title: Decreases in body temperature and body mass constitute pre-hibernation remodelling in the Syrian golden hamster, a facultative mammalian hibernator.
abstract: Hibernation is an adaptive strategy for surviving during periods with little or no food availability, by profoundly reducing the metabolic rate and the core body temperature (T b). Obligate hibernators (e.g. bears, ground squirrels, etc.) hibernate every winter under the strict regulation of endogenous circannual rhythms, and they are assumed to undergo adaptive remodelling in autumn, the pre-hibernation period, prior to hibernation. However, little is known about the nature of pre-hibernation remodelling. Syrian hamsters (Mesocricetus auratus) are facultative hibernators that can hibernate irrespective of seasons when exposed to prolonged short photoperiod and cold ambient temperature (SD-Cold) conditions. Their T b set point reduced by the first deep torpor (DT) and then increased gradually after repeated cycles of DT and periodic arousal (PA), and finally recovered to the level observed before the prolonged SD-Cold in the post-hibernation period. We also found that, before the initiation of hibernation, the body mass of animals decreased below a threshold, indicating that hibernation in this species depends on body condition. These observations suggest that Syrian hamsters undergo pre-hibernation remodelling and that T b and body mass can be useful physiological markers to monitor the remodelling process during the pre-hibernation period.
authors.affiliation: Department of Genetics, Graduate School of Pharmaceutical Sciences , The University of Tokyo , Bunkyo-ku, Tokyo 113-0033 , Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Chayama
authors.affiliation: Department of Genetics, Graduate School of Pharmaceutical Sciences , The University of Tokyo , Bunkyo-ku, Tokyo 113-0033 , Japan.
authors.forename: Lisa
authors.initials: L
authors.lastname: Ando
authors.affiliation: Department of Pharmacology, Faculty of Pharmacy and Pharmaceutical Sciences , Fukuyama University , Fukuyama 729-0292 , Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Tamura
authors.affiliation: Department of Genetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan; AMED-CREST, Japan Agency for Medical Research and Development, Chiyoda-ku, Tokyo 100-0004, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Miura
authors.affiliation: Department of Genetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan; Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Chiyoda-ku, Tokyo 102-0076, Japan.
authors.forename: Yoshifumi
authors.identifier: 0000-0001-7340-4557
authors.initials: Y
authors.lastname: Yamaguchi
keywords: Syrian hamster; body temperature control; body mass; cold acclimation; hibernation; photoperiod