Psychedelic compounds directly excite 5-HT2A Layer 5 Pyramidal Neurons in the Prefrontal Cortex through a 5-HT2A Gq-mediated activation mechanism

Psilocin, the active compound in Psilocybe sp. mushrooms, is a serotonergic psychedelic that has recently gained renewed interest due to its potential as a therapeutic tool. Despite promising clinical findings, the underlying signaling mechanisms and brain region-specific effects of psilocin and other psychedelic drugs remain unclear. Psilocin, like other psychedelic compounds, is an agonist at many serotonin and other biogenic amine receptors; however, activation of serotonin (5-Hydroxytryptamine, or 5-HT) 2A receptors (5-HT2ARs) is understood as the main molecular target for the psychoactive effects in animals and humans. 5-HT2ARs are abundantly expressed in the prefrontal cortex (PFC); however, the biochemical actions of psilocin on PFC neurons remain poorly understood. In this study, we used in vitro slice electrophysiology to examine how psilocin acutely alters the activity and electrophysiological properties of layer 5 pyramidal neurons in the mouse PFC. Focal application of psilocin (10M) onto nonspecified Layer 5 Pyramidal neurons in the prelimbic PFC of C57BL/6J mice produced variable effects on firing (increase, decrease, or no change). 5-HT2AR layer 5 pyramidal neurons in the mouse prelimbic PFC were identified via labeling in a 5-HT2A-ERT2-Cre mouse crossed with an Ai9 tdTomato reporter. Focal application of psilocin increased firing in all identified 5-HT2AR neurons but did not result in any significant changes in synaptic transmission. Overall, the results demonstrate that psilocin evokes strong firing changes in the PFC that are 5-HT2AR and Gq dependent, thereby providing valuable insights into the effects of psilocin on a brain region implicated in mediating psychedelic drug actions.