Topographic pharmaco-EEG mapping of the effects of the South American psychoactive beverage ayahuasca in healthy volunteers.
OBJECTIVE
Ayahuasca is a traditional South American psychoactive beverage used in Amazonian shamanism, and in the religious ceremonies of Brazilian-based syncretic religious groups with followers in the US and several European countries. This tea contains measurable amounts of the psychotropic indole N,N-dimethyltryptamine (DMT), and beta-carboline alkaloids with MAO-inhibiting properties. In a previous report we described a profile of stimulant and psychedelic effects for ayahuasca as measured by subjective report self-assessment instruments. In the present study the cerebral bioavailability and time-course of effects of ayahuasca were assessed in humans by means of topographic quantitative-electroencephalography (q-EEG), a noninvasive method measuring drug-induced variations in brain electrical activity.


METHODS
Two doses (one low and one high) of encapsulated freeze-dried ayahuasca, equivalent to 0.6 and 0.85 mg DMT kg(-1) body weight, were administered to 18 healthy volunteers with previous experience in psychedelic drug use in a double-blind crossover placebo-controlled clinical trial. Nineteen-lead recordings were undertaken from baseline to 8 h after administration. Subjective effects were measured by means of the Hallucinogen Rating Scale (HRS).


RESULTS
Ayahuasca induced a pattern of psychoactive effects which resulted in significant dose-dependent increases in all subscales of the HRS, and in significant and dose-dependent modifications of brain electrical activity. Absolute power decreased in all frequency bands, most prominently in the theta band. Mean absolute power decreases (95% CI) at a representative lead (P3) 90 min after the high dose were -20.20+/-15.23 microV2 and -2.70+/-2.21 microV2 for total power and theta power, respectively. Relative power decreased in the delta (-1.20+/-1.31% after 120 min at P3) and theta (-3.30+/-2.59% after 120 min at P3) bands, and increased in the beta band, most prominently in the faster beta-3 (1.00+/-0.88% after 90 min at P3) and beta-4 (0.30+/-0.24% after 90 min at P3) subbands. Finally, an increase was also seen for the centroid of the total activity and its deviation. EEG modifications began as early as 15-30 min, reached a peak between 45 and 120 min and decreased thereafter to return to baseline levels at 4-6 h after administration.


CONCLUSIONS
The central effects of ayahuasca could be objectively measured by means of q-EEG, showing a time pattern which closely paralleled that of previously reported subjective effects. The modifications seen for the individual q-EEG variables were in line with those previously described for other serotonergic psychedelics and share some features with the profile of effects shown by pro-serotonergic and pro-dopaminergic drugs. The q-EEG profile supports the role of 5-HT2 and dopamine D2-receptor agonism in mediating the effects of ayahuasca on the central nervous system.
Riba
Jordi
J
Area d'Investigació Farmacològica, Institut de Recerca, Hospital de la Santa Creu i Sant Pau (HSCSP), Departament de Farmacologia i Terapèutica, Universitat Autònoma de Barcelona, Spain.
Anderer
Peter
P
Morte
Adelaida
A
Urbano
Gloria
G
Jané
Francesc
F
Saletu
Bernd
B
Barbanoj
Manel J
MJ
D000328:Adult; D031581:Banisteriopsis; D001628:Beverages; D001682:Biological Availability; D001921:Brain / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008297:Male; D028321:Plant Preparations / Q000009:adverse effects / Q000493:pharmacokinetics / Q000494:pharmacology*; D011619:Psychotropic Drugs / Q000009:adverse effects / Q000493:pharmacokinetics / Q000494:pharmacology*; D013020:South America; D013997:Time Factors
D028321:Plant Preparations; D011619:Psychotropic Drugs