Effect of Genetic Obesity on Thermoregulatory Activity Responses to Inversion of the Light/Dark Cycle

In this pilot work, the authors compared the circadian rhythm responses of 3-month-old female fatty Zucker rats with those of lean Zucker rats and Sprague-Dawley rats to reversal of the light/dark (LD) cycle. Core temperature and spontaneous cage activity were continuously monitored by implanted mic...

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Bibliographic Details
Published in:Biological research for nursing 2001-04, Vol.2 (4), p.249-256
Main Authors: Jarosz, Patricia A., Lennie, Terry A., Rowsey, Pamela J., Metzger, Bonnie L.
Format: Article
Language:English
Subjects:
Animals
Body Temperature Regulation
Darkness
Female
Light
Nursing
Obesity - genetics
Obesity - physiopathology
Rats
Rats, Sprague-Dawley
Rats, Zucker
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Summary:In this pilot work, the authors compared the circadian rhythm responses of 3-month-old female fatty Zucker rats with those of lean Zucker rats and Sprague-Dawley rats to reversal of the light/dark (LD) cycle. Core temperature and spontaneous cage activity were continuously monitored by implanted microtelemetry devices prior to and for 5 days following complete LD cycle reversal. By the 5th day after LD reversal, temperature rhythm nadir had phase-advanced 10.5 hours in the lean Zucker rats, 10.8 hours in the Sprague-Dawley rats, and only 3.8 hours in the fatty Zucker rats. Similarly, total activity increased in lean Zucker rats and Sprague-Dawley rats after LD reversal but declined in the fatty Zucker rat during the same time. Results of this study show that obese Zucker rats displayed an impaired ability to reentrain circadian rhythms for temperature and activity when compared to lean Zucker rats and Sprague-Dawley rats. These findings suggest that dysfunction in the circadian pacemaker previously shown to manifest itself by 43 weeks of age in fatty Zucker rats may already be present at 3 months of age and suggest that altered thermoregulation may play a role in the development of obesity in this animal model of genetic obesity.
ISSN:1099-8004
1552-4175
DOI:10.1177/109980040100200404