Sleep deprivation in the rat: XIV. Comparison of waking hypothalamic and peritoneal temperatures

Muscle temperature is least altered during total sleep deprivation in rats

It has often been said that the brain is mostly benefitted from sleep. To understand the importance of sleep, extensive studies on other organs are too required. One such unexplored area is the understanding of muscle physiology during the sleep-wake cycle. Changes in muscle tone with different sleep phases are evident from the rapid eye movement sleep muscle atonia. There is variation in brain and body temperature during sleep stages, the brain temperature being higher during rapid eye movement sleep than slow-wave sleep. However, the change in muscle temperature with different sleep stages is not known. In this study, we have implanted pre-calibrated K-type thermocouples in the hypothalamus and the dorsal nuchal muscle, and a peritoneal transmitter to monitor the hypothalamic, muscle, and body temperature respectively in rats during 24 h sleep-wake cycle. The changes in muscle, body, and hypothalamic temperature during total sleep deprivation were also monitored. During normal sleep-wake stages, the temperature in the decreasing order was that of the hypothalamus, body, and muscle. Total sleep deprivation by gentle handling caused a significant increase in hypothalamic and body temperature, while there was least change in the muscle temperature. The circadian rhythm of the hypothalamic and body temperature in the sleep-deprived rats was disrupted, while the same was preserved in the muscle temperature. The results of our study show that muscle atonia during rapid eye movement sleep is a physiologically regulated thermally quiescent muscle state offering a conducive environment for muscle rest and repair.

Sub-minute prediction of brain temperature based on sleep-wake state in the mouse

Although brain temperature has neurobiological and clinical importance, it remains unclear which factors contribute to its daily dynamics and to what extent. Using a statistical approach, we previously demonstrated that hourly brain temperature values co-varied strongly with time spent awake (Hoekstra et al., 2019). Here we develop and make available a mathematical tool to simulate and predict cortical temperature in mice based on a 4-s sleep-wake sequence. Our model estimated cortical temperature with remarkable precision and accounted for 91% of the variance based on three factors: sleep-wake sequence, time-of-day ('circadian'), and a novel 'prior wake prevalence' factor, contributing with 74%, 9%, and 43%, respectively (including shared variance). We applied these optimized parameters to an independent cohort of mice and predicted cortical temperature with similar accuracy. This model confirms the profound influence of sleep-wake state on brain temperature, and can be harnessed to differentiate between thermoregulatory and sleep-wake-driven effects in experiments affecting both.

Exposure to total 36-hr sleep deprivation reduces physiological and psychological thermal strain to whole-body uncompensable passive heat stress in young adult men

Total sleep deprivation (TSD) is associated with endothelial dysfunction and a consequent decrease in vascular reactivity and increase in peripheral vascular resistance. These effectors compromise the body's ability to thermoregulate in hot and cold stress conditions. We investigated heat-unacclimated young adult men (26 ± 2 years) to determine whether 36 hr of TSD compared to an 8 or 4-hr sleep condition, would suppress the responses of the autonomic system (body rectal temperature [T_re ], heart rate [HR], root mean square of successive interbeat intervals, physiological strain, blood pressure [BP], circulating blood catecholamines, sweating rate and subjective sensations) to whole-body uncompensable passive heat stress in traditional Finnish sauna heat (T_air  = 80-90°C, rh = 30%). Sauna bathing that induced whole-body hyperthermia had a residual effect on reducing BP in the 8-hr and 4-hr sleep per night conditions according to BP measurements. By contrast, 36 hr of total wakefulness led to an increase in BP. These observed sleep deprivation-dependent differences in BP modifications were not accompanied by changes in the blood plasma epinephrine and norepinephrine concentrations. However, during sauna bathing, an increase in BP following 36 hr of TSD was accompanied by significant decreases in body T_re , HR and physiological strain, together with a diminished sweating rate, enhanced vagus-mediated autonomic control of HR variability, and improved thermal perception by the subjects. Our results suggest the impaired ability of the body to accumulate external heat in the body's core under uncompensable passive heat conditions following 36 hr of TSD, because of the TSD-attenuated autonomic system response to acute heat stress.

Acute sleep deprivation elevates brain and body temperature in rats

Available sleep deprivation studies lack data on simultaneous changes in hypothalamic, cortical and body temperature during sleep deprivation and recovery. Ten adult male Wistar rats chronically implanted with electroencephalogram, electro-oculogram and electromyogram electrodes for recording sleep were used in this study. Hypothalamic and cortical temperatures were measured by pre-implanted thermocouples. A radio transmitter (TA10TAF-40, DSI USA) was implanted intraperitoneally to measure body temperature. All the temperatures were measured simultaneously at 15-s intervals during baseline conditions, sleep deprivation and recovery sleep. Sleep deprivation was carried out for 24 hr by the gentle handling method; however, sleep and temperature were only recorded during the first 12 hr of deprivation. During sleep deprivation the body, hypothalamic and cortical temperatures increased significantly as compared to baseline. During recovery sleep, body and cortical temperature recovered earlier than the hypothalamic temperature. Hypothalamic temperature remained higher than the baseline values throughout 12 hr of recovery sleep. In the recovery sleep, cortical temperature decreased immediately and reached near baseline by 4 hr. We observed a quicker return of cortical temperature towards control temperature during recovery sleep compared with hypothalamic and body temperature. The results of the present study show that acute sleep deprivation results in a rise in both cortical and hypothalamic temperature, along with body temperature. A rise in cortical temperature may be a contributing factor for cognitive dysfunction resulting from sleep deprivation.

Possible Involvement of Nitric Oxide Modulatory Mechanisms in the Neuroprotective Effect of Centella asiatica Against Sleep Deprivation Induced Anxiety Like Behaviour, Oxidative Damage and Neuroinflammation

Sleep deprivation (SD) is an experience of inadequate or poor quality of sleep that may produce significant alterations in multiple neural systems. Centella asiatica (CA) is a psychoactive medicinal herb with immense therapeutic potential. The present study was designed to explore the possible nitric oxide (NO) modulatory mechanism in the neuroprotective effect of CA against SD induced anxiety like behaviour, oxidative damage and neuroinflammation. Male laca mice were sleep deprived for 72 h, and CA (150 and 300 mg/kg) was administered alone and in combination with NO modulators for 8 days, starting five days before 72-h SD exposure. Various behavioural (locomotor activity, elevated plus maze) and biochemical (lipid peroxidation, reduced glutathione, catalase, nitrite levels and superoxide dismutase activity), neuroinflammation marker (TNF-alpha) were assessed subsequently. CA (150 and 300 mg/kg) treatment for 8 days significantly improved locomotor activity, anti-anxiety like effect and attenuated oxidative damage and TNF α level as compared to sleep-deprived 72-h group. Also while the neuroprotective effect of CA was increased by NO antagonists, it was diminished by NO agonists. The present study suggests that NO modulatory mechanism could be involved in the protective effect of CA against SD-induced anxiety-like behaviour, oxidative damage and neuroinflammation in mice.

Repeated exposure to severely limited sleep results in distinctive and persistent physiological imbalances in rats

Chronic sleep disruption in laboratory rats leads to increased energy expenditure, connective tissue abnormalities, and increased weights of major organs relative to body weight. Here we report on expanded findings and the extent to which abnormalities become long-lasting, potentially permanent changes to health status after apparent recuperation from chronic sleep disruption. Rats were exposed 6 times to long periods of disrupted sleep or control conditions during 10 weeks to produce adaptations and then were permitted nearly 4 months of undisturbed sleep. Measurements were made in tissues from these groups and in preserved tissue from the experimental and control groups of an antecedent study that lacked a lengthy recuperation period. Cycles of sleep restriction resulted in energy deficiency marked by a progressive course of hyperphagia and major (15%) weight loss. Analyses of tissue composition in chronically sleep-restricted rats indicated that protein and lipid amounts in internal organs were largely spared, while adipose tissue depots appeared depleted. This suggests high metabolic demands may have preserved the size of the vital organs relative to expectations of severe energy deficiency alone. Low plasma corticosterone and leptin concentrations appear to reflect low substrate availability and diminished adiposity. After nearly 4 months of recuperation, sleep-restricted rats were consuming 20% more food and 35% more water than did comparison control rats, despite normalized weight, normalized adipocytes, and elevated plasma leptin concentrations. Plasma cholesterol levels in recuperated sleep-restricted rats were diminished relative to those of controls. The chronically increased intake of nutriments and water, along with altered negative feedback regulation and substrate use, indicate that internal processes are modified long after a severe period of prolonged and insufficient sleep has ended.

Effect of oxidative stress induced by paradoxical sleep deprivation on the activities of Na+, K+-ATPase and acetylcholinesterase in the cortex and hippocampus of rat

Several studies revealed the importance of paradoxical sleep as a homeostatic mechanism by which the brain can control oxidative stress. The aim of the present study is to investigate the effect of 72 h of paradoxical sleep deprivation on the oxidative stress markers and its insults on the activities of Na(+), K(+)-ATPase and acetylcholinesterase in the cortex and hippocampus of albino rat. Animals were subjected to paradoxical sleep deprivation for 72 h. At the end of the experiment, the rats were sacrificed, and catalase activity, levels of reduced glutathione, lipid peroxidation, and nitric oxide were assayed together with the activities of Na(+), K(+)-ATPase and acetylcholinesterase in the cortex and hippocampus. The present study revealed a significant increase in lipid peroxidation accompanied by a significant decrease in reduced glutathione in the cortex and hippocampus. Na(+), K(+)-ATPase decreased significantly in both areas. However, acetylcholinesterase showed a significant increase in the investigated brain regions. The present data showed that 72 h of paradoxical sleep deprivation induced oxidative stress in the cortex and hippocampus. It could be suggested that the inhibition of Na(+), K(+)-ATPase and the increased acetylcholinesterase activity may underlie memory impairment, increased brain excitability, and anxiety induced by paradoxical sleep deprivation.

Recurrent restriction of sleep and inadequate recuperation induce both adaptive changes and pathological outcomes

Chronic restriction of a basic biological need induces adaptations to help meet requisites for survival. The adaptations to chronic restriction of sleep are unknown. A single episode of 10 days of partial sleep loss in rats previously was shown to be tolerated and to result in increased food intake and loss of body weight as principal signs. The purpose of the present experiment was to investigate the extent to which adaptation to chronic sleep restriction would ameliorate short-term effects and result in a changed internal phenotype. Rats were studied during 10 wk of multiple periods of restricted and unrestricted sleep to allow adaptive changes to develop. Control rats received the same ambulatory requirements only consolidated into periods that lessened interruptions of their sleep. The results indicate a latent period of relatively stable food and water intake without weight gain, followed by a dynamic phase marked by enormous increases in food and water intake and progressive loss of body weight, without malabsorption of calories. Severe consequences ensued, marked especially by changes to the connective tissues, and became fatal for two individuals. The most striking changes to internal organs in sleep-restricted rats included lengthening of the small intestine, decreased size of adipocytes, and increased incidence of multilocular adipocytes. Major organs accounted for an increased proportion of total body mass. These changes to internal tissues appear adaptive in response to high energy production, decomposition of lipids, and increased need to absorb nutrients, but ultimately insufficient to compensate for inadequate sleep.

Possible nitric oxide modulation in protective effect of (Curcuma longa, Zingiberaceae) against sleep deprivation-induced behavioral alterations and oxidative damage in mice

Sleep is essential for the physical and mental health of a human being. Problems of sleep deprivation are increasing in modern society nowadays. Recently, various antioxidants have been implicated as neuroprotectants in the treatment of stress and stress related problems. The present study was designed to explore the possible role of nitric oxide in the protective effect of Curcumin (Curcuma longa, Zingiberaceae) against 72-h sleep deprivation-induced behavioral alterations and oxidative damage in mice. 72-h sleep deprivation significantly caused weight loss, anxiety like behavior, impaired locomotor activity and oxidative damage (increased lipid peroxidation, nitrite level and deplete glutathione and catalase activity) in animals. Treatment with Curcumin extract (10 and 20mg/kg, ip) for 5 days significantly prevented weight loss, impairment in locomotor activity, anxiety like effects in all behavioral paradigms tasks (mirror chamber, plus maze, zero maze) as compared to control (72-h sleep-deprived) (P<0.05). Biochemically, Curcumin extract treatment significantly restored depleted reduced glutathione, catalase activity, attenuated raised lipid peroxidation and nitrite level as compared to control (72-h sleep-deprived) animals. Further, pretreatment of l-arginine (50mg/kg, ip), nitric oxide precursor reversed the protective effect of Curcumin (10 mg/kg, ip) (P<0.05). However, pretreatment of l-NAME (5 mg/kg, ip), nitric oxide synthase inhibitor caused a potentiation in the protective effect of Curcumin (P<0.05). The present study suggests that nitric oxide modulation is involved in the protective effect of Curcumin in ameliorating sleep deprivation-induced behavioral alterations and oxidative damage.

Effect of rapid-eye-movement sleep deprivation on rat hypothalamic prostaglandins

In this study, we investigated thyroid hormones, thyroid stimulating hormone (TSH), prostaglandin D(2) (PGD(2)) and prostaglandin E(2) (PGE(2)) levels in rapid-eye-movement (REM) sleep-deprived rats compared with controls. The aim of the present study was to detect the effect of REM sleep deprivation (RSD) especially on hypothalamic prostaglandin levels. Twenty-seven male rats were randomly assigned in three groups as dry cage control, yoked control, and RSD. RSD rats were sleep deprived for 10 consecutive days. At the end of 10th day all rats were sacrificed for measurement. Our results indicated that total triiodothyronine (T(3)) and thyroxine (T(4)) decreased in the RSD group while there was no change in TSH. We also measured hypothalamic PGD(2) and PGE(2) levels, but we could not find any significant change between groups.

Clinical assessment of blood leukocytes, serum cytokines, and serum immunoglobulins as responses to sleep deprivation in laboratory rats

The specific systems and mechanisms affected by sleep deprivation that may perpetuate disease processes in humans still are speculative. In laboratory rats, prolonged sleep deprivation induces a state marked by abnormal control over indigenous bacteria that results in transient infections of internal tissues and eventual lethal septicemia. The present studies investigated changes in blood, serum, and bone marrow parameters that may provide diagnostic clues to immunopathology. Prolonged sleep deprivation was produced in rats by the disk-over-water method, a well-established and selective means that does not interfere with normal waking behaviors. Measurements included bone and blood differential white blood cell counts, multiple serum cytokines and chemokines, several major Ig classes and subclasses, and serum endotoxin concentrations. The results indicated mild, regenerative neutrophilia in sleep-deprived rats, initially accompanied by immature neutrophils and later by monocytosis. The corresponding serum cytokine profile revealed an evolving proinflammatory state, particularly by high incidence of interleukin-1β, implicating mononuclear phagocytes and resident tissue cells as main intermediary sources. In addition, multiple serum Ig classes were increased by sleep deprivation without experimental administration of an exogenous antigen. Despite this immune activation, there was failure to eradicate invading bacteria and toxins, suggesting competing anti-inflammatory processes or interference with immune effector functions during sleep deprivation. Nearly all of the immune-related events that emerged as responses to sleep deprivation have been implicated as etiological or provocative factors in other disease processes and may provide means by which sleep deprivation as a risk factor in disease may become understood.

Systemic bacterial invasion induced by sleep deprivation

Profound sleep disruption in humans is generally believed to cause health impairments. Through comparative research, specific physical effects and underlying mechanisms altered by sleep deprivation are being elucidated. Studies of sleep-deprived animals previously have shown a progressive, chronic negative energy balance and gradual deterioration of health, which culminate in fatal bloodstream infection without an infectious focus. The present study investigated the conditions antecedent to advanced morbidity in sleep-deprived rats by determining the time course and distribution of live microorganisms in body tissues that are normally sterile. The tissues cultured for microbial growth included the blood, four major organs, six regional lymph nodes, the intestine, and the skin. The principal finding was early infection of the mesenteric lymph nodes by bacteria presumably translocated from the intestine and bacterial migration to and transient infection of extraintestinal sites. Presence of pathogenic microorganisms and their toxins in tissues constitutes a septic burden and chronic antigenic challenge for the host. Bacterial translocation and pathogenic sequelae provide mechanisms by which sleep deprivation appears to adversely affect health.

Endogenous and exogenous factors on sleep-wake cycle regulation

A number of theories have proposed the involvement of different brain structures and neurotransmitters in order to explain the regulation of the sleep wake cycle. However, there is no clear consensus as to the mechanisms through which the brain structures and their various neurotransmitters interact to produce theses phases. Perhaps the problem is related to the fact sleep is a very fragile state, easily modified or influenced by a variety of substances or experimental manipulations. In this paper, we describe the evidence of two different groups of factors that induce important changes on the sleep wake cycle. The endogenous factors: neurotransmitters; hormone; peptides; and some substances of lipidic nature and exogenous factors: stress, food intake, learning, sleep deprivation, sensorial stimulation, exercise and temperature on the regulation the sleep-wake cycle. Likewise, we propose a hypothesis which attempts to reconcile the fact that endogenous and exogenous factors have similar effects.

Sleep deprivation in rats with preoptic/anterior hypothalamic lesions

Chronic total sleep deprivation (TSD) of rats by the disk-over-water method reliably produces initial increases and subsequent decreases in waking intraperitoneal (Tip) and hypothalamic (Thy) temperatures, progressive increases in energy expenditure, skin lesions on the tail and plantar surfaces, debilitated appearance, and eventual death. We investigated the possible role of the preoptic/anterior hypothalamus (POAH) in the mediation of the TSD effects by comparing these effects in POAH-lesioned and unlesioned rats. Bilateral POAH lesions sufficient in size to impair homeothermic responses to changes in ambient temperature did not produce TSD-like temperature changes under baseline ambient temperatures of 28-29 degrees C, implying that the thermoregulatory changes produced by TSD do not result from impairment of the lesioned area. However, the possibility remains that the TSD effects are mediated by damage to POAH areas that were not lesioned. During TSD, lesioned and unlesioned rats showed similar progressive increases in energy expenditure, but the lesioned rats showed earlier, steeper, and eventually greater declines in Tip and Thy. This result suggests that in unlesioned rats the POAH may counter-regulate against, and thereby attenuate, the reduction in heat retention caused by TSD. This failure of regulation in lesioned rats is consistent with their impaired response to ambient temperature change and implies that, in unlesioned rats, some POAH thermoregulatory mechanisms continue to function normally during TSD. Lesioned rats did not show the characteristic TSD-induced early increases in Tip and Thy. This result could imply either that heat retention was so compromised that body temperatures did not rise in spite of a TSD-induced increases in thermoregulatory setpoint, or that the setpoint increase in unlesioned rats is POAH-mediated. Notwithstanding the greater Tip and Thy declines in lesioned rats, they survived the TSD procedure longer than the unlesioned rats, thus supporting previous indications that death did not result from hypothermia.

Sleep deprivation in the rat by the disk-over-water method

Chronic sleep deprivation may be required to reveal the most serious physiological consequences of sleep loss, but it usually requires strong stimulation which can obscure the interpretation of effects. The disk-over-water method permits chronic sleep deprivation of rats with gentle physical stimulation that can be equally applied to yoked control rats. A series of studies with this method has revealed little or no pathology in the control rats. The deprived rats show a reliable syndrome that includes temperature changes (which vary with the sleep stages that are lost); heat seeking behavior; increased food intake; weight loss; increased metabolic rate; increased plasma norepinephrine; decreased plasma thyroxine; an increased triiodothyronine-thyroxine ratio; and an increase of an enzyme which mediates thermogenesis by brown adipose tissue. The temperature changes are attributable to excessive heat loss and an elevated thermoregulatory setpoint, both of which increase thermoregulatory load, and the other changes are interpretable as responses to this increased load. This pattern indicates that sleep serves a thermoregulatory function in the rat. The sleep deprived rats also show stereotypic ulcerative and hyperkeratotic lesions localized to the tail and plantar surfaces of the paws, and they die within a matter of weeks; the mediation of these changes is unresolved.

Functional consequences of sustained sleep deprivation in the rat

Sleep deprivation disrupts vital biological processes that are necessary for cognitive ability and physical health, but the physiological changes that underlie these outward effects are largely unknown. The purpose of the present studies in the laboratory rat is to prolong sleep deprivation to delineate the pathophysiology and to determine its mediation. In the rat, the course of prolonged sleep deprivation has a syndromic nature and eventuates in a life-threatening state. An early and central symptom of sleep deprivation is a progressive increase in peripheral energy expenditure to nearly double normal levels. An attempt to alleviate this negative energy balance by feeding rats a balanced diet that is high in its efficiency of utilization prolongs survival and attenuates or delays development of malnutrition-like symptoms, indicating that several symptoms can be manipulated to some extent by energy and nutrient consumption. Most changes in neuroendocrine parameters appear to be responses to metabolic demands, such as increased plasma catecholamines indicating sympathetic activation. Plasma total thyroid hormones, however, decline to severely low levels; a metabolic complication that is associated with other sleep deprivation-induced symptoms, such as a decline in body temperature to hypothermic levels despite increased energy expenditure. Metabolic mapping of the brain revealed a dissociation between the energy metabolism of the brain and that of the body. Sleep deprivation's effects on cerebral structures are heterogeneous and unidirectional toward decreased functional activity. The hypometabolic brain structures are concentrated in the hypothalamus, thalamus and limbic systems, whereas few regions in the rest of the brain and none in the medulla, are affected. Correspondence can be found between some of the affected cerebral structures and several of the peripheral symptoms, such as hyperphagia and possible heat retention problems. The factor predisposing to mortality is a decreased resistance to infection. Lethal opportunistic organisms are permitted to infect the bloodstream, which presumably results in a cascade of toxic-like reactions. Host defense is thus the first system to fail. There is neither fever nor marked tissue inflammatory reactions typical of infectious disease states, suggesting that sleep deprivation is immunosuppressive. Each of the four abnormalities identified--(1) a deep negative energy balance and associated malnutrition; (2) heterogeneous decreases in cerebral function; (3) low thyroid hormone concentrations; and (4) decrease resistance to infection--can be viewed as having an early origin during the sleep deprivation process to signify the foremost pathogenic situation to which the other abnormalities might be secondarily related.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of chronic REM sleep deprivation on pituitary, hypothalamus and hippocampus PGE2 and PGD2 biosynthesis in the mouse

Given the often reported relationships between sleep-wake regulation and the cerebral prostaglandins (PGs), the effect of chronic rapid eye movement (REM) sleep deprivation on brain PGE2 and PGD2 biosynthesis in mouse was evaluated, since they are known to have opposite actions as respectively wake- and sleep-inducing substances. Mice were subjected to 5 and 10 days of REM sleep deprivation by the flower pot technique. After sacrifice, PGE2 and PGD2 were determined in the pituitary, hypothalamus and hippocampus. Except in the pituitary where no changes were shown, the PGE2/PGD2 ratio was significantly enhanced after 5 and 10 days of REM sleep loss, when compared to control. These results showed an alteration of cerebral PGE2 and PGD2 biosynthesis, resulting in a shift from PGD2 toward PGE2. These results were not consistent with a role of PGD2 as a sleep-promoting substance as, if that was the case, it would be increased during the REM sleep deprivation. But they do not rule out its involvement as a facilitating substance.

Effects of chronic sleep deprivation on central cholinergic receptors in rat brain

Rats subjected to chronic total sleep deprivation (TSD) by the disk-over-water method have shown very large, sustained rebounds in paradoxical sleep (PS) (also known as REM sleep). Other studies have indicated that cholinergic mechanisms are involved in the instigation and maintenance of PS. Hypothetically, the large PS rebounds could be mediated by an upregulation of cholinergic receptors during TSD. To evaluate this hypothesis, regional brain cholinergic receptors were compared in rats subjected to 10-day TSD by the disk-over-water method (TSD rats), yoked control (TSC) rats which received the same physical stimulation but with much smaller reductions in sleep, and home cage control (HCC) rats. L-[3H]nicotine and [3H]quinuclidinyl benzilate were used as specific cholinergic radioligands for nicotinic and muscarinic receptor binding assays, respectively. Nicotinic receptor binding was not significantly different among groups for any of the brain regions assayed, including frontal cortex, parietal cortex, thalamus, amygdala, hippocampus, anterior hypothalamus, posterior hypothalamus, caudate, limbic system (including septal area, olfactory tubercle, and nucleus accumbens), midbrain, pons, and medulla. Thus, there was no evidence that changes in nicotinic receptors mediate the PS rebounds. For muscarinic receptor binding, TSD rats differed significantly from control rats only in showing a higher binding affinity than TSC rats in the limbic system and a lower binding density than HCC rats in the hippocampus. On the other hand, significant differences in muscarinic receptor binding sites between rats selectively deprived of PS and their yoked controls were found only for the septal area.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective increases in non-rapid eye movement sleep following whole body heating in rats

Afternoon body heating has been reported to increase amounts of slow wave sleep (SWS) during the subsequent night in humans. This delayed effect of body heating on SWS has not been previously studied in laboratory animals. We examined the effect of whole body heating during the last 4 h of the light period on sleep and brain temperature (Tbr) during the subsequent twelve hour period in rats. Whole body heating was accomplished by elevating ambient temperature, typically to 33-35 degrees C, which increased Tbr to 40 +/- 0.5 degrees C. This condition was compared to a sleep-matched control condition, a sleep-deprived control condition and to a baseline condition. Following heating, non-rapid eye movement sleep 2 (NREMS2 or deep NREMS) was significantly increased during the first 2 h of the recovery period compared with baseline and sleep-matched control conditions and during the first hour compared with the totally sleep-deprived condition. NREMS1 was not significantly changed by heating. Rapid eye movement sleep was not different following heating compared to the sleep-matched and sleep-deprived control conditions but was significantly increased during the first hour of the recovery period following heating compared to baseline. Tbr was significantly lower for the first 5 h and the 7th h following heating compared to all three other conditions. Possible relationships between the regulation of sleep and temperature are discussed.

Effects of chronic total sleep deprivation on central noradrenergic receptors in rat brain

The effect of chronic total sleep deprivation (TSD) on the regulation of central noradrenergic receptors was evaluated. Rats were subjected to 10 days of TSD by the disk-over-water method. As in previous TSD studies, these rats showed greater increases in food intake and energy expenditure and greater eventual declines in waking body temperature than their yoked-control (TSC) rats. After sacrifice, alpha 1-, alpha 2-, and beta-adrenoceptors were determined in 11 brain regions using radioligand binding assays with [3H]prazosin, [3H]rauwolscine, and 125I-iodocyanopindolol, respectively. Adrenoceptor density and affinity values were significantly different among TSD, TSC, and normally caged control rat groups only for the cerebellum, which showed higher alpha 2-binding density concomitant with lower affinity and lower beta-binding density than cage control rats. Such changes are attributable to apparatus or stimulus effects common to TSD and TSC rats. Given the absence of firm evidence for a TSD-induced downregulation of central noradrenergic receptors, the present results offer no support for the hypothesis of Siegel and Rogawski that a major function of paradoxical sleep is to upregulate these receptors.