Torpor expression in juvenile and adult Djungarian hamsters (Phodopus sungorus) differs in frequency, duration and onset in response to a daily cycle in ambient temperature

Diedrich, Victoria; Bank, Jonathan; Scherbarth, Frank; Steinlechner, Stephan

doi:10.1016/j.jtherbio.2015.08.006

Journal of Thermal Biology

2015

DOI: 10.1016/j.jtherbio.2015.08.006

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Torpor expression in juvenile and adult Djungarian hamsters (Phodopus sungorus) differs in frequency, duration and onset in response to a daily cycle in ambient temperature

Victoria Diedrich¹,

Jonathan Bank²,

Frank Scherbarth³

et al.

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Cited by 3 publications

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References 41 publications

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“…Photoresponsiveness does not correlate with sex (Puchalski and Lynch 1991) but is heritable (Lynch et al 1989;Goldman and Goldman 2003). Despite numerous studies Lynch 1986, 1988;Lynch et al 1989;Kliman and Lynch 1992;Bernard et al 1997, Freeman andGoldman 1997a, b;Freeman and Goldman 1997a;Gorman and Zucker 1997;Anchordoquy and Lynch 2000;Goldman et al 2000;Goldman and Goldman 2003;Diedrich et al 2015), the phenomenon of polymorphism in winter phenotype still remains unexplained, although it may affect fitness, altering both longevity (Turbill et al 2012) and reproduction (Place et al 2004;Heideman et al 2005;Place and Cruickshank 2009;Przybylska et al 2019b).…”

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confidence: 99%

Predictive and reactive changes in antioxidant defence system in a heterothermic rodent

2020

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Living in a seasonal environment requires periodic changes in animal physiology, morphology and behaviour. Winter phenotype of small mammals living in Temperate and Boreal Zones may differ considerably from summer one in multiple traits that enhance energy conservation or diminish energy loss. However, there is a considerable variation in the development of winter phenotype among individuals in a population and some, representing the non-responding phenotype (non-responders), are insensitive to shortening days and maintain summer phenotype throughout a year. Differences in energy management associated with the development of different winter phenotypes should be accompanied by changes in antioxidant defence capacity, leading to effective protection against oxidative stress resulting from increased heat production in winter. To test it, we analysed correlation of winter phenotypes of Siberian hamsters (Phodopus sungorus) with facultative non-shivering thermogenesis capacity (NST) and oxidative status. We found that in both phenotypes acclimation to winter-like conditions increased NST capacity and improved antioxidant defence resulting in lower oxidative stress (OS) than in summer, and females had always lower OS than males. Although NST capacity did not correlate with the intensity of OS, shortly after NST induction responders had lower OS than non-responders suggesting more effective mechanisms protecting from detrimental effects of reactive oxygen metabolites generated during rewarming from torpor. We suggest that seasonal increase in antioxidant defence is programmed endogenously to predictively prevent oxidative stress in winter. At the same time reactive upregulation of antioxidant defence protects against reactive oxygen species generated during NST itself. It suggests that evolution of winter phenotype with potentially harmful characteristics was counterbalanced by the development of protective mechanisms allowing for the maintenance of phenotypic adjustments to seasonally changing environment.

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Predictive and reactive changes in antioxidant defence system in a heterothermic rodent

2020

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Gene expression analysis and microdialysis suggest hypothalamic triiodothyronine (T3) gates daily torpor in Djungarian hamsters (Phodopus sungorus)

et al. 2017

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Thyroid hormones play an important role in regulating seasonal adaptations of mammals. Several studies suggested that reduced availability of 3,3',5-triiodothyronine (T3) in the hypothalamus is required for the physiological adaptation to winter in Djungarian hamsters. We have previously shown that T3 is involved in the regulation of daily torpor, but it remains unclear, whether T3 affects torpor by central or peripheral mechanisms. To determine the effect of T3 concentrations within the hypothalamus in regulating daily torpor, we tested the hypothesis that low hypothalamic T3 metabolism would favour torpor and high T3 concentrations would not. In experiment 1 gene expression in torpid hamsters was assessed for transporters carrying thyroid hormones between cerebrospinal fluid and hypothalamic cells and for deiodinases enzymes, activating or inactivating T3 within hypothalamic cells. Gene expression analysis suggests reduced T3 in hypothalamic cells during torpor. In experiment 2, hypothalamic T3 concentrations were altered via microdialysis and torpor behaviour was continuously monitored by implanted body temperature transmitters. Increased T3 concentrations in the hypothalamus reduced expression of torpor as well as torpor bout duration and depth. Subsequent analysis of gene expression in the ependymal layer of the third ventricle showed clear up-regulation of T3 inactivating deiodinase 3 but no changes in several other genes related to photoperiodic adaptations in hamsters. Finally, serum analysis revealed that increased total T3 serum concentrations were not necessary to inhibit torpor expression. Taken together, our results are consistent with the hypothesis that T3 availability within the hypothalamus significantly contributes to the regulation of daily torpor via a central pathway.

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Physiological differences between winter phenotypes of Siberian hamsters do not correlate with their behaviour

2019

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Torpor expression in juvenile and adult Djungarian hamsters (Phodopus sungorus) differs in frequency, duration and onset in response to a daily cycle in ambient temperature

Cited by 3 publications

References 41 publications

Predictive and reactive changes in antioxidant defence system in a heterothermic rodent

Predictive and reactive changes in antioxidant defence system in a heterothermic rodent

Gene expression analysis and microdialysis suggest hypothalamic triiodothyronine (T3) gates daily torpor in Djungarian hamsters (Phodopus sungorus)

Physiological differences between winter phenotypes of Siberian hamsters do not correlate with their behaviour

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