Identifying factors that contribute to the behavioral effects of psilocybin in preclinical mouse models

Psychedelic drugs offer a potentially promising avenue for novel therapeutics for the treatment of psychiatric conditions, including for mood and anxiety disorders. Emerging clinical studies have prompted increased preclinical research into mechanisms of action. However, post-acute behavioral outcomes in rodents remain inconsistent and difficult to reproduce across laboratories. To address this, we collected a large dataset of behavioral responses to psilocybin in mice (N=693) and used data-driven analyses to identify biological and experimental factors that modulated behavioral readouts. We examined the effects of sex, age, strain, stress protocol, and 5-HT1B signaling on the response to a single high dose of psilocybin measured in acute (head twitch responding and locomotion) or post-acute (sucrose preference, elevated plus maze, novelty-suppressed feeding) behavioral outcomes. We found that psilocybin displays a robust acute behavioral response and a more variable post-acute behavioral profile with a most robust response in sucrose preference. Sex, stress model, and 5-HT1BR activation emerged as key modulators of post-acute antidepressant-like and anxiolytic effects. Random forest classification was narrowly able to predict drug treatment based on post-acute behavioral outcomes and biological and experimental factors. These findings suggest that the heterogeneity seen in the response to psilocybin in mice reflects meaningful biological and experimental variables. Accounting for these factors may enhance translational relevance by identifying the conditions under which therapeutic-like effects are most robust and can support more reproducible models for understanding the neural mechanisms underlying the persisting behavioral effects of psilocybin.