Psychedelics Recruit Multiple Cellular Types and Produce Complex Transcriptional Responses Within the Brain.

There has recently been a resurgence of interest in psychedelics, substances that profoundly alter perception and cognition and have recently demonstrated therapeutic efficacy to treat anxiety, depression, and addiction in the clinic. The receptor mechanisms that drive their molecular and behavioral effects involve activation of cortical serotonin 5-HT receptors, but the responses of specific cellular populations remain unknown. Here, we provide evidence that a small subset of 5-HT-expressing excitatory neurons is directly activated by psychedelics and subsequently recruits other select cell types including subpopulations of inhibitory somatostatin and parvalbumin GABAergic interneurons, as well as astrocytes, to produce distinct and regional responses. To gather data regarding the response of specific neuronal populations, we developed methodology for fluorescence-activated cell sorting (FACS) to segregate and enrich specific cellular subtypes in the brain. These methods allow for robust neuronal sorting based on cytoplasmic epitopes followed by downstream nucleic acid analysis, expanding the utility of FACS in neuroscience research.