New research published in European Neuropsychopharmacology provides evidence that the psychedelic brew ayahuasca can facilitate the extinction of severe, trauma-like fear memories in rats. The findings suggest that this effect depends on specific neuroplasticity mechanisms within the prefrontal cortex involving a protein known as brain-derived neurotrophic factor. By targeting these pathways, the treatment also appears to reduce the tendency to perceive safe environments as threatening.

Post-traumatic stress disorder is characterized by fear memories that are overgeneralized and resistant to standard extinction procedures. Standard laboratory models often use mild aversive conditioning that does not fully capture the persistence or intensity of traumatic memories found in humans.

The authors of the new study sought to address this gap by utilizing protocols that induce stronger, more resilient fear memories. They aimed to determine if ayahuasca could help attenuate these maladaptive memories and to identify the specific brain mechanisms responsible for such effects.

Previous studies have indicated that the infralimbic region of the medial prefrontal cortex is essential for fear extinction. This brain area exerts inhibitory control over fear circuits in the amygdala. It is also rich in serotonin receptors, which are the primary targets of the psychoactive compounds found in ayahuasca. The researchers hypothesized that the brew might enhance extinction learning by modulating plasticity in this region through brain-derived neurotrophic factor signaling.

“Rodent studies showing that psychedelic compounds enhance memory extinction have used standard fear conditioning procedures, producing moderate and specific aversive memories that do not capture key features of the memories underlying post-traumatic stress disorder (PTSD), including a relative resistance to extinction and fear overgeneralization,” explained study author Leandro J. Bertoglio, a professor of pharmacology at the Federal University of Santa Catarina.

“We aimed to test whether ayahuasca, a brew containing the serotonergic psychedelic N,N-dimethyltryptamine (DMT), could facilitate fear extinction and reduce generalization under more trauma-like conditions, and to examine the brain mechanisms involved. We focused on brain-derived neurotrophic factor (BDNF)-tyrosine kinase B (TrkB) receptor signaling in the infralimbic cortex because fear extinction depends on this neuroplastic pathway.”

The researchers employed a total of 303 adult Wistar rats, split almost evenly between males and females. The study utilized a batch of ayahuasca donated by a branch of the Santo Daime church in Brazil. The brew was analyzed to ensure specific concentrations of its active alkaloids, including DMT and harmine. The animals received an oral dose containing 0.3 mg/kg of DMT. This dose was selected because prior research indicated it enhances fear extinction without causing significant changes in locomotor activity.

The researchers conducted four distinct experiments to isolate variables and mechanisms. In the first experiment, they investigated the effect of prior stress on fear extinction. Half of the rats were subjected to restraint stress, where they were confined in a perforated plastic tube for 30 minutes. This procedure is known to impair the ability to extinguish fear later. On the following day, all animals underwent fear conditioning, where they were placed in a specific chamber (Context A) and received mild electric foot shocks.

After conditioning, the rats underwent two extinction sessions on consecutive days. During these sessions, they were placed back in the dangerous context without receiving any shocks. The researchers administered either ayahuasca or a water vehicle orally one hour before each of these sessions. The primary measure of fear was “freezing behavior,” defined as the complete absence of movement except for breathing.

The results showed that the rats exposed to restraint stress exhibited deficits in extinguishing their fear compared to non-stressed controls. They continued to freeze at high rates even after repeated exposure to the safe context. However, the stressed rats treated with ayahuasca showed a marked improvement. They learned that the context was safe much faster than the vehicle-treated stressed rats.

In addition to extinction, the researchers measured fear generalization. This occurs when an animal shows fear in a neutral, novel environment (Context B) that was never associated with pain. Stressed animals typically show high fear generalization. The study found that ayahuasca treatment reduced freezing in the neutral context, effectively restoring the ability of the rats to discriminate between dangerous and safe environments.

The second experiment tested whether ayahuasca could mitigate the effects of high-intensity trauma. Instead of restraint stress, the researchers varied the intensity of the electric shock during the initial conditioning phase. One group received standard shocks (1.0 mA), while another received high-intensity shocks (1.3 mA). The high-intensity group displayed persistent fear that was difficult to extinguish and showed high levels of generalization.

Consistent with the first experiment, ayahuasca treatment facilitated extinction in the high-intensity shock group. These rats reduced their freezing levels more than the control group receiving the same high-intensity shocks. The treatment also successfully reduced fear generalization in both male and female rats, preventing them from freezing in the neutral environment.

“Ayahuasca with low DMT content helped both female and male rats learn and later remember that an environment previously associated with danger (footshocks) was now safe,” Bertoglio told PsyPost. “This treatment also decreased the tendency to misinterpret a neutral environment as threatening (and thus express fear responses).”

The third and fourth experiments were designed to pinpoint the biological mechanism behind these behavioral changes. The researchers focused on the infralimbic cortex. They performed stereotaxic surgery to implant guide cannulas directly into this brain region. This allowed them to infuse drugs locally to block specific molecular pathways.

In the third experiment, the researchers infused an antibody that neutralizes brain-derived neurotrophic factor (BDNF) directly into the infralimbic cortex. This was done ten minutes before the extinction sessions, following the oral administration of ayahuasca. The goal was to see if removing available BDNF would prevent ayahuasca from working.

The data revealed that blocking BDNF in the infralimbic cortex completely abolished the beneficial effects of ayahuasca on fear extinction. Rats treated with ayahuasca and the anti-BDNF antibody froze just as much as the vehicle-treated controls. This suggests that the presence of BDNF in this brain region is required for ayahuasca to enhance the relearning of safety.

The researchers also observed a sex difference regarding fear generalization in this experiment. Blocking BDNF in the infralimbic cortex prevented the reduction of generalized fear in female rats. However, in male rats, the antibody did not stop ayahuasca from reducing fear in the neutral context.

The fourth experiment targeted the TrkB receptor, which is the primary receptor that BDNF activates. The researchers infused a selective antagonist called ANA-12 into the infralimbic cortex. This drug prevents BDNF from binding to its receptor and initiating intracellular signaling.

The results mirrored those of the antibody experiment. Blocking the TrkB receptor prevented ayahuasca from facilitating fear extinction in both male and female rats. This confirms that the entire BDNF-TrkB signaling pathway in the infralimbic cortex is necessary for the therapeutic-like effects of the drug on traumatic memories. Similar to the previous experiment, blocking this receptor prevented the reduction of fear generalization in females but not in males.

“We found that blocking BDNF-TrkB receptor signaling in the infralimbic cortex prevented the beneficial effects of ayahuasca on fear extinction, providing evidence of a causal mechanism,” Bertoglio explained. “Interestingly, we observed sex-dependent effects on fear generalization. The tested experimental interventions prevented ayahuasca-induced reductions in fear generalization in females but not in males.”

“These findings indicate biological differences that warrant further study. Brain circuits responsible for fear overgeneralization differ between sexes, which could lead to personalized therapeutic strategies based on sex/gender differences.”

These findings suggest that the infralimbic cortex is a critical site of action for ayahuasca. The drug appears to stimulate plasticity in this region, likely by increasing the excitability of neurons and promoting the release of neurotrophic factors. This plasticity allows the brain to overwrite the traumatic memory with a new safety memory.

“The effects were replicated in two protocols that induce aversive memories with PTSD-like features, including prior stress exposure and stronger, trauma-like conditioning,” Bertoglio said. “The measured effect size was large, with a decrease in the fear response of more than 70% relative to the control groups. These data indicate that the effects are substantial and not limited to normative laboratory conditions, suggesting potential translational relevance.”

But the study still has some limitations. The experiments were conducted on rodents, and translational research in humans is necessary to confirm if similar mechanisms apply. The researchers utilized a specific low dose of DMT within the brew, and it is unknown if higher, hallucinogenic doses would recruit different mechanisms or brain regions.

“These results come from controlled animal experiments and do not indicate that ayahuasca is ready for clinical use in treating trauma,” Bertoglio noted. “Instead, the study identifies mechanisms and conditions that may guide future research and clinical translation.”

The sex differences observed in the mechanism of fear generalization also warrant further investigation. While the infralimbic cortex was essential for females, males appeared to rely on other neural circuits for this specific aspect of fear processing. Other regions such as the hippocampus or the amygdala might play a more prominent role in males for distinguishing between contexts under the influence of ayahuasca.

The research highlights the potential of psychedelic compounds to treat conditions involving rigid, maladaptive memories. By combining behavioral protocols that mimic the severity of trauma with precise molecular manipulations, the study provides a detailed map of how ayahuasca may help the brain recover from intense stress.

“The following steps include testing boundary conditions and potential moderating factors in rodents and translating these mechanistic findings and insights into clinical research through our human studies arm,” Bertoglio said. “We are particularly interested in how psychedelics can safely enhance extinction-based treatments.”

“A noteworthy aspect of the work is that the oral ayahuasca treatment was repeated twice but did not alter locomotion or anxiety, suggesting that neuroplastic mechanisms may be sufficient to enhance extinction. This supports the idea that therapeutic effects may not require strong acute behavioral effects. For context, the DMT content in our rodent study is approximately one-third of that typically used in human studies.”

The study, “Ayahuasca modulation of traumatic-like fear memories requires infralimbic cortex BDNF-dependent mechanisms in rats,” was authored by Isabel Werle, Francisco S. Guimarães, Rafael G. dos Santos, Jaime E.C. Hallak, and Leandro J. Bertoglio.