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


OBJECTIVE
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.
Centre d'Investigació de Medicaments, Institut de Recerca, Servei de Farmacologia Clínica, Hospital de la Santa Creu i Sant Pau, and Departament de Farmacologia i Terapéutica, Universitat Autònoma de Barcelona, Spain. jriba@santpau.es
Jordi
J
Riba
Sergio
S
Romero
Eva
E
Grasa
Esther
E
Mena
Ignasi
I
Carrió
Manel J
MJ
Barbanoj
D000328:Adult; D000339:Affect / Q000187:drug effects; D031581:Banisteriopsis / Q000737:chemistry*; D001921:Brain / Q000187:drug effects* / Q000502:physiology; D004311:Double-Blind Method; D005059:Euphoria / Q000187:drug effects; D006801:Humans; D008297:Male; D028321:Plant Preparations / Q000494:pharmacology*; D011619:Psychotropic Drugs / Q000494:pharmacology*; D015899:Tomography, Emission-Computed, Single-Photon
D028321:Plant Preparations; D011619:Psychotropic Drugs