Hibernation and the Endocrines

Lyman, Charles P.

doi:10.1016/b978-0-12-460420-9.50016-7

Cited by 30 publications

(38 citation statements)

References 83 publications

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“…Once the animals enter into hibernation, they develop an energy conserving behavior and undergo deep bouts of hypothermia (or torpor) alternated with short euthermic intervals termed periodic arousals (3). By using fat stores as their primary source of energy and reducing carbohydrate metabolism, hibernating mammals sustain vital functions during prolonged periods without feeding and support periodic rewarming during interbout arousals (4).…”

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confidence: 99%

Rapid and reversible changes in intrahippocampal connectivity during the course of hibernation in European hamsters

Magariños

McEwen

Saboureau

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

124

102

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The hippocampal formation is a highly plastic brain structure that undergoes structural remodeling in response to internal and external challenges such as metabolic imbalance and repeated stress. We investigated whether the extreme alterations in metabolic status that occur during the course of hibernation in European hamsters cause structural changes in the dendritic arborizations of the CA3 pyramidal neurons and their main excitatory afferents, the mossy fiber terminals (MFT), that originate in the dentate gyrus. We report that apical, but not basal, dendritic trees of Golgiimpregnated CA3 principal neurons are significantly shorter, less branched, and less spiny in hypothermic hamsters compared with active animals. After the induction of arousal from torpor, within 2 h, the apical dendritic lengths, branching patterns, and spine density estimations returned to levels found in active, euthermic hamsters. The ultrastructure of MFT in hibernating hamsters showed a significant reduction in synaptic vesicle density and in the percentage of MFT area covered by spine profiles. Awakened hamsters showed restoration of MFT morphology to that seen in active animals. MFT of torpid animals also showed a significant increase in the percentage area of mitochondrial profiles that remained higher 3 h after induced arousal from hibernation compared with euthermic controls. Thus, the torpid/awakening cycle of the hibernating European hamster causes a rapid and reversible morphological reorganization of intrahippocampal subregions involved in information processing. The reported reductions in morphological connectivity between the dentate gyrus and the CA3 subregions could underlie the cessation of exploratory activity and spatial navigation skills during hibernation.CA3 region ͉ hippocampus ͉ mossy fibers ͉ spines ͉ Golgi impregnation H ibernation is a highly regulated physiological response to adverse environmental conditions characterized by hypothermia and drastic reductions of metabolic rate (1). Hibernating species can adapt to anticipated scarcity in food supply and decreases in ambient temperature by storing food and increasing food intake for several weeks before winter starts (2). Once the animals enter into hibernation, they develop an energy conserving behavior and undergo deep bouts of hypothermia (or torpor) alternated with short euthermic intervals termed periodic arousals (3). By using fat stores as their primary source of energy and reducing carbohydrate metabolism, hibernating mammals sustain vital functions during prolonged periods without feeding and support periodic rewarming during interbout arousals (4).The physiological mechanisms triggering hibernation are very complex and far from being well known. Its seasonal occurrence is primarily regulated by the annual photoperiodic variations, and the neuroendocrine and neural mechanisms involved have been partly identified (5-8). The hippocampus, a target brain region for stressful challenges and adrenal steroids (9), has been postulated as a key structure in th...

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mentioning

confidence: 99%

Rapid and reversible changes in intrahippocampal connectivity during the course of hibernation in European hamsters

Magariños

McEwen

Saboureau

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

124

102

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“…3). Because T skin in torpor is to a large extent a function of T a , 28 and the metabolic rate of small heterotherms decreases exponentially with a fall in body temperature, 22,29,30 a fast reduction in T skin inside fast cooling roosts will result in a more pronounced reduction of energy and water expenditure. Moreover, such perforated roosts can actually facilitate convectional heat loss in normothermic bats during the day as generally heat exchange in mammals increases with wind speed 31,32 .…”

Section: Resultsmentioning

confidence: 99%

How to keep cool in a hot desert: Torpor in two species of free-ranging bats in summer

2016

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Small insectivorous tree-roosting bats are among the most taxonomically diverse group of mammals in Australia's desert, yet little is known about their thermal physiology, torpor patterns and roosting ecology, especially during summer. We used temperature-telemetry to quantify and compare thermal biology and roost selection by broad-nosed bats Scotorepens greyii (6.3 g; n = 11) and Scotorepens balstoni (9.9 g; n = 5) in Sturt National Park (NSW Australia) over 3 summers (2010–13). Both vespertilionids used torpor often and the total time bats spent torpid was ∼7 h per day. Bats rewarmed using entirely passive rewarming on 44.8% (S. greyii) and 29.4% (S. balstoni) of all torpor arousals. Both bat species roosted in hollow, cracked dead trees relatively close to the ground (∼3 m) in dense tree stands. Our study shows that torpor and passive rewarming are 2 common and likely crucial survival traits of S. greyii and S. balstoni.

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“…Seasonal hibernators that rely on endogenous fuels during winter typically exhibit circannual cycles of hibernation, reproduction, growth and fattening (Lyman et al, 1982), as exemplified by many ground-dwelling sciurid rodents such as ground squirrels and marmots. Ground squirrels are homeothermic during most of the active season and become heterothermic during the hibernation season, which is characterized by weeks of torpor when animals profoundly decrease body temperature (T b ) and metabolic rate (MR).…”

Section: Circannual Hibernation Rhythmsmentioning

confidence: 99%

Animal-microbial symbioses in changing environments

Carey

Duddleston

2014

Journal of Thermal Biology

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The environments in which animals have evolved and live have profound effects on all aspects of their biology. Predictable rhythmic changes in the physical environment are arguably among the most important forces shaping the evolution of behavior and physiology of animals, and to anticipate and prepare for these predictable changes animals have evolved biological clocks. Unpredictable changes in the physical environment have important impacts on animal biology as well. The ability of animals to cope with and survive unpredictable perturbations depends on phenotypic plasticity and/or microevolution. From the time metazoans first evolved from their protistan ancestors they have lived in close association with a diverse array of microbes that have influenced, in some way, all aspects of the evolution of animal structure, function and behavior. Yet, few studies have addressed whether daily or seasonal rhythms may affect, or be affected by, an animal’s microbial symbionts. This survey highlights how biologists interested in the ecological and evolutionary physiology of animals whose lifestyles are influenced by environmental cycles may benefit from considering whether symbiotic microbes have shaped the features they study.

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Hibernation and the Endocrines

Cited by 30 publications

References 83 publications

Rapid and reversible changes in intrahippocampal connectivity during the course of hibernation in European hamsters

Rapid and reversible changes in intrahippocampal connectivity during the course of hibernation in European hamsters

How to keep cool in a hot desert: Torpor in two species of free-ranging bats in summer

Animal-microbial symbioses in changing environments

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