A single oral dose of ayahuasca, equivalent to 1.0 mg DMT per kilogram of body weight, increased blood flow in frontal and paralimbic brain regions of fifteen male volunteers with prior psychedelic experience. Greater perfusion was observed bilaterally in the anterior insula, with stronger effects in the right hemisphere, and in the right anterior cingulate/frontomedial cortex—areas linked to somatic awareness, subjective feeling states, and emotional arousal. Additional increases occurred in the left amygdala/parahippocampal gyrus, a structure involved in emotional processing. These findings indicate that ayahuasca interacts with neural systems central to interoception and emotional processing, suggesting a modulatory role for serotonergic neurotransmission.
The human pharmacology of ayahuasca, an Amazonian tea containing the psychedelic DMT, was evaluated after repeated doses. In a double-blind, crossover, placebo-controlled trial, nine experienced psychedelic drug users received either a placebo followed by ayahuasca, or two ayahuasca doses four hours apart. DMT plasma concentrations, subjective and neurophysiological effects, and serum prolactin and cortisol were higher after two doses. When effects were adjusted for plasma DMT, no differences appeared for subjective, neurophysiological, autonomic, or immunological measures. A trend toward reduced systolic blood pressure and heart rate, and significant tolerance to growth hormone secretion, were observed after the second dose. No clear tolerance or sensitization occurred in psychological or most physiological variables.
Ayahuasca, a traditional South American psychoactive beverage containing DMT and beta-carboline alkaloids, did not impair subjective sleep quality or disrupt sleep initiation and maintenance in 22 healthy male volunteers, unlike d-amphetamine which delayed sleep onset, disrupted maintenance, and reduced deep sleep. Both ayahuasca and d-amphetamine reduced REM sleep duration and increased high-frequency EEG power during stage 2 sleep. However, while d-amphetamine decreased slow-wave sleep power in the first night cycle (an indicator of sleep pressure), ayahuasca enhanced it. The findings suggest that serotonergic psychedelics interact with brain circuits regulating REM and slow-wave sleep.