Sleep and circadian rhythm of senescence-accelerated mice (SAM)P8 and R1

The circadian rhythm and sleep architecture of senescence-accelerated mice (SAM)P8 and SAMR1 were evaluated to utilize SAM as a model of age-related sleep disorders. The evaluation of the circadian rhythm based on the locomotor activity was performed from 1 to 5 months old SAMP8 and SAMR1. At 6 months of age, mice were chronically implanted with electroencephalograph and electromyogram electrodes for polysomnographic recording of sleep-wake states. The vigilance states were automatically classified by SleepSign ver.3 software. First, the circadian rhythm was evaluated. Comparing the locomotor activity ratio of 12 h dark period vs.12 h light period, SAMR1 showed its ratio between 3.7 to 5.4, while that of SAMP8 showed between 1.6 to 2.5. Therefore, it was shown that SAMP8 has a smaller circadian rhythm amplitude than SAMR1. Next, the sleep architecture was evaluated. The non-rapid eye movement (REM) sleep amount and the REM sleep amount of SAMP8 mice showed significantly lower than those of SAMR1. The duration of non-REM sleep in SAMP8 mice was significantly shorter than that of SAMR1, suggesting that sleep quality deteriorated with sleep fragmentation. Therefore, it was shown that SAMP8 is effective as a model of age-related sleep disorders and can be used for exploratory research on food ingredients that improve sleep.