Human Cortical Serotonin 2A Receptor Occupancy by Psilocybin Measured Using [11C]MDL 100,907 Dynamic PET and a Resting-State fMRI-Based Brain Parcellation

A psychoactive dose of psilocybin (10 mg/70 kg) occupied an average of 39.5% of serotonin 2A receptors in the brains of four healthy volunteers, as measured by PET imaging. The highest occupancy occurred in regions of the default mode network, including the subgenual anterior cingulate and bilateral angular gyri, with values between 63.12% and 74.72%. Individual variability in regional occupancy was marked. These findings support further research into how differences in receptor occupancy relate to psilocybin's acute and lasting effects.

Study at a glance

Abstract

Psilocybin (a serotonin 2A, or 5-HT 2A , receptor agonist) has shown preliminary efficacy as a treatment for mood and substance use disorders. The current report utilized positron emission tomography (PET) with the selective 5-HT 2A receptor inverse agonist radioligand [ 11 C]MDL 100,907 (a.k.a. M100,907) and cortical regions of interest (ROIs) derived from resting-state functional connectivity-based brain parcellations in 4 healthy volunteers (2 females) to determine regional occupancy/target engagement of 5-HT 2A receptors after oral administration of a psychoactive dose of psilocybin (10 mg/70 kg). Average 5-HT 2A receptor occupancy across all ROIs was 39.5% (± 10.9% SD). Three of the ROIs with greatest occupancy (between 63.12 and 74.72% occupancy) were within the default mode network (subgenual anterior cingulate and bilateral angular gyri). However, marked individual variability in regional occupancy was observed across individuals. These data support further investigation of the relationship between individual differences in the acute and enduring effects of psilocybin and the degree of regional 5-HT 2A receptor occupancy.