title: Effects of hypoxia and hypercapnia on circadian rhythms in the golden hamster (Mesocricetus auratus).
abstract: This study was designed to determine whether respiratory stimuli can influence the mammalian circadian timing system. Three-hour pulses of hypoxia (inspired O(2) concentration = 8%) or hypercapnia (inspired CO(2) concentration = 11%) were presented for 7 days at mid-subjective day (circadian time 6-9) under constant darkness. Hypoxic and hypercapnic pulses caused cumulative phase delays of 46. 4 +/- 6.9 and 25.9 +/- 12.3 min, respectively. Distance run per day was significantly reduced on hypoxic and hypercapnic pulse days, compared with nonpulsed days. Phase shifts were correlated with the reduction in daily running activity (multiple r(2) = 0.521, P = 0.036), metabolic depression (multiple r(2) = 0.772, P < 0.001), and reduction in body temperature (multiple r(2) = 0.539, P = 0.027), but not lung ventilation (multiple r(2) = 0.306, P = 0.414) during pulses. We conclude that hypoxia and hypercapnia can influence the phase and quantity of activity in free-running hamsters.
authors.affiliation: Department of Zoology, University of Toronto, Toronto, Ontario, Canada M5S 3G5.
authors.forename: T M
authors.initials: TM
authors.lastname: Jarsky
authors.forename: R
authors.initials: R
authors.lastname: Stephenson
mesh_terms: D000818:Animals; D001831:Body Temperature; D002940:Circadian Rhythm; D006224:Cricetinae; D006935:Hypercapnia / Q000503:physiopathology*; D000860:Hypoxia / Q000503:physiopathology*; D008647:Mesocricetus; D009043:Motor Activity