• Jeffrey Hubbard, Elisabeth Ruppert, Laurent Calvel, Ludivine Robin-Choteau, Claire-Marie Gropp, Caroline Allemann, Sophie Reibel, Dominique Sage-Ciocca, and Patrice Bourgin.
• Centre National de la Recherche Scientifique (CNRS)-UPR 3212, Institute of Cellular and Integrative Neurosciences, Strasbourg, France.
• Sleep. 2015 Jan 1;38(6):979-88.

Study ObjectivesSleep neurobiology studies use nocturnal species, mainly rats and mice. However, because their daily sleep/wake organization is inverted as compared to humans, a diurnal model for sleep studies is needed. To fill this gap, we phenotyped sleep and waking in Arvicanthis ansorgei, a diurnal rodent widely used for the study of circadian rhythms.DesignVideo-electroencephalogram (EEG), electromyogram (EMG), and electrooculogram (EOG) recordings.SettingRodent sleep laboratory.ParticipantsFourteen male Arvicanthis ansorgei, aged 3 mo.Interventions12 h light (L):12 h dark (D) baseline condition, 24-h constant darkness, 6-h sleep deprivation.Measurements And ResultsWake and rapid eye movement (REM) sleep showed similar electrophysiological characteristics as nocturnal rodents. On average, animals spent 12.9 h ± 0.4 awake per 24-h cycle, of which 6.88 h ± 0.3 was during the light period. NREM sleep accounted for 9.63 h ± 0.4, which of 5.13 h ± 0.2 during dark period, and REM sleep for 89.9 min ± 6.7, which of 52.8 min ± 4.4 during dark period. The time-course of sleep and waking across the 12 h light:12 h dark was overall inverted to that observed in rats or mice, though with larger amounts of crepuscular activity at light and dark transitions. A dominant crepuscular regulation of sleep and waking persisted under constant darkness, showing the lack of a strong circadian drive in the absence of clock reinforcement by external cues, such as a running wheel. Conservation of the homeostatic regulation was confirmed with the observation of higher delta power following sustained waking periods and a 6-h sleep deprivation, with subsequent decrease during recovery sleep.ConclusionsArvicanthis ansorgei is a valid diurnal rodent model for studying the regulatory mechanisms of sleep and so represents a valuable tool for further understanding the nocturnality/diurnality switch.© 2015 Associated Professional Sleep Societies, LLC.

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