title: Daily torpor affects the molecular machinery of the circadian clock in Djungarian hamsters (Phodopus sungorus).
abstract: Daily torpor in the Djungarian hamster (Phodopus sungorus) is a precisely timed event gated by the circadian clock situated in the suprachiasmatic nuclei (SCN) of the hypothalamus. Timing-controlled hypothermia during which body temperature (Tb) decreases to approximately 15 degrees C implies temperature compensation of the circadian system. Nevertheless, it remains controversial how the molecular clockwork functions at those low Tb values and whether the torpor bout affects the circadian system. In this study, we investigated rhythmic clock and clock-related gene as well as protein expression in the SCN and pineal gland of torpid and normothermic Djungarian hamsters over a 48 h cycle. We clearly demonstrate rhythmic gene expression of Per1, Bmal1 and Avp in the SCN as well as Aa-nat in the pineal gland on a day of torpor. Alterations in the phase and amplitude of these rhythms, however, may be due to decreased protein synthesis during hypothermia. This decreased protein feedback resulting from the hypothermia might also be responsible for changes in gene expression observed 1 day after a torpor bout. We conclude that temperature has at least a modulatory effect on the circadian system.
authors.affiliation: Département de Neurobiologie des Rythmes, Institut des Neurosciences Cellulaires et Intégratives, UMR-7168/LC2, CNRS-Université Louis Pasteur, Strasbourg, France. A.Herwig@rri.sari.ac.uk
authors.forename: Annika
authors.initials: A
authors.lastname: Herwig
authors.forename: Michel
authors.initials: M
authors.lastname: Saboureau
authors.forename: Paul
authors.initials: P
authors.lastname: Pevet
authors.forename: Stephan
authors.initials: S
authors.lastname: Steinlechner
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001127:Arginine Vasopressin / Q000235:genetics / Q000378:metabolism; D001831:Body Temperature / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology*; D006224:Cricetinae; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology*; D006605:Hibernation / Q000502:physiology*; D017403:In Situ Hybridization / Q000379:methods; D008297:Male; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D017111:Phodopus / Q000502:physiology*; D017440:Photoperiod; D010870:Pineal Gland / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D013493:Suprachiasmatic Nucleus / Q000502:physiology
chemical_list: D009687:Nuclear Proteins; D012333:RNA, Messenger; D001127:Arginine Vasopressin