Japanese Journal of Veterinary Research;Volume 68 Number 1

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The effect of temperature acclimation on torpor expression pattern in mice

Sakamoto, Kentaro Q.;Okamatsu-Ogura, Yuko

Permalink : http://hdl.handle.net/2115/76754
JaLCDOI : 10.14943/jjvr.68.1.51
KEYWORDS : mouse;thermogenesis;torpor;ucp1

Abstract

Torpor is a hibernation like status which drops core body temperature, and continues for several hours. Although torpor is observed among a wide range of mammals, most of the body mass of torpor expressing species is less than 100 g, suggesting the size of the body would be a key factor of torpor expression. In the small animals, continuous heat production is essential to keep body temperature within a certain range. Thus, we hypothesized that torpor expression pattern would be affected by the capacity of heat production. We prepared mice with different capacities of shivering and nonshivering thermogenesis, two major heat producing systems in mice. To modulate the capacity of both thermogenesis, mice were acclimated to cool (18 ℃) or warm (28 ℃) ambient temperature. Mice deficient in uncoupling protein 1 (UCP1), a protein that mediates non-shivering thermogenesis, were acclimated to cool ambient temperature to enhance capacity of shivering, but not non-shivering thermogenesis. By food deprivation, all mice in all groups expressed torpor. Although the time for induction and duration of torpor did not show any differences among the groups, the minimum body temperature during torpor in warm-acclimated mice was lower than that in cool-acclimated UCP1-knockout mice. Cool-acclimated UCP1-knockout mice did not show any significant difference in torpor expression pattern compared to cool-acclimated wild-type mice, indicating a minor role of non-shivering thermogenesis in torpor expression in our experiment condition.

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