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-HT2A 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.