Effects of the hallucinogenic beverage ayahuasca on voluntary ethanol intake by rats and on cFos expression in brain areas relevant to drug addiction

Epigenetic drugs and psychedelics as emerging therapies for alcohol use disorder: insights from preclinical studies

Alcohol use disorder (AUD) is a public health issue that affects millions of people worldwide leading to physical, mental and socio-economic consequences. While current treatments for AUD have provided relief to individuals, their effectiveness on the long term is often limited, leaving a number of affected individuals without sustainable solutions. In this review, we aim to explore two emerging approaches for AUD: psychedelics and epigenetic drugs (i.e., epidrugs). By examining preclinical studies, different animal species and procedures, we delve into the potential benefits of each of these treatments in terms of addictive behaviors (alcohol drinking and seeking, motivation to drink alcohol and prevention of relapse). Because psychedelics and epidrugs may share common and complementary mechanisms of action, there is an exciting opportunity for exploring synergies between these approaches and their parallel effectiveness in treating AUD and the diverse associated psychiatric conditions.

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 Systematic Review on the Therapeutic Effects of Ayahuasca

Traditional therapies, resorting to the use of plants, have acquired a great demand over the years, both for economic reasons and the preference for natural treatments. Some studies suggest that ayahuasca may have beneficial properties in treating some physical and psychological imbalances. Thus, we carried out a systematic review of studies published up to December 2022, where these themes were addressed. The search was carried out in the PubMed database, and only studies written in English and published in peer-reviewed journals were included. Thus, 228 publications were identified, of which 66 were included in the present study. The reviewed studies suggest that ayahuasca may have beneficial effects on various physical and psychological conditions, namely in the treatment of depression, anxiety and various diseases of the neurobiological system, as well as anti-inflammatory and antimicrobial properties, demonstrating its therapeutic potential. The number of studies that address this issue has also been growing, demonstrating interest in the search for alternative treatments. However, to the best of our knowledge, this is the first systematic review where all the findings of therapeutic effects associated with the consumption of ayahuasca are reviewed.

The current state of ayahuasca research in animal models: A systematic review

RATIONALE

The psychedelic brew ayahuasca is increasingly being investigated for its therapeutic potential. Animal models are essential to investigate the pharmacological effects of ayahuasca since they can control important factors influencing it, such as the set and setting.

OBJECTIVE

Review and summarise data available on ayahuasca research using animal models.

METHODS

We systematically searched five databases (PubMed, Web of Science, EMBASE, LILACS and PsycInfo) for peer-reviewed studies in English, Portuguese or Spanish published up to July 2022. The search strategy included ayahuasca- and animal model-related terms adapted from the SYRCLE search syntax.

RESULTS

We identified 32 studies investigating ayahuasca effects on toxicological, behavioural and (neuro)biological parameters in rodents, primates and zebrafish. Toxicological results show that ayahuasca is safe at ceremonial-based doses but toxic at high doses. Behavioural results indicate an antidepressant effect and a potential to reduce the reward effects of ethanol and amphetamines, while the anxiety-related outcomes are yet inconclusive; also, ayahuasca can influence locomotor activity, highlighting the importance of controlling the analysis for locomotion when using tasks depending on it. Neurobiological results show that ayahuasca affects brain structures involved in memory, emotion and learning and that other neuropathways, besides the serotonergic action, are important in modulating its effects.

CONCLUSIONS

Studies using animal models indicate that ayahuasca is toxicologically safe in ceremonial-comparable doses and indicates a therapeutic potential for depression and substance use disorder while not supporting an anxiolytic effect. Essential gaps in the ayahuasca field can still be sufficed using animal models.

Ayahuasca's therapeutic potential: What we know - and what not

The therapeutic potential of the psychedelic brew ayahuasca has been investigated in preclinical and clinical studies. Currently, the most consistent evidence refers to depression. However, various studies suggest that ayahuasca may comprise therapeutic benefits in other health conditions. This narrative review provides a comprehensive, up-to-date overview of ayahuasca's therapeutic effects in diverse clinical conditions in human (clinical, cross-sectional, observational, and qualitative) and preclinical (animal and in vitro) studies. In addition to summarizing and discussing the most commonly studied conditions, such as depression, anxiety, and substance use disorders (SUD), we also examine less frequently studied psychiatric, neurological, and physical conditions. Moreover, we discuss evidence from epidemiological studies on the impact of regular, long-term ayahuasca use on health and psychosocial outcomes. Overall, evidence for depression and SUD is more consistent, with numerous and diverse studies. However, a growing body of evidence suggests that other conditions equally relevant to public health might be promising targets for ayahuasca's therapeutic effects. This includes preliminary studies indicating potential for grief, eating disorders, posttraumatic stress disorder, personality disorders, Parkinson's and Alzheimer's disease, and severe physical illnesses (e.g., cancer, chronic conditions). Moreover, preliminary evidence in long-term ayahuasca users does not suggest detrimental effects but possible benefits for individual and collective health. In light of the emerging evidence of psychedelic drugs as therapeutic agents, it is essential to further investigate in rigorous designs the therapeutic potential of ayahuasca in conditions other than depression.

Classic psychedelics and alcohol use disorders: A systematic review of human and animal studies

Classic psychedelics refer to substances such as lysergic acid diethylamide (LSD), psilocybin, ayahuasca, and mescaline, which induce altered states of consciousness by acting mainly on 5-HT_2A receptors. Recently, the interest of psychedelics as pharmacological treatment for psychiatric disorders has increased significantly, including their use on problematic use of alcohol. This systematic review is aimed to analyse the last two decades of studies examining the relationship between classic psychedelics and alcohol consumption. We searched PubMed and PsycInfo for human and preclinical studies published between January 2000 to December 2021. The search identified 639 publications. After selection, 27 studies were included. Human studies (n = 20) generally show promising data and seem to indicate that classic psychedelics could help reduce alcohol consumption. Nevertheless, some of these studies present methodological concerns such as low number of participants, lack of control group or difficulty in determining the effect of classic psychedelics in isolation. On the other hand, preclinical studies (n = 7) investigating the effect of these compounds on voluntary alcohol consumption are scarce and show some conflicting data. Among these compounds, psilocybin seems to show the most consistent data indicating that this compound could be a potential candidate to treat alcohol use disorders. In the absence of understanding the biological and/or psychological mechanisms, more studies including methodological quality parameters are needed to finally determine the effects of classic psychedelics on alcohol consumption.

Effects of ayahuasca and its alkaloids on substance use disorders: an updated (2016-2020) systematic review of preclinical and human studies

Ayahuasca is a hallucinogenic/psychedelic traditionally used for ritual and therapeutic purposes. One such therapeutic use is related to Substance Use Disorders (SUDs). A previous systematic review of preclinical and human studies published until 2016 suggested that ayahuasca and its alkaloids have therapeutic effects in the treatment of SUDs. To conduct an update of this previous review. A systematic review of quantitative studies which analyzed the effects of ayahuasca and its alkaloids on drug use (primary outcome) and other measures (secondary outcomes) related to SUDs was conducted, including articles from 2016 to 2020. Nine studies (four preclinical, five observational) were included in the review. Preclinical studies in rodents reported reductions in amphetamine self-administration and anxiety, and in alcohol- and methylphenidate-induced conditioned place preference. Observational studies among healthy ritual ayahuasca users and patients with SUDs reported reductions in drug use, anxiety, and depression, and increases in quality of life and well-being. We replicated the findings of the previous review suggesting that ayahuasca and its alkaloids have therapeutic effects in the treatment of SUDs. However, translation of preclinical data to humans is limited, observational studies do not allow us to infer causality, and there is a lack of standardization on ayahuasca doses. Although promising, randomized, controlled trials are needed to better elucidate these results. The PROSPERO ID for this study is CRD42020192046.

Role of 5-HT2A receptors in the effects of ayahuasca on ethanol self-administration using a two-bottle choice paradigm in male mice

RATIONALE

Ayahuasca has been proposed as a potential treatment of alcohol (ethanol) use disorder (AUD). The serotonin 5-HT2A receptor agonist N,N-dimethyltryptamine (DMT) is the main psychoactive component of ayahuasca, suggesting that its therapeutic effects may be mediated by 5-HT2A receptors.

OBJECTIVES

The aim of the present study was to investigate the effects of ayahuasca on the expression of ethanol self-administration using a two-bottle choice procedure and the role of 5-HT2A receptors in those effects.

METHODS

Male mice had intermittent access to ethanol (10% v/v) in a two-bottle choice procedure for 30 days. Animals were then submitted to 3 treatment phases, each followed by ethanol re-exposure tests. During the treatment phase, every 3 days, animals received i.p. injections of either vehicle or the 5-HT2A receptor antagonist M100907 (M100, 1 mg/kg) followed by an i.g. (gavage) administration of vehicle or ayahuasca (100 mg/kg) and were exposed to the self-administration apparatus with no ethanol availability. During re-exposure tests, animals were submitted to the same conditions as during acquisition, with no treatments prior to those sessions.

RESULTS

Treatment with ayahuasca blocked the expression of ethanol self-administration, decreasing ethanol intake and preference during re-exposure tests. Pretreatment with M100 blocked the effects of ayahuasca on ethanol drinking without significantly attenuating ethanol self-administration.

CONCLUSIONS

Treatment with ayahuasca during alcohol abstinence blocked the expression of alcohol self-administration in mice, and 5-HT2A receptor activation is critical for those effects to emerge. Our findings support a potential for ayahuasca and other 5-HT2A receptor agonists as adjunctive pharmacotherapies for the treatment of AUD.

Components of Banisteriopsis caapi, a Plant Used in the Preparation of the Psychoactive Ayahuasca, Induce Anti-Inflammatory Effects in Microglial Cells

Banisteriopsis caapi is used to prepare the psychoactive beverage ayahuasca, and both have therapeutic potential for the treatment of many central nervous system (CNS) conditions. This study aimed to isolate new bioactive compounds from B. caapi extract and evaluate their biological activity, and that of the known β-carboline components of the plant (harmine, harmaline, and tetrahydroharmine), in BV-2 microglial cells, the in vivo activation of which is implicated in the physiopathology of CNS disorders. B. caapi extract was fractionated using semipreparative liquid chromatography (HPLC-DAD) and the exact masses ([M + H]⁺m/z) of the compounds in the 5 isolated fractions were determined by high-resolution LC-MS/MS: F1 (174.0918 and 233.1289), F2 (353.1722), F3 (304.3001), F4 (188.1081), and F5 (205.0785). Harmine (75.5–302 µM) significantly decreased cell viability after 2 h of treatment and increased the number of necrotic cells and production of reactive oxygen species at equal or lower concentrations after 24 h. F4 did not impact viability but was also cytotoxic after 24 h. Most treatments reduced proinflammatory cytokine production (IL-2, IL-6, IL-17, and/or TNF), especially harmaline and F5 at 2.5 µM and higher concentrations, tetrahydroharmine (9.3 µM and higher), and F5 (10.7 µM and higher). The results suggest that the compounds found in B. caapi extract have anti-inflammatory potential that could be explored for the development of treatments for neurodegenerative diseases.

Ayahuasca blocks ethanol preference in an animal model of dependence and shows no acute toxicity

ETHNOPHARMACOLOGICAL RELEVANCE

Ayahuasca, a psychoactive beverage prepared from Banisteriopsis caapi and Psychotria viridis, is originally used by Amazon-based indigenous and mestizo groups for medicinal and ritualistic purposes. Nowadays, ayahuasca is used in religious and shamanic contexts worldwide, and preliminary evidence from preclinical and observational studies suggests therapeutic effects of ayahuasca for the treatment of substance (including alcohol) use disorders.

AIM OF THE STUDY

To investigate the initial pharmacological profile of ayahuasca and its effects on ethanol rewarding effect using the conditioned place preference (CPP) paradigm in mice.

MATERIALS AND METHODS

Ayahuasca beverage was prepared using extracts of B. caapi and P. viridis, and the concentration of active compounds was assessed through high performance liquid chromatography (HPLC). The following behavioral tests were performed after ayahuasca administration: general pharmacological screening (13, 130, or 1300 mg/kg - intraperitoneally - i.p., and 65, 130, 1300, or 2600 mg/kg - via oral - v.o.); acute toxicity test with elevated doses (2600 mg/kg - i.p., and 5000 mg/kg - v.o.); motor activity, motor coordination, and hexobarbital-induced sleeping time potentiation (250, 500, or 750 mg/kg ayahuasca or vehicle - v.o.). For the CPP test, the animals received ayahuasca (500 mg/kg - v.o.) prior to ethanol (1.8 g/kg - i.p.) or vehicle (control group - i.p.) during conditioning sessions.

RESULTS

Ayahuasca treatment presented no significant effect on motor activity, motor coordination, hexobarbital-induced sleeping latency or total sleeping time, and did not evoke signs of severe acute toxicity at elevated oral doses. Ayahuasca pre-treatment successfully inhibited the ethanol-induced CPP and induced CPP when administered alone.

CONCLUSIONS

Our results indicate that ayahuasca presents a low-risk acute toxicological profile when administered orally, and presents potential pharmacological properties that could contribute to the treatment of alcohol use disorders.

Plants with Anti-Addictive Potential

Drug addiction is prevalent among individuals of modern society, being a major cause of disability and premature loss of life. Although the drug addiction have profound social, economical and health impact in the world population, its management remains a challenge as available pharmacological treatments remains ineffective for most people. The limited efficacy and adverse effects have led to a search for alternative therapies to treat drug addiction. In this context, natural products are an important source for new chemical substances with a potential therapeutic applicability. Therefore, this chapter will present data obtained after an extensive literature search regarding the use of medicinal plants as a pharmacological alternative for drug addiction treatment.

Biodiversity of β-Carboline Profile of Banisteriopsis caapi and Ayahuasca, a Plant and a Brew with Neuropharmacological Potential

Ayahuasca is a psychoactive infusion with a large pharmacological application normally prepared with Banisteriopsis caapi, which contains the monoamine oxidase inhibitors β-carbolines, and Psichotria virids, which contains the serotonin receptor agonist N,N dimethyltryptamine (DMT). The objectives of this study were to investigate the chemical profile of B. caapi and of ayahuasca collected in various Brazilian regions. In total, 176 plant lianas, of which 159 B.caapi and 33 ayahuasca samples were analyzed. Dried liana samples were powdered, extracted with methanol, diluted, and analyzed by LC-MS/MS. Ayahuasca samples were diluted and analyzed. Mean concentrations in B. caapi were 4.79 mg/g harmine, 0.451 mg/g harmaline, and 2.18 mg/g tetrahydroharmine (THH), with a high variability among the samples (RSD from 78.9 to 170%). Native B. caapi samples showed significantly higher harmine concentrations than cultivated ones, and samples from the Federal District/Goiás had higher THH content than those collected in the State of Acre. The other Malpighiaceae samples did not contain β-carbolines, except for one D. pubipetala sample. Concentrations in ayahuasca samples ranged from 0.109 to 7.11 mg/mL harmine, 0.012 to 0.945 mg/mL harmaline, 0.09 to 3.05 mg/mL THH, and 0.10 to 3.12 mg/mL DMT. The analysis of paired ayahuasca/B. caapi confirmed that harmine is reduced to harmaline and to THH during the brew preparation. This is the largest study conducted with Malpighiaceae samples and showed a large variability in the main β-carbolines present in B. caapi. This biodiversity is a challenge for standardization of the material used in ethnopharmacological studies of B.caapi and ayahuasca.