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O. de Lima

Possible Interactions Between 5-HT2A Receptors and the Endocannabinoid System in Humans: Preliminary Evidence of Interactive Effects of Ayahuasca and Endocannabinoids in a Healthy Human Subject

Excerpt

To the Editors

Ayahuasca is an ethnobotanical hallucinogenic preparation traditionally used for ritual and therapeutic purposes in the Northwestern Amazon Basin. It is prepared by the decoction of the bark of the vine Banisteriopsis caapi with the leaves of the shrub Psychotria viridisBanisteriopsis caapi contains the β-carbolines harmine, tetrahydroharmine, and harmaline, which are reversible inhibitors of monoamine oxidase type A (MAO-A), whereas P. viridis contains N,N-dimethyltryptamine (DMT), an agonist at 5-HT1A/2A/2C receptors. Pure DMT is not active orally because it is metabolized by MAO-A, but the β-carbolines in ayahuasca inhibit peripheral MAO-A and allow DMT to reach the brain. The β-carbolines also reach the systemic circulation in humans, but their effects are poorly characterized.

A recent randomized controlled trial (RCT) with 29 patients with treatment-resistant depression showed that, compared with placebo, a single ayahuasca dose induced significant antidepressant effects 7 days after drug intake. The mechanisms behind these effects are not clear but seem to involve agonism at cortical 5-HT2A receptors in brain areas related to emotional processing. 5-HT2A receptor activation also leads to the formation and release of endocannabinoids (ECs), and both the production and release of the EC 2-arachidonoylglycerol (2-AG) are induced by 5-HT2A agonists. Considering that the 5-HT2Areceptor and the EC system (ECS) are coexpressed in brain regions related to emotional processing, they could be involved in the antidepressive effect of ayahuasca. To test the possible interaction between both systems, we administered in an open-label design a single oral ayahuasca dose (1 mL/kg) to a healthy 34-year-old man and assessed subjective effects (Visual Analog Mood Scale [VAMS], Bodily Symptoms Scale, Beck Anxiety Inventory [BAI]), tolerability (blood pressure and heart rate, self-report), and EC plasma levels (anandamide [AEA], 2-AG) at several time points: VAMS, Bodily Symptoms Scale, blood pressure, and heart rate at baseline and 40, 90, 120, 150, and 240 minutes after drug intake; BAI–baseline, 240 minutes after drug intake; AEA, 2-AG (blood samples) at baseline and 90 and 240 minutes after drug intake. Analysis of the ayahuasca sample using gas chromatography with nitrogen-phosphorus detection showed the following alkaloid content (in mg/mL): 0.702 DMT, 1.748 harmine, 0.780 tetrahydroharmine, and 0.039 harmaline. Analysis of plasma ECs was performed using ultrahigh-performance liquid chromatography–tandem mass spectrometry. Detailed information on subjective measures and ayahuasca and EC analyses is described in the Supplemental Digital Content, http://links.lww.com/JCP/A532

The volunteer was not taking any medication and was requested to abstain from alcohol, tobacco, and caffeinated drinks 12 hours before ayahuasca intake. He arrived in the laboratory at 7:00 AM under fasting conditions, and urinalysis for illicit drug use was performed before ayahuasca intake (the test measured cannabis and cocaine and was negative for both drugs). Afterward, a cannula was introduced in his arm for collecting blood samples. Ayahuasca was administered at approximately 8:00 AM, and the experimental session lasted 5 hours. The experimental session consisted in the administration of the drug followed by application of the scales and assessment of tolerability measures at the aforementioned time points. During measurements, the volunteer remained seated in a comfortable reclining chair in a quiet dimly lit room. There was no psychological intervention before, during, or after the session.The volunteer remained in the laboratory under observation to see if the effects had subsided and was discharged around 6 hours after drug intake, which is the approximate duration of the psychoactive effects of ayahuasca.

dos Santos, R. G., Crippa, J. A., de Lima Osório, F., Rocha, J. M., Rossi, G. N., Marchioni, C., … & Hallak, J. E. C. (2018). Possible Interactions Between 5-HT2A Receptors and the Endocannabinoid System in Humans: Preliminary Evidence of Interactive Effects of Ayahuasca and Endocannabinoids in a Healthy Human Subject. Journal of clinical psychopharmacology38(6), 644-646., 10.1097/JCP.0000000000000973
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Antidepressant Effects of a Single Dose of Ayahuasca in Patients With Recurrent Depression: A SPECT Study

Abstract

Ayahuasca is an Amazonian botanical hallucinogenic brew which contains dimethyltryptamine, a 5-HT2A receptor agonist, and harmine, a monoamine-oxidase A inhibitor. Our group recently reported that ayahuasca administration was associated with fast-acting antidepressive effects in 6 depressive patients. The objective of the present work was to assess the antidepressive potentials of ayahuasca in a bigger sample and to investigate its effects on regional cerebral blood flow. In an open-label trial conducted in an inpatient psychiatric unit, 17 patients with recurrent depression received an oral dose of ayahuasca (2.2 mL/kg) and were evaluated with the Hamilton Rating Scale for Depression, the Montgomery-Asberg Depression Rating Scale, the Brief Psychiatric Rating Scale, the Young Mania Rating Scale, and the Clinician Administered Dissociative States Scale during acute ayahuasca effects and 1, 7, 14, and 21 days after drug intake. Blood perfusion was assessed eight hours after drug administration by means of single photon emission tomography. Ayahuasca administration was associated with increased psychoactivity (Clinician Administered Dissociative States Scale) and significant score decreases in depression-related scales (Hamilton Rating Scale for Depression, Montgomery-Asberg Depression Rating Scale, Brief Psychiatric Rating Scale) from 80 minutes to day 21. Increased blood perfusion in the left nucleus accumbens, right insula and left subgenual area, brain regions implicated in the regulation of mood and emotions, were observed after ayahuasca intake. Ayahuasca was well tolerated. Vomiting was the only adverse effect recorded, being reported by 47% of the volunteers. Our results suggest that ayahuasca may have fast-acting and sustained antidepressive properties. These results should be replicated in randomized, double-blind, placebo-controlled trials.
Sanches, R. F., de Lima, O. F., Dos Santos, R. G., Macedo, L. R., Maia-de-Oliveira, J. P., Wichert-Ana, L., … & Hallak, J. E. (2015). Antidepressant Effects of a Single Dose of Ayahuasca in Patients With Recurrent Depression: A SPECT Study. Journal of clinical psychopharmacology. http://dx.doi.org/10.1097/JCP.0000000000000436
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