Psychedelic 4-AcO-DMT attenuated looming-induced freezing behaviors by activating PrL ^CaMKIIα neurons in mice

Psychedelics modulate emotion and cognition, yet the underlying mechanisms remain unclear. Given the ability of psychedelics to induce visual hallucinations, we employed the looming model-a visual threat assay that combines visual stimulation with innate fear-to investigate the effects of psychedelics. Unexpectedly, 4-acetoxy-N,N-dimethyltryptamine (4-AcO-DMT), a psychedelic compound that acts as a prodrug of psilocin and exhibits comparable central nervous system effects to psilocybin, significantly reduced looming-induced freezing behavior compared to R/S-MDMA, without eliciting overt hallucinogen-like effects under the current experimental conditions. This anti-fear effect was independent of β-arrestin 2 signaling and visual function, but associated with decreased innate fear emotion. We identified that 4-AcO-DMT activates CaMKIIα neurons in the prelimbic cortex (PrL) via 5-HT_2A receptors, and the PrL ^CaMKIIα-MD ^CaMKIIα circuit mediates this response. Our findings reveal that despite being designed from a visual hallucination perspective, the looming model unexpectedly uncovers a robust anti-innate fear effect of psychedelics, providing new insights into their emotional modulation and therapeutic potential.