Ayahuasca is a psychedelic mix used for ceremonial purposes by the indigenous Amazon tribes since times immemorial. Once under its influence, a medium facilitating introspection and self knowledge is opened. Among other things, ayahuasca contains DMT which is an illegal substance in most western countries. This has made any research that might uncover beneficial pharmacological effects very difficult. One new research on rats, however, suggests that the magic brew could be very potent against anxiety if ingested over a prolonged time.

Ayahuasca being prepared in the Napo region of Ecuador.

When prepared, Ayahuasca is a brown-reddish drink with a strong taste and smell. To make it, the Amazon shamans infuse the shredded stalk of the malpighiaceous plant Banisteriopsis caapi with the leaves of other plants, generally Dyplopteris cabrerana or Psychotria viridis. During the cooking process, which may last for hours, a plethora of chemical compounds from these plants enter the infusion.

The brew contains several substances that alter brain chemistry. Among them, some regulate the neurotransmitters serotonin and MAO-A. It was also previously shown that ayahuasca directly affects activity in the hippocampus and amygdala, areas of the brain responsible for memory and emotions, respectively.

Vanesa Favaro, of the Universidade Federal de São Paulo, made a series of experiments on rats meant to determine whether or not ayahuasca therapy had any effect on anxiety. Four experimental groups consisting of 46 rats in total were established. The first three received different doses of the potent brew daily for 30 days, while the fourth received a placebo.

The rats were trained to navigate two different types of mazes. Then, the researchers induced a fear conditioning by teaching the rats to associate a distinct sound with receiving an electric shock.

To measure fear response, Favaro and colleagues recorded the time each rat froze its movements when exposed to the chamber where the shocks were received (contextual fear) and when the sound was played (tone fear).

The rats who received the lowest dose of ayahuasca froze longer than those in the placebo group after being placed in the contextual fear condition, but not after hearing the tone. This reaction suggests that the rats’ emotional memory formation process was affected by certain levels of ayahuasca exposure. Ayahuasca did not affect rats’ ability to learn and remember how to complete the mazes, the researchers report.

When used repeatedly, ayahuasca seems to affect memories related to emotional content, without affecting other memories. This seems to mirror self-reports from people who ventured into the Amazon to partake the brew. It’s unclear when, if ever,  clinical trials using ayahuasca for anxiety therapy might be made.