Chronic chemogenetic slow-wave sleep enhancement in mice

Abstract

While epidemiological associations and brief studies of sleep effects in human disease have been conducted, rigorous long-term studies of sleep manipulations 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 once daily with, sequentially, the 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 following the administration of the chemogenetic ligand, and at the same magnitude for at least six months. This phenotype is associated with longer SWS episode duration and an increase of slow wave activity (SWA) of similar magnitude throughout the six-month dosing period. Interestingly, following the end of the six-month dosing period, SWA remains increased for at least a week. In control mice, six-month long daily administration of the chemogenetic ligands did not affect SWS quantity or quality. 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.