Fear memory generalization is a fundamental hallmark of post-traumatic stress disorder (PTSD) that enables animals to use past experience to adapt to changing conditions. The infralimbic cortex (IL) i Show more
Fear memory generalization is a fundamental hallmark of post-traumatic stress disorder (PTSD) that enables animals to use past experience to adapt to changing conditions. The infralimbic cortex (IL) is implicated in suppressing generalized fear, but the underlying molecular mechanisms remain unknown. Here, we demonstrate that S-nitrosylation of Dexras1 (SNO-Dexras1) in the IL drives fear generalization. Dexras1 is activated by nitric oxide (NO) donors as well as by N-methyl-D-aspartic acid (NMDA) receptor-stimulated NO synthesis in cortical neurons. It is found that the level of SNO-Dexras1 is significantly increased in the IL of generalized mice and downregulation of SNO-Dexras1 attenuates fear generalization. Mechanistically, inhibition of SNO-Dexras1 increases the expression of phosphorylated extracellular regulated protein kinases (pERK) and brain derived neurotrophic factor (BDNF), implicating synaptic remodeling in the IL. Our study reveals a key role of SNO-Dexras1 in the fear generalization, which may provide a potential therapeutic strategy for PTSD. Show less
Rodent studies have shown that psychedelic drugs can enhance fear extinction. However, investigations to date have relied on normative aversive conditioning procedures, which limit their relevance to Show more
Rodent studies have shown that psychedelic drugs can enhance fear extinction. However, investigations to date have relied on normative aversive conditioning procedures, which limit their relevance to trauma-related memories, as these tend to be overgeneralized and resistant to extinction. Fear extinction depends on activity and plasticity within the infralimbic (IL) region of the medial prefrontal cortex and is regulated by brain-derived neurotrophic factor (BDNF). Ayahuasca (AYA), a brew containing the serotonergic psychedelic N,N-dimethyltryptamine (DMT), facilitates fear extinction in rodents and increases BDNF levels/signaling. Here, we investigated whether AYA attenuates extinction deficits and generalized fear induced by preconditioning restraint stress or high-intensity contextual fear conditioning, and whether these effects depend on BDNF-TrkB receptor signaling in the IL cortex. Adult male and female rats underwent the protocols above and received oral AYA one hour before each of the two extinction sessions conducted on consecutive days. Repeated administration of AYA containing 0.3 mg/kg of DMT enhanced extinction learning and its retention, effects that were abolished by bilateral intra-IL cortex infusion of an anti-BDNF antibody or the TrkB receptor antagonist ANA-12. AYA treatment also reduced fear generalization, an action that was BDNF-dependent in the IL cortex of females but not males. Overall, these findings indicate that AYA can modulate maladaptive fear memories through cortical mechanisms involving BDNF signaling, highlighting the potential of psychedelics as enhancers for extinguishing difficult-to-treat memories like those underlying post-traumatic stress disorder. Show less