ICEERS

Ayahuasca is a serotonergic-acting psychotropic brew. The most common botanical sources of Ayahuasca are Banisteriopsis caapi and Psychotria viridis. B. caapi contains beta-carboline alkaloids with MAOI (Monoamino Oxidase Inhibitor) action, mainly harmine, harmaline, and tetrahydroharmine (THH); whereas P. viridis contains the serotonergic receptor agonist N,N-Dimetiltryptamine (DMT). DMT is not active orally because it is destroyed by the action of the MAO enzymes in the gastrointestinal tract, but the combination with MAOI harmala alkaloids blocks its metabolic breakdown and renders it orally active (4)

It is generally accepted that the main neurobiology mechanism of action of hallucinogens is acting as agonistis of the 5-HT2A receptors located at the pyramidal glutamatergic neurons of the layer V of the prefrontal cortex. When 5-HT2A receptors are activated, a release of the excitatory neurotransmitter glutamate occurs, increasing the neural firing all along the frontal cortex (5). One EEG study in humans has demonstrated the cognitive stimulant properties of ayahuasca, showing an increase in the relative power of the EEG beta band (6), an effect induced by Ayahuasca but not by d-amphetamine.

In a recent study using the neuroimaging technique SPECT, where Ayahuasca was administered to healthy volunteers (7), activation in frontal regions, specifically in the medial frontal and anterior cingulate cortices was found, areas implicated in somatic awareness, subjective feeling states, and emotional arousal. Parahippocampal areas, also involved in the processing of emotional arousal and memory, were also activated. This neurobiologic mechanism of action may imply that Ayahuasca allows subjects to “travel” throughout personal past experiences being aware of emotions, thoughts and memories that are usually difficult to access in ordinary states. Frontal areas are also involved in anticipatory and planning behaviour, and in abstract reasoning, so the activation of those areas may be the basis to explain the complex and meaningful cognitive experiences that take place under the effects of Ayahuasca.