The effect of 2G on mouse circadian rhythms

This study examined the effect of chronic 2G exposure on the regulation of body temperature (T(b)), activity (ACT), and circadian rhythms of mice. Five mice were implanted with biotelemetry units to record T(b) and ACT. The mice exhibited a stable daily mean of T(b) (37.1 +/- 2.1 degrees C) and ACT...

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Bibliographic Details
Published inJournal of gravitational physiology Vol. 7; no. 3; p. 79
Main Authors Murakami, D M, Fuller, C A
Format Journal Article
LanguageEnglish
Published United States 01.12.2000
Subjects
Activity Cycles - physiology
Adaptation, Physiological
Animals
Body Temperature - physiology
Centrifugation
Circadian Rhythm - physiology
Hypergravity
Male
Mice
Mice, Inbred C57BL
Monitoring, Physiologic
Telemetry
Time Factors
NASA Discipline Regulatory Physiology
Non-NASA Center
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Summary:This study examined the effect of chronic 2G exposure on the regulation of body temperature (T(b)), activity (ACT), and circadian rhythms of mice. Five mice were implanted with biotelemetry units to record T(b) and ACT. The mice exhibited a stable daily mean of T(b) (37.1 +/- 2.1 degrees C) and ACT and robust circadian rhythms during the control 1G period. Mice exhibited a significant decline in T(b) (30.1 +/- 1.5 degrees C; t(4)=8.32, p<.01) and cessation of ACT within two hours following 2G onset. After 6 hours of continuous 2G exposure there was a recovery in T(b) (34.4 +/- 1.6 degrees C) that remained significantly below that of baseline (t(4)=3.66, p<.05). A similar pattern of recovery was seen following 12 hours of continuous 2G for ACT. A slower pattern of adaptation toward baseline levels occurred steadily over the next 6-13 days. Exposure to 2G also caused an immediate 4 day loss in circadian rhythm amplitude in both T(b) and ACT. Recovery to new steady state levels was achieved by 8 days and 13 days, respectively. These results demonstrate that under chronic 2G, the recovery time for the homeostatic steady-state values and circadian rhythms are shorter for the mouse than for the rat. These differences may be related to the scaling effects of 2G resulting from the mass difference between mice and rats.
ISSN:1077-9248