Psilocybin Shows Acute Effects on Mouse Behavior in Multi-Lab Study

A multi-institutional study published in Nature Neuroscience investigated the effects of psilocybin on mouse behavior. Five laboratories conducted parallel experiments to assess the acute and persistent effects of psilocybin (2 mg/kg, IP) on various behaviors, including anxiety-related responses, exploration, sociability, depression-like behaviors, fear extinction, and social reward learning.

The findings indicated that psilocybin produced several robust acute effects on mouse behavior, such as increased anxiety and avoidance behaviors, along with decreased fear expression. However, the study revealed that psilocybin did not produce replicable effects 24 hours after administration regarding anxiety and depression-like behaviors or fear extinction learning. Additionally, no alterations in social preference or social reward learning were observed.

The comprehensive analysis involved approximately 200 male and female mice per experiment across the five independent labs. This coordinated approach demonstrated unique certainty regarding several acute effects of psilocybin, suggesting that its persistent effects may be more modest and inconsistent than previously thought. The authors emphasized the importance of multi-laboratory collaboration to generate replicable results and reduce reliance on unreliable findings.

The study also highlighted the limitations of animal models in assessing complex human emotions and experiences. While some behavioral changes were noted shortly after psilocybin administration, such as increased anxiety and avoidance of open spaces, the long-term effects were minimal. The researchers plan to focus on the confirmed short-term effects and investigate the impact of repeated psilocybin administration on the brain.