Skip to content

Brandon Richardson

2 papers in the library · 5 citations · publishing 2025

Papers

High dose of psilocybin induces acute behavioral changes without inducing conditioned place preference in Sprague-Dawley rats

Journal of Psychopharmacology September 22, 2025 Vítor Bruno, Martha López-canul, Brandon Richardson et al. 3 citations

Psilocybin, at a dose of 10 mg/kg administered every other day, does not produce conditioned place preference (CPP) in Sprague-Dawley rats, indicating a lack of rewarding or reinforcing effects under this regimen. During conditioning, psilocybin increased head twitching, wet-dog shaking, and defecation, while decreasing grooming, body licking, and rearing compared to vehicle. However, 48 hours after the final injection, no behavioral differences remained between groups. These findings suggest that psilocybin's acute behavioral effects are transient and that it does not induce reward-related learning in the CPP paradigm, though further research is needed to assess addiction liability across different protocols.

Differential effects of psilocybin and lisuride on serotonin and dopamine neuronal activity and behavior

Progress in Neuro-Psychopharmacology and Biological Psychiatry October 1, 2025 Brandon Richardson, Antonio Inserra, Michael Pileggi et al. 2 citations

Psilocybin and lisuride both activate 5-HT2A receptors, but only psilocybin triggers the head twitch response (HTR) in mice, a proxy for hallucinogenic activity. In adult male C57BL/6N mice, psilocybin (0.3–3 mg/kg) inhibited serotonin neuron firing in the dorsal raphe nucleus via 5-HT2A receptors, while lisuride (0.1–0.5 mg/kg) did not. Both drugs reduced dopamine neuron firing in the substantia nigra, but lisuride's effect was more sensitive to 5-HT2A antagonism. Psilocybin elicited HTR; lisuride did not. Only high-dose lisuride reduced immobility in the forced swim test. Both drugs reduced locomotion in open field and elevated plus maze tests. Principal component analysis separated the drug effects, indicating distinct neurobiological pathways: psilocybin produces psychedelic-like, serotonin-dominant effects, while lisuride displays dopamine-linked improvements in coping behavior.