In the past few years, thrill-seekers from Hollywood, Silicon Valley and beyond have been travelling to South America to take part in so-called Ayahuasca retreats. Their goal: to partake in a brewed concoction made from a vine plant Banisteriopsis caapi, traditionally used by indigenous people for sacred religious ceremonies. Drinkers of Ayahuasca experience short-term hallucinogenic episodes many describe as life-changing.
The active ingredient responsible for these psychedelic visions is a molecule called dimethyltryptamine (DMT). For the first time, a team has discovered the widespread presence of naturally-occurring DMT in the mammalian brain. The finding is the first step toward studying DMT-- and figuring out its role -- within the brains of humans. Additionally, extracellular concentrations of DMT in the cerebral cortex of normal behaving rats, with or without the pineal gland, were similar to those of canonical monoamine neurotransmitters including serotonin.
"DMT is not just in plants, but also can be detected in mammals," says the senior author.
Using a process in which microdialysis tubing is inserted into a rat brain through the pineal gland, the researchers collected a sample that was analyzed for -- and confirmed -- the presence of DMT. That experiment resulted in a paper published in 2013.
These results show for the first time that the rat brain is capable of synthesizing and releasing DMT at concentrations comparable to known monoamine neurotransmitters and raise the possibility that this phenomenon may occur similarly in human brains.
The authors set up an experiment using a process called in situ hybridization, which uses a labeled complementary strand of DNA to localize a specific RNA sequence in a tissue section.
The authors found co-expression of INMT and AADC mRNA in rat brain and periphery, and brain concentrations of DMT in rats. INMT transcripts were identified in the cerebral cortex, pineal gland, and choroid plexus of both rats and humans via in situ hybridization. Notably, INMT mRNA was colocalized with AADC transcript in rat brain tissues, in contrast to rat peripheral tissues where there existed little overlapping expression of INMT with AADC transcripts.
"With this technique, we found brain neurons with the two enzymes required to make DMT," says the author. And they were not just in the pineal gland.
"They are also found in other parts of the brain, including the neocortex and hippocampus that are important for higher-order brain functions including learning and memory." The results are published in the journal Scientific Reports.
The team also revealed that the levels of DMT increase in some rats experiencing cardiac arrest. A significant increase of DMT levels in the rat visual cortex was observed following induction of experimental cardiac arrest, a finding independent of an intact pineal gland.
A paper published in 2018 by researchers in the U.K. purported that DMT simulates the near death experience, wherein people report the sensation of transcending their bodies and entering another realm. The senior author hopes to probe further to discover the function of naturally occurring levels of DMT in the brain -- and what if any role it plays in normal brain functions.
"We don't know what it's doing in the brain. All we're saying is we discovered the neurons that make this chemical in the brain, and they do so at levels similar to other monoamine neurotransmitters."
Psychedelic compound synthesized in normal rat brains
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