Psilocybin and a similar psychedelic, DOI, reduced pain-related behaviors in mice with chronic pain. In a mouse model of chemotherapy-induced nerve damage, both drugs reversed sensitivity to cold and touch in a dose-dependent manner, with different timing of effects. In a model of persistent inflammatory pain, they also reversed sensitivity to heat. These pain-relieving effects depended on activation of the 5-HT2A serotonin receptor. The findings suggest that classical psychedelics may be effective for treating chronic pain through this receptor pathway.
A single dose of the psychedelic psilocybin reduces conditioned behavior and withdrawal caused by the opioid oxycodone in male mice but not in females. This sex-specific effect is mediated by the 5-HT2A receptor in frontal cortex pyramidal neurons that project to the nucleus accumbens. Psilocybin also alters epigenomic regulation after repeated oxycodone exposure and induces sex-specific structural plasticity in the nucleus accumbens independently of the 5-HT2A receptor. Female frontal cortex and nucleus accumbens show fewer changes at gene enhancer regions in response to psilocybin, repeated oxycodone, or their combination compared to males, with the frontal cortex displaying more pronounced sex differences at the epigenomic level.