Multi-scale effects of single-dose psilocybin in the macaque brain

Abstract Psilocybin holds strong therapeutic promise for treating major depressive disorder. However, the cellular and molecular substrates underlying its action have not been fully elucidated, especially in the primate brain. We combined multimodal MRI, magnetic resonance spectroscopy (MRS), cerebrospinal fluid (CSF) proteomics and metabolomics, and single-nucleus RNA sequencing (snRNA-seq) to map the multiscale temporospatial dynamics induced by a single dose of psilocybin in cynomolgus macaques. Psilocybin increased the integration of the frontoparietal network (FPN) with the default-mode and limbic networks, transiently reduced integration of the FPN with the somatomotor network, and induced global network segregation. Several regions in the cortex, striatum, and thalamus as well as certain of the frontoparietal white matter pathways showed persistent enhancement lasting 1 week. Notably, these changes were accompanied by a CSF multi-omics shift from acute prostaglandin-dominated inflammation to a sustained enrichment of an omega-3 fatty acid-associated anti-inflammatory state together with a bidirectional reorganization of extracellular matrix (ECM)-related signatures, characterized by increased CD44 and decreased fibulin-family proteins. In addition, we found lasting upregulation of TCA-cycle and NAD(P)-dependent redox enzymes. This was further supported by sustained elevations of glutamate/glutamine and total creatine in the dorsolateral prefrontal cortex (dlPFC), which was found using in vivo MRS. At the cellular level, psilocybin promoted HTR2A selective upregulation in deep-layer excitatory neurons along with a widespread enhancement of mitochondrial oxidative phosphorylation centered on the complex I subunit ND3 across diverse excitatory and inhibitory neuronal subtypes in the dorsolateral prefrontal cortex. Glial-state remodeling, including a shift of astrocytes toward ECM remodeling states and microglia toward an anti-inflammatory state, also occurred. Collectively, these findings provide evidence in the primate brain that psilocybin induces functional integration and segregation of brain networks, enhances energy metabolism and synaptic plasticity, and modulates neuroimmune signaling. All the data will be shared as an integrated resource for primate psilocybin research.