Pure psilocybin reduces reward-associated preference while mushroom extract shows transient exploratory effects in rats

Abstract

Introduction: Psilocybin, the main psychoactive compound in Psilocybe mushrooms, has attracted interest for its potential therapeutic effects in neuropsychiatric disorders (Erkizia-Santamaría et al., 2025). However, preclinical data comparing its behavioral properties to whole mushroom extracts remain limited (Ali et al., 2023; Johnson-Groh, 2025).

Objective: To investigate the reinforcing and preference-related effects of these compounds, we evaluated pure psilocybin and Psilocybe cubensis extract in Wistar Han rats using a conditioned place preference (CPP) paradigm.

Material and Methods: Eighteen male Wistar Han rats (250–275 g) were randomly assigned to three groups (n=6): control (0.9 % NaCl), pure psilocybin (3 mg kg⁻¹), and P. cubensis extract (3 mg kg⁻¹ psilocybin/psilocin). Treatments were administered by oral gavage. Animals were confined to drug- or saline-paired compartments following a schedule to establish associative learning. Post-conditioning preference was evaluated at 1, 7, and 14 days after the last treatment. CPP scores were calculated as the fraction of time spent in the drug-paired compartment, and the number of entries into each compartment was recorded. Statistical analysis was performed using ANOVA with post hoc tests (p < 0.05).

Results and Discussion: Pure psilocybin significantly reduced CPP scores at 1- and 7-days post-treatment compared to controls, indicating aversive or non-reinforcing effects. No significant changes in CPP scores were observed for the mushroom extract group. Notably, the extract group showed a transient increase in entries into the drug-paired compartment on day 7, suggesting temporary exploratory interest, while the pure psilocybin group maintained fewer entries into the drug-paired compartment.

Conclusions: Pure psilocybin and P. cubensis extract elicited distinct behavioral profiles in the CPP test, likely reflecting differences in bioactive composition. The results highlight differential reinforcing properties of psilocybin alone versus the complex mushroom extract, providing valuable preclinical insight into their central effects.