The Endogenous Hallucinogen and Trace Amine N,N-Dimethyltryptamine (DMT) Displays Potent Protective Effects against Hypoxia via Sigma-1 Receptor Activation in Human Primary iPSC-Derived Cortical Neurons and Microglia-Like Immune Cells

Therapeutic modulation of the kynurenine pathway in severe mental illness and comorbidities: A potential role for serotonergic psychedelics

Mounting evidence points towards a crucial role of the kynurenine pathway (KP) in the altered gut-brain axis (GBA) balance in severe mental illness (SMI, namely depression, bipolar disorder, and schizophrenia) and cardiometabolic comorbidities. Preliminary evidence shows that serotonergic psychedelics and their analogues may hold therapeutic potential in addressing the altered KP in the dysregulated GBA in SMI and comorbidities. In fact, aside from their effects on mood, psychedelics elicit therapeutic improvement in preclinical models of obesity, metabolic syndrome, and vascular inflammation, which are highly comorbid with SMI. Here, we review the literature on the therapeutic modulation of the KP in the dysregulated GBA in SMI and comorbidities, and the potential application of psychedelics to address the altered KP in the brain and systemic dysfunction underlying SMI and comorbidities. Psychedelics might therapeutically modulate the KP in the altered GBA in SMI and comorbidities either directly, via altering the metabolic pathway by influencing the rate-limiting enzymes of the KP and affecting the levels of available tryptophan, or indirectly, by affecting the gut microbiome, gut metabolome, metabolism, and the immune system. Despite promising preliminary evidence, the mechanisms and outcomes of the KP modulation with psychedelics in SMI and systemic comorbidities remain largely unknown and require further investigation. Several concerns are discussed surrounding the potential side effects of this approach in specific cohorts of individuals with SMI and systemic comorbidities.

Human pluripotent stem cells as a translational toolkit in psychedelic research in vitro

Psychedelics, recognized for their impact on perception, are resurging as promising treatments with rapid onset for mood and substance use disorders. Despite increasing evidence from clinical trials, questions persist about the cellular and molecular mechanisms and their precise correlation with treatment outcomes. Murine neurons and immortalized non-neural cell lines harboring overexpressed constructs have shed light on neuroplastic changes mediated by the serotonin 2A receptor (5-HT2AR) as the primary mechanism. However, limitations exist in capturing human- and disease-specific traits. Here, we discuss current accomplishments and prospects for incorporating human pluripotent stem cells (PSCs) to complement these models. PSCs can differentiate into various brain cell types, mirroring endogenous expression patterns and cell identities to recreate disease phenotypes. Brain organoids derived from PSCs resemble cell diversity and patterning, while region-specific organoids simulate circuit-level phenotypes. PSC-based models hold significant promise to illuminate the cellular and molecular substrates of psychedelic-induced phenotypic recovery in neuropsychiatric disorders.

N, N-Dimethyltryptamine, a natural hallucinogen, ameliorates Alzheimer's disease by restoring neuronal Sigma-1 receptor-mediated endoplasmic reticulum-mitochondria crosstalk

BACKGROUND

Aberrant neuronal Sigma-1 receptor (Sig-1r)-mediated endoplasmic reticulum (ER)- mitochondria signaling plays a key role in the neuronal cytopathology of Alzheimer's disease (AD). The natural psychedelic N, N-dimethyltryptamine (DMT) is a Sig-1r agonist that may have the anti-AD potential through protecting neuronal ER-mitochondrial interplay.

METHODS

3×TG-AD transgenic mice were administered with chronic DMT (2 mg/kg) for 3 weeks and then performed water maze test. The Aβ accumulation in the mice brain were determined. The Sig-1r level upon DMT treatment was tested. The effect of DMT on the ER-mitochondrial contacts site and multiple mitochondria-associated membrane (MAM)-associated proteins were examined. The effect of DMT on calcium transport between ER and mitochondria and the mitochondrial function were also evaluated.

RESULTS

chronic DMT (2 mg/kg) markedly alleviated cognitive impairment of 3×TG-AD mice. In parallel, it largely diminished Aβ accumulation in the hippocampus and prefrontal cortex. DMT restored the decreased Sig-1r levels of 3×TG-AD transgenic mice. The hallucinogen reinstated the expression of multiple MAM-associated proteins in the brain of 3×TG-AD mice. DMT also prevented physical contact and calcium dynamic between the two organelles in in vitro and in vivo pathological circumstances. DMT modulated oxidative phosphorylation (OXPHOS) and ATP synthase in the in vitro model of AD.

CONCLUSION

The anti-AD effects of DMT are associated with its protection of neuronal ER-mitochondria crosstalk via the activation of Sig-1r. DMT has the potential to serve as a novel preventive and therapeutic agent against AD.

Network medicine informed multi-omics integration identifies drug targets and repurposable medicines for Amyotrophic Lateral Sclerosis

Amyotrophic Lateral Sclerosis (ALS) is a devastating, immensely complex neurodegenerative disease by lack of effective treatments. To date, the challenge to establishing effective treatment for ALS remains formidable, partly due to inadequate translation of existing human genetic findings into actionable ALS-specific pathobiology for subsequent therapeutic development. This study evaluates the feasibility of network medicine methodology via integrating human brain-specific multi-omics data to prioritize drug targets and repurposable treatments for ALS. Using human brain-specific genome-wide quantitative trait loci (x-QTLs) under a network-based deep learning framework, we identified 105 putative ALS-associated genes enriched in various known ALS pathobiological pathways, including regulation of T cell activation, monocyte differentiation, and lymphocyte proliferation. Specifically, we leveraged non-coding ALS loci effects from genome-wide associated studies (GWAS) on brain-specific expression quantitative trait loci (QTL) (eQTL), protein QTLs (pQTL), splicing QTL (sQTL), methylation QTL (meQTL), and histone acetylation QTL (haQTL). Applying network proximity analysis of predicted ALS-associated gene-coding targets and existing drug-target networks under the human protein-protein interactome (PPI) model, we identified a set of potential repurposable drugs (including Diazoxide, Gefitinib, Paliperidone, and Dimethyltryptamine) for ALS. Subsequent validation established preclinical and clinical evidence for top-prioritized repurposable drugs. In summary, we presented a network-based multi-omics framework to identify potential drug targets and repurposable treatments for ALS and other neurodegenerative disease if broadly applied.

"Immunohistochemical analysis of Sigma-1 receptor (σ-1R) expression in human pineal gland in relation to different causes of death"

Sigma-1 receptor (σ-1R) modulates cellular signaling pathways, probably acting as a ligand operated chaperone. When activated, the receptor translocates from the interface mitochondrion associated membrane of the endoplasmic reticulum to the cell membrane. σ-1R was demonstrated in some brain regions, including the pineal gland, and was proposed to be involved in several cerebral processes, including neuroprotective responses against homeostasis alterations. On this basis, the immunohistochemical expression of σ-1R in human pineal glands was evaluated, with particular regard to the different causes of death. Thirty-eight pineal glands obtained from forensic autopsies were divided into five groups according to the cause of death: sudden death, drowning, fire fatality, hanging, and hemorrhagic shock, and examined with hematoxylin-eosin stain and immunohistochemistry for σ-1R. Both pinealocytes and perivascular spaces were evaluated. The pineal glands from sudden death were only mildly positive for σ-1R, while a more evident immunopositivity was observed in hanging, fire fatality, hemorrhagic shock, and drowning. These results were confirmed in a two-by-two comparison between the sudden death group and other groups. Our data demonstrate for the first time with immunohistochemical techniques the presence of σ-1R expression in the human pineal gland and propose a direct correlation between σ-1R expression and duration of the death process, in particular when hypoxic conditions and/or excessive psychological stress are present.

Psychedelics for acquired brain injury: a review of molecular mechanisms and therapeutic potential

Acquired brain injury (ABI), such as traumatic brain injury and stroke, is a leading cause of disability worldwide, resulting in debilitating acute and chronic symptoms, as well as an increased risk of developing neurological and neurodegenerative disorders. These symptoms can stem from various neurophysiological insults, including neuroinflammation, oxidative stress, imbalances in neurotransmission, and impaired neuroplasticity. Despite advancements in medical technology and treatment interventions, managing ABI remains a significant challenge. Emerging evidence suggests that psychedelics may rapidly improve neurobehavioral outcomes in patients with various disorders that share physiological similarities with ABI. However, research specifically focussed on psychedelics for ABI is limited. This narrative literature review explores the neurochemical properties of psychedelics as a therapeutic intervention for ABI, with a focus on serotonin receptors, sigma-1 receptors, and neurotrophic signalling associated with neuroprotection, neuroplasticity, and neuroinflammation. The promotion of neuronal growth, cell survival, and anti-inflammatory properties exhibited by psychedelics strongly supports their potential benefit in managing ABI. Further research and translational efforts are required to elucidate their therapeutic mechanisms of action and to evaluate their effectiveness in treating the acute and chronic phases of ABI.

The Effects of Psychedelics on Neuronal Physiology

Psychedelics are quite unique among drugs that impact the central nervous system, as a single administration of a psychedelic can both rapidly alter subjective experience in profound ways and produce sustained effects on circuits relevant to mood, fear, reward, and cognitive flexibility. These remarkable properties are a direct result of psychedelics interacting with several key neuroreceptors distributed across the brain. Stimulation of these receptors activates a variety of signaling cascades that ultimately culminate in changes in neuronal structure and function. Here, we describe the effects of psychedelics on neuronal physiology, highlighting their acute effects on serotonergic and glutamatergic neurotransmission as well as their long-lasting effects on structural and functional neuroplasticity in the cortex. We propose that the neurobiological changes leading to the acute and sustained effects of psychedelics might be distinct, which could provide opportunities for engineering compounds with optimized safety and efficacy profiles.

Effects of microplastics and phenanthrene on gut microbiome and metabolome alterations in the marine medaka Oryzias melastigma

Plastic pollution of the oceans is increasing, and toxic interactions between microplastics (MPs) and organic pollutants have become a major environmental concern. However, the combined effects of organic pollutants and MPs on microbiomes and metabolomes have not been studied extensively. In the present study, to evaluate whether MPs and phenanthrene (Phe) act synergistically in the guts of marine medaka (Oryzias melastigma), we performed toxicity assessments, 16 S rRNA gene sequencing, and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses. Our investigations revealed increased toxicity induced by Phe, as well as disturbances in gut microbiota (known as dysbiosis) when MPs were present. Furthermore, combined exposure to Phe and MPs resulted in greater alterations to microbiota composition and metabolite profiles. Notably, MP exposure was distinctly associated with the abundance of Shewanella and Spongiibacteraceae, while Phe exposure was associated with the abundance of Marimicrobium. Among key microbiota, Marimicrobium and Roseibacillus were significantly correlated with metabolites responsible for coenzyme A and glycerophospholipid metabolism in medaka. These results suggest that interactions between Phe and MPs may have significant effects on the gut microbiota and metabolism of aquatic organisms and underscore the importance of acknowledging the interplay between MPs and contaminants in aquatic environments.

The potential of psychedelics for the treatment of Alzheimer's disease and related dementias

Alzheimer's Disease (AD) is a currently incurable but increasingly prevalent fatal and progressive neurodegenerative disease, demanding consideration of therapeutically relevant natural products and their synthetic analogues. This paper reviews evidence for effectiveness of natural and synthetic psychedelics in the treatment of AD causes and symptoms. The plastogenic effects of serotonergic psychedelics illustrate that they have efficacy for addressing multiple facets of AD pathology. We review findings illustrating neuroplasticity mechanisms of classic (serotonergic) and non-classic psychedelics that indicate their potential as treatments for AD and related dementias. Classic psychedelics modulate glutamatergic neurotransmission and stimulate synaptic and network remodeling that facilitates synaptic, structural and behavioral plasticity. Up-regulation of neurotrophic factors enable psychedelics to promote neuronal survival and glutamate-driven neuroplasticity. Muscimol modulation of GABAAR reduces Aβ-induced neurotoxicity and psychedelic Sig-1R agonists provide protective roles in Aβ toxicity. Classic psychedelics also activate mTOR intracellular effector pathways in brain regions that show atrophy in AD. The potential of psychedelics to treat AD involves their ability to induce structural and functional neural plasticity in brain circuits and slow or reverse brain atrophy. Psychedelics stimulate neurotrophic pathways, increase neurogenesis and produce long-lasting neural changes through rewiring pathological neurocircuitry. Psychedelic effects on 5-HT receptor target genes and induction of synaptic, structural, and functional changes in neurons and networks enable them to promote and enhance brain functional connectivity and address diverse mechanisms underlying degenerative neurological disorders. These findings provide a rationale for immediate investigation of psychedelics as treatments for AD patients.

A mechanistic insight for the biosynthesis of N,N-dimethyltryptamine: An ONIOM theoretical approach

Psychoactive natural products are potent serotonergic agonists capable of modulating brain functions such as memory and cognition. These substances have shown therapeutic potential for treating various mental disorders. The fact that N,N-dimethyltryptamine (DMT) is produced endogenously in several plants and animals, including humans, makes it particularly attractive. As an amino acid-derived alkaloid, the DMT biosynthetic pathway is part of the L-tryptophan biochemical cascade and can be divided into the decarboxylation by an aromatic L-amino acid decarboxylase (AADC) for tryptamine formation and the subsequent double-methylation by the indolethylamine-N-methyltransferase (INMT) through the cofactor S-adenosyl-L-methionine (SAM), a methyl donor. Unlike the decarboxylation mechanism of L-tryptophan, the molecular details of the double methylation of tryptamine have not been elucidated. Therefore, we propose an in silico model using molecular dynamics (MD), non-covalent interaction index (NCI) and density functional theory (DFT) calculations with the ONIOM QM:MM B3LYP/6-31+G(d,p):MM/UFF level of theory. Based on the obtained energetic data, the potential energy surface (PES) indicates an SN2 mechanism profile, with the second methylation energy barrier being the rate-limiting step with δG‡=60kJ∙mol-1 larger than the previous methylation, following the NCI analysis showing more repulsive interactions for the second transition state. In addition, the hybridization information of each reaction step provides geometric details about the double-methylation.

Back from the rabbit hole. Theoretical considerations and practical guidelines on psychedelic integration for mental health specialists

The growing interest in and prevalence of the use of psychedelics, as well as the potential benefits and negative consequences associated with psychedelic experiences, create a need for mental health specialists to be able to provide adequate and effective intervention regarding the content and consequences of these experiences, that is, psychedelic integration. At the same time, current graduate training in psychiatry, psychology, psychotherapy, counseling, etc., fails to adequately prepare professionals for such interventions. In order to fill this gap, an international, bottom-up project was established to attempt developing guidelines. This project was conducted by means of literature reviews as well as roundtable discussions among project participants, leading to a consensus on the guidelines' final scope and content. Drawing from the outcomes of this project, this article presents proposed comprehensive guidelines covering both theoretical and practical aspects of psychedelic integration, that are intended to serve as a resource for various mental health specialists who may encounter individuals in need of support considering their psychedelic experiences. These guidelines encompass clinician-friendly information on the effects of psychedelics, a definition of psychedelic integration, the general theoretical considerations linked to utilization of psychedelic experiences in clinical practice, a simple model organizing the course of psychedelic integration practice, as well as an overview of the current models of psychedelic integration, along with a selective presentation of basic and specific interventions derived from various psychotherapeutic approaches that can be employed in the practice of psychedelic integration.

Bedside to bench: the outlook for psychedelic research

There has recently been a resurgence of interest in psychedelic compounds based on studies demonstrating their potential therapeutic applications in treating post-traumatic stress disorder, substance abuse disorders, and treatment-resistant depression. Despite promising efficacy observed in some clinical trials, the full range of biological effects and mechanism(s) of action of these compounds have yet to be fully established. Indeed, most studies to date have focused on assessing the psychological mechanisms of psychedelics, often neglecting the non-psychological modes of action. However, it is important to understand that psychedelics may mediate their therapeutic effects through multi-faceted mechanisms, such as the modulation of brain network activity, neuronal plasticity, neuroendocrine function, glial cell regulation, epigenetic processes, and the gut-brain axis. This review provides a framework supporting the implementation of a multi-faceted approach, incorporating in silico, in vitro and in vivo modeling, to aid in the comprehensive understanding of the physiological effects of psychedelics and their potential for clinical application beyond the treatment of psychiatric disorders. We also provide an overview of the literature supporting the potential utility of psychedelics for the treatment of brain injury (e.g., stroke and traumatic brain injury), neurodegenerative diseases (e.g., Parkinson's and Alzheimer's diseases), and gut-brain axis dysfunction associated with psychiatric disorders (e.g., generalized anxiety disorder and major depressive disorder). To move the field forward, we outline advantageous experimental frameworks to explore these and other novel applications for psychedelics.

Exploring the Potential Utility of Psychedelic Therapy for Patients With Amyotrophic Lateral Sclerosis

Background: Amyotrophic lateral sclerosis (ALS) is an aggressive, terminal neurodegenerative disease that causes death of motor neurons and has an average survival time of 3-4 years. ALS is the most common motor neuron degenerative disease and is increasing in prevalence. There is a pressing need for more effective ALS treatments as available pharmacotherapies do not reverse disease progression or provide substantial clinical benefit. Furthermore, despite psychological distress being highly prevalent in ALS patients, psychological treatments remain understudied. Psychedelics (i.e., serotonergic psychedelics and related compounds like ketamine) have seen a resurgence of research into therapeutic applications for treating a multitude of neuropsychiatric conditions, including psychiatric and existential distress in life-threatening illnesses. Methods: We conducted a narrative review to examine the potential of psychedelic assisted-psychotherapy (PAP) to alleviate psychiatric and psychospiritual distress in ALS. We also discussed the safety of using psychedelics in this population and proposed putative neurobiological mechanisms that may therapeutically intervene on ALS neuropathology. Results: PAP has the potential to treat psychological dimensions and may also intervene on neuropathological dimensions of ALS. Robust improvements in psychiatric and psychospiritual distress from PAP in other populations provide a strong rationale for utilizing this therapy to treat ALS-related psychiatric and existential distress. Furthermore, relevant neuroprotective properties of psychedelics warrant future preclinical trials to investigate this area in ALS models. Conclusion: PAP has the potential to serve as an effective treatment in ALS. Given the lack of effective treatment options, researchers should rigorously explore this therapy for ALS in future trials.

The sigma-1 receptor-TAMM41 axis modulates neuroinflammation and attenuates memory impairment during the latent period of epileptogenesis

BACKGROUND

Therapy in the latent period is favorable for retarding the process of epileptogenesis. Recently, we have discovered that the activated sigma-1 receptor (Sig-1R) attenuates the hippocampus pathological injury and memory impairment in the latent period of epileptogenesis. But the molecular mechanism needs further investigation.

METHODS

PRE-084 was utilized as a research tool to highly selectively activate Sig-1R in epileptic mice. After the treatment of PRE-084, the pro-inflammatory cytokines, neuropathological traits, and the level of mitochondrial translocator assembly and maintenance 41 homolog (TAMM41) in the hippocampus were examined. The mode in which the Sig-1R interacts with TAMM41 was explored. The role of TAMM41 in the protecting effect of PRE-084 was established.

RESULTS

PRE-084 inhibited the growth of pro-inflammatory cytokines, reduced the formation of gliosis, alleviated neuronal damage in the hippocampus, and attenuated memory impairment in the latent period of epileptogenesis. The protein level of TAMM41 decreased in the hippocampi of epileptic mice and increased in the PRE-084-treated mice. The Sig-1R bound with TAMM41 directly, maintaining the stability of TAMM41. Knockdown of TAMM41 reversed the protective effect of PRE-084, and overexpression of TAMM41 exhibited a similar protective action to that of PRE-084.

CONCLUSION

We presented the concept of the "sigma-1 receptor-TAMM41 axis" and proposed that augmenting this axis can attenuate neuroinflammation and memory impairment in the process of epileptogenesis.

N, N-Dimethyltryptamine (DMT)-Occasioned Familiarity and the Sense of Familiarity Questionnaire (SOF-Q)

This study investigated the sense of familiarity attributed to N, N-dimethyltryptamine (DMT) experiences. 227 naturalistic inhaled-DMT experiences reporting a sense of familiarity were included. No experiences referenced a previous DMT or psychedelic experience as the source of the familiarity. A high prevalence of concomitant features discordant from ordinary consciousness were identified: features of a mystical experience (97.4%), ego-dissolution (16.3%), and a "profound experience of death" (11.0%). The Sense of Familiarity Questionnaire (SOF-Q) was developed assessing 19 features of familiarity across 5 themes: (1) Familiarity with the Feeling, Emotion, or Knowledge Gained; (2) Familiarity with the Place, Space, State, or Environment; (3) Familiarity with the Act of Going Through the Experience; (4) Familiarity with Transcendent Features; and (5) Familiarity Imparted by an Entity Encounter. Bayesian latent class modeling yielded two stable classes of participants who shared similar SOF-Q responses. Class 1 participants responded, "yes" more often for items within "Familiarity Imparted by an Entity Encounter" and "Familiarity with the Feeling, Emotion, or Knowledge Gained." Results catalogued features of the sense of familiarity imparted by DMT, which appears to be non-referential to a previous psychedelic experience. Findings provide insights into the unique and enigmatic familiarity reported during DMT experiences and offer a foundation for further exploration into this intriguing phenomenon.

Seeking the Psilocybiome: Psychedelics meet the microbiota-gut-brain axis

Moving towards a systems psychiatry paradigm embraces the inherent complex interactions across all levels from micro to macro and necessitates an integrated approach to treatment. Cortical 5-HT2A receptors are key primary targets for the effects of serotonergic psychedelics. However, the therapeutic mechanisms underlying psychedelic therapy are complex and traverse molecular, cellular, and network levels, under the influence of biofeedback signals from the periphery and the environment. At the interface between the individual and the environment, the gut microbiome, via the gut-brain axis, plays an important role in the unconscious parallel processing systems regulating host neurophysiology. While psychedelic and microbial signalling systems operate over different timescales, the microbiota-gut-brain (MGB) axis, as a convergence hub between multiple biofeedback systems may play a role in the preparatory phase, the acute administration phase, and the integration phase of psychedelic therapy. In keeping with an interconnected systems-based approach, this review will discuss the gut microbiome and mycobiome and pathways of the MGB axis, and then explore the potential interaction between psychedelic therapy and the MGB axis and how this might influence mechanism of action and treatment response. Finally, we will discuss the possible implications for a precision medicine-based psychedelic therapy paradigm.

The Missing Piece? A Case for Microglia's Prominent Role in the Therapeutic Action of Anesthetics, Ketamine, and Psychedelics

There is much excitement surrounding recent research of promising, mechanistically novel psychotherapeutics - psychedelic, anesthetic, and dissociative agents - as they have demonstrated surprising efficacy in treating central nervous system (CNS) disorders, such as mood disorders and addiction. However, the mechanisms by which these drugs provide such profound psychological benefits are still to be fully elucidated. Microglia, the CNS's resident innate immune cells, are emerging as a cellular target for psychiatric disorders because of their critical role in regulating neuroplasticity and the inflammatory environment of the brain. The following paper is a review of recent literature surrounding these neuropharmacological therapies and their demonstrated or hypothesized interactions with microglia. Through investigating the mechanism of action of psychedelics, such as psilocybin and lysergic acid diethylamide, ketamine, and propofol, we demonstrate a largely under-investigated role for microglia in much of the emerging research surrounding these pharmacological agents. Among others, we detail sigma-1 receptors, serotonergic and γ-aminobutyric acid signalling, and tryptophan metabolism as pathways through which these agents modulate microglial phagocytic activity and inflammatory mediator release, inducing their therapeutic effects. The current review includes a discussion on future directions in the field of microglial pharmacology and covers bidirectional implications of microglia and these novel pharmacological agents in aging and age-related disease, glial cell heterogeneity, and state-of-the-art methodologies in microglial research.

Effects of repeated lysergic acid diethylamide (LSD) on the mouse brain endocannabinoidome and gut microbiome

BACKGROUND AND PURPOSE

Psychedelics elicit prosocial, antidepressant and anxiolytic effects via neuroplasticity, neurotransmission and neuro-immunomodulatory mechanisms. Whether psychedelics affect the brain endocannabinoid system and its extended version, the endocannabinoidome (eCBome) or the gut microbiome, remains unknown.

EXPERIMENTAL APPROACH

Adult C57BL/6N male mice were administered lysergic acid diethylamide (LSD) or saline for 7 days. Sociability was assessed in the direct social interaction and three chambers tests. Prefrontal cortex and hippocampal endocannabinoids, endocannabinoid-like mediators and metabolites were quantified via high-pressure liquid chromatography with tandem mass spectrometry (HPLC-MS/MS). Neurotransmitter levels were assessed via HPLC-UV/fluorescence. Gut microbiome changes were investigated by 16S ribosomal DNA sequencing.

KEY RESULTS

LSD increased social preference and novelty and decreased hippocampal levels of the N-acylethanolamines N-linoleoylethanolamine (LEA), anandamide (N-arachidonoylethanolamine) and N-docosahexaenoylethanolamine (DHEA); the monoacylglycerol 1/2-docosahexaenoylglycerol (1/2-DHG); the prostaglandins D₂ (PGD₂ ) and F2α (PGF_2α ); thromboxane 2 and kynurenine. Prefrontal eCBome mediator and metabolite levels were less affected by the treatment. LSD decreased Shannon alpha diversity of the gut microbiota, prevented the decrease in the Firmicutes:Bacteroidetes ratio observed in saline-treated mice and altered the relative abundance of the bacterial taxa Bifidobacterium, Ileibacterium, Dubosiella and Rikenellaceae RC9.

CONCLUSIONS AND IMPLICATIONS

The prosocial effects elicited by repeated LSD administration are accompanied by alterations of hippocampal eCBome and kynurenine levels, and the composition of the gut microbiota. Modulation of the hippocampal eCBome and kynurenine pathway might represent a mechanism by which psychedelic compounds elicit prosocial effects and affect the gut microbiome.

The Bright Side of Psychedelics: Latest Advances and Challenges in Neuropharmacology

The need to identify effective therapies for the treatment of psychiatric disorders is a particularly important issue in modern societies. In addition, difficulties in finding new drugs have led pharmacologists to review and re-evaluate some past molecules, including psychedelics. For several years there has been growing interest among psychotherapists in psilocybin or lysergic acid diethylamide for the treatment of obsessive-compulsive disorder, of depression, or of post-traumatic stress disorder, although results are not always clear and definitive. In fact, the mechanisms of action of psychedelics are not yet fully understood and some molecular aspects have yet to be well defined. Thus, this review aims to summarize the ethnobotanical uses of the best-known psychedelic plants and the pharmacological mechanisms of the main active ingredients they contain. Furthermore, an up-to-date overview of structural and computational studies performed to evaluate the affinity and binding modes to biologically relevant receptors of ibogaine, mescaline, N,N-dimethyltryptamine, psilocin, and lysergic acid diethylamide is presented. Finally, the most recent clinical studies evaluating the efficacy of psychedelic molecules in some psychiatric disorders are discussed and compared with drugs already used in therapy.

Insight into the Effects of High-Altitude Hypoxic Exposure on Learning and Memory

The earth land area is heterogeneous in terms of elevation; about 45% of its land area belongs to higher elevation with altitude above 500 meters compared to sea level. In most cases, oxygen concentration decreases as altitude increases. Thus, high-altitude hypoxic stress is commonly faced by residents in areas with an average elevation exceeding 2500 meters and those who have just entered the plateau. High-altitude hypoxia significantly affects advanced neurobehaviors including learning and memory (L&M). Hippocampus, the integration center of L&M, could be the most crucial target affected by high-altitude hypoxia exposure. Based on these points, this review thoroughly discussed the relationship between high-altitude hypoxia and L&M impairment, in terms of hippocampal neuron apoptosis and dysfunction, neuronal oxidative stress disorder, neurotransmitters and related receptors, and nerve cell energy metabolism disorder, which is of great significance to find potential targets for medical intervention. Studies illustrate that the mechanism of L&M damaged by high-altitude hypoxia should be further investigated based on the entire review of issues related to this topic.

Significance of mammalian N, N-dimethyltryptamine (DMT): A 60-year-old debate

N,N-dimethyltryptamine (DMT) is a potent psychedelic naturally produced by many plants and animals, including humans. Whether or not DMT is significant to mammalian physiology, especially within the central nervous system, is a debate that started in the early 1960s and continues to this day. This review integrates historical and recent literature to clarify this issue, giving special attention to the most controversial subjects of DMT's biosynthesis, its storage in synaptic vesicles and the activation receptors like sigma-1. Less discussed topics, like DMT's metabolic regulation or the biased activation of serotonin receptors, are highlighted. We conclude that most of the arguments dismissing endogenous DMT's relevance are based on obsolete data or misleading assumptions. Data strongly suggest that DMT can be relevant as a neurotransmitter, neuromodulator, hormone and immunomodulator, as well as being important to pregnancy and development. Key experiments are addressed to definitely prove what specific roles DMT plays in mammalian physiology.

The Link Between Energy-Related Sensations and Metabolism: Implications for Treating Fatigue

Energy-related sensations include sensation of energy and fatigue as well as subjective energizability and fatigability. First, we introduce interdisciplinary useful definitions of all constructs and review findings regarding the question of whether sensations of fatigue and energy are two separate constructs or two ends of a single dimension. Second, we describe different components of the bodily energy metabolism system (e.g., mitochondria; autonomic nervous system). Third, we review the link between sensation of fatigue and different components of energy metabolism. Finally, we present an overview of different treatments shown to affect both energy-related sensations and metabolism before outlining future research perspectives.

N,N-dimethyltryptamine and Amazonian ayahuasca plant medicine

OBJECTIVE

Reports have indicated possible uses of ayahuasca for the treatment of conditions including depression, addictions, post-traumatic stress disorder, anxiety and specific psychoneuroendocrine immune system pathologies. The article assesses potential ayahuasca and N,N-dimethyltryptamine (DMT) integration with contemporary healthcare. The review also seeks to provide a summary of selected literature regarding the mechanisms of action of DMT and ayahuasca; and assess to what extent the state of research can explain reports of unusual phenomenology.

DESIGN

A narrative review.

RESULTS

Compounds in ayahuasca have been found to bind to serotonergic receptors, glutaminergic receptors, sigma-1 receptors, trace amine-associated receptors, and modulate BDNF expression and the dopaminergic system. Subjective effects are associated with increased delta and theta oscillations in amygdala and hippocampal regions, decreased alpha wave activity in the default mode network, and stimulations of vision-related brain regions particularly in the visual association cortex. Both biological processes and field of consciousness models have been proposed to explain subjective effects of DMT and ayahuasca, however, the evidence supporting the proposed models is not sufficient to make confident conclusions. Ayahuasca plant medicine and DMT represent potentially novel treatment modalities.

CONCLUSIONS

Further research is required to clarify the mechanisms of action and develop treatments which can be made available to the general public. Integration between healthcare research institutions and reputable practitioners in the Amazon is recommended.

Therapeutic Properties of Ayahuasca Components in Ischemia/Reperfusion Injury of the Eye

Ischemic eye diseases are major causes of vision impairment. Thus, potential retinoprotective effects of N’N-dimethyltryptamine (DMT) were investigated. To inhibit its rapid breakdown by monoamine-oxidase A (MAO-A) enzyme, DMT was co-administered with harmaline, a β-carboline in the Amazonian Ayahuasca brew. Using ligation, 60 min of ischemia was provoked in eyes of rats, followed by 7 days of reperfusion whilst animals received harmaline alone, DMT + harmaline, or vehicle treatment. After 1 week of reperfusion, electroretinographical (ERG) measurements, histological analysis, and Western blot were performed. Harmaline alone exhibited retinoprotection in ischemia–reperfusion (I/R) which was, surprisingly, counterbalanced by DMT in case of co-administration. As both MAO-A inhibition and DMT increase serotoninergic tone synergistically, communicated to be anti-ischemic, thus, involvement of other pathways was investigated. Based on our experiments, DMT and harmaline exert opposite effects on important ocular proteins such as PARP1, NFκB, MMP9, or HSP70, each having a critical role in a different mechanism of eye-ischemia-related pathologies, e.g., cell death, inflammation, tissue destruction, and oxidative stress. Since DMT is proclaimed to be a promising drug candidate, its potentially undesirable effect on eye-ischemia should be further investigated. Meanwhile, this experiment revealed the potential therapeutic effect of MAO-A inhibitor harmaline in I/R-related eye diseases.

Psychedelics: Alternative and Potential Therapeutic Options for Treating Mood and Anxiety Disorders

The word “psychedelic” (psyche (i.e., the mind or soul) and delos (i.e., to show)) has Greek origin and was first coined by psychiatrist Humphry Osmond in 1956, who had been conducting research on lysergic acid diethylamide (LSD) at the time. Psychedelic drugs such as N,N-DMT/DMT (N,N-dimethyltryptamine), 5-MeO-DMT (5-methoxy-N,N-dimethyltryptamine), LSD (lysergic acid diethylamide), MDMA (3,4-methylenedioxymethamphetamine) and psilocybin have had significant value as an entheogen in spiritual, religious (shamanic) and sociocultural rituals in Central and South American cultures for thousands of years. In the 1960s, the globalization of these drugs and their subsequent spread outside of their indigenous, old-world cultures, led to the subsequent implementation of strict drug control laws in many Western countries. Even today, psychedelics are still classified as Schedule I drugs, resulting in a still lingering negative stigmatization/perception, vilification, and ultimate criminalization of psychedelics. This controversy still lingers and still limits scientific research and full medical acceptance. For many years up until recently, the spiritual, religious and medicinal value of these drugs could not be explored in a scientific context. More recently, a second wave of psychedelic research is now focusing on psychedelics as neuropharmaceuticals to treat alcohol and tobacco addiction, general mood and anxiety disorders and cancer-related depression. There is now a vast array of promising evidence-based data to confirm the years of anecdotal evidence of the medicinal values of psychedelics. Natural therapeutic alternatives such as psychedelic drugs may provide a safe and efficacious alternate to conventional drugs used to treat mood and anxiety disorders. In a Western context in particular, psychedelic drugs as therapeutic agents for mood and anxiety disorders are becoming increasingly of interest amidst increasing rates of such disorders globally, changing social constructions, the implementation of government regulations and increasing investment opportunities, that ultimately allow for the scientific study to generate evidenced-based data. Alternative psychotherapeutic interventions are gaining interest also, because of their low physiological toxicity, relatively low abuse potential, safe psychological effects, and no associated persisting adverse physiological or psychological effects during and after use. On the other hand, conventional psychotic drugs and anti-depressants are becoming less favorable because of their adverse side effects. Psychedelic neuropharmaceutical interventions may with medical oversight be the solution to conventional psychiatric disorders such as depression and anxiety, and an alternative to conventional psychiatric treatment options. This paper will review the therapeutic potential of psychedelic drugs as alternative therapeutic options for mood and anxiety disorders in a controlled, clinical setting, where the chances of adverse psychological episodes occurring are mitigated.

Impact of Two Neuronal Sigma-1 Receptor Modulators, PRE084 and DMT, on Neurogenesis and Neuroinflammation in an Aβ1-42-Injected, Wild-Type Mouse Model of AD

Alzheimer's disease (AD) is the most common form of dementia characterized by cognitive dysfunctions. Pharmacological interventions to slow the progression of AD are intensively studied. A potential direction targets neuronal sigma-1 receptors (S1Rs). S1R ligands are recognized as promising therapeutic agents that may alleviate symptom severity of AD, possibly via preventing amyloid-β-(Aβ-) induced neurotoxicity on the endoplasmic reticulum stress-associated pathways. Furthermore, S1Rs may also modulate adult neurogenesis, and the impairment of this process is reported to be associated with AD. We aimed to investigate the effects of two S1R agonists, dimethyltryptamine (DMT) and PRE084, in an Aβ-induced in vivo mouse model characterizing neurogenic and anti-neuroinflammatory symptoms of AD, and the modulatory effects of S1R agonists were analyzed by immunohistochemical methods and western blotting. DMT, binding moderately to S1R but with high affinity to 5-HT receptors, negatively influenced neurogenesis, possibly as a result of activating both receptors differently. In contrast, the highly selective S1R agonist PRE084 stimulated hippocampal cell proliferation and differentiation. Regarding neuroinflammation, DMT and PRE084 significantly reduced Aβ1-42-induced astrogliosis, but neither had remarkable effects on microglial activation. In summary, the highly selective S1R agonist PRE084 may be a promising therapeutic agent for AD. Further studies are required to clarify the multifaceted neurogenic and anti-neuroinflammatory roles of these agonists.

Pharmahuasca and DMT Rescue ROS Production and Differentially Expressed Genes Observed after Predator and Psychosocial Stress: Relevance to Human PTSD

Post-traumatic stress disorder (PTSD) is associated with cognitive deficits, oxidative stress, and inflammation. Animal models have recapitulated features of PTSD, but no comparative RNA sequencing analysis of differentially expressed genes (DEGs) in the brain between PTSD and animal models of traumatic stress has been carried out. We compared DEGs from the prefrontal cortex (PFC) of an established stress model to DEGs from the dorsolateral PFC (dlPFC) of humans. We observed a significant enrichment of rat DEGs in human PTSD and identified 20 overlapping DEGs, of which 17 (85%) are directionally concordant. N,N-dimethyltryptamine (DMT) is a known indirect antioxidant, anti-inflammatory, and neuroprotective compound with antidepressant and plasticity-facilitating effects. We tested the capacity of DMT, the monoamine oxidase inhibitor (MAOI) harmaline, and "pharmahuasca" (DMT + harmaline) to reduce reactive oxygen species (ROS) production and inflammatory gene expression and to modulate neuroplasticity-related gene expression in the model. We administered DMT (2 mg/kg IP), harmaline (1.5 mg/kg IP), pharmahuasca, or vehicle every other day for 5 days, following a 30 day stress regiment. We measured ROS production in the PFC and hippocampus (HC) by electron paramagnetic resonance spectroscopy and sequenced total mRNA in the PFC. We also performed in vitro assays to measure the affinity and efficacy of DMT and harmaline at 5HT_2AR compared to 5-HT. DMT and pharmahuasca reduced ROS production in the PFC and HC, while harmaline had mixed effects. Treatments normalized 9, 12, and 14 overlapping DEGs, and pathway analysis implicated that genes were involved in ROS production, inflammation, growth factor signaling, neurotransmission, and neuroplasticity.

Administration of N,N-dimethyltryptamine (DMT) in psychedelic therapeutics and research and the study of endogenous DMT

As with all drugs, the route, form, and/or dose of a substance administered or applied can play a defining role in its overall pharmacology and use as a therapeutic. This review will focus on these factors as they relate to the psychedelic N,N-dimethyltryptamine (DMT). It will examine the positive and negative aspects of different formulations and routes of administration of DMT and the observed effects from such administrations in the form of ayahuasca teas; oral "pharmahuasca"; injections by intravenous (IV) and intramuscular (IM) routes; inhalation, insufflation; and other routes; and high-dose, low-dose, and "micro-dose" effects. The review will consider possible oral route of administration alternatives that would not require concomitant use of a monoamine oxidase inhibitor. The review will then address the current research findings for DMT from in vivo and in vitro studies as well as the possibility that these findings may be revealing the role of endogenous DMT in normal brain function.

Psychedelic Therapy's Transdiagnostic Effects: A Research Domain Criteria (RDoC) Perspective

Accumulating clinical evidence shows that psychedelic therapy, by synergistically combining psychopharmacology and psychological support, offers a promising transdiagnostic treatment strategy for a range of disorders with restricted and/or maladaptive habitual patterns of emotion, cognition and behavior, notably, depression (MDD), treatment resistant depression (TRD) and addiction disorders, but perhaps also anxiety disorders, obsessive-compulsive disorder (OCD), Post-Traumatic Stress Disorder (PTSD) and eating disorders. Despite the emergent transdiagnostic evidence, the specific clinical dimensions that psychedelics are efficacious for, and associated underlying neurobiological pathways, remain to be well-characterized. To this end, this review focuses on pre-clinical and clinical evidence of the acute and sustained therapeutic potential of psychedelic therapy in the context of a transdiagnostic dimensional systems framework. Focusing on the Research Domain Criteria (RDoC) as a template, we will describe the multimodal mechanisms underlying the transdiagnostic therapeutic effects of psychedelic therapy, traversing molecular, cellular and network levels. These levels will be mapped to the RDoC constructs of negative and positive valence systems, arousal regulation, social processing, cognitive and sensorimotor systems. In summarizing this literature and framing it transdiagnostically, we hope we can assist the field in moving toward a mechanistic understanding of how psychedelics work for patients and eventually toward a precise-personalized psychedelic therapy paradigm.

Psilocybin, a Naturally Occurring Indoleamine Compound, Could Be Useful to Prevent Suicidal Behaviors

The available interventions for people who are at risk of suicide have limited efficacy. Recently, research on new mental health treatments has started to consider psychedelic compounds, particularly psilocybin, a molecule with a few thousand years of history of use in human societies. The possible effects of psilocybin on suicidal ideation and behaviors have not been specifically studied yet; however, the current knowledge on the suicidal process and the available data on es/ketamine suggest that psylocibin could be used to modulate the thoughts and behavioral patterns in individuals who are at risk of suicidal behaviors. Here, we summarize the available evidence on the possible mechanisms underlying psilocybin positive effects on suicide risk. Major pathways related to suicidal behaviors that might be modulated by psylocibin include serotonin receptors. Specifically, psylocibin directly stimulates the serotonin 2A receptor (5HT_2A), targeting the inflammatory and oxidative stress pathways and leading to a rapid increase in brain plasticity and inflammation suppression and increases in cognitive flexibility, spirituality, and empathy. We also present preliminary epidemiological data and provide a rationale for studying psilocybin in individuals with suicidal ideation or who are at risk of suicidal behaviors. This review presents a framework to understand the basis for psilocybin use in individuals who are at risk of suicidal behaviors and calls for clinical studies.

Psychedelic-inspired approaches for treating neurodegenerative disorders

Psychedelics are increasingly being recognized for their potential to treat a wide range of brain disorders including depression, post-traumatic stress disorder (PTSD), and substance use disorder. Their broad therapeutic potential might result from an ability to rescue cortical atrophy common to many neuropsychiatric and neurodegenerative diseases by impacting neurotrophic factor gene expression, activating neuronal growth and survival mechanisms, and modulating the immune system. While the therapeutic potential of psychedelics has not yet been extended to neurodegenerative disorders, we provide evidence suggesting that approaches based on psychedelic science might prove useful for treating these diseases. The primary target of psychedelics, the 5-HT_2A receptor, plays key roles in cortical neuron health and is dysregulated in Alzheimer's disease. Moreover, evidence suggests that psychedelics and related compounds could prove useful for treating the behavioral and psychological symptoms of dementia (BPSD). While more research is needed to probe the effects of psychedelics in models of neurodegenerative diseases, the robust effects of these compounds on structural and functional neuroplasticity and inflammation clearly warrant further investigation.

From psychiatry to neurology: Psychedelics as prospective therapeutics for neurodegenerative disorders

The studies of psychedelics, especially psychedelic tryptamines like psilocybin, are rapidly gaining interest in neuroscience research. Much of this interest stems from recent clinical studies demonstrating that they have a unique ability to improve the debilitating symptoms of major depressive disorder (MDD) long-term after only a single treatment. Indeed, the Food and Drug Administration (FDA) has recently designated two Phase III clinical trials studying the ability of psilocybin to treat forms of MDD with "Breakthrough Therapy" status. If successful, the use of psychedelics to treat psychiatric diseases like depression would be revolutionary. As more evidence appears in the scientific literature to support their use in psychiatry to treat MDD on and substance use disorders (SUD), recent studies with rodents revealed that their therapeutic effects might extend beyond treating MDD and SUD. For example, psychedelics may have efficacy in the treatment and prevention of brain injury and neurodegenerative diseases such as Alzheimer's Disease. Preclinical work has highlighted psychedelics' ability to induce neuroplasticity and synaptogenesis, and neural progenitor cell proliferation. Psychedelics may also act as immunomodulators by reducing levels of proinflammatory biomarkers, including IL-1β, IL-6, and tumor necrosis factor-α (TNF-α). Their exact molecular mechanisms, and induction of cellular interactions, especially between neural and glial cells, leading to therapeutic efficacy, remain to be determined. In this review, we discuss recent findings and information on how psychedelics may act therapeutically on cells within the central nervous system (CNS) during brain injuries and neurodegenerative diseases.

N,N-Dimethyltryptamine attenuates spreading depolarization and restrains neurodegeneration by sigma-1 receptor activation in the ischemic rat brain

Dimethyltryptamine (DMT), an endogenous ligand of sigma-1 receptors (Sig-1Rs), acts against systemic hypoxia, but whether DMT may prevent cerebral ischemic injury is unexplored. Here global forebrain ischemia was created in anesthetized rats and aggravated with the induction of spreading depolarizations (SDs) and subsequent short hypoxia before reperfusion. Drugs (DMT, the selective Sig-1R agonist PRE-084, the Sig-1R antagonist NE-100, or the serotonin receptor antagonist asenapine) were administered intravenously alone or in combination while physiological variables and local field potential from the cerebral cortex was recorded. Neuroprotection and the cellular localization of Sig-1R were evaluated with immunocytochemistry. Plasma and brain DMT content was measured by 2D-LC-HRMS/MS. The affinity of drugs for cerebral Sig-1R was evaluated with a radioligand binding assay. Both DMT and PRE-084 mitigated SDs, counteracted with NE-100. Further, DMT attenuated SD when co-administered with asenapine, compared to asenapine alone. DMT reduced the number of apoptotic and ferroptotic cells and supported astrocyte survival. The binding affinity of DMT to Sig-1R matched previously reported values. Sig-1Rs were associated with the perinuclear cytoplasm of neurons, astrocytes and microglia, and with glial processes. According to these data, DMT may be considered as adjuvant pharmacological therapy in the management of acute cerebral ischemia.

Biosynthesis and synthetic biology of psychoactive natural products

Psychoactive natural products play an integral role in the modern world. The tremendous structural complexity displayed by such molecules confers diverse biological activities of significant medicinal value and sociocultural impact. Accordingly, in the last two centuries, immense effort has been devoted towards establishing how plants, animals, and fungi synthesize complex natural products from simple metabolic precursors. The recent explosion of genomics data and molecular biology tools has enabled the identification of genes encoding proteins that catalyze individual biosynthetic steps. Once fully elucidated, the "biosynthetic pathways" are often comparable to organic syntheses in elegance and yield. Additionally, the discovery of biosynthetic enzymes provides powerful catalysts which may be repurposed for synthetic biology applications, or implemented with chemoenzymatic synthetic approaches. In this review, we discuss the progress that has been made toward biosynthetic pathway elucidation amongst four classes of psychoactive natural products: hallucinogens, stimulants, cannabinoids, and opioids. Compounds of diverse biosynthetic origin - terpene, amino acid, polyketide - are identified, and notable mechanisms of key scaffold transforming steps are highlighted. We also provide a description of subsequent applications of the biosynthetic machinery, with an emphasis placed on the synthetic biology and metabolic engineering strategies enabling heterologous production.

Pivotal mental states

This paper introduces a new construct, the 'pivotal mental state', which is defined as a hyper-plastic state aiding rapid and deep learning that can mediate psychological transformation. We believe this new construct bears relevance to a broad range of psychological and psychiatric phenomena. We argue that pivotal mental states serve an important evolutionary function, that is, to aid psychological transformation when actual or perceived environmental pressures demand this. We cite evidence that chronic stress and neurotic traits are primers for a pivotal mental state, whereas acute stress can be a trigger. Inspired by research with serotonin 2A receptor agonist psychedelics, we highlight how activity at this particular receptor can robustly and reliably induce pivotal mental states, but we argue that the capacity for pivotal mental states is an inherent property of the human brain itself. Moreover, we hypothesize that serotonergic psychedelics hijack a system that has evolved to mediate rapid and deep learning when its need is sensed. We cite a breadth of evidences linking stress via a variety of inducers, with an upregulated serotonin 2A receptor system (e.g. upregulated availability of and/or binding to the receptor) and acute stress with 5-HT release, which we argue can activate this primed system to induce a pivotal mental state. The pivotal mental state model is multi-level, linking a specific molecular gateway (increased serotonin 2A receptor signaling) with the inception of a hyper-plastic brain and mind state, enhanced rate of associative learning and the potential mediation of a psychological transformation.

Hypoxia Routes Tryptophan Homeostasis Towards Increased Tryptamine Production

The liver is the central hub for processing and maintaining homeostatic levels of dietary nutrients especially essential amino acids such as tryptophan (Trp). Trp is required not only to sustain protein synthesis but also as a precursor for the production of NAD, neurotransmitters and immunosuppressive metabolites. In light of these roles of Trp and its metabolic products, maintaining homeostatic levels of Trp is essential for health and well-being. The liver regulates global Trp supply by the immunosuppressive enzyme tryptophan-2,3-dioxygenase (TDO2), which degrades Trp down the kynurenine pathway (KP). In the current study, we show that isolated primary hepatocytes when exposed to hypoxic environments, extensively rewire their Trp metabolism by reducing constitutive Tdo2 expression and differentially regulating other Trp pathway enzymes and transporters. Mathematical modelling of Trp metabolism in liver cells under hypoxia predicted decreased flux through the KP while metabolic flux through the tryptamine branch significantly increased. In line, the model also revealed an increased accumulation of tryptamines under hypoxia, at the expense of kynurenines. Metabolic measurements in hypoxic hepatocytes confirmed the predicted reduction in KP metabolites as well as accumulation of tryptamine. Tdo2 expression in cultured primary hepatocytes was reduced upon hypoxia inducible factor (HIF) stabilisation by dimethyloxalylglycine (DMOG), demonstrating that HIFs are involved in the hypoxic downregulation of hepatic Tdo2. DMOG abrogated hepatic luciferase signals in Tdo2 reporter mice, indicating that HIF stability also recapitulates hypoxic rewiring of Trp metabolism in vivo. Also in WT mice HIF stabilization drove homeostatic Trp metabolism away from the KP towards enhanced tryptamine production, leading to enhanced levels of tryptamine in liver, serum and brain. As tryptamines are the most potent hallucinogens known, the observed upregulation of tryptamine in response to hypoxic exposure of hepatocytes may be involved in the generation of hallucinations occurring at high altitude. KP metabolites are known to activate the aryl hydrocarbon receptor (AHR). The AHR-activating properties of tryptamines may explain why immunosuppressive AHR activity is maintained under hypoxia despite downregulation of the KP. In summary our results identify hypoxia as an important factor controlling Trp metabolism in the liver with possible implications for immunosuppressive AHR activation and mental disturbances.

Psychedelics and Neuroplasticity: A Systematic Review Unraveling the Biological Underpinnings of Psychedelics

Clinical studies suggest the therapeutic potential of psychedelics, including ayahuasca, DMT, psilocybin, and LSD, in stress-related disorders. These substances induce cognitive, antidepressant, anxiolytic, and antiaddictive effects suggested to arise from biological changes similar to conventional antidepressants or the rapid-acting substance ketamine. The proposed route is by inducing brain neuroplasticity. This review attempts to summarize the evidence that psychedelics induce neuroplasticity by focusing on psychedelics' cellular and molecular neuroplasticity effects after single and repeated administration. When behavioral parameters are encountered in the selected studies, the biological pathways will be linked to the behavioral effects. Additionally, knowledge gaps in the underlying biology of clinical outcomes of psychedelics are highlighted. The literature searched yielded 344 results. Title and abstract screening reduced the sample to 35; eight were included from other sources, and full-text screening resulted in the final selection of 16 preclinical and four clinical studies. Studies (n = 20) show that a single administration of a psychedelic produces rapid changes in plasticity mechanisms on a molecular, neuronal, synaptic, and dendritic level. The expression of plasticity-related genes and proteins, including Brain-Derived Neurotrophic Factor (BDNF), is changed after a single administration of psychedelics, resulting in changed neuroplasticity. The latter included more dendritic complexity, which outlasted the acute effects of the psychedelic. Repeated administration of a psychedelic directly stimulated neurogenesis and increased BDNF mRNA levels up to a month after treatment. Findings from the current review demonstrate that psychedelics induce molecular and cellular adaptations related to neuroplasticity and suggest those run parallel to the clinical effects of psychedelics, potentially underlying them. Future (pre)clinical research might focus on deciphering the specific cellular mechanism activated by different psychedelics and related to long-term clinical and biological effects to increase our understanding of the therapeutic potential of these compounds.

Psychedelics as a novel approach to treating autoimmune conditions

With a rise in the incidence of autoimmune diseases (AiD), health care providers continue to seek out more efficacious treatment approaches for the AiD patient population. Classic serotonergic psychedelics have recently been gaining public and professional interest as novel interventions to a number of mental health afflictions. Psychedelics have also been shown to be able to modulate immune functions, however, while there has been great interest to researching into their psychotherapeutic applications, there has so far been very little exploration into the potential to treat inflammatory and immune-related diseases with these compounds. A handful of studies from a variety of fields suggest that psychedelics do indeed have effects in the body that may attenuate the outcome of AiD. This literature review explores existing evidence that psychedelic compounds may offer a potential novel application in the treatment of pathologies related to autoimmunity. We propose that psychedelics hold the potential to attenuate or even resolve autoimmunity by targeting psychosomatic origins, maladaptive chronic stress responses, inflammatory pathways, immune modulation and enteric microbiome populations.

Low Doses of LSD Acutely Increase BDNF Blood Plasma Levels in Healthy Volunteers

Despite preclinical evidence for psychedelic-induced neuroplasticity, confirmation in humans is grossly lacking. Given the increased interest in using low doses of psychedelics for psychiatric indications and the importance of neuroplasticity in the therapeutic response, this placebo-controlled within-subject study investigated the effect of single low doses of LSD (5, 10, and 20 μg) on circulating BDNF levels in healthy volunteers. Blood samples were collected every 2 h over 6 h, and BDNF levels were determined afterward in blood plasma using ELISA. The findings demonstrated an increase in BDNF blood plasma levels at 4 h (5 μg) and 6 h (5 and 20 μg) compared to that for the placebo. The finding that LSD acutely increases BDNF levels warrants studies in patient populations.

Synthesis and characterization of high-purity N,N-dimethyltryptamine hemifumarate for human clinical trials

Since 2006, there has been a resurgent interest in the pharmacology and therapeutics of psychedelic drugs. Psilocybin, the 4-phosphoryl ester of N,N-dimethyltryptamine (DMT), has been studied most often, but DMT itself is also appealing because of its brief but profound psychological effects and its presence as an endogenous substance in mammalian brain. Although there have been a few studies of ayahuasca, a DMT-containing water infusion, only one human study with pure DMT has been reported since the early 2000s. Newly planned clinical trials to assess the safety and efficacy of DMT in humans with major depressive disorders require high-purity water-soluble DMT for intravenous administration. Accordingly, we synthesized and characterized DMT hemifumarate for these upcoming studies. The synthetic approach of Speeter and Anthony was slightly modified to gain some efficiency in time. In particular, this is the first known report to use aluminum hydride, generated in situ from lithium aluminum hydride, to reduce the intermediate 2-(1H-indol-3-yl)-N,N-dimethyl-2-oxoacetamide to DMT. A quench protocol was developed to produce a good yield of exceptionally pure free base DMT upon workup, which was then converted to the hemifumarate salt. Analysis of the final product included differential scanning calorimetry, thermogravimetric analysis, gas chromatography-mass spectrometry (GC-MS), ¹ H and ¹³ C nuclear magnetic resonance spectroscopy, high-performance liquid chromatography, residual solvent analysis by GC headspace sampling, X-ray powder diffraction analysis, and residual lithium analysis by inductively coupled plasma-mass spectrometry. The DMT hemifumarate was minimally 99.9% pure, with no significant impurities or residual solvents, thus meeting regulatory standards for administration to humans.

N,N-dimethyltryptamine reduces infarct size and improves functional recovery following transient focal brain ischemia in rats

BACKGROUND AND PURPOSE

N,N-dimethyltryptamine (DMT) is an endogenous ligand of the Sigma 1 receptor (Sig-1R) with documented in vitro cytoprotective properties against hypoxia. Our aim was to demonstrate the in vivo neuroprotective effect of DMT following ischemia-reperfusion injury in the rat brain.

METHODS

Transient middle cerebral occlusion (MCAO) was induced for 60 min in male Wistar rats using the filament occlusion model under general anaesthesia. Before the removal of the filament the treatment group (n = 10) received an intra-peritoneal (IP) bolus of 1 mg/kg-body weight (bw) DMT dissolved in 1 ml 7% ethanol/saline vehicle, followed by a maintenance dose of 2 mg/Kg-bw/h delivered over 24 h via osmotic minipumps. Controls (n = 10) received a vehicle bolus only. A third group (n = 10) received a Sig-1R antagonist (BD1063, 1 mg/kg-bw bolus +2 mg/kg-bw/h maintenance) in parallel with the DMT. Lesion volume was measured by MRI 24 h following the MCAO. Shortly after imaging the animals were terminated, and the native brains and sera were removed. Four rats were perfusion fixed. Functional recovery was studied in two separate group of pre-trained animals (n = 8-8) using the staircase method for 30 days. The expression levels of proteins involved in apoptosis, neuroplasticity and inflammatory regulation were assessed by real-time qPCR and ELISA.

RESULTS

DMT treated rats were characterized by lower ischemic lesion volume (p = .0373), and better functional recovery (p = .0084) compared to the controls. Sig-1R was expressed both in neurons and in microglia in the peri-infarct cortex, and the DMT induced change in the lesion volume was hindered by BD1063. Lower APAF1 expression (mRNA and protein) and higher BNDF levels were documented on DTM, while decreased TNF-α, IL1-β, IL-6 and increased IL-10 expressions indicated the compound's anti-inflammatory potential.

CONCLUSION

Our results indicate a Sig-1R dependent reduction of the ischemic brain injury following exogenous DMT administration in rats, presumably through a combined anti-apoptotic, pro-neurotrophic and anti-inflammatory treatment effect.

Toxicological Aspects and Determination of the Main Components of Ayahuasca: A Critical Review

Ayahuasca is a psychoactive beverage prepared traditionally from a mixture of the leaves and stems of Psychotria viridis and Banisteriopsis caapi, respectively, being originally consumed by indigenous Amazonian tribes for ritual and medicinal purposes. Over the years, its use has spread to other populations as a means to personal growth and spiritual connection. Also, the recreational use of its isolated compounds has become prominent. The main compounds of this tea-like preparation are N,N-dimethyltryptamine (DMT), β-Carbolines, and harmala alkaloids, such as harmine, tetrahydroharmine, and harmaline. The latter are monoamine-oxidase inhibitors and are responsible for DMT psychoactive and hallucinogenic effects on the central nervous system. Although consumers defend its use, its metabolic effects and those on the central nervous system are not fully understood yet. The majority of studies regarding the effects of this beverage and of its individual compounds are based on in vivo experiments, clinical trials, and even surveys. This paper will not only address the toxicological aspects of the ayahuasca compounds but also perform a comprehensive and critical review on the analytical methods available for their determination in biological and non-biological specimens, with special focus on instrumental developments and sample preparation approaches.

Semiology and Mechanisms of Near-Death Experiences

PURPOSE OF REVIEW

Near-death experiences (NDEs) are conscious perceptual experiences, including self-related emotional, spiritual, and mystical experiences, occurring in close encounters with death or in non-life-threatening situations. The origin of NDEs remains unknown. Here, we review recent advances in the understanding of NDE semiology and pathophysiology.

RECENT FINDINGS

Recent prospective studies confirm that NDEs reflect a spectrum of highly distinctive memories which are associated with negative or positive emotions and can be influenced by the nature of the causal event, but the temporal sequence with which these images unfold is variable. Some drugs, notably ketamine, may lead to experiences that are similar or even identical to NDEs. New models extend previous neural network theories and include aspects of evolutionary and quantum theories. Although the factual existence of NDEs is no longer doubted and the semiology well-described, a pathophysiological model that includes all aspects of NDEs is still lacking.

The Sigma-1 Receptor in Cellular Stress Signaling

After decades of research, the sigma-1 receptor (Sig-1R)’s structure, and molecular functions are being unveiled. Sig-1R is an integral endoplasmic reticulum (ER) membrane protein which forms an oligomer and binds a variety of psychotropic drugs. It forms a complex with the ER chaperone BiP that controls specific signaling molecules’ stability and function at the ER to regulate Ca²⁺ signaling, bioenergetics, and ER stress. Sig-1R is highly enriched in ER subdomains that are physically linked to outer mitochondrial membranes, reflecting its role in regulating ER–mitochondria communications. Thus, Sig-1R ligands are expected to serve as novel neuroprotective agents which treat certain psychiatric and neurodegenerative disorders. In this short review, the cell biological aspects of Sig-1R are discussed, with a particular focus on its role in fundamental ER functions.

Biosynthesis and Extracellular Concentrations of N,N-dimethyltryptamine (DMT) in Mammalian Brain

N,N-dimethyltryptamine (DMT), a psychedelic compound identified endogenously in mammals, is biosynthesized by aromatic-L-amino acid decarboxylase (AADC) and indolethylamine-N-methyltransferase (INMT). Whether DMT is biosynthesized in the mammalian brain is unknown. We investigated brain expression of INMT transcript in rats and humans, co-expression of INMT and AADC mRNA in rat brain and periphery, and brain concentrations of DMT in rats. INMT transcripts were identified in the cerebral cortex, pineal gland, and choroid plexus of both rats and humans via in situ hybridization. Notably, INMT mRNA was colocalized with AADC transcript in rat brain tissues, in contrast to rat peripheral tissues where there existed little overlapping expression of INMT with AADC transcripts. Additionally, extracellular concentrations of DMT in the cerebral cortex of normal behaving rats, with or without the pineal gland, were similar to those of canonical monoamine neurotransmitters including serotonin. A significant increase of DMT levels in the rat visual cortex was observed following induction of experimental cardiac arrest, a finding independent of an intact pineal gland. These results show for the first time that the rat brain is capable of synthesizing and releasing DMT at concentrations comparable to known monoamine neurotransmitters and raise the possibility that this phenomenon may occur similarly in human brains.

N,N-dimethyltryptamine Prevents Renal Ischemia-Reperfusion Injury in a Rat Model

BACKGROUND

Ischemia reperfusion (I/R) injury remains one of the most challenging fields of organ transplantation. It is highly associated with the use of expanded criteria donors that might conclude to delayed graft function or early or late graft failure.

OBJECTIVE

To investigate the metabolic, microcirculatory parameters, and histologic changes under the effect of N,N-dimethyltryptamine (DMT) in a renal I/R model in rats.

METHOD

In 26 anesthetized rats both kidneys were exposed. In the control group (n = 6) no other intervention happened. In 20 other animals, the right renal vessels were ligated, and after 60 minutes the right kidney was removed. The left renal vessels were clamped for 60 minutes then released, followed by 120 minutes of reperfusion. In the I/R group (n = 10), there was no additive treatment, while in I/R + DMT group (n = 10) DMT was administered 15 minutes before ischemia. Blood samples were taken, laser Doppler measurement was performed, and both kidneys were evaluated histologically.

RESULTS

Microcirculation (blood flux units [BFU]) diminished in all groups, but remarkably so in the I/R + DMT group. This group compensated better after the 30th minute of reperfusion. The control and I/R + DMT groups had similar BFUs after 120 minutes of reperfusion, but in the I/R group BFU was higher. Tubular necrosis developed in the I/R and I/R + DMT groups too; it was moderated under DMT effect, and severe without. Histologic injuries were less in I/R + DMT Group compared to non-treated animals.

CONCLUSION

Histologic changes characteristic to I/R injuries were reversible and microcirculation recovered at the end of 120 minutes reperfusion under the administration of DMT. DMT can be used for renoprotection in kidney transplantation.

Neurochemical models of near-death experiences: A large-scale study based on the semantic similarity of written reports

The real or perceived proximity to death often results in a non-ordinary state of consciousness characterized by phenomenological features such as the perception of leaving the body boundaries, feelings of peace, bliss and timelessness, life review, the sensation of traveling through a tunnel and an irreversible threshold. Near-death experiences (NDEs) are comparable among individuals of different cultures, suggesting an underlying neurobiological mechanism. Anecdotal accounts of the similarity between NDEs and certain drug-induced altered states of consciousness prompted us to perform a large-scale comparative analysis of these experiences. After assessing the semantic similarity between ≈15,000 reports linked to the use of 165 psychoactive substances and 625 NDE narratives, we determined that the N-methyl-D-aspartate (NMDA) receptor antagonist ketamine consistently resulted in reports most similar to those associated with NDEs. Ketamine was followed by Salvia divinorum (a plant containing a potent and selective κ receptor agonist) and a series of serotonergic psychedelics, including the endogenous serotonin 2A receptor agonist N,N-Dimethyltryptamine (DMT). This similarity was driven by semantic concepts related to consciousness of the self and the environment, but also by those associated with the therapeutic, ceremonial and religious aspects of drug use. Our analysis sheds light on the long-standing link between certain drugs and the experience of "dying", suggests that ketamine could be used as a safe and reversible experimental model for NDE phenomenology, and supports the speculation that endogenous NMDA antagonists with neuroprotective properties may be released in the proximity of death.

Dark Classics in Chemical Neuroscience: N, N-Dimethyltryptamine (DMT)

Though relatively obscure, N, N-dimethyltryptamine (DMT) is an important molecule in psychopharmacology as it is the archetype for all indole-containing serotonergic psychedelics. Its structure can be found embedded within those of better-known molecules such as lysergic acid diethylamide (LSD) and psilocybin. Unlike the latter two compounds, DMT is ubiquitous, being produced by a wide variety of plant and animal species. It is one of the principal psychoactive components of ayahuasca, a tisane made from various plant sources that has been used for centuries. Furthermore, DMT is one of the few psychedelic compounds produced endogenously by mammals, and its biological function in human physiology remains a mystery. In this review, we cover the synthesis of DMT as well as its pharmacology, metabolism, adverse effects, and potential use in medicine. Finally, we discuss the history of DMT in chemical neuroscience and why this underappreciated molecule is so important to the field of psychedelic science.