Ambient temperature during torpor affects NREM sleep EEG during arousal episodes in hibernating European ground squirrels (original) (raw)
Related papers
Journal of Sleep Research, 1997
EEG's were recorded in hibernating European ground squirrels during euthermic arousal episodes at an ambient temperature of 5.5°C. Spontaneous torpor bouts ranged from 6 to 15 days, body temperature during torpor was 7.5°C. The torpor duration prior to EEG measurements was experimentally manipulated: the animals were induced to arouse by gentle handling after torpor of less then 1 day (n=3), 1-2 days (n=6), 3-4 days (n=9) and 5-12 days (n=9). The animals slept 71.5% of euthermic time, of which 61.4% NREM and 10.2% REM sleep. NREM percentage was slightly positively and REM percentage negatively correlated with prior torpor duration (TD). Spectral analysis showed changes in EEG activity during the euthermic phase in the slow wave frequency range (1-4 Hz) and in higher frequencies. Prior TD specifically affected the slow waves. Slow wave activity decreased exponentially during the euthermic phase. The initial slow wave activity showed a systematic increase with prior TD, which could be described by an exponentially saturating function, albeit with a relatively small time constant compared with spontaneous torpor duration. It is concluded that sleep during arousal episodes following torpor at an ambient temperature of 5.5°C is affected both in structure and intensity by prior TD. The results are consistent with the proposition that torpor inhibits the restorative function of sleep.
Warming up for sleep? - ground squirrels sleep during arousals from hibernation
Neuroscience Letters, 1991
Hypothermia during mammalian hibernation is periodically interrupted by arousals to euthermy, the function of which is unknown. We report that arctic ground squirrels (Spermophilus parryiO consistently sleep during these arousals, and that their EEG shows the decrease in slow wave activity (8 power) that is characteristic of a declining requirement for sleep. These results are consistent with the novel hypothesis that the need for sleep slowly accumulates during torpor, and that returning to euthermy is periodically required to allow sleep. Sleep thus seems to be energetically expensive for a hibernating mammal, and cannot be considered solely a strategy for saving energy.
The Relationship of Sleep with Temperature and Metabolic Rate in a Hibernating Primate
PLoS ONE, 2013
Study Objectives: It has long been suspected that sleep is important for regulating body temperature and metabolic-rate. Hibernation, a state of acute hypothermia and reduced metabolic-rate, offers a promising system for investigating those relationships. Prior studies in hibernating ground squirrels report that, although sleep occurs during hibernation, it manifests only as non-REM sleep, and only at relatively high temperatures. In our study, we report data on sleep during hibernation in a lemuriform primate, Cheirogaleus medius. As the only primate known to experience prolonged periods of hibernation and as an inhabitant of more temperate climates than ground squirrels, this animal serves as an alternative model for exploring sleep temperature/metabolism relationships that may be uniquely relevant to understanding human physiology.
Journal of Comparative Physiology B, 2012
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Are ground squirrels sleep deprived during hibernation?
The American journal of physiology, 1991
Hibernation is an adaptation for energy conservation, which probably evolved as an extension of non-rapid-eye-movement sleep mechanisms. Yet, during periodic arousals from bouts of deep hibernation, ground squirrels (Spermophilus lateralis) spend most of their time asleep. Spectral analysis of the electroencephalogram revealed that cortical slow-wave intensity during sleep is high at the beginning of a euthermic period and declines thereafter. Sleep slow-wave intensity is greater after longer bouts of hibernation than after shorter bouts. We hypothesize that low body temperatures during hibernation are incompatible with the restorative function of sleep as reflected in cortical slow-wave activity. Animals must incur the energetic costs of periodic arousals from hibernation to receive the restorative benefits of euthermic slow-wave sleep. The timing of arousals from hibernation may be a function of accumulated sleep debt.
Energetics of arousal episodes in hibernating arctic ground squirrels
Journal of Comparative Physiology B, 2009
Arctic ground squirrels overwintering in northern Alaska experience average soil temperature of-10°C. To examine energetic costs of arousing from hibernation under arctic compared to temperate conditions, captive ground squirrels were maintained in ambient temperatures (T a) of 2,-5 and-12°C. Rates of oxygen consumption and carbon dioxide production were used to estimate metabolic rate and fuel use during the three phases of arousal episodes: rewarming, euthermia, and recooling. Respiratory quotient comparisons suggest exclusive use of lipid during rewarming and mixed fuel use during euthermia. Animals rewarming from torpor at T a-12°C took longer, consumed more oxygen, and attained higher peak rates of oxygen consumption when compared to 2°C. T a had no significant effect on cost or duration of the euthermic phase. Animals recooled faster at-12°C than at 2°C, but total oxygen consumption was not different. T a had no significant effect on the total cost of arousal episodes when all three phases are included. Arousal episodes account for 86% of estimated costs of a complete hibernation cycle including torpor when at 2°C and only 23% at-12°C. Thus, due to the higher costs of steady-state metabolism during torpor, proportional metabolic costs of arousal episodes at T a characteristic of the Arctic are diminished compared to relative costs of arousals in more temperate conditions. Keywords Oxygen consumption Á Ground squirrel Á Spermophilus Á Metabolic rate Á Arousal Á Arctic Abbreviations T a Ambient temperature T b Body temperature MR Metabolic rate BMR Basal metabolic rate RQ Respiratory quotient Communicated by H. V. Carey.
CNS control of body temperature during hibernation
Cryobiology, 1971
The hypothalami of golden-mantled ground squirrels at various stages of hibernation were heated and cooled while rates of heat production and loss were continuously monitored. 2. The hypothalamus of the euthermic squirrel between bouts of torpor is extremely sensitive to temperature displacement and activates thermoregulatory mechanisms with little or no negative feedback from extrahypothalamic core or peripheral receptors. 3. During deep hibernation the CNS regulator of body temperature is inactive. 4. Low temperatures which induce arousals are sensed in the brain but probably not in the hypothalamus. 5. Arousals involve a rapid re-activation of the hypothalamic temperature regulator and a rapid rise in the set point for body temperature to the euthermic level.