Short light–dark cycles affect sleep in mice

Abstract

Environmental light has a strong impact on human physiology and behaviour, including cognitive functioning and alertness. Previous studies have shown that short light-dark (LD) cycles influence sleep in the albino rat. Rapid eye movement (REM) sleep increases after the onset of darkness and increases after light onset. In the present study, we investigated whether light affects sleep in mice. To this purpose the electroencephalogram and electromyogram of nine adult male C57BL ⁄ 6 mice was recorded under 12 : 12 h baseline LD conditions, followed by 24 h continuous darkness (DD) and 6 days with LD cycles of different durations (2 h, 30 min, 14 min, 10 min, 4 min and 2 min), presented in a randomized order. NREM sleep was evenly distributed over the light and dark intervals of all short LD cycles. REM sleep, however, was increased during the dark intervals of short (10-30 min) LD cycles. Analysis showed that in these LD cycles, the increment in REM sleep was maximal in the second minute after dark onset, where the percentage of epochs with REM sleep increased significantly to 175% of baseline values. This increase was attributable to an increase in REM sleep episode duration. The recorded responses show that sleep in mice is affected by photic stimulation. The results demonstrate that pigmented animals can show REM sleep induction after dark onset and indicate that light has significant effects on the regulation of sleep.

Evidence for Neuronal Desynchrony in the Aged Suprachiasmatic Nucleus Clock

“…Under deep anesthesia [ketamine (Aesculaap); xylazine (Bayer); and atropine (Teva Pharmachemie], the animals were implanted with miniature electroencephalogram (EEG) recording screws and electromyogram (EMG) electrodes (Plastics One) as described previously (Deboer et al, 2002. The EEG and EMG were recorded with a portable system as described previously (Vyazovskiy et al, 2006;Deboer et al, 2007).…”

Methylphenidate Modifies the Motion of the Circadian Clock

“…Animals in the behavioral part of the study were individually housed in cages equipped with running wheels (n ¼ 24), with passive infrared motion sensors (PIRs, n ¼ 12), or with both (n ¼ 9). Animals in the electrophysiology and sleep part of the study were individually housed in standard mouse cages before recording, and were transferred to large recording chambers (Deboer et al, 2007b;Houben et al, 2009). Animals started the experiment under a 12 h : 12 h lightdark cycle, with ad libitum access to food and drink throughout the experiment.…”

“…Animals (n ¼ 8) were implanted under deep anesthesia (ketamine, 100 mg/kg; xylazine, 20 mg/kg; atropine 1 mg/kg) with electroencephalogram (EEG) and electromyogram (EMG) electrodes as described previously (Deboer et al, 2007b). The electrodes were connected to a miniature receptacle and the assembly was fixed to the skull with two support screws and dental cement.…”

“…The EEG and EMG were simultaneously and continuously recorded for 48 h. EEG and EMG were recorded, amplified, filtered, and scored as previously described (Deboer et al, 2007b).…”

Retino-hypothalamic regulation of light-induced murine sleep

“…We suggest that the decrease in photically induced sleep is part of compensatory changes that return sleep to baseline levels (i.e., the response is homeostatically regulated). Support for this notion is further substantiated by the recent finding in mice where 24-h total sleep remains the same across a wide range of short LD cycles (Deboer et al, 2007). Similarly, total sleep during the entire 12-h dark period does not change when compared to baseline in both WT and MKO mice in our study.…”