Glucocorticoids are not responsible for paradoxical sleep deprivation-induced memory impairments.
ABSTRACT To evaluate whether paradoxical sleep deprivation-induced memory impairments are due to release of glucocorticoids, by means of corticosterone inhibition with metyrapone.
The design was a 2 (Groups [control, paradoxical sleep-deprived]) x 2 (Treatments [vehicle, metyrapone]) study, performed in 2 experiments: Acute treatment (single injection given immediately after 96 hours of sleep deprivation) and chronic treatment (8 injections, twice per day, throughout the sleep-deprivation period). Animals were either paradoxical sleep-deprived or remained in their home cages for 96 hours before training in contextual fear conditioning and received intraperitoneal injections of a corticosterone synthesis inhibitor, metyrapone. Memory performance was tested 24 hours after training.
Three-month old Wistar male rats. Measurements: Freezing behavior was considered as the conditioning index, and adrenocorticotropic hormone and corticosterone plasma levels were determined from trunk blood of animals sacrificed in different time points. Animals were weighed before and after the paradoxical sleep-deprivation period.
Acute metyrapone treatment impaired memory in control animals and did not prevent paradoxical sleep deprivation-induced memory impairment. Likewise, in the chronic treatment, paradoxical sleep-deprived animals did not differ from control rats in their corticosterone or adrenocorticotropic hormone response to training, but still did not learn as well, and did not show any stress responses to the testing. Chronic metyrapone was, however, effective in preventing the weight loss typically observed in paradoxical sleep-deprived animals.
Our results suggest that glucocorticoids do not mediate memory impairments but might be responsible for the weight loss induced by paradoxical sleep deprivation.
SourceAvailable from: Karim A Alkadhi[Show abstract] [Hide abstract]
ABSTRACT: The dentate gyrus (DG) and CA1 regions of the hippocampus are intimately related physically and functionally, yet they react differently to insults. The purpose of this study was to determine the protective effects of regular treadmill exercise on late phase long-term potentiation (L-LTP) and its signaling cascade in the DG region of the hippocampus of rapid eye movement (REM) sleep-deprived rats. Adult Wistar rats ran on treadmills for 4 weeks then were acutely sleep deprived for 24 h using the modified multiple platform method. After sleep deprivation, the rats were anesthetized and L-LTP was induced in the DG region. Extracellular field potentials from the DG were recorded in vivo, and levels of L-LTP-related signaling proteins were assessed both before and after L-LTP expression using immunoblot analysis. Sleep deprivation reduced the basal levels of phosphorylated cAMP response element-binding protein (P-CREB) as well as other upstream modulators including calcium/calmodulin kinase IV (CaMKIV) and brain-derived neurotrophic factor (BDNF) in the DG of the hippocampus. Regular exercise prevented impairment of the basal levels of P-CREB and total CREB as well as those of CaMKIV in sleep-deprived animals. Furthermore, regular exercise prevented sleep deprivation-induced inhibition of L-LTP and post-L-LTP downregulation of P-CREB and BDNF levels in the DG. The current findings show that our exercise regimen prevents sleep deprivation-induced deficits in L-LTP as well as the basal and poststimulation levels of key signaling molecules.Molecular Neurobiology 04/2015; DOI:10.1007/s12035-015-9176-4 · 5.29 Impact Factor
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ABSTRACT: Abstract In the current study, the possible beneficial effect of vitamin C (VitC) against sleep deprivation induced memory impairment was examined. Chronic sleep deprivation was induced via placing rats in a modified multiple platform apparatus for 8 hrs/day for a period of 6 weeks. Concomitantly, VitC was administered to animals at doses of 150 and 500 mg/kg/day. After 6 weeks of treatment, the Radial Arm Water Maze (RAWM) was used to test for spatial learning and memory performance. Moreover, the hippocampus was dissected; and levels/activities of antioxidant defense biomarkers glutathione reduced (GSH), glutathione oxidized (GSSG), GSH/GSSG ratio, catalase, superoxide dismutase (SOD), and thiobarbituric acid reactive substances (TBARS), were evaluated. Results revealed that chronic sleep deprivation impaired short- and long- term memories (P < 0.05). This impairment was prevented by chronic VitC treatments. In addition, VitC normalized sleep deprivation-induced decreases in hippocamppal GSH/GSSG ratio (P < 0.05), and activities of catalase, and SOD, and increase in GSSG levels (P < 0.05). Collectively, spatial memory impairment was induced by chronic sleep deprivation, and VitC treatment prevented such impairment. This was possibly achieved via normalizing antioxidant defense mechanisms of the hippocampus.Brain Research Bulletin 02/2015; 113. DOI:10.1016/j.brainresbull.2015.02.002 · 2.97 Impact Factor
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ABSTRACT: Objective. Describe multicompartmental changes in the fat and various muscle fiber types, as well as the hormonal profile and metabolic rate induced by SD in rats. Methods. Twenty adult male Wistar rats were equally distributed into two groups: experimental group (EG) and control group (CG). The EG was submitted to SD for 96 h. Blood levels of corticosterone (CORT), total testosterone (TESTO), insulin like growth factor-1 (IGF-1), and thyroid hormones (T3 and T4) were used to assess the catabolic environment. Muscle trophism was measured using a cross-sectional area of various muscles (glycolytic, mixed, and oxidative), and lipolysis was inferred by the weight of fat depots from various locations, such as subcutaneous, retroperitoneal, and epididymal. The metabolic rate was measured using oxygen consumption ([Formula: see text]O2) measurement. Results. SD increased CORT levels and decreased TESTO, IGF-1, and T4. All fat depots were reduced in weight after SD. Glycolytic and mixed muscles showed atrophy, whereas atrophy was not observed in oxidative muscle. Conclusion. Our data suggest that glycolytic muscle fibers are more sensitive to atrophy than oxidative fibers during SD and that fat depots are reduced regardless of their location.International Journal of Endocrinology 01/2015; 2015:908159. DOI:10.1155/2015/908159 · 1.52 Impact Factor