Chemogenetic Induction of Sleep via Targeted Manipulation of Sleep Regulatory Circuits of the Brain

Abstract

In the U.S. alone, more than fifty million people suffer from chronic sleep disorders and sleep deprivation. Although sleep aids are commonly used as a remedy, they generally do not replicate natural sleep. Manipulation of sleep/wake-regulating centers can drive the system into either sleep or wake states by leveraging the brain’s natural sleep circuits. In a series of studies, we used chemogenetics as a neuromodulation tool to activate neurons of three sleep-promoting centers in transgenic mice: A2a receptor-expressing neurons of the Nucleus Accumbens core (NAccA2aR), GABAergic neurons of the Ventral Tegmental Area (VTAGABA), and the Parafacial Zone (PZGABA). Our objective was to determine whether this induced sleep could affect cognition and behaviors in a mouse model. We transfected each neuronal population with a Cre-dependent adeno-associated viral (AAV) vector encoding the excitatory hM3Dq receptors and administered varying concentrations of Clozapine-N-Oxide (CNO) to activate them. The resulting sleep/wake states were analyzed using EEG/EMG recordings. To assess the effects of sleep on behavior, we divided the mice into three groups: normal sleep, sleep-deprived, and extra sleep. Extra sleep was induced by activating the hM3Dq-expressing neurons. Using multiple behavioral tests, we assessed the effects of sleep on learning and memory, anxiety-like, and depression-like behaviors. Our results indicate that following CNO administration, NAccA2aR increases both NREM and REM sleep for 4 hours; VTAGABA selectively increases NREM sleep with no effect on REM sleep for 8 hours; and PZGABA significantly increases NREM sleep for 3 hours but suppresses REM sleep for 6 hours. Importantly, the delta frequency 3 distribution of the induced NREM sleep from each region is comparable to natural sleep, suggesting that activating the brain’s endogenous sleep circuits produces physiologically normal sleep. Results from the behavioral tests demonstrate that acute sleep deprivation may improve anxiety and depression-like behaviors in mice, and the memory tests suggest that the timing of sleep interventions is important in memory consolidation and recall. Collectively, our studies validate three distinct sleep-promoting regions that can be activated to increase NREM sleep significantly, and we demonstrate that this increase in NREM sleep can be used to modulate cognition and behaviors in mice.