スイミン ト セイタイ リズム
Sleep and Biological Clock
Circadian rhythm is an endogenous rhythm controlled by a master oscillator (biological clock) in the supra-chiasmatic nucleus (SCN), affecting on the almost all physiological functions including sleep/wake regulation. Recently the biological clock has been shown to function at the molecular level, and several circadian-related genes have been identified, such as the Clock, Per 1-3, Bmal 1 or Cry 1, 2.
We observed the sleep/wake rhythm in cry 1, 2 double knockout mice and clock mutant mice. Both strains have lost the circadian oscillation in the expression of circadian-related genes. Cry 1, 2 double knockout mice show the entrained sleep/wake rhythm to ordinary light-dark (LD) cycle, although they show completely flattened rhythm under the constant dark (DD) condition. On the other hand, clock mutant mice show the persistent circadian sleep/wake rhythm under even DD conditions. Although the expression of circadian-related genes do not oscillate, the clock mutant mice have potent circadian rhythm in body core temperature, behavior, sleep/wake and cortisol etc. The clock mutant mice have a longer (27 hrs) period of free-running rhythm under DD condition, and the phase of sleep/wake rhythm is delayed for about two hours comparing to the wild-type under LD condition.
The important role of the circadian-related genes in the sleep/wake regulation has been indicated. The functional impairment of the circadian-related genes may be involved in the sleep disorders, such as insomnia or hypersomnia.
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