Psilocybin causes sex, time, and dose dependent alterations in brain signaling pathways

Psilocybin, a psychedelic tryptamine, shows promise for treating conditions like treatment-resistant depression and PTSD by rapidly improving depression scores. Its primary mechanism involves activating the serotonin 2A receptor, but downstream therapeutic effects remain unclear. This study analyzed dose- and sex-dependent transcriptional changes in mouse forebrains at 8 hours, 24 hours, and 7 days after a single low (0.25 mg/kg) or high (1 mg/kg) dose. Females showed faster transcriptional changes and attenuation at low doses compared to males, and more robust responses to high doses at early timepoints. Low-dose effects persisted at 7 days, outlasting high-dose changes, and involved pathways related to neuronal differentiation and neurogenesis. These sexually divergent and temporal molecular effects should inform treatment strategies and timing with cognitive behavioral therapy.

Study at a glance

Abstract

Abstract Psilocybin is a psychedelic tryptamine that has emerged as a potential candidate for the treatment of a variety of conditions, including treatment resistant depression and post-traumatic stress disorder. Clinical trials which have assessed the efficacy of psilocybin for these conditions report a rapid and sustained improvement in patient- and clinician-rated depression scores. The established mechanism of action for psychedelics such as psilocybin is agonism of the serotonin 2A receptor (5HT 2A R), however, the downstream events that mediate their therapeutic effects remain uncertain. As high doses of psychedelics are known to induce strong perceptual alterations, an additional outstanding question is whether subperceptual doses induce similar molecular effects as psychoactive dosages. Here, we report the first analysis of dose- and sex-dependent transcriptional changes in forebrains of female and male mice at 3 timepoints (8 hours, 24 hours, and 7 days) following a single administration of psilocybin at low (0.25 mg/kg) or high (1 mg/kg) doses. Grouped analysis of both sexes reveals dose- and time-dependent transcriptomic alterations. We report more rapid transcriptional changes and attenuation of such changes in females following a single low-dose relative to males treated identically. Females also responded more robustly to high-dose administration relative to males at 8 and 24 hours, with signal attenuation in both sexes by 7 days. A notable observation was the persistent transcriptional effect of low-dose psilocybin at 7 days, which outlasted high-dose changes, and which suggests that low doses may have prolonged biological effects. A myriad of pathways were altered depending on sex and timepoint, but common features included functions related to neuronal differentiation, neurogenesis, and changes in receptor signaling. These data reveal dose- and sex-dependent molecular effects of psilocybin and support previous studies demonstrating its effect on dendritogenesis. Given ongoing clinical interest in psilocybin for treating mental health disorders, our results suggest that these sexually divergent changes should be considered when weighing treatment strategies. Additional consideration should be given to temporal effects of low vs high dosages on gene transcription, especially when timing psilocybin with adjuvant cognitive behavioral therapy.