Dataset Information

Millisecond light pulses make mice stop running, then display prolonged sleep-like behavior in the absence of light.

ABSTRACT: Masking, measured as a decrease in nocturnal rodent wheel running, is a visual system response to rod/cone and retinal ganglion cell photoreception. Here, the authors show that a few milliseconds of light are sufficient to initiate masking, which continues for many minutes without additional photic stimulation. C57J/B6 mice were tested using flash stimuli previously shown to elicit large circadian rhythm phase shifts. Ten flashes, 2 msec each and equally distributed over 5 min, activate locomotor suppression that endures for an additional 25 to 35 min in the dark and does not differ in magnitude or duration from that elicited by 5-min saturating light pulse. Locomotor activity by mice without access to running wheels is also suppressed by light flashes. The effects of various light flash patterns on mouse locomotor suppression are similar to those previously described for hamster phase shifts. Video analysis of active mice indicates that light flashes initiated at ZT13 rapidly induce an interval of behavioral quiescence that lasts about 10 min at which time the animals assume a typical sleep posture that is maintained for an additional 25 min. Thus, the period coincident with light-induced wheel running suppression appears to consist of two distinct behavioral states, one interval during which locomotor quiescence is initiated and maintained, followed by a second interval characterized by behavioral sleep. Given this sequence effected by light stimulation, we suggest that it be referred to as "photosomnolence," the term reflecting upon both the nature of the stimulus and the associated behavioral change.

SUBMITTER: Morin LP

PROVIDER: S-EPMC2853800 | biostudies-literature | 2009 Dec

REPOSITORIES: biostudies-literature

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Millisecond light pulses make mice stop running, then display prolonged sleep-like behavior in the absence of light.

Morin L P LP Studholme K M KM

Journal of biological rhythms 20091201 6

Masking, measured as a decrease in nocturnal rodent wheel running, is a visual system response to rod/cone and retinal ganglion cell photoreception. Here, the authors show that a few milliseconds of light are sufficient to initiate masking, which continues for many minutes without additional photic stimulation. C57J/B6 mice were tested using flash stimuli previously shown to elicit large circadian rhythm phase shifts. Ten flashes, 2 msec each and equally distributed over 5 min, activate locomoto ...[more]

PMID: 19926809

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Project description:The human circadian timing system is most sensitive to the phase-shifting effects of light during the biological nighttime, a time at which humans are most typically asleep. The overlap of sleep with peak sensitivity to the phase-shifting effects of light minimizes the effectiveness of using light as a countermeasure to circadian misalignment in humans. Most current light exposure treatments for such misalignment are mostly ineffective due to poor compliance and secondary changes that cause sleep deprivation. Using a 16-day, parallel group design, we examined whether a novel sequence of light flashes delivered during sleep could evoke phase changes in the circadian system without disrupting sleep. Healthy volunteers participated in a 2-week circadian stabilization protocol followed by a 2-night laboratory stay. During the laboratory session, they were exposed during sleep to either darkness (n = 7) or a sequence of 2-msec light flashes given every 30 sec (n = 6) from hours 2 to 3 after habitual bedtime. Changes in circadian timing (phase) and micro- and macroarchitecture of sleep were assessed. Subjects exposed to the flash sequence during sleep exhibited a delay in the timing of their circadian salivary melatonin rhythm compared with the control dark condition (p < 0.05). Confirmation that the flashes penetrated the eyelids is presented by the occurrence of an evoked response in the EEG. Despite the robust effect on circadian timing, there were no large changes in either the amount or spectral content of sleep (p values > 0.30) during the flash stimulus. Exposing sleeping individuals to 0.24 sec of light spread over an hour shifted the timing of the circadian clock and did so without major alterations to sleep itself. While a greater number of matched subjects and more research will be necessary to ascertain whether these light flashes affect sleep, our data suggest that this type of passive phototherapy might be developed as a useful treatment for circadian misalignment in humans.

Project description:These studies address temporal changes in gene expression during spontaneous sleep and extended wakefulness in the mouse cerebral cortex, a neuronal target for processes that control sleep; and the hypothalamus, an important site of sleep regulatory processes. We determined these changes by comparing expression in sleeping animals sacrificed at different times during the lights on period, to that in animals sleep deprived and sacrificed at the same diurnal time. Experiment Overall Design: Experiments were performed on male mice (C57/BL6), 10 weeks of age Â±1 week. Animals were housed in a light/dark cycle of 12 hrs, in a pathogen free, temperature- and humidity-controlled room (22Â°C and 45-55%, respectively) with water available ad libitum. Food was accessible for 12 hrs only during the active period. Animals were subjected to 14 days of acclimatization during which a nighttime feeding pattern was established. This was done to avoid differential food intake between mice that were subsequently sleep deprived during the lights on period and those allowed to sleep. Mice were sacrificed following 3, 6, 9 and 12 hrs of total sleep deprivation (n=5 at each time point). Deprivation was initiated at lights-on, and performed through gentle handling. Sleeping animals, which were left undisturbed, were sacrificed at the same diurnal time points as sleep deprived mice (n=5 at each time point). An additional control group of mice were sacrificed at time zero, i.e., at the time of lights-on (n=5). All mice were behaviorally monitored using the AccuScan infrared monitoring system that detects movement when the mouse crosses electronic beams (Columbus Instruments). Mice were sacrificed by cervical dislocation. Brain sectioning was performed according to the mouse brain atlas of Franklin and Paxinos . The primary and secondary motor areas (M1 and M2) of the cerebral cortex and broadly defined regions and zones of the hypothalamus were sampled. RNA was isolated with Trizol (Invitrogen) and further purified using RNeasy columns (Qiagen) as per the manufacturer's instructions.

Dataset Information

Millisecond light pulses make mice stop running, then display prolonged sleep-like behavior in the absence of light.

Publications

Millisecond light pulses make mice stop running, then display prolonged sleep-like behavior in the absence of light.

Similar Datasets

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