Hypersomnolence in a rat model of obesity
Michlin, Charles Philip
MetadataShow full item record
Introduction . The obese Zucker rat demonstrates many of the same respiratory deficits found in morbidly obese humans, such as blunted ventilatory responses to hypoxia and hypercapnia, reduced lung function, a decrease in chest wall compliance, and an increase in chest wall resistance. The Zucker rat has been used as a model for obesity and diabetes, and offers the possibility of it being used as a naturally occurring model for sleep disordered breathing and hypersomnolence. Methods . Nine pair of age-matched lean and obese adult male Zucker rats were implanted with EEG and EMG electrodes, habituated, and had a 24 hour recording of sleep-wake patterns analyzed in ten second epochs. Delta, theta, and sigma power were normalized and computed for each animal during the entire 24 hour period, during six hours in the day (10 am-4 pm), and during six hours at night (10 pm-4 am). Results . The obese Zucker rats displayed a significant increase in non-rapid eye movement (NREM) sleep and a significant decrease in wake time over a 24 hour period of time, six hours of day, and six hours of night, compared with its lean counterparts. Normalized delta power of the obese rats for 24 hours and six hours-day were significantly higher than the leans' respective spectral power; normalized theta power of the obese rats for 24 hours and six hours-day were significantly lower than the leans' respective spectral power. The increase in body weight was positively correlated with the normalized 24 hour and 6 Hour-Day delta power, and was negatively correlated with the normalized 24 hour and 6 Hour-Day theta power. The increase in body weight was positively correlated with NREM sleep (both in the 24 hour and the 6 Hour-Night periods), and was negatively correlated with Wake time (both in the 24 hour and the 6 Hour-Night periods). Conclusion . The increased NREM and increased normalized delta power of the obese adult male Zucker rat demonstrates that it is hypersomnolent compared with the lean adult male Zucker rat. The confirmation of the adult obese Zucker rat's role as a naturally occurring model for hypersomnolence will facilitate future sleep research, including the development of pharmacological interventions to alleviate or eliminate the effects of hypersomnolence.