Chronic chemogenetic slow-wave sleep enhancement in mice.

While epidemiological associations and brief studies of sleep effects in human disease have been conducted, rigorous long-term studies of sleep manipulations and in animal models are needed to establish causation and to understand mechanisms. We have previously developed a mouse model of acute slow-wave-sleep (SWS) enhancement using chemogenetic activation of parafacial zone GABAergic neurons (PZGABA) in the parvicellular reticular formation of the pontine brainstem. However, it was unknown if SWS could be enhanced chronically in this model. In the present study, mice expressing the chemogenetic receptor hM3Dq in PZGABA were administered daily with one of three chemogenetic ligands, clozapine N-oxide (CNO), deschloroclozapine (DCZ) and compound 21 (C21), and sleep-wake phenotypes were analyzed using electroencephalogram (EEG) and electromyogram (EMG). We found that SWS time is increased for three hours, and at the same magnitude for at least six months. This phenotype is associated with an increase of slow wave activity (SWA) of similar magnitude throughout the 6-month dosing period. Interestingly, at the end of the 6-month dosing period, SWA remains increased for at least a week. This study validates a mouse model of chronic SWS enhancement that will allow mechanistic investigations into how SWS promotes physiological function and prevents diseases. The approach of a rotating schedule of three chemogenetic ligands may be broadly applicable in chemogenetic studies that require chronic administration.