LAUSR

STUDY OBJECTIVES Because in various brain regions the activity of GABA neurons is largely unknown, we measured in-vivo changes in calcium fluorescence in GABA neurons in the zona incerta (ZI) and the ventral lateral periaqueductal grey (vlPAG), two areas that have been implicated in regulating sleep. METHODS vGAT-Cre mice were implanted with sleep electrodes, microinjected with rAAV-DIO-GCaMP6 into the ZI (n=6) or vlPAG (n=5)(isoflurane anesthesia) and a GRIN lens inserted atop the injection site. Twenty-one days later a miniscope recorded fluorescence in individual vGAT neurons over multiple REM cycles. Regions of interest corresponding to individual vGAT somata were automatically extracted with PCA-ICA analysis. RESULTS In the ZI, 372 neurons were identified. Previously, we had recorded activity of 310 vGAT neurons in the ZI (Blanco-Centurion et al., 2021) and we combined the published dataset with the new dataset to create a comprehensive dataset of ZI vGAT neurons (total neurons=682; mice=11). In the vlPAG, 169 neurons (mice=5) were identified. In both regions most neurons were maximally active in REM sleep (R-Max; ZI=51.0%, vlPAG=60.9%). The second most abundant group was W-Max (ZI=23.9%, vlPAG=25.4%). In the ZI, but not in vlPAG, there were neurons that were NREMS-Max (11.7%). vlPAG had REMS-Off neurons (8.3%). In both areas there were two minor classes: wake/REMS-Max and state indifferent. In the ZI, the NREMS-Max neurons fluoresced 30s ahead of sleep onset. CONCLUSIONS These descriptive data show that the activity of GABA neurons is biased in favor of sleep in two brain regions implicated in sleep.