Telemetric study of sleep architecture and sleep homeostasis in the day-active tree shrew Tupaia belangeri.
STUDY OBJECTIVES
In this study the authors characterized sleep architecture and sleep homeostasis in the tree shrew, Tupaia belangeri, a small, omnivorous, day-active mammal that is closely related to primates.


DESIGN
Adult tree shrews were individually housed under a 12-hr light/12-hr dark cycle in large cages containing tree branches and a nest box. The animals were equipped with radio transmitters to allow continuous recording of electroencephalogram (EEG), electromyogram (EMG), and body temperature without restricting their movements. Recordings were performed under baseline conditions and after sleep deprivation (SD) for 6 hr or 12 hr during the dark phase.


MEASUREMENTS AND RESULTS
Under baseline conditions, the tree shrews spent a total of 62.4 ± 1.4% of the 24-hr cycle asleep, with 91.2 ± 0.7% of sleep during the dark phase and 33.7 ± 2.8% sleep during the light phase. During the dark phase, all sleep occurred in the nest box; 79.6% of it was non-rapid eye movement (NREM) sleep and 20.4% was rapid eye movement (REM) sleep. In contrast, during the light phase, sleep occurred almost exclusively on the top branches of the cage and only consisted of NREM sleep. SD was followed by an immediate increase in NREM sleep time and an increase in NREM sleep EEG slow-wave activity (SWA), indicating increased sleep intensity. The cumulative increase in NREM sleep time and intensity almost made up for the NREM sleep that had been lost during 6-hr SD, but did not fully make up for the NREM sleep lost during 12-hr SD. Also, only a small fraction of the REM sleep that was lost was recovered, which mainly occurred on the second recovery night.


CONCLUSIONS
The day-active tree shrew shares most of the characteristics of sleep structure and sleep homeostasis that have been reported for other mammalian species, with some peculiarities. Because the tree shrew is an established laboratory animal in neurobiological research, it may be a valuable model species for studies of sleep regulation and sleep function, with the added advantage that it is a day-active species closely related to primates.
['Coolen|Alex|A|', 'Hoffmann|Kerstin|K|', 'Barf|R Paulien|RP|', 'Fuchs|Eberhard|E|', 'Meerlo|Peter|P|']
D000818:Animals D001831:Body Temperature D002940:Circadian Rhythm D004569:Electroencephalography D004576:Electromyography D005260:Female D006706:Homeostasis D012890:Sleep D012894:Sleep Stages D013686:Telemetry D014417:Tupaia
sleep homeostasis Tree shrew day-active mammal body temperature sleep deprivation circadian rhythm diurnal activity radio telemetry