International Union for Circumpolar Health Ministry of Public Health and Social Development of RF Russian Academy of Medical Sciences Siberian Branch of Russian Academy of Medical Sciences Siberian Branch of Russian Academy of Sciences Medical Polar Fund “Science” The Northern Forum

Abstracts

Environmental health

Background. The master circadian clock, located in the mammalian suprachiasmatic nuclei (SCN), generates and coordinates circadian rhythmicity. Light is the most powerful synchronizer of the SCN. Although other non-photic cues also have the potential to influence the circadian clock, their effects can be masked by photic cues. We have previously shown that scheduled feeding entrains the SCN under constant dark conditions.

Objectives. The purpose of this study was to investigate which non-photic signals are responsible for entrainment of the SCN to scheduled feeding in constant darkness in house mouse (Mus musculus) lines that differ in their ability to entrain.

Methods. In the standard scheduled feeding paradigm, mice were initially housed in 12:12 light-dark cycle with access to food for 6 hours during the light period followed by 4-6 months of constant dark under the same feeding schedule. Wheel running behavior was used to assess the phase of the SCN. To assess signals used for entrainment, the standard paradigm was altered to assess the role of locomotor activity (blocking of wheel), phase relationship between food and light (food initially available in the dark period), disturbance (ad libitum food with disturbances associated with food handling), neural signals from the digestive system (subdiaphragmatic vagotomies).

Results. Comparisons of experimental and control groups revealed that locomotor activity did not influence the ability to entrain to scheduled feeding. The phase relationship between food and light, disturbance, and neural signals from the digestive system all appeared to contribute to the ability to entrain to scheduled feeding. However, none of these signals alone fully explains entrainment ability.

Conclusions. Our results indicate that entrainment to scheduled feeding in mice is a complex trait dependant on a variety of non-photic (neuro-) physiological and environmental signals. The relevance of these findings to human health in the Arctic will be discussed.

Note. Abstracts are published in author's edition

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Last update: 06-Jul-2012 (11:52:05)