The Suprachiasmatic Nucleus Regulates Sleep Timing and Amount in Mice

Dec 14, 2004Sleep

The brain’s internal clock controls when and how much mice sleep

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Abstract

SCN-lesioned mice showed a decrease in sleep consolidation and wakefulness during the dark phase compared to sham controls.

The suprachiasmatic nuclei (SCN) are linked to the timing and consolidation of the sleep-wake cycle.
SCN-lesioned mice had reduced sleep consolidation compared to controls.
After sleep deprivation, SCN-lesioned mice had a diminished increase in non-rapid eye movement sleep time.
Despite changes in sleep time, SCN-lesioned mice exhibited a similar increase in electroencephalographic delta power as sham controls after sleep deprivation.
These results suggest that while the SCN influence sleep consolidation and wakefulness, they may not regulate sleep recovery mechanisms.

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CONTEXT: Sleep is regulated by circadian and homeostatic processes. The circadian pacemaker, located in the suprachiasmatic nuclei (SCN), regulates the timing and consolidation of the sleep-wake cycle, while a homeostatic mechanism governs the accumulation of sleep debt and sleep recovery. Recent studies using mice with deletions or mutations of circadian genes show that components of the circadian pacemaker can influence the total amount of baseline sleep and recovery from sleep deprivation, indicating a broader role for the SCN in sleep regulation.

OBJECTIVE: To further investigate the role of the circadian pacemaker in sleep regulation in mice, we recorded sleep in sham and SCN-lesioned mice under baseline conditions and following sleep deprivation.

RESULTS: Compared to sham controls, SCN-lesioned mice exhibited a decrease in sleep consolidation and a decrease in wakefulness during the dark phase. Following sleep deprivation, SCN-lesioned mice exhibited an attenuated increase in non-rapid eye movement sleep time but an increase in non-rapid eye movement sleep electroencephalographic delta power that was similar to that of the sham controls.

CONCLUSIONS: These findings support the hypothesis that the SCN consolidate the sleep-wake cycle by generating a signal of arousal during the subjective night (ie. the active period), thereby having the capacity to alter baseline sleep amount. Although the SCN are not involved in sleep homeostasis as defined by the increase in electroencephalographic delta power after sleep deprivation, the SCN does play a central role in the regulation of sleep and wakefulness beyond just the timing of vigilance states.

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The Suprachiasmatic Nucleus Regulates Sleep Timing and Amount in Mice

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