Synthetic modulation of brain-wide anesthesia-activated neural ensembles using a transgenic mouse system.

Anesthetics are commonly used to produce unconsciousness, but the neural substrates of unconsciousness remain poorly understood. Here we test the hypothesis that general anesthesia works by targeting discrete cell types and neural circuits distributed brain-wide, rather than non-specific binding, using a mouse transgenic system. We take advantage of a mouse that expresses chemogenetic designer receptors exclusively activated by a designer drug (DREADDs) in an inducible Cre-dependent manner driven by Fos immediate early gene expression. Since Fos expression peaks with metabolic activity, we use this system to insert synthetic DREADDs into brain-wide neurons that are active under isoflurane anesthesia. We then test the behavioral consequences of chemogenetic stimulation of anesthesia-activated neural ensembles. We observe immobility, discoordination, anti-nociception, and significantly increased anesthetic sensitivity, but not a loss of consciousness as measured by the righting reflex. We next describe brain-wide expression of the captured neurons across the intact mouse brain using iDisco+ whole brain clearing and light sheet microscopy, revealing unique morphological characteristics of sparse, spatially distributed cells. This provides a brain-wide morphologic map with detailed neurite labeling of anesthesia-activated neurons at cellular resolution as a technical resource for the field.