Behavioural and pharmacological evaluation of the psilocybin analogue baeocystin in Wistar rats.

Baeocystin is a naturally occurring tryptamine-based compound found in various psychoactive mushrooms, including in several species of Psilocybe genus. Due to its structural similarity to psilocybin, which has shown a therapeutic potential in treatment of psychiatric disorders, there is a growing interest in investigating whether baeocystin exhibits comparable effects. This study investigated the pharmacokinetic profile and acute behavioural effects of baeocystin in Wistar rats. Behavioural assessments including locomotor activity and its spatial characteristics (in the open field test) and sensorimotor gating measured by prepulse inhibition were evaluated after subcutaneous administration of 1.25 or 5 mg/kg baeocystin. Pharmacokinetics and brain-serum ratios were analysed after the 5 mg/kg sc. dose. Pharmacokinetics demonstrated that both baeocystin and its metabolite, norpsilocin, have a very limited ability to cross the blood-brain barrier. Consistent with the pharmacokinetic profile, baeocystin had no significant effects on locomotor activity, exploratory behaviour, anxiety-like responses, or sensorimotor gating at doses of either 1.25 or 5 mg/kg. In conclusion, our results suggest that baeocystin has minimal to no behavioural effects in rats, probably due to its poor permeability across the blood-brain barrier. This limited penetration may account for its negligible neurobiological and psychedelic activity.