Validation of a Walking Wheel Method to Fragment Sleep in Rats

Background and Objective Many attempts have sought to devise an animal model of sleep fragmentation (SF) to understand the clinical effects of sleep loss, but no study has investigated the usefulness of the walking wheel method to interrupt sleep in rats. Methods Seven-week-old male Wistar rats were divided into a SF group and an exercise control (EC) group, with five rats in each. SF was achieved with a walking wheel using a 30 s on, 90 s off interval (total walking time 6 h/day). The EC group walked the same distance. Rat multiple sleep latency test was performed to measure sleepiness in rats. Sleep data were collected at baseline, and 4, 12, and 18 days after treatment. Percent (%) time spent awake and in non-rapid eye movement (NREM) and rapid eye movement (REM) sleep, NREM and wake bout number, NREM bout length, and mean sleep latency were analyzed. Results Numbers of NREM and wake bout were higher in the SF group, whereas the NREM bout length was smaller than in the baseline group. Unlike NREM, REM sleep (%) in the SF group was significantly lower than in the baseline and EC groups. Mean sleep latency was shortened in the SF group compared to the baseline and EC groups. EC did not differ significantly with respect to the amount of sleep time (%), bout number of NREM and wakefulness, NREM bout length, and mean sleep latency, compared to its own baseline. Conclusions Use of a walking wheel is an effective means of interrupting sleep in rats during a long-term period.