onset of effects is rapid seconds to minutes by these routes and short lived 15—60 min depending on dose and route.
However, these latter metabolites have yet to be identified in vivo. Future Research on the Metabolism of DMT While the metabolism of DMT has been thoroughly studied and a number of metabolites, both major and minor, have been identified Figure 2 , one of the complications in understanding the role and function of endogenous DMT has been the fact that, to date, no study examining body fluids blood, urine, saliva has ever been conducted to correlate such data with human physiological events, such as circadian changes, sex differences, etc.
Sitaram and McLeod, ; Barker et al. All of these factors need to be examined. Given that peripherally administered DMT, at what must be considered as much higher doses than would be expected to occur naturally in the entire organism, is rapidly metabolized and cleared, measuring endogenous DMT alone in an attempt to assess its role and function is probably doomed to failure. This is particularly true if endogenous DMT is mainly produced, stored and metabolized in discreet brain areas and that DMT and its metabolites so produced never attain measurable levels in peripheral fluids.
These compounds have been variously reported in tissue, blood and urine samples.
However, this approach is complicated by the fact that the major MAO metabolite of all three of these latter compounds, IAA Figure 2 , is also derived from dietary sources and is produced from the action of bacteria in the gut.
It is not unreasonable to question whether measurement of DMT and its metabolites, and thus the role and function of endogenous DMT, can be understood by simply trying to measure these compounds in the periphery.
Peripheral measurements may not be the way to determine the central role of DMT and DMT produced in the brain may never be available for measurement in the periphery. Nonetheless, additional studies should determine if there is validity in such measurements and examine possible circadian, ultradian or diurnal variations in DMT synthesis as well as the changes that may occur due to alterations in other physiological parameters.
In total, the 69 studies examined DMT in thousands of subjects. The reasons for this conclusion were: 1 Based on current analytical requirements for unequivocal structure identification, it is highly probable that many of these studies misidentified the target analyte. Nevertheless, it was also concluded that, particularly where mass spectral evidence was provided, DMT and HDMT are endogenous and can often be successfully measured in human body fluids.
There was no mass spectral data demonstrating detection of MDMT in blood or urine. In conducting studies to determine the natural occurrence of a compound as being endogenous, it is also necessary to eliminate other possible dietary or environmental sources. Of the 69 studies reviewed, many addressed the possible source of DMT as being from diet or gut bacteria Barker et al.
Of those conducted, it was determined that neither was a source but additional research in this area using more modern technology and a more standard diet across studies is a necessity.
There have also been only a few efforts to examine the many variables that may influence the levels of these compounds, such as circadian or diurnal variations, sleep stages and gender-age-related differences. Indeed, most of the studies collected only a single time point or were from 24 h collections urine. Such infrequent sampling makes it impossible to assess central DMT production from peripheral measurements and suggests, perhaps incorrectly, that DMT only appears intermittently or not at all.
Future analyses to determine endogenous N, N-dimethyl-indolethylamines should also include a search for their major metabolites. The methodology applied in such analyses must include rigorous validated protocols for sample collection, storage, extraction and analyte stability and appropriate criteria for unequivocal detection and confirmation of the analytes using validated methods. Modern exact-mass liquid chromatography-mass spectrometry instrumentation should be the analytical method of choice.
In fact, there have been no efforts to quantify the actual levels of endogenous DMT and its metabolites in human brain and only a few have attempted to address the issue in rats. Barker et al. As noted, no circadian studies of DMT production or release from the pineal as a function of time have ever been conducted. This study's information is unfortunately quite limited in terms of sample number and did not address extraction recoveries, method validation or brain distribution of DMT.
The highest levels were Values for other days ranged from undetected limit of detection of 1. Since pooled whole brain 2. The data necessarily expressed the DMT concentration as if it was homogeneously distributed.
Rats were also sacrificed at constant times during the study and no accounting was made for possible circadian or ultradian variations.
Given these facts, any speculation that attempts to dismiss the relevance of DMT in vivo because the concentrations in brain are too low Nichols, necessarily ignores the fact that data concerning the actual levels of DMT in brain, particularly humans and levels that may be observed in different brain areas, simply does not exist.
Future Research to Determine the Concentration of DMT in Brain Tissues While more research into the brain concentrations and distribution of DMT is obviously warranted, it is possible, as with many other substances, that it may only be found in specific brain areas or cell types.
For example, the pineal gland of an adult rat weighs between 0. If all of the DMT found, on average, at day 17 While converting g to ml regarding tissue is by no means exact, the point to be made is that DMT in brain could have significant concentrations in discrete brain areas and exist in sufficient concentrations in such areas to readily affect various receptors and neuronal functions.
Lower concentrations could occur in other brain areas as well with their concentrations being enhanced by mechanisms for DMT uptake and vesicular storage.
What is obvious from these speculative calculations is the fact that more research into DMT brain distribution and concentrations is needed, recognizing its rapid metabolism and possible sequestration.
As with measurements in other matrices, well validated and sensitive methods for such quantitative analyses will be required.
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However, DMT has been shown to interact with a variety of ionotropic and metabotropic receptors. While the subjective behavioral effects of exogenously administered DMT appear to be primarily acting via 5-HT2A receptors, the interaction of other receptors, such as other serotonergic and glutaminergic receptors, may also play a synergistic and confounding role.
Indeed, the activation of frontocortical glutamate receptors, secondary to serotonin 5-HT2A receptor-mediated glutamate release, appears to be a controlling mechanism of serotonergic hallucinogens dos Santos et al. However, although this type of receptor research is quite mature, these findings have yet to define and accurately correlate what makes a compound hallucinogenic vs. For example, Keiser et al. Nonetheless, it was observed that DMT was not only a potent partial agonist at 5-HT2A but also that the DMT-induced head twitch response, a common measure of hallucinogenic activity, occurred only in wild-type mice but not in 5-HT2A knockout mice.
Furthermore, DMT-enhanced inositol trisphosphate production has been shown to persist even in the presence of the 5-HT2A antagonist ketanserin Deliganis et al.
Collectively, these data suggest that DMT may be actively synthesized and released in mammalian tissues, and stored in or transported to the mammalian brain.
This, coupled to DMT's close structural similarity to melatonin and serotonin see Figure 1 , has led to several hypotheses of elevated levels of endogenous DMT being involved in naturally occurring altered states of consciousness such as dreaming, religious experience, the near-death state, psychosis, and creativity. One approach to understanding the possible role of an endogenous hallucinogen was the transmethylation hypothesis Osmond and Smythies, Osmond and Smythies hypothesized that schizophrenia may involve aberrant adrenal metabolism leading to methylation of stress compounds such as adrenaline to form mescaline-like compounds with psychedelic properties that contribute to the clinical symptoms of schizophrenia.
This hypothesis has been extended to encompass the possibility of similar altered functioning of DMT enzymatic pathways see Figure 1 leading to elevated levels of the dimethylated tryptamines DMTs ; e.
Evolving analytical chemistry-based techniques, from thin layer chromatography to liquid chromatography combined with high resolution mass spectrometry, have been used to compare DMT concentrations in bodily fluids e.
Some of these studies reported a correlation between elevated DMT levels and psychosis, but when considered collectively, ultimately failed to support this hypothesis Gillin et al. Moreover, upon extrapolation of the concentrations of DMT reported in mammalian bodily fluids and whole tissues to what has been demonstrated via in vitro binding assays, it has been hypothesized endogenous DMT concentrations cannot functionally activate brain receptors shown critical for psychedelic effects Nichols, This hypothesis is partly based, however, on concentrations observed from exogenous administration and levels observed in the periphery, without consideration for the possibility of direct synthesis and cellular concentration mechanisms for DMT in the brain.
Nonetheless, accurate quantitation of DMT concentrations in bodily fluids has been further plagued by its rapid breakdown via MAO Riba et al.
The first half of this review will focus on summarizing this literature. These studies demonstrate that research approaches that circumvent the limitations of direct detection of endogenous DMT altogether are needed. Monitoring changes in the activity or a more thorough understanding of the biochemistry of the enzymes involved in DMT synthesis may offer such a solution.
Variation in the nucleotide sequence of a gene occurs frequently in human populations, and a single individual may have multiple nucleotides that differ from a consensus reference sequence of the gene. These variants are termed single nucleotide polymorphisms SNPs when they occur at a single nucleotide and at a notable frequency in a population.
Though SNPs do not always manifest at a phenotypic level, they often impact mRNA expression or protein structure via a change in the coding region of a gene, which leads to a change in cellular or behavioral phenotype or even a disease state. Thus, whether or not a SNP has a phenotypic impact relates to the aspect of gene structure that it disrupts.
When present in coding regions of the gene, SNPs can either result in 1 no change in the amino acid residue in which it occurs in the translated protein, a synonymous SNP, although such a SNP may alter translational or folding events; 2 a change in an amino acid residue, a nonsynonymous missense SNP; or 3 the generation of a stop codon in the transcribed mRNA, a nonsynonymous nonsense SNP, that often results in a truncated, nonfunctional protein.
Additionally, insertions and deletions indels of nucleotides can alter the reading frame and subsequently the coding of amino acids that follow its occurrence, often leading to completely nonfunctional protein products being translated.
SNPs in non-coding regions can also affect mRNA structure and impact the expression of the gene and the protein it codes through altering the splicing of a gene or binding to DNA of other proteins which regulate expression. The range of impacts a SNP may have can in part be predicted by assessing the SNP's location, the amino acid it changes, or the region it disrupts.
This in turn can allow prediction of the level of impact on protein function and expression with relation to a phenotype of interest. The assessment of SNPs at the single gene and population level is a central tool of genetic studies which have shed light on the biological nature of many disease states. A well-studied example of a disease where a single nucleotide variant in a single gene is responsible is sickle-cell anemia, which results from being homozygous for a SNP nucleotide A—T in codon 6 of the beta-globin gene.
This elicits aggregation of a sickling hemoglobin in red blood cells in low oxygen environments Frenette and Atweh, While the simple Mendelian inheritance pattern of this and other diseases allows for the identification of a single responsible mutation through genetic screens, such as genome wide association studies GWAS , it is more often the case that mutations in multiple genes associate with complex phenotypes; e.
Coupling such genetic approaches with molecular studies provides a powerful framework to investigate the impact of genomic variation. Moreover, identification of INMT SNPs in genetic studies not related to psychiatry may also shed light on a non-psychoactive role for endogenous DMT, and such studies will be discussed in the review that follows.
This is the focus of the second half of the manuscript, accomplished through review of current genetic and biochemical literature and databases on INMT. Endogenous DMT and the Transmethylation Hypothesis The fact that the subjective effects of exogenous doses of DMT sometimes parallel the positive symptoms of psychosis in schizophrenics—e. Additionally, stress has been shown to both increase DMT levels in rodents Christian et al. Elevated INMT levels have also been reported in schizophrenics vs.
Thus, there have been attempts by researchers to quantify DMT levels in the bodily fluids of psychiatric populations vs. In the largest review of this literature taking into account all such studies to date, Barker et al.
Disruption of large-scale cortical synchronization is a correlate of schizophrenia Uhlhaas and Singer, , and 5-MeO-DMT was found to alter both the firing pattern of rodent medial prefrontal cortex pyramidal neurons as well as decrease cortically generated slow oscillations that underlie the synchronization of global cortical networks.
The latter effect was subsequently reversed by the antipsychotic medications clozapine and haloperidol Riga et al. Experimental data to date suggest that peripheral endogenous DMT levels are extremely low, and it has been suggested that plasma DMT levels following administration of an exogenous psychedelic dose of DMT are incompatible with what the brain is capable of synthesizing Nichols, DMT has been identified in the pineal gland Barker et al.
But there is not, to date, data quantitating DMT's levels therein or within the brains of any other species via such contemporary analytical techniques. Similarly, studies investigating the possible regional biosynthesis of DMT in the brain are lacking as is research into the possible influence of other physiological factors that could alter its rate of synthesis. It is also inappropriate to assume that the pineal is the sole source of DMT production in the brain.
Although it is true that INMT has yet to be reported outside of the pineal gland in mammalian brain, the Northern blot assay employed by Thompson et al. But peripheral levels of DMT may or may not be reflective of brain concentrations, and such samples are from bodily fluids removed from theoretical cellular sources of DMT and thus are further diluted or metabolized.
For instance, the average concentration of serotonin in brain tissues is in the micromolar range, but synaptic concentrations can reach the millimolar range Bruns et al. Moreover, these pharmacological assays that assess DMT activation thresholds at its receptors come with several caveats, the most salient being the shortcomings of removing a receptor from its native environment for subsequent testing.
These assays overexpress the protein in a variety of cell culture systems: e.
Overexpression of receptors in these cell systems often leads to artifacts. All are also likely highly mutated from several generations of culturing. This may distance the model from how the receptor functions in vivo.
However, these are invaluable model systems that allow for control of variables in a manner not possible in intact animals and are intended to be for comparative studies. Here, inter-experimental ratios may be more reliable across several experiments; e. Thus, although it is reasonable to suggest that the low amounts of DMT found in peripheral tissues may not occasion a psychedelic response at 5-HT2A and other 5-HT receptors, the ability of DMT to do so, cannot be ruled out based on the current body of literature.
As will be discussed, SNPs in INMT may alter the endogenous concentrations of DMT, and research on what such concentrations are in vivo the intact living mammalian brain where such events occur is needed. With regard to the former, most in vitro assays of DMT pharmacology have been conducted on the reference genetic sequences for serotonin receptors, and as such, the currently reported range should not dictate a cutoff ECvalue.
Short term changes in the proteome of human cerebral organoids induced by 5-MeO-DMT
One study assayed mutant variants of 5-HT2A and found that non-synonymous SNPs in the coding region of the 5-HT2A receptor increased the potency of tryptamine and decreased that of 5-MeO-DMT, and also increased the affinity and functional effects of several antipsychotic agents in vitro Davies et al.
The authors further concluded that even SNPs predicted to have little impact on 5-HT2A receptor function had unpredictable and substantial effects on its local pharmacology. Davies et al. To suggest schizophrenia is a psychedelic state that requires a threshold amount of endogenous DMT at 5-HT2A also requires understanding dose-response effects for the compound; i.
With regard to G-protein coupled receptor signal transduction involving 5-HT2A, the most well-known pathway involves biding of a ligand to 5-HT2A to activate Gq, which induces phospholipase C to hydrolyze phosphatidylinositol, which leads to, amongst other biochemical events, calcium release, and potentially gene transcription.
These data suggest the phospholipase A2 pathway may be specific to the hallucinogenic effects of psychedelic compounds, although their ability to selectively activate one pathway over the other did not differ Kurrasch-Orbaugh et al.
Moreover, SNPs in 5-HT2C have shown to impact the ability of agonists to induce specific signaling cascades within these pathways Berg et al. The use of human cerebral organoid models in teasing apart which ligands activate which pathways may prove useful, as these systems are made up of heterologous cell clusters capable of differentiating into tissues containing the cellular makeup of broad brain regions. Sensitivity to the DMTs may also vary across clinical populations.
Although use of psychedelics is generally well-tolerated with judicious regard for dosage and set and setting, there are reports of adverse psychological effects which tend to associate with those harboring preexisting cases of psychosis or nonpsychotic bipolar disorder Bowers and Swigar, ; Hendricks et al.
This may be extended to include a mechanism for how endogenous DMTs play a role in the development of psychosis; that is, certain SNPs in 5-HT2A may increase one's responsiveness to them. It has similarly been proposed that exogenous psychedelics may modulate the activity of INMT and the endogenous DMTs and that this may be intrinsic to their mechanism of action Barker et al.
As such, SNPs of these kinds may be of interest to proponents of administering psychedelics in clinical settings for amelioration of depression and other ailments, and genetic screening could reveal patients for whom this practice may not be advisable due to their heightened propensity for adverse reactions.
For instance, polymorphisms in the promoter region of the serotonin transporter gene, which may likewise function to remove DMT from the synapse for storage into vesicles Cozzi et al. Deficiencies in melatonin, a hormone produced mainly in the pineal gland in response to the circadian clock signal to provide circadian cues, are prevalent in autism Melke et al.
Melatonin likewise utilizes tryptophan as a synthetic precursor see Figure 1 , and such lowered melatonin levels could be reflective of shunting of tryptophan toward the synthetic pathway favoring endogenous DMT synthesis.
DMT bears a striking chemical resemblance to melatonin see Figure 1 and has recently been identified in the mammalian pineal gland Barker et al. The correlations between melatonin pathways, sleep, and autism have been well-studied Pagan et al.
In summary, current literature does not show a definitive association of endogenous DMT or INMT with schizophrenia and the transmethylation hypothesis. Moreover, it has not been unequivocally demonstrated whether or not endogenous DMT levels ever reach concentrations necessary to activate receptors associated with its psychedelic exogenous effects. However, genetic and biochemical studies on SNPs in INMT and its translated protein may provide insight into whether endogenous DMT may be involved in naturally occurring altered states of consciousness or serve other physiological roles, and will be the focus of the remainder of this review.Cerebral organoids may well recapitulate environmental effects on human nervous system, particularly related to plasticity and growth 24 , 25 , 26 , and circumvent problems of discrepancies in metabolic pathways occurring in translational studies involving animal models.
Taking results from these and more classical studies of DMT biochemistry and pharmacology together, this report examines some of the past and current data in the field and proposes several new directions and experiments to ascertain the role of endogenous DMT. INMT immunoreactivity in spinal cord was found to be localized in ventral horn motoneurons. This being the case, there is already a significant body of work regarding DMT's binding and effects, especially relative to effects on serotonin, acting as a serotonergic modulator.
That is, they perform a certain function for God. There has yet to be any follow-on research as to the significance of this change in DMT concentrations during rat brain neurodevelopment or correlation with possible changes of INMT activity in other developing tissues, specifically during days 12— In , Saavedra et al.