Cognitive, Behavioral, and Systems NeuroscienceResearch PaperChronic sleep restriction causes a decrease in hippocampal volume in adolescent rats, which is not explained by changes in glucocorticoid levels or neurogenesis
Highlights
▶Chronic sleep restriction reduces hippocampal volume in adolescent rats. ▶The sleep restriction induced reduction in hippocampal volume is not explained by a decreased neurogenesis. ▶The sleep restriction induced reduction in hippocampal volume is not explained by elevations of the stress hormone corticosterone. ▶Chronic sleep restriction does not affect anxiety levels in rats.
Section snippets
Animals and housing
This study was performed with 48 male Wistar rats, 25 or 28 days old at the start of the experiments. Animals were housed in pairs in a room with a 12 h: 12 h light-dark cycle (lights on 9 am–9 pm) and temperature of 21±1 °C. Standard laboratory chow and water were provided ad libitum. Experiments were approved by the Ethical Committee of Animal Experiments of the University of Groningen.
Experimental design
Two experiments were performed in this study. In the first one, we examined effects of sleep restriction on
Behavior
The rats in the present study coped with the protocol of 1-month SR without visible signs of deterioration or illness. Growth was slightly suppressed in both the sleep-restricted rats and forced-activity controls as compared to the home cage controls, resulting in a significantly lower body weight by the end of the experimental period (SR: 234.6±8.1 g, FA: 222.6±7.1 g, HC: 260.1±6.4 g; treatment effect F2,21=7.01, P=0.005; post hoc Tukey test P<0.05 for both SR and FA vs. HC).
No significant
Discussion
The main finding of this study is that rats subjected to chronic SR during adolescence displayed a 10% reduction in dorsal hippocampal volume. This reduction in size of the hippocampus was not associated with significant changes in survival of newly generated BrdU-labeled cells or changes in DCX expression as a marker of young neurons. Therefore, the volume reduction is not likely explained by a reduction in neurogenesis. During the extended period of SR, the young rats displayed a temporary
Acknowledgments
The authors thank Josè Vidal for helpful suggestions concerning the behavioral tests, Jan Bruggink for performing the radioimmunoassays, Folkert Postema for assistance with the immunochemistry, Jan Keijser for contributing to the immunostaining quantification and Dick Visser for his help with the figures. This study was supported by the Nederlands Organization for Scientific Research (VIDI grant 864.04.002 to P.M.). P.J.L. is supported by the EU (NEURAD), ISAO and the Dutch Brain foundation.
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