title: Entrainment of temperature and activity rhythms to restricted feeding in orexin knock out mice.
abstract: Ablation of the SCN, an established circadian clock, does not abolish food entrainment, suggesting that the food-entrainable oscillator (FEO) must lie outside the SCN. Typically, animals show anticipatory locomotor activity and rise in core body temperature under the influence of the FEO. Signals from the FEO would, therefore, converge onto arousal neurons so that the animal might forage for food. In the present study, we investigate whether the neuropeptide orexin, which has been linked to arousal, might transduce the arousal signal. Orexin-knockout (orexin-KO) and wildtype (WT) mice (both C57BL/6J derived) were implanted with MiniMitter transmitters that recorded core body temperature and activity (12 h LD cycle). After a week of ad-libitum feeding, the mice were given access to food for 4 h (ZT 4-8) for nine days followed by 2-days of fasting. When orexin-KO mice were placed in a restricted feeding schedule, both core body temperature and activity entrained to the feeding schedule. In these mice gross locomotor activity was severely blunted during the nine day period of restricted feeding (-79.4+/-6.3%) from the WT, but they showed an increase in core body temperature in anticipation to the meal time similar to the WT mice. There was no difference in the amount of food intake between the genotypes. We conclude that orexin is not required for entrainment of activity and temperature to a restricted feeding schedule, but is required for the robust expression of gross locomotor activity in anticipation of the scheduled feeding.
authors.affiliation: West Roxbury VA Medical Center and Harvard Medical School, 1400 VFW Parkway, West Roxbury, MA 02132, USA.
authors.forename: Satvinder
authors.initials: S
authors.lastname: Kaur
authors.forename: Stephen
authors.initials: S
authors.lastname: Thankachan
authors.forename: Suraiya
authors.initials: S
authors.lastname: Begum
authors.forename: Carlos
authors.initials: C
authors.lastname: Blanco-Centurion
authors.forename: Takeshi
authors.initials: T
authors.lastname: Sakurai
authors.forename: Masashi
authors.initials: M
authors.lastname: Yanagisawa
authors.forename: Priyattam J
authors.initials: PJ
authors.lastname: Shiromani
mesh_terms: D000818:Animals; D001143:Arousal / Q000502:physiology; D031204:Caloric Restriction; D005215:Fasting / Q000502:physiology; D005838:Genotype; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics* / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009043:Motor Activity / Q000502:physiology*; D009479:Neuropeptides / Q000235:genetics* / Q000502:physiology*; D000068797:Orexins; D010507:Periodicity; D015398:Signal Transduction / Q000502:physiology; D013696:Temperature
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D000068797:Orexins