Psilocybin, a psychedelic compound, causes repetitive, stereotyped movements and reduces defensive reactions in planarian flatworms. These effects are mediated by the neurotransmitter serotonin (5-hydroxytryptamine). The findings suggest that psilocybin's behavioral actions in this simple animal model are linked to serotonergic signaling.
Psilocybin, the active compound in Psilocybe mushrooms, reduced pain-related behaviors in adult male rats exposed to formalin-induced noxious stimuli, a model of both acute and persistent inflammatory pain. Doses of 0.1 and 0.3 mg/kg significantly decreased flinching and licking during both early and late pain phases. Pretreatment with volinanserin, a selective blocker of the 5-HT 2A receptor, eliminated this pain-relieving effect, indicating that psilocybin produces analgesia at least partly by activating that receptor.