Monoamine oxidase inhibition in brain and liver produced by beta-carbolines: structure-activity relationships and substrate specificity

Harnessing Pharmacogenomics in Clinical Research on Psychedelic-Assisted Therapy

Psychedelics have recently re-emerged as potential treatments for various psychiatric conditions that impose major public health costs and for which current treatment options have limited efficacy. At the same time, personalized medicine is increasingly being implemented in psychiatry to provide individualized drug dosing recommendations based on genetics. This review brings together these topics to explore the utility of pharmacogenomics (a key component of personalized medicine) in psychedelic-assisted therapies. We summarized the literature and explored the potential implications of genetic variability on the pharmacodynamics and pharmacokinetics of psychedelic drugs including lysergic acid diethylamide (LSD), psilocybin, N,N-dimethyltryptamine (DMT), 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT), ibogaine and 3,4-methylenedioxymethamphetamine (MDMA). Although existing evidence is limited, particularly concerning pharmacodynamics, studies investigating pharmacokinetics indicate that genetic variants in drug-metabolizing enzymes, such as cytochrome P450, impact the intensity of acute psychedelic effects for LSD and ibogaine, and that a dose reduction for CYP2D6 poor metabolizers may be appropriate. Furthermore, based on the preclinical evidence, it can be hypothesized that CYP2D6 metabolizer status might contribute to altered acute psychedelic experiences with 5-MeO-DMT and psilocybin when combined with monoamine oxidase inhibitors. In conclusion, considering early evidence that genetic factors can influence the effects of certain psychedelics, we suggest that pharmacogenomic testing should be further investigated in clinical research. This is necessary to evaluate its utility in improving the safety and therapeutic profile of psychedelic therapies and a potential future role in personalizing psychedelic-assisted therapies, should these treatments become available.

Ayahuasca: pharmacology, safety, and therapeutic effects

Ayahuasca is a botanical hallucinogen traditionally used for therapeutic and ritual purposes by indigenous groups from Northwestern Amazonian countries such as Brazil, Peru, Colombia, and Ecuador. Ayahuasca is made by the decoction of two plants, which are rich in the 5-HT1A/2A partial agonist dimethyltryptamine or DMT (from the leaves of the Psychotria viridis bush) and β-carbolines such as harmine, from the stalks of the Banisteriopsis caapi vine. There is an increasing interest in the possible therapeutic effects of ayahuasca, especially for psychiatric disorders (major depression, posttraumatic stress disorder, and substance use disorder). This review summarizes information on the pharmacology, safety, and therapeutic potentials of ayahuasca. Although human experimental and naturalist studies published until now suggest a good safety and tolerability profile, often associated with improvements in depressive and anxious symptoms, there are few controlled studies, with small sample sizes, using only single doses, and with short follow-ups. Potential benefits of ayahuasca should be evaluated in larger samples in both experimental and observational studies and using different doses in controlled trials.

Ayahuasca: A review of historical, pharmacological, and therapeutic aspects

Ayahuasca is a psychedelic plant brew originating from the Amazon rainforest. It is formed from two basic components, the Banisteriopsis caapi vine and a plant containing the potent psychedelic dimethyltryptamine (DMT), usually Psychotria viridis. Here we review the history of ayahuasca and describe recent work on its pharmacology, phenomenological responses, and clinical applications. There has been a significant increase in interest in ayahuasca since the turn of the millennium. Anecdotal evidence varies significantly, ranging from evangelical accounts to horror stories involving physical and psychological harm. The effects of the brew on personality and mental health outcomes are discussed in this review. Furthermore, phenomenological analyses of the ayahuasca experience are explored. Ayahuasca is a promising psychedelic agent that warrants greater empirical attention regarding its basic neurochemical mechanisms of action and potential therapeutic application.

A journey with psychedelic mushrooms: From historical relevance to biology, cultivation, medicinal uses, biotechnology, and beyond

Psychedelic mushrooms containing psilocybin and related tryptamines have long been used for ethnomycological purposes, but emerging evidence points to the potential therapeutic value of these mushrooms to address modern neurological, psychiatric health, and related disorders. As a result, psilocybin containing mushrooms represent a re-emerging frontier for mycological, biochemical, neuroscience, and pharmacology research. This work presents crucial information related to traditional use of psychedelic mushrooms, as well as research trends and knowledge gaps related to their diversity and distribution, technologies for quantification of tryptamines and other tryptophan-derived metabolites, as well as biosynthetic mechanisms for their production within mushrooms. In addition, we explore the current state of knowledge for how psilocybin and related tryptamines are metabolized in humans and their pharmacological effects, including beneficial and hazardous human health implications. Finally, we describe opportunities and challenges for investigating the production of psychedelic mushrooms and metabolic engineering approaches to alter secondary metabolite profiles using biotechnology integrated with machine learning. Ultimately, this critical review of all aspects related to psychedelic mushrooms represents a roadmap for future research efforts that will pave the way to new applications and refined protocols.

N, N-dimethyltryptamine forms oxygenated metabolites via CYP2D6 - an in vitro investigation

N, N-dimethyltryptamine (DMT) is a psychedelic compound that has shown potential in the treatment of depression. Aside from the primary role of monoamine oxidase A (MAO-A) in DMT metabolism, the metabolic pathways are poorly understood. Increasing this understanding is an essential aspect of ensuring safe and efficacious use of DMT.This work aimed to investigate the cytochrome 450 (CYP) mediated metabolism of DMT by incubating DMT with recombinant human CYP enzymes and human liver microsomes (HLM) followed by analysis using high-resolution mass spectrometry for metabolite identification.DMT was rapidly metabolised by CYP2D6, while stable with all other investigated CYP enzymes. The metabolism of DMT in HLM was reduced after inclusion of harmine and SKF-525A whereas quinidine did not affect the metabolic rate, likely due to MAO-A residues present in HLM. Analysis of the CYP2D6 incubates showed formation of mono-, di- and tri-oxygenated metabolites, likely as a result of hydroxylation on the indole core.More research is needed to investigate the role of this metabolic pathway in vivo and any pharmacological activity of the proposed metabolites. Our findings may impact on safety issues following intake of ayahuasca in slow CYP2D6 metabolizers or with concomitant use of CYP2D6 inhibitors.

Molecular Pathways of the Therapeutic Effects of Ayahuasca, a Botanical Psychedelic and Potential Rapid-Acting Antidepressant

Ayahuasca is a psychoactive brew traditionally used in indigenous and religious rituals and ceremonies in South America for its therapeutic, psychedelic, and entheogenic effects. It is usually prepared by lengthy boiling of the leaves of the bush Psychotria viridis and the mashed stalks of the vine Banisteriopsis caapi in water. The former contains the classical psychedelic N,N-dimethyltryptamine (DMT), which is thought to be the main psychoactive alkaloid present in the brew. The latter serves as a source for β-carbolines, known for their monoamine oxidase-inhibiting (MAOI) properties. Recent preliminary research has provided encouraging results investigating ayahuasca's therapeutic potential, especially regarding its antidepressant effects. On a molecular level, pre-clinical and clinical evidence points to a complex pharmacological profile conveyed by the brew, including modulation of serotoninergic, glutamatergic, dopaminergic, and endocannabinoid systems. Its substances also interact with the vesicular monoamine transporter (VMAT), trace amine-associated receptor 1 (TAAR1), and sigma-1 receptors. Furthermore, ayahuasca's components also seem to modulate levels of inflammatory and neurotrophic factors beneficially. On a biological level, this translates into neuroprotective and neuroplastic effects. Here we review the current knowledge regarding these molecular interactions and how they relate to the possible antidepressant effects ayahuasca seems to produce.

Serotonin toxicity of serotonergic psychedelics

RATIONALE

In recent years, psychedelic substances with serotonergic mechanisms have accumulated substantial evidence that they may provide therapeutic benefits for people suffering with psychiatric symptoms. Psychiatric disorders targeted by these psychedelic-assisted therapies are managed with serotonergic drugs like selective serotonin reuptake inhibitors (SSRIs) as the current standard of care, so it is important to evaluate the potential risks of drug-drug interactions and serotonin toxicity (ST) between these agents.

OBJECTIVES

A critical evaluation of the scientific literature is necessary to delineate the risks of ST when combining psychedelics with available serotonergic pharmacotherapy options. This review article describes signs and symptoms of ST, characterizes mechanisms of ST risk, summarizes what is known about serotonergic psychedelic drug interactions, and outlines potential management strategies.

RESULTS

True ST typically occurs with a serotonergic drug overdose or in combinations in which a drug that can increase intrasynaptic serotonin is combined with a monoamine oxidase inhibitor (MAOI). Serotonergic psychotropics that do not contain MAOIs are low risk in combination with psychedelics that also do not contain MAOIs. Signs and symptoms warranting immediate medical attention include myoclonus, extreme and fluctuating vital signs, agitation or comatose mental state, muscle rigidity, pronounced hyperthermia (fever), and/or seizure activity.

CONCLUSIONS

Serotonin-related adverse reactions exist along a spectrum with serotonin syndrome being the most severe manifestations of ST. Due to varying serotonergic mechanisms of psychedelics and psychotropics, with varying propensities to increase intrasynaptic serotonin, some combinations may present a significant risk for serotonin toxicity (ST) while others are likely benign.

The pharmacological interaction of compounds in ayahuasca: a systematic review

Ayahuasca is a South American psychoactive plant brew used as traditional medicine in spiritual and in cultural rituals. This is a review of the current understanding about the pharmacological mechanisms that may be interacting in ayahuasca. Searches were performed using PubMed, PsycINFO, and Web of Science databases and 16 papers were selected. As hypothesized, the primary narrative in existing research revolved around prevention of deamination of N,N-dimethyltryptamine (N,N-DMT, also referred to as DMT) by monoamine oxidase inhibitors (MAOIs) in ayahuasca. Two of the constituents, DMT and harmine, have been studied more than the secondary harmala alkaloids. At present, it is unclear whether the pharmacological interactions in ayahuasca act synergistically or additively to produce psychoactive drug effects. The included studies suggest that our current understanding of the preparation's synergistic mechanisms is limited and that more complex processes may be involved; there is not yet enough data to determine any potential synergistic interaction between the known compounds in ayahuasca. Our pharmacological understanding of its compounds must be increased to avoid the potential risks of ayahuasca use.

DMT alters cortical travelling waves

Psychedelic drugs are potent modulators of conscious states and therefore powerful tools for investigating their neurobiology. N,N, Dimethyltryptamine (DMT) can rapidly induce an extremely immersive state of consciousness characterized by vivid and elaborate visual imagery. Here, we investigated the electrophysiological correlates of the DMT-induced altered state from a pool of participants receiving DMT and (separately) placebo (saline) while instructed to keep their eyes closed. Consistent with our hypotheses, results revealed a spatio-temporal pattern of cortical activation (i.e. travelling waves) similar to that elicited by visual stimulation. Moreover, the typical top-down alpha-band rhythms of closed-eyes rest were significantly decreased, while the bottom-up forward wave was significantly increased. These results support a recent model proposing that psychedelics reduce the 'precision-weighting of priors', thus altering the balance of top-down versus bottom-up information passing. The robust hypothesis-confirming nature of these findings imply the discovery of an important mechanistic principle underpinning psychedelic-induced altered states.

Four Weekly Ayahuasca Sessions Lead to Increases in "Acceptance" Capacities: A Comparison Study With a Standard 8-Week Mindfulness Training Program

Background: The therapeutic effects of the Amazonian plant tea ayahuasca may relate to its ability to enhance mindfulness capacities. Ayahuasca induces a modified state of awareness through the combined action of its active principles: the psychedelic N,N-dimethyltryptamine (DMT) and a series of centrally acting β-carbolines, mainly harmine and tetrahydroharmine. To better understand the therapeutic potential of ayahuasca, here we compared the impact on mindfulness capacities induced by two independent interventions: (a) participation in four ayahuasca sessions without any specific purpose related to improving mindfulness capacities; and (b) participation in a standard mindfulness training course: 8 weeks mindfulness-based stress reduction (MBSR), with the specific goal of improving these skills.

Methods: Participants of two independent groups completed two self-report instruments: The Five Facet Mindfulness Questionnaire (FFMQ) and the Experiences Questionnaire (EQ). The MINDSENS Composite Index was also calculated, including those EQ and FFMQ items that have proven to be the most sensitive to meditation practice. Group A (n = 10) was assessed before and after the last of four closely spaced consecutive ayahuasca sessions. Group B (n = 10) was assessed before and after completion of a standard 8-week MBSR course.

Results: MBSR training led to greater increases in overall mindfulness scores after the 8-week period. MBSR but not ayahuasca led to increases in the MINDSENS Composite Index. However, the ayahuasca sessions induced comparable increases in the Non-Judging subscale of the FFMQ, specifically measuring “acceptance.” Improving this capacity allows for a more detached and less judgmental stance toward potentially distressing thoughts and emotions.

Results: The present findings suggest that a small number of ayahuasca sessions can be as effective at improving acceptance as more lengthy and costly interventions. Future studies should address the benefits of combining ayahuasca administration with mindfulness-based interventions. This will allow us to investigate if ayahuasca will improve the outcome of psychotherapeutic interventions.

The alkaloids of Banisteriopsis caapi, the plant source of the Amazonian hallucinogen Ayahuasca, stimulate adult neurogenesis in vitro

Banisteriopsis caapi is the basic ingredient of ayahuasca, a psychotropic plant tea used in the Amazon for ritual and medicinal purposes, and by interested individuals worldwide. Animal studies and recent clinical research suggests that B. caapi preparations show antidepressant activity, a therapeutic effect that has been linked to hippocampal neurogenesis. Here we report that harmine, tetrahydroharmine and harmaline, the three main alkaloids present in B. caapi, and the harmine metabolite harmol, stimulate adult neurogenesis in vitro. In neurospheres prepared from progenitor cells obtained from the subventricular and the subgranular zones of adult mice brains, all compounds stimulated neural stem cell proliferation, migration, and differentiation into adult neurons. These findings suggest that modulation of brain plasticity could be a major contribution to the antidepressant effects of ayahuasca. They also expand the potential application of B. caapi alkaloids to other brain disorders that may benefit from stimulation of endogenous neural precursor niches.

Ayahuasca Exposure: Descriptive Analysis of Calls to US Poison Control Centers from 2005 to 2015

BACKGROUND

Ayahuasca is a hallucinogenic plant preparation which usually contains the vine Banisteriopsis caapi and the shrub Psychotria viridis. This tea originates from the Amazon Basin where it is used in religious ceremonies. Because interest in these religious groups spreading as well as awareness of use of ayahuasca for therapeutic and recreational purposes, its use is increasing. Banisteriopsis caapi is rich in β-carbolines, especially harmine, tetrahydroharmine and harmaline, which have monoamine oxidase inhibiting (MAOI) activity. Psychotria viridis contains the 5HT2A/2C/1A receptor agonist hallucinogen N,N-dimethyltryptamine (DMT). Usual desired effects include hallucination, dissociation, mood alteration and perception change. Undesired findings previously reported are nausea, vomiting, hypertension, and tachycardia.

METHODS

All human exposure calls reported to the American Association of Poison Controls Centers' (AAPCC) National Poison Data System (NPDS) between September 1, 2005 and September 1, 2015 were reviewed. Cases were filtered for specific plant derived ayahuasca-related product codes. Abstracted data included the following: case age and gender, exposure reason, exposure route, clinical manifestations, treatments given, medical outcomes and fatality.

RESULTS

Five hundred and thirty-eight exposures to ayahuasca botanical products were reported. The majority of the calls to poison control centers came from healthcare facilities (83%). The most common route of exposure was ingestion. Most cases were men (437, 81%, 95% CI 77.7% - 84.3%). The median age was 21 (IQR 18-29). Most exposures were acute. Three hundred thirty-seven (63%) were reported to have a major or moderate clinical effect. The most common clinical manifestations reported were hallucinations (35%), tachycardia (34%), agitation (34%), hypertension (16%), mydriasis (13%) and vomiting (6%). Benzodiazepines were commonly given (30%). There were 28 cases in the series who required endotracheal intubation (5%). Four cases were reported to have had a cardiac arrest and 7 a respiratory arrest. Twelve cases had a seizure. Reports of exposures called to poison centers appeared to increase during this period based on annual estimates. Three fatalities were reported.

CONCLUSIONS

Ayahuasca use appears to be rising in the United States based on calls to poison control centers. While most use is reported to be safe and well tolerated, with possible beneficial effects, serious and life threatening adverse manifestations are possible. Most of the exposures reported to poison control centers were young people, more likely to be men and already in a healthcare facility. Further research, which includes comprehensive drug testing, will be needed to better identify the risks and effects of ayahuasca use.

Inhibition of alpha oscillations through serotonin-2A receptor activation underlies the visual effects of ayahuasca in humans

Ayahuasca is an Amazonian psychotropic plant tea typically obtained from two plants, Banisteriopsis caapi and Psychotria viridis. It contains the psychedelic 5-HT2A and sigma-1 agonist N,N-dimethyltryptamine (DMT) plus β-carboline alkaloids with monoamine-oxidase (MAO)-inhibiting properties. Although the psychoactive effects of ayahuasca have commonly been attributed solely to agonism at the 5-HT2A receptor, the molecular target of classical psychedelics, this has not been tested experimentally. Here we wished to study the contribution of the 5-HT2A receptor to the neurophysiological and psychological effects of ayahuasca in humans. We measured drug-induced changes in spontaneous brain oscillations and subjective effects in a double-blind randomized placebo-controlled study involving the oral administration of ayahuasca (0.75mg DMT/kg body weight) and the 5-HT2A antagonist ketanserin (40mg). Twelve healthy, experienced psychedelic users (5 females) participated in four experimental sessions in which they received the following drug combinations: placebo+placebo, placebo+ayahuasca, ketanserin+placebo and ketanserin+ayahuasca. Ayahuasca induced EEG power decreases in the delta, theta and alpha frequency bands. Current density in alpha-band oscillations in parietal and occipital cortex was inversely correlated with the intensity of visual imagery induced by ayahuasca. Pretreatment with ketanserin inhibited neurophysiological modifications, reduced the correlation between alpha and visual effects, and attenuated the intensity of the subjective experience. These findings suggest that despite the chemical complexity of ayahuasca, 5-HT2A activation plays a key role in the neurophysiological and visual effects of ayahuasca in humans.

Antidepressive, anxiolytic, and antiaddictive effects of ayahuasca, psilocybin and lysergic acid diethylamide (LSD): a systematic review of clinical trials published in the last 25 years

To date, pharmacological treatments for mood and anxiety disorders and for drug dependence show limited efficacy, leaving a large number of patients suffering severe and persistent symptoms. Preliminary studies in animals and humans suggest that ayahuasca, psilocybin and lysergic acid diethylamide (LSD) may have antidepressive, anxiolytic, and antiaddictive properties. Thus, we conducted a systematic review of clinical trials published from 1990 until 2015, assessing these therapeutic properties. Electronic searches were performed using the PubMed, LILACS, and SciELO databases. Only clinical trials published in peer-reviewed journals were included. Of these, 151 studies were identified, of which six met the established criteria. Reviewed studies suggest beneficial effects for treatment-resistant depression, anxiety and depression associated with life-threatening diseases, and tobacco and alcohol dependence. All drugs were well tolerated. In conclusion, ayahuasca, psilocybin and LSD may be useful pharmacological tools for the treatment of drug dependence, and anxiety and mood disorders, especially in treatment-resistant patients. These drugs may also be useful pharmacological tools to understand psychiatric disorders and to develop new therapeutic agents. However, all studies reviewed had small sample sizes, and half of them were open-label, proof-of-concept studies. Randomized, double-blind, placebo-controlled studies with more patients are needed to replicate these preliminary findings.

Behavioral and pharmacokinetic interactions between monoamine oxidase inhibitors and the hallucinogen 5-methoxy-N,N-dimethyltryptamine

Monoamine oxidase inhibitors (MAOIs) are often ingested together with tryptamine hallucinogens, but relatively little is known about the consequences of their combined use. We have shown previously that monoamine oxidase-A (MAO-A) inhibitors alter the locomotor profile of the hallucinogen 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT) in rats, and enhance its interaction with 5-HT2A receptors. The goal of the present studies was to investigate the mechanism for the interaction between 5-MeO-DMT and MAOIs, and to determine whether other behavioral responses to 5-MeO-DMT are similarly affected. Hallucinogens disrupt prepulse inhibition (PPI) in rats, an effect typically mediated by 5-HT2A activation. 5-MeO-DMT also disrupts PPI but the effect is primarily attributable to 5-HT1A activation. The present studies examined whether an MAOI can alter the respective contributions of 5-HT1A and 5-HT2A receptors to the effects of 5-MeO-DMT on PPI. A series of interaction studies using the 5-HT1A antagonist WAY-100,635 and the 5-HT2A antagonist MDL 11,939 were performed to assess the respective contributions of these receptors to the behavioral effects of 5-MeO-DMT in rats pretreated with an MAOI. The effects of MAO-A inhibition on the pharmacokinetics of 5-MeO-DMT and its metabolism to bufotenine were assessed using liquid chromatography-electrospray ionization-selective reaction monitoring-tandem mass spectrometry (LC-ESI-SRM-MS/MS). 5-MeO-DMT (1mg/kg) had no effect on PPI when tested 45-min post-injection but disrupted PPI in animals pretreated with the MAO-A inhibitor clorgyline or the MAO-A/B inhibitor pargyline. The combined effect of 5-MeO-DMT and pargyline on PPI was antagonized by pretreatment with either WAY-100,635 or MDL 11,939. Inhibition of MAO-A increased the level of 5-MeO-DMT in plasma and whole brain, but had no effect on the conversion of 5-MeO-DMT to bufotenine, which was found to be negligible. The present results confirm that 5-MeO-DMT can disrupt PPI by activating 5-HT2A, and indicate that MAOIs alter 5-MeO-DMT pharmacodynamics by increasing its accumulation in the central nervous system.

Exploring the therapeutic potential of Ayahuasca: acute intake increases mindfulness-related capacities

BACKGROUND

Ayahuasca is a psychotropic plant tea used for ritual purposes by the indigenous populations of the Amazon. In the last two decades, its use has expanded worldwide. The tea contains the psychedelic 5-HT2A receptor agonist N,N-dimethyltryptamine (DMT), plus β-carboline alkaloids with monoamine-oxidase-inhibiting properties. Acute administration induces an introspective dream-like experience characterized by visions and autobiographic and emotional memories. Studies of long-term users have suggested its therapeutic potential, reporting that its use has helped individuals abandon the consumption of addictive drugs. Furthermore, recent open-label studies in patients with treatment-resistant depression found that a single ayahuasca dose induced a rapid antidepressant effect that was maintained weeks after administration. Here, we conducted an exploratory study of the psychological mechanisms that could underlie the beneficial effects of ayahuasca.

METHODS

We assessed a group of 25 individuals before and 24 h after an ayahuasca session using two instruments designed to measure mindfulness capacities: The Five Facets Mindfulness Questionnaire (FFMQ) and the Experiences Questionnaire (EQ).

RESULTS

Ayahuasca intake led to significant increases in two facets of the FFMQ indicating a reduction in judgmental processing of experiences and in inner reactivity. It also led to a significant increase in decentering ability as measured by the EQ. These changes are classic goals of conventional mindfulness training, and the scores obtained are in the range of those observed after extensive mindfulness practice.

CONCLUSIONS

The present findings support the claim that ayahuasca has therapeutic potential and suggest that this potential is due to an increase in mindfulness capacities.

Soma, food of the immortals according to the Bower Manuscript (Kashmir, 6th century A.D.)

ETHNOPHARMACOLOGICAL RELEVANCE

Food is medicine and vice versa. In Hindu and Ayurvedic medicine, and among human cultures of the Indian subcontinent in general, the perception of the food-medicine continuum is especially well established. The preparation of the exhilarating, gold-coloured Soma, Amrita or Ambrosia, the elixir and food of the 'immortals'-the Hindu pantheon-by the ancient Indo-Aryans, is described in the Rigveda in poetic hymns. Different theories regarding the botanical identity of Soma circulate, but no pharmacologically and historically convincing theory exists to date. We intend to contribute to the botanical, chemical and pharmacological characterisation of Soma through an analysis of two historical Amrita recipes recorded in the Bower Manuscript. The recipes are referred therein as panaceas (clarified butter) and also as a medicine to treat nervous diseases (oil), while no exhilarating properties are mentioned. Notwithstanding this, we hypothesise, that these recipes are related to the ca. 1800 years older Rigvedic Soma. We suppose that the psychoactive Soma ingredient(s) are among the components, possibly in smaller proportions, of the Amrita recipes preserved in the Bower Manuscript.

MATERIALS AND METHODS

The Bower Manuscript is a medical treatise recorded in the 6th century A.D. in Sanskrit on birch bark leaves, probably by Buddhist monks, and unearthed towards the end of the 19th century in Chinese Turkestan. We analysed two Amrita recipes from the Bower Manuscript, which was translated by Rudolf Hoernle into English during the early 20th century. A database search with the updated Latin binomials of the herbal ingredients was used to gather quantitative phytochemical and pharmacological information.

RESULTS

Together, both Amrita recipes contain around 100 herbal ingredients. Psychoactive alkaloid containing species still important in Ayurvedic, Chinese and Thai medicine and mentioned in the recipe for 'Amrita-Prâsa clarified butter' and 'Amrita Oil' are: Tinospora cordifolia (Amrita, Guduchi), three Sida spp., Mucuna pruriens, Nelumbo nucifera, Desmodium gangeticum, and Tabernaemontana divaricata. These species contain several notorious and potential psychoactive and psychedelic alkaloids, namely: tryptamines, 2-phenylethylamine, ephedrine, aporphines, ibogaine, and L-DOPA. Furthermore, protoberberine alkaloids, tetrahydro-β-carbolines, and tetrahydroisoquinolines with monoamine oxidase inhibitor (MAO-I) activity but also neurotoxic properties are reported.

CONCLUSIONS

We propose that Soma was a combination of a protoberberine alkaloids containing Tinospora cordifolia juice with MAO-I properties mixed together with a tryptamine rich Desmodium gangeticum extract or a blending of Tinospora cordifolia with an ephedrine and phenylethylamine-rich Sida spp. extract. Tinospora cordifolia combined with Desmodium gangeticum might provide a psychedelic experience with visual effects, while a combination of Tinospora cordifolia with Sida spp. might lead to more euphoric and amphetamine-like experiences.

Discriminative stimulus effects of N,N-diisopropyltryptamine

RATIONALE

Serotonergic hallucinogens such as (+)-lysergic acid diethylamide (LSD) and dimethyltryptamine (DMT) produce distinctive visual effects, whereas the synthetic hallucinogen N,N-diisopropyltryptamine (DiPT) is known for its production of auditory distortions.

OBJECTIVE

This study compares the discriminative stimulus effects of DiPT to those of visual hallucinogens.

METHODS

Adult male rats were trained to discriminate DiPT (5 mg/kg, 15 min) from saline under a FR10 schedule. A dose-effect and time course of DiPT's discriminative stimulus effects were established. DMT, (-)-2,5-dimethoxy-4-methylamphetamine (DOM), LSD, (±)-methylenedioxymethamphetamine (MDMA), and (+)-methamphetamine were tested for cross-substitution in DiPT-trained animals.

RESULTS

Rats learned to discriminate DiPT from saline in an average of 60 training sessions (30 drug and 30 saline). DiPT (0.5-5 mg/kg) produced dose-dependent increases in drug-appropriate responding (DAR) to 99 % (ED(50) = 2.47 mg/kg). Onset of the discriminative stimulus effects was within 5 min, and the effects dissipated within 4 h. Full substitution for the discriminative stimulus effects of DiPT occurred with LSD, DOM, and MDMA. DMT only partially substituted for DiPT (65 % DAR), whereas (+)-methamphetamine failed to substitute for DiPT (29 % DAR).

CONCLUSIONS

The discriminative stimulus effects of DiPT were similar those of a number of synthetic hallucinogens, only partially similar to those of DMT, but not similar to (+)-methamphetamine. The putative DiPT-induced auditory distortions do not lead to discriminative stimulus effects distinguishable from other hallucinogens.

Monoamine oxidase inhibition by monoterpene indole alkaloids and fractions obtained from Psychotria suterella and Psychotria laciniata

Alkaloid fractions of Psychotria suterella (SAE) and Psychotria laciniata (LAE) as well as two monoterpene indole alkaloids (MIAs) isolated from these fractions were evaluated against monoamine oxidases (MAO-A and -B) obtained from rat brain mitochondria. SAE and LAE were analysed by HPLC-PDA and UHPLC/HR-TOF-MS leading to the identification of the compounds 1, 2, 3 and 4, whose identity was confirmed by NMR analyses. Furthermore, SAE and LAE were submitted to the enzymatic assays, showing a strong activity against MAO-A, characterized by IC(50) values of 1.37 ± 1.05 and 2.02 ± 1.08 μg/mL, respectively. Both extracts were also able to inhibit MAO-B, but in higher concentrations. In a next step, SAE and LAE were fractionated by RP-MPLC affording three and four major fractions, respectively. The RP-MPLC fractions were subsequently tested against MAO-A and -B. The RP-MPLC fractions SAE-F3 and LAE-F4 displayed a strong inhibition against MAO-A with IC(50) values of 0.57 ± 1.12 and 1.05 ± 1.15 μg/mL, respectively. The MIAs 1 and 2 also inhibited MAO-A (IC(50) of 50.04 ± 1.09 and 132.5 ± 1.33 μg/mL, respectively) and -B (IC(50) of 306.6 ± 1.40 and 162.8 ± 1.26 μg/mL, respectively), but in higher concentrations when compared with the fractions. This is the first work describing the effects of MIAs found in neotropical species of Psychotria on MAO activity. The results suggest that species belonging to this genus could consist of an interesting source in the search for new MAO inhibitors.

Autonomic, neuroendocrine, and immunological effects of ayahuasca: a comparative study with d-amphetamine

Ayahuasca is an Amazonian psychotropic plant tea combining the 5-HT2A agonist N,N-dimethyltryptamine (DMT) and monoamine oxidase-inhibiting β-carboline alkaloids that render DMT orally active. The tea, obtained from Banisteriopsis caapi and Psychotria viridis, has traditionally been used for religious, ritual, and medicinal purposes by the indigenous peoples of the region. More recently, the syncretistic religious use of ayahuasca has expanded to the United States and Europe. Here we conducted a double-blind randomized crossover clinical trial to investigate the physiological impact of ayahuasca in terms of autonomic, neuroendocrine, and immunomodulatory effects. An oral dose of encapsulated freeze-dried ayahuasca (1.0 mg DMT/kg body weight) was compared versus a placebo and versus a positive control (20 mg d-amphetamine) in a group of 10 healthy volunteers. Ayahuasca led to measurable DMT plasma levels and distinct subjective and neurophysiological effects that were absent after amphetamine. Both drugs increased pupillary diameter, with ayahuasca showing milder effects. Prolactin levels were significantly increased by ayahuasca but not by amphetamine, and cortisol was increased by both, with ayahuasca leading to the higher peak values. Ayahuasca and amphetamine induced similar time-dependent modifications in lymphocyte subpopulations. Percent CD4 and CD3 were decreased, whereas natural killer cells were increased. Maximum changes occurred around 2 hours, returning to baseline levels at 24 hours. In conclusion, ayahuasca displayed moderate sympathomimetic effects, significant neuroendocrine stimulation, and a time-dependent modulatory effect on cell-mediated immunity. Future studies on the health impact of long-term ayahuasca consumption should consider the assessment of immunological status in regular users.

Seeing with the eyes shut: neural basis of enhanced imagery following Ayahuasca ingestion

The hallucinogenic brew Ayahuasca, a rich source of serotonergic agonists and reuptake inhibitors, has been used for ages by Amazonian populations during religious ceremonies. Among all perceptual changes induced by Ayahuasca, the most remarkable are vivid "seeings." During such seeings, users report potent imagery. Using functional magnetic resonance imaging during a closed-eyes imagery task, we found that Ayahuasca produces a robust increase in the activation of several occipital, temporal, and frontal areas. In the primary visual area, the effect was comparable in magnitude to the activation levels of natural image with the eyes open. Importantly, this effect was specifically correlated with the occurrence of individual perceptual changes measured by psychiatric scales. The activity of cortical areas BA30 and BA37, known to be involved with episodic memory and the processing of contextual associations, was also potentiated by Ayahuasca intake during imagery. Finally, we detected a positive modulation by Ayahuasca of BA 10, a frontal area involved with intentional prospective imagination, working memory and the processing of information from internal sources. Therefore, our results indicate that Ayahuasca seeings stem from the activation of an extensive network generally involved with vision, memory, and intention. By boosting the intensity of recalled images to the same level of natural image, Ayahuasca lends a status of reality to inner experiences. It is therefore understandable why Ayahuasca was culturally selected over many centuries by rain forest shamans to facilitate mystical revelations of visual nature.

Beta-carboline alkaloids harmaline and harmalol induce melanogenesis through p38 mitogen-activated protein kinase in B16F10 mouse melanoma cells

Melanin synthesis is regulated by melanocyte specific enzymes and related transcription factors. β-carboline alkaloids including harmaline and harmalol are widely distributed in the environment including several plant families and alcoholic beverages. Presently, melanin content and tyrosinase activity were increased in melanoma cells by harmaline and harmalol in concentration- and time-dependent manners. Increased protein levels of tyrosinase, tyrosinase-related protein-1 (TRP-1), and TRP-2 were also evident. In addition, immunofluorescence and Western blot analyses revealed harmaline and harmalol increased cAMP response element binding protein phosphorylation and microphthalmia-associated transcription factor expression. In addition to studying the signaling that leads to melanogenesis, roles of the p38 MAPK pathways by the harmaline and harmalol were investigated. Harmaline and harmalol induced time-dependent phosphorylation of p38 MAPK. Harmaline and harmalol stimulated melanin synthesis and tyrosinase activity, as well as expression of tyrosinase and TRP-1 and TRP-2 indicating that these harmaline and harmalol induce melanogenesis through p38 MAPK signaling.

Bioactive Alkaloids from South American Psychotria and Related Species

Many important molecules have been discovered from tropical and sub-tropical plant biodiversity. However, the largest part of the chemical profile of such biodiversity remains unknown. Combining ethnopharmacological and chemotaxonomical investigation can be a good strategy in bioactive compound discovery. South American Psychotria species studied by this approach proved to be a rich source of new bioactive alkaloids, some of which bear unique chemical skeletons.

Harmol induces apoptosis by caspase-8 activation independently of Fas/Fas ligand interaction in human lung carcinoma H596 cells

The beta-carboline alkaloids are naturally existing plant substances. It is known that these alkaloids have a wide spectrum of neuropharmacological, psychopharmacological, and antitumor effects. Therefore, they have been traditionally used in oriental medicine for the treatment of various diseases including cancers and malaria. In this study, harmol and harmalol, which are beta-carboline alkaloids, were examined for their antitumor effect on human lung carcinoma cell lines, and structure-activity relationship was also investigated. H596, H226, and A549 cells were treated with harmol and harmalol, respectively. Apoptosis was induced by harmol only in H596 cells. In contrast, harmalol had negligible cytotoxicity in three cell lines. Harmol induced caspase-3, caspase-8, and caspase-9 activities and caspase-3 activities accompanied by cleavage of poly-(ADP-ribose)-polymerase. Furthermore, harmol treatment decreased the native Bid protein, and induced the release of cytochrome c from mitochondria to cytosol. The apoptosis induced by harmol was completely inhibited by caspase-8 inhibitor and partially inhibited by caspase-9 inhibitor. The antagonistic antibody ZB4 blocked Fas ligand-induced apoptosis, but had no effect on harmol-induced apoptosis. Harmol had no significant effect on the expression of Fas. In conclusion, our results showed that the harmol could cause apoptosis-inducing effects in human lung H596 cells through caspase-8-dependent pathway but independent of Fas/Fas ligand interaction.

Modification of the effects of 5-methoxy-N,N-dimethyltryptamine on exploratory behavior in rats by monoamine oxidase inhibitors

RATIONALE

The hallucinogenic tea known as ayahuasca is made from a combination of psychoactive plants that contribute the active components N,N-dimethyltryptamine (DMT) and 5-methoxy-DMT (5-MeO-DMT), as well as the monoamine oxidase (MAO) inhibitors (MAOIs) harmine and harmaline for oral activity.

OBJECTIVE

The present study examined the effects of 5-MeO-DMT in combination with MAOIs in rats using the behavioral pattern monitor, which enables analyses of patterns of locomotor activity and exploration. Interaction studies using the serotonin (5-HT)(1A) antagonist WAY-100635 (1.0 mg/kg) and the 5-HT(2A) antagonist MDL 11,939 (1.0 mg/kg) were also performed to assess the respective contributions of these receptors to the behavioral effects of 5-MeO-DMT in MAOI-treated animals.

RESULTS

5-MeO-DMT (0.01, 0.1, and 1.0 mg/kg) decreased locomotor activity and investigatory behavior. In rats pretreated with a behaviorally inactive dose of harmaline (0.1 mg/kg), 1.0 mg/kg 5-MeO-DMT had biphasic effects on locomotor activity, initially reducing locomotion and then increasing activity as time progressed. The ability of harmaline to shift 5-MeO-DMT to a biphasic locomotor pattern was shared by the selective MAO(A) inhibitor clorgyline, whereas the selective MAO(B) inhibitor (-)-deprenyl was ineffective. The late hyperactivity induced by the combination of 1.0 mg/kg 5-MeO-DMT and 0.3 mg/kg clorgyline was blocked by pretreatment with MDL 11,939. Pretreatment with WAY-100635 failed to attenuate either the early hypoactivity or the late hyperactivity.

CONCLUSIONS

The ability of harmaline to modify the behavioral effects of 5-MeO-DMT is mediated by the inhibition of MAO(A). Furthermore, 5-HT(2A) receptors are responsible for the late hyperactivity induced by 5-MeO-DMT in the presence of MAO(A) inhibitors.

A case of beta-carboline alkaloid intoxication following ingestion of Peganum harmala seed extract

Beta-carboline alkaloids harmine, harmaline, and tetrahydroharmine can stimulate the central nervous system by inhibiting the metabolism of amine neurotransmitters, or by direct interaction with specific receptors; they are found in numerous plants, including Peganum harmala, Passiflora incarnata and Banisteriopsis caapi, and in the entheogen preparation Ayahuasca, which is traditionally brewed using B. caapi to enhance the activity of amine hallucinogenic drugs. The ingestion of plant preparations containing beta-carboline alkaloids may result in toxic effects, namely visual and auditory hallucinations, locomotor ataxia, nausea, vomiting, confusion and agitation. We report a case of intoxication following intentional ingestion of P. harmala seed infusion; P. harmala seeds were bought over the Internet. The harmala alkaloids were identified by gas chromatography-mass spectrometry in the seed extract and the patient's urine. This is, to our knowledge, the first case of P. harmala intoxication corroborated by toxicological findings.

Daytime Ayahuasca administration modulates REM and slow-wave sleep in healthy volunteers

OBJECTIVES

Ayahuasca is a traditional South American psychoactive beverage and the central sacrament of Brazilian-based religious groups, with followers in Europe and the United States. The tea contains the psychedelic indole N,N-dimethyltryptamine (DMT) and beta-carboline alkaloids with monoamine oxidase-inhibiting properties that render DMT orally active. DMT interacts with serotonergic neurotransmission acting as a partial agonist at 5-HT(1A) and 5-HT(2A/2C) receptor sites. Given the role played by serotonin in the regulation of the sleep/wake cycle, we investigated the effects of daytime ayahuasca consumption in sleep parameters.

MEASUREMENTS AND RESULTS

Subjective sleep quality, polysomnography (PSG), and spectral analysis were assessed in a group of 22 healthy male volunteers after the administration of a placebo, an ayahuasca dose equivalent to 1 mg DMT kg(-1) body weight, and 20 mg d-amphetamine, a proaminergic drug, as a positive control. Results show that ayahuasca did not induce any subjectively perceived deterioration of sleep quality or PSG-measured disruptions of sleep initiation or maintenance, in contrast with d-amphetamine, which delayed sleep initiation, disrupted sleep maintenance, induced a predominance of 'light' vs 'deep' sleep and significantly impaired subjective sleep quality. PSG analysis also showed that similarly to d-amphetamine, ayahuasca inhibits rapid eye movement (REM) sleep, decreasing its duration, both in absolute values and as a percentage of total sleep time, and shows a trend increase in its onset latency. Spectral analysis showed that d-amphetamine and ayahuasca increased power in the high frequency range, mainly during stage 2. Remarkably, whereas slow-wave sleep (SWS) power in the first night cycle, an indicator of sleep pressure, was decreased by d-amphetamine, ayahuasca enhanced power in this frequency band.

CONCLUSIONS

Results show that daytime serotonergic psychedelic drug administration leads to measurable changes in PSG and sleep power spectrum and suggest an interaction between these drugs and brain circuits modulating REM and SWS.

Coupled hydrogen-bonding interactions between beta-carboline derivatives and acetic acid

In this work, we have analysed the tendency of two beta-carboline derivatives, harmane and norharmane, in the formation of hydrogen bonds. We obtained the (1)H and (13)C NMR spectra of different mixtures of these derivatives with acetic acid (AcOH) in CDCl(3). A cyclic 1:3 complex is proposed between harmane and AcOH, while a 1:2 complex is proposed for norharmane. Chemical shifts at temperatures between 233 and 323 K were measured: lowering the temperature produces the same effect as increasing the amount of AcOH in solution. The (13)C data confirm a delocalisation of the pi electron density towards the pyridinic ring that occurs when AcOH is added.

Increased frontal and paralimbic activation following ayahuasca, the pan-Amazonian inebriant

RATIONALE

Ayahuasca is a South American psychoactive plant tea which contains the serotonergic psychedelic N,N-dimethyltryptamine (DMT) and monoamine-oxidase inhibitors that render DMT orally active. Previous investigations with ayahuasca have highlighted a psychotropic effect profile characterized by enhanced introspective attention, with individuals reporting altered somatic perceptions and intense emotional modifications, frequently accompanied by visual imagery. Despite recent advances in the study of ayahuasca pharmacology, the neural correlates of acute ayahuasca intoxication remain largely unknown.

OBJECTIVES

To investigate the effects of ayahuasca administration on regional cerebral blood flow.

METHODS

Fifteen male volunteers with prior experience in the use of psychedelics received a single oral dose of encapsulated freeze-dried ayahuasca equivalent to 1.0 mg DMT/kg body weight and a placebo in a randomized double-blind clinical trial. Regional cerebral blood flow was measured 100-110 min after drug administration by means of single photon emission tomography (SPECT).

RESULTS

Ayahuasca administration led to significant activation of frontal and paralimbic brain regions. Increased blood perfusion was observed bilaterally in the anterior insula, with greater intensity in the right hemisphere, and in the anterior cingulate/frontomedial cortex of the right hemisphere, areas previously implicated in somatic awareness, subjective feeling states, and emotional arousal. Additional increases were observed in the left amygdala/parahippocampal gyrus, a structure also involved in emotional arousal.

CONCLUSIONS

The present results suggest that ayahuasca interacts with neural systems that are central to interoception and emotional processing and point to a modulatory role of serotonergic neurotransmission in these processes.

Bringing Ayahuasca to the Clinical Research Laboratory

Since the winter of 1999, the authors and their research team have been conducting clinical studies involving the administration of ayahuasca to healthy volunteers. The rationale for conducting this kind of research is twofold. First, the growing interest of many individuals for traditional indigenous practices involving the ingestion of natural psychotropic drugs such as ayahuasca demands the systematic study of their pharmacological profiles in the target species, i.e., human beings. The complex nature of ayahuasca brews combining a large number of pharmacologically active compounds requires that research be carried out to establish the safety and overall pharmacological profile of these products. Second, the authors believe that the study of psychedelics in general calls for renewed attention. Although the molecular and electrophysiological level effects of these drugs are relatively well characterized, current knowledge of the mechanisms by which these compounds modify the higher order cognitive processes in the way they do is still incomplete, to say the least. The present article describes the development of the research effort carried out at the Autonomous University of Barcelona, commenting on several methodological aspects and reviewing the basic clinical findings. It also describes the research currently underway in our laboratory, and briefly comments on two new studies we plan to undertake in order to further our knowledge of the pharmacology of ayahuasca.

Synthesis, acute toxicities, and antitumor effects of novel 9-substituted β-carboline derivatives

A series of novel 9-substituted beta-carboline derivatives was synthesized from harmine and l-tryptophan, respectively. Cytotoxic activities of these compounds in vitro were investigated. The results showed that most compounds of 9-substituted beta-carboline derivatives had more remarkable cytotoxic activities in vitro than their corresponding parent compounds. Acute toxicities and antitumor effects of the selected beta-carboline derivatives in mice were also examined. The results demonstrated that a short alkyl or benzyl substituent at position-9 increased the antitumor activities significantly and a ethoxycarbonyl or carboxyl substituent at position-3 reduced the acute toxicity and neurotoxicity of these beta-carboline derivatives dramatically. Moreover the compounds both with an alkoxycarbonyl or carboxyl substituent at position-3 and a short alkyl or benzyl substituent at positon-9 exhibited more significant antitumor activities and lower acute toxicities and neurotoxicities than the other compounds. The compound 8c, having an n-butyl and a carboxyl substituent at position-9 and 3, respectively, was found to have the highest antitumor effect and the lowest acute toxicity and neurotoxicity. These data suggested that (1) appropriate substituents at both position-9 and 3 of beta-carboline derivatives might play a crucial role in determining their enhanced antitumor activities and decreased acute toxicities and neurotoxic effects; (2) the beta-carboline derivatives have the potential to be used as antitumor drug leads.

Clinical investigations of the therapeutic potential of ayahuasca: rationale and regulatory challenges

Ayahuasca is a hallucinogenic beverage that is prominent in the ethnomedicine and shamanism of indigenous Amazonian tribes. Its unique pharmacology depends on the oral activity of the hallucinogen, N,N-dimethyltryptamine (DMT), which results from inhibition of monoamine oxidase (MAO) by beta-carboline alkaloids. MAO is the enzyme that normally degrades DMT in the liver and gut. Ayahuasca has long been integrated into mestizo folk medicine in the northwest Amazon. In Brazil, it is used as a sacrament by several syncretic churches. Some of these organizations have incorporated in the United States. The recreational and religious use of ayahuasca in the United States, as well as "ayahuasca tourism" in the Amazon, is increasing. The current legal status of ayahuasca or its source plants in the United States is unclear, although DMT is a Schedule I controlled substance. One ayahuasca church has received favorable rulings in 2 federal courts in response to its petition to the Department of Justice for the right to use ayahuasca under the Religious Freedom Restoration Act. A biomedical study of one of the churches, the Uñiao do Vegetal (UDV), indicated that ayahuasca may have therapeutic applications for the treatment of alcoholism, substance abuse, and possibly other disorders. Clinical studies conducted in Spain have demonstrated that ayahuasca can be used safely in normal healthy adults, but have done little to clarify its potential therapeutic uses. Because of ayahuasca's ill-defined legal status and variable botanical and chemical composition, clinical investigations in the United States, ideally under an approved Investigational New Drug (IND) protocol, are complicated by both regulatory and methodological issues. This article provides an overview of ayahuasca and discusses some of the challenges that must be overcome before it can be clinically investigated in the United States.

Human pharmacology of ayahuasca: subjective and cardiovascular effects, monoamine metabolite excretion, and pharmacokinetics

The effects of the South American psychotropic beverage ayahuasca on subjective and cardiovascular variables and urine monoamine metabolite excretion were evaluated, together with the drug's pharmacokinetic profile, in a double-blind placebo-controlled clinical trial. This pharmacologically complex tea, commonly obtained from Banisteriopsis caapi and Psychotria viridis, combines N,N-dimethyltryptamine (DMT), an orally labile psychedelic agent showing 5-hydroxytryptamine2A agonist activity, with monoamine oxidase (MAO)-inhibiting beta-carboline alkaloids (harmine, harmaline, and tetrahydroharmine). Eighteen volunteers with prior experience in the use of psychedelics received single oral doses of encapsulated freeze-dried ayahuasca (0.6 and 0.85 mg of DMT/kg of body weight) and placebo. Ayahuasca produced significant subjective effects, peaking between 1.5 and 2 h, involving perceptual modifications and increases in ratings of positive mood and activation. Diastolic blood pressure showed a significant increase at the high dose (9 mm Hg at 75 min), whereas systolic blood pressure and heart rate were moderately and nonsignificantly increased. Cmax values for DMT after the low and high ayahuasca doses were 12.14 ng/ml and 17.44 ng/ml, respectively. Tmax (median) was observed at 1.5 h after both doses. The Tmax for DMT coincided with the peak of subjective effects. Drug administration increased urinary normetanephrine excretion, but, contrary to the typical MAO-inhibitor effect profile, deaminated monoamine metabolite levels were not decreased. This and the negligible harmine plasma levels found suggest a predominantly peripheral (gastrointestinal and liver) site of action for harmine. MAO inhibition at this level would suffice to prevent first-pass metabolism of DMT and allow its access to systemic circulation and the central nervous system.

The psychoactive flora of Papua New Guinea

This article reviews the literature and current information on the psychoactive flora of Papua New Guinea. The use of psychoactive plants in Papua New Guinea has often been reported in the literature. However, most of these species are still poorly understood. It is recommended in this article that more systematic and multidisciplinary research is required on the psychoactive flora of Papua New Guinea. This rsearch has the potential for the discovery and understanding of new psychoactive drugs.

Isolation and identification of two [(3)H]norharman- ([(3)H]beta-carboline)-binding proteins from rat liver

Norharman (9H-pyrido-[3,4-b]indol) represents a member of the mammalian alkaloids with the group name beta-carbolines. In mammals, it exhibits psychotropic and co-mutagenic actions. Highly specific [(3)H]norharman binding sites have been detected in the liver of rats (B(max): 11 pmol mg(-1) protein; K(D): lower nanomolar range). Two [(3)H]norharman binding proteins with apparent molecular masses of 60 and 80 kDa (SDS-PAGE) were isolated from rat liver crude membrane fraction and identified as the enzyme carboxylesterase (EC 3.1.1.1; 60 kDa) and the stress protein glucose-regulated protein 78 (GRP78; 78 kDa). Possible functional consequences of the interaction of norharman with these two proteins are discussed.

Elevation of blood beta-carboline alkaloids in essential tremor

BACKGROUND

beta-Carboline alkaloids are normal body constituents but are also potent tremor-producing chemicals that are naturally present in the food chain.

OBJECTIVE

To explore the hypothesis that high concentrations of beta-carboline alkaloids are associated with essential tremor (ET).

METHODS

One hundred cases and 100 controls were frequency matched on age, sex, and ethnicity. Blood concentrations of harmane and harmine were quantified by high-performance liquid chromatography, blinded to clinical information.

RESULTS

The mean log blood concentration of harmane was higher in cases than controls (0.72 +/- 0.53 vs 0.51 +/- 0.64 g(-10)/mL; p = 0.01). A nonparametric test on nontransformed data (median harmane = 5.21 g(-10)/mL in cases and 2.28 g(-10)/mL in controls) confirmed this difference (p = 0.005). The mean log blood concentration of harmine was 0.20 +/- 0.48 g(-10)/mL in cases and 0.10 +/- 0.65 g (-10)/mL in controls (p = 0.20). Log harmane concentrations were stratified based on the median value; 62% of cases vs 39% of controls had a high log harmane concentration (p = 0.001). Mean log harmane concentration was similar in the cases with (0.74 +/- 0.58 g(-10)/mL) and without (0.71 +/- 0.50 g(-10)/mL) an affected relative (p = 0.83).

CONCLUSIONS

Blood concentrations of harmane were measured in ET cases compared with controls. Concentrations were elevated in cases with and without a family history of ET.

Snuff synergy: preparation, use and pharmacology of yopo and Banisteriopsis caapi among the Piaroa of southern Venezuela

Current understanding of the preparation and use of yopo, a hallucinogenic snuff made from the ground seeds of the Anadenanthera peregrina tree, has departed little from the accounts of scientists and travelers made over a century ago. Schultes and others have made refinements to these early accounts. While several scholars have drawn attention to the fact that little ethnographic work has been conducted to assess the ethnobotanical diversity and cultural framework of the snuff hallucinogen complex, few subsequent studies deal with botanical variations in preparation and use. This article contrasts historical accounts of yopo preparation with ethnographic data I have recently collected among the Piaroa of southern Venezuela to demonstrate one way in which yopo preparation and use deviates from the basic model established by Humboldt, Spruce and Safford. Piaroa shamans include B. caapi cuttings in the preparation of yopo and consume doses of B. caapi prior to snuff inhalation concomitant with the strength of visions desired for particular tasks. I argue that the combined use of yopo and B. caapi by Piaroa shamans is pharmacologically and ethnobotanically significant, and substantiates claims of the use of admixtures in snuff; further ethnographic investigation of the snuff hallucinogen complex is necessary.

Characterization of the discriminable stimulus produced by 2-BFI: effects of imidazoline I(2)-site ligands, MAOIs, beta-carbolines, agmatine and ibogaine

1. The molecular nature and functions of the I(2) subtype of imidazoline binding sites are unknown but evidence suggests an association with monoamine oxidase (MAO). Rats can distinguish the selective imidazoline I(2)-site ligand 2-BFI from vehicle in drug discrimination, indicating functional consequences of occupation of these sites. We have used drug discrimination to investigate the nature of the discriminable stimulus, especially in relation to MAO inhibition. 2. Following training to distinguish 2-BFI 7 mg kg(-1) i.p. from saline vehicle in two-lever operant-chambers, male Hooded Lister rats underwent sessions where test substances were given instead and the proportion of lever presses on the 2-BFI-associated lever (substitution) recorded. 3. 2-BFI; its cogeners BU216, BU224, BU226 and LSL60101; the reversible MAO-A inhibitors moclobemide and RO41-1049; the beta-carbolines harmane, norharmane and harmaline which also reversibly inhibit MAO-A, and the anti-addictive substance ibogaine exhibited potent, dose-dependent substitution for 2-BFI. 4. Agmatine, and LSL60125 substituted at one dose only. The reversible MAO-B inhibitors lazabemide and RO16-1649; the sigma(2)-site ligand SKF10,047 and the I(2A)-site ligand, amiloride, failed to substitute. The irreversible inhibitor of MAO, deprenyl, substituted for 2-BFI while clorgyline did not. 5. These results suggest imidazoline I(2) site ligands produce a common discriminable stimulus that appears associated with reversible inhibition of MAO-A rather than MAO-B, possibly through increases in extracellular concentration of one or more monoamines. Ibogaine exhibits a commonality in its subjective effects with those of I(2)-site ligands.

Comparative effects of dehydropirlindole and other compounds on rat brain monoamine oxidase type A

Dehydropirlindole (DHP) is the dehydroderivative of pirlindole, a short-acting inhibitor of monoamine oxidase type A (MAO-A). DHP would be formed in vivo from oxidation of pirlindole by MAO-A. The aim of this work is to compare the inhibitory potency of DHP with three reference compounds: harmaline, befloxatone and clorgyline; the two former are reversible inhibitors and the later is an irreversible inhibitor of MAO-A. Both in vitro and ex vivo assays were performed on rat brain homogenates, and IC50 and ID50 were calculated by a fluorometric method with octopamine as selective MAO-A substrate. In vitro clorgyline and befloxatone were more potent inhibitors than DHP and harmaline with IC50 values of 1.6 and 7.7 nM vs. 40 and 55 nM; ex vivo ID50 values were 1.5 and 32 micromol/kg vs. 41 and 49 micromol/kg. Befloxatone had an ID50/IC50 ratio four to five times higher than DHP and harmaline. Preincubation time experiments did not distinguish befloxatone from DHP and harmaline. In conclusion, this study shows that DHP behaves as a reversible MAO-A inhibitor whose potency is situated between that of befloxatone and harmaline.