Changes in the expression of steroid metabolism-related genes in rat adrenal glands during selective REM sleep deprivation

Selective REM sleep deprivation was carried out under the conditions designed to minimize the adverse influence of environmental conditions and restricted movement, and the influence of REM sleep deprivation on adrenocortical steroid metabolism was investigated by measuring the steady-state levels of mRNAs encoding steroid metabolism-related genes, steroidogenic acute regulatory protein (StAR), cholesterol side-chain cleavage enzyme cytochrome P450 (P450scc) and steroid 5alpha-reductase (5alpha-R), in rat adrenal glands. Selective REM sleep deprivation caused a significant decrease in StAR mRNA and an increase in 5alpha-R mRNA levels without any notable change in P450scc mRNA levels in the adrenal gland. In contrast, non-selective sleep disturbance, resulting in the partial reductions of non-REM and REM sleep, tended to increase both StAR and P450scc mRNA levels without any statistical significance. These results indicate that REM sleep deprivation by itself may affect the expression of steroid metabolism-related genes in the adrenal gland, suggesting a possible relation between REM sleep and adrenocortical steroid metabolism.     

Effects of selective sleep deprivation on ventilation during recovery sleep in normal humans.

To assess the effects of selective sleep loss on ventilation during recovery sleep, we deprived 10 healthy young adult humans of rapid-eye-movement (REM) sleep for 48 h and compared ventilation measured during the recovery night with that measured during the baseline night. At a later date we repeated the study using awakenings during non-rapid-eye-movement (NREM) sleep at the same frequency as in REM sleep deprivation. Neither intervention produced significant changes in average minute ventilation during presleep wakefulness, NREM sleep, or the first REM sleep period. By contrast, both interventions resulted in an increased frequency of breaths, in which ventilation was reduced below the range for tonic REM sleep, and in an increased number of longer episodes, in which ventilation was reduced during the first REM sleep period on the recovery night. The changes after REM sleep deprivation were largely due to an increase in the duration of the REM sleep period with an increase in the total phasic activity and, to a lesser extent, to changes in the relationship between ventilatory components and phasic eye movements. The changes in ventilation after partial NREM sleep deprivation were associated with more pronounced changes in the relationship between specific ventilatory components and eye movement density, whereas no change was observed in the composition of the first REM sleep period. These findings demonstrate that sleep deprivation leads to changes in ventilation during subsequent REM sleep.     

Selective REM Sleep Deprivation Improves Expectation-Related Placebo Analgesia

The placebo effect is a neurobiological and psychophysiological process known to influence perceived pain relief. Optimization of placebo analgesia may contribute to the clinical efficacy and effectiveness of medication for acute and chronic pain management. We know that the placebo effect operates through two main mechanisms, expectations and learning, which is also influenced by sleep. Moreover, a recent study suggested that rapid eye movement (REM) sleep is associated with modulation of expectation-mediated placebo analgesia. We examined placebo analgesia following pharmacological REM sleep deprivation and we tested the hypothesis that relief expectations and placebo analgesia would be improved by experimental REM sleep deprivation in healthy volunteers. Following an adaptive night in a sleep laboratory, 26 healthy volunteers underwent classical experimental placebo analgesic conditioning in the evening combined with pharmacological REM sleep deprivation (clonidine: 13 volunteers or inert control pill: 13 volunteers). Medication was administered in a double-blind manner at bedtime, and placebo analgesia was tested in the morning. Results revealed that 1) placebo analgesia improved with REM sleep deprivation; 2) pain relief expectations did not differ between REM sleep deprivation and control groups; and 3) REM sleep moderated the relationship between pain relief expectations and placebo analgesia. These results support the putative role of REM sleep in modulating placebo analgesia. The mechanisms involved in these improvements in placebo analgesia and pain relief following selective REM sleep deprivation should be further investigated.     

Coupled Flip-Flop Model for REM Sleep Regulation in the Rat

Recent experimental studies investigating the neuronal regulation of rapid eye movement (REM) sleep have identified mutually inhibitory synaptic projections among REM sleep-promoting (REM-on) and REM sleep-inhibiting (REM-off) neuronal populations that act to maintain the REM sleep state and control its onset and offset. The control mechanism of mutually inhibitory synaptic interactions mirrors the proposed flip-flop switch for sleep-wake regulation consisting of mutually inhibitory synaptic projections between wake- and sleep-promoting neuronal populations. While a number of synaptic projections have been identified between these REM-on/REM-off populations and wake/sleep-promoting populations, the specific interactions that govern behavioral state transitions have not been completely determined. Using a minimal mathematical model, we investigated behavioral state transition dynamics dictated by a system of coupled flip-flops, one to control transitions between wake and sleep states, and another to control transitions into and out of REM sleep. The model describes the neurotransmitter-mediated inhibitory interactions between a wake- and sleep-promoting population, and between a REM-on and REM-off population. We proposed interactions between the wake/sleep and REM-on/REM-off flip-flops to replicate the behavioral state statistics and probabilities of behavioral state transitions measured from experimental recordings of rat sleep under ad libitum conditions and after 24 h of REM sleep deprivation. Reliable transitions from REM sleep to wake, as dictated by the data, indicated the necessity of an excitatory projection from the REM-on population to the wake-promoting population. To replicate the increase in REM-wake-REM transitions observed after 24 h REM sleep deprivation required that this excitatory projection promote transient activation of the wake-promoting population. Obtaining the reliable wake-nonREM sleep transitions observed in the data required that activity of the wake-promoting population modulated the interaction between the REM-on and REM-off populations. This analysis suggests neuronal processes to be targeted in further experimental studies of the regulatory mechanisms of REM sleep.     

Restricted sleep regime in rhesus monkeys: differential effect of one night's sleep loss and selective REM deprivation.

The differential effect of either one night's total sleep deprivation (TSD) or of selective REM deprivation (REMD) was examined on post-deprivation daytime EEG patterns with respect to control, in the same group of rhesus monkeys. TSD resulted in significantly decreased wakefulness and increased amounts of NREM and REM on the first day following TSD. In contrast, highly significant REM elevation without alteration of other EEG states occurred for 3 days after REMD. Post-deprivation behavioural and photic-induced neural changes were minor. The results obtained after sleep deprivation in simians are comparable with similar findings in human subjects.     

The effect of valproic acid on sleep structure and ethanol consumption in rats with various types of individual reactivity before and after stress exposure

The influence of valproic acid on sleep structure and alcohol motivation was studied in pretyped rats prior and following REM sleep deprivation. During EEG recording of wake-sleep cycle valporoic acid was shown to produce hypnotic action dependent on drug dosage in high active and low active animals. There was also shown that following REM sleep deprivation low active animals significantly reduced ethanol consumption under valproic acid influence. It seems likely from the results obtained that valproic acid could be used as hypnotic and antialcoholic drug.     

Cardiopulmonary regulation after rapid-eye-movement sleep deprivation.

Arterial blood pressure, chest movement, electroencephalogram, and electromyogram were monitored in six normotensive Sprague-Dawley rats for 4 h/day 3 days before and 4 days after 114 h of rapid-eye-movement (REM) sleep deprivation. During recovery sleep immediately after REM sleep deprivation (RD), there was a significant increase in the amount of time spent in REM sleep. During this rebound in REM sleep, there was a significant rise (26%) in heart rate in wakefulness, non-REM sleep, and REM sleep during the first 4 h after RD. Systolic blood pressure was also significantly elevated (14%) but only during wakefulness before recovery sleep. Rats with the greatest waking systolic blood pressure after RD had the lowest REM sleep rebound in the 4 h immediately after RD (r = -0.885, P less than 0.05). The rise in heart rate, systolic blood pressure, and REM sleep time evident on day 1 immediately after RD was absent on recovery days 2-4. The respiratory rate tended to be higher throughout the recovery period in every state of consciousness; however, these values never reached the level of significance. In the initial recovery sleep period, regulation of heart rate was more disrupted by REM sleep deprivation than either arterial blood pressure or respiratory rate.     

Enzymes of adenosine metabolism in the brain: diurnal rhythm and the effect of sleep deprivation

Adenosine plays a role in promoting sleep, an effect that is thought to be mediated in the basal forebrain. Adenosine levels vary in this region with prolonged wakefulness in a unique way. The basis for this is unknown. We examined, in rats, the activity of the major metabolic enzymes for adenosine - adenosine deaminase, adenosine kinase, ecto- and cytosolic 5'-nucleotidase - in sleep/wake regulatory regions as well as cerebral cortex, and how the activity varies across the day and with sleep deprivation. There were robust spatial differences for the activity of adenosine deaminase, adenosine kinase, and cytosolic and ecto-5'-nucleotidase. However, the basal forebrain was not different from other sleep/wake regulatory regions apart from the tuberomammillary nucleus. All adenosine metabolic enzymes exhibited diurnal variations in their activity, albeit not in all brain regions. Activity of adenosine deaminase increased during the active period in the ventrolateral pre-optic area but decreased significantly in the basal forebrain. Enzymatic activity of adenosine kinase and cytosolic-5'-nucleotidase was higher during the active period in all brain regions tested. However, the activity of ecto-5'-nucleotidase was augmented during the active period only in the cerebral cortex. This diurnal variation may play a role in the regulation of adenosine in relationship to sleep and wakefulness across the day. In contrast, we found no changes specifically with sleep deprivation in the activity of any enzyme in any brain region. Thus, changes in adenosine with sleep deprivation are not a consequence of alterations in adenosine enzyme activity.     

Brain prolactin is involved in stress-induced REM sleep rebound

REM sleep rebound is a common behavioural response to some stressors and represents an adaptive coping strategy. Animals submitted to multiple, intermittent, footshock stress (FS) sessions during 96 h of REM sleep deprivation (REMSD) display increased REM sleep rebound (when compared to the only REMSD ones, without FS), which is correlated to high plasma prolactin levels. To investigate whether brain prolactin plays a role in stress-induced REM sleep rebound two experiments were carried out. In experiment 1, rats were either not sleep-deprived (NSD) or submitted to 96 h of REMSD associated or not to FS and brains were evaluated for PRL immunoreactivity (PRL-ir) and determination of PRL concentrations in the lateral hypothalamus and dorsal raphe nucleus. In experiment 2, rats were implanted with cannulas in the dorsal raphe nucleus for prolactin infusion and were sleep-recorded. REMSD associated with FS increased PRL-ir and content in the lateral hypothalamus and all manipulations increased prolactin content in the dorsal raphe nucleus compared to the NSD group. Prolactin infusion in the dorsal raphe nucleus increased the time and length of REM sleep episodes 3 h after the infusion until the end of the light phase of the day cycle. Based on these results we concluded that brain prolactin is a major mediator of stress-induced REMS. The effect of PRL infusion in the dorsal raphe nucleus is discussed in light of the existence of a bidirectional relationship between this hormone and serotonin as regulators of stress-induced REM sleep rebound.     

Rapid eye movement (rem) sleep deprivation: effect on acid mucopolysaccharides in rat brain.

The effect of rapid eye movement (REM) sleep deprivation on the total content and proportion of different mucopolysaccharides (AMPS) containing uronic acid in rat brain was studied. REM sleep deprivation was induced by the water tank methods. Five experimental groups of animals were used: control, stressed, REM sleep deprived, post-stress sleeping and post-deprivation sleeping rats. No changes of AMPS were observed in any of the experimental groups when the whole brain was analysed. A significant increase of AMPS was found in the cerebral hemispheres of stressed and REM deprived rats. A significant decrease of AMPS was observed in the cerebellum and brain stem. A further increase of AMPS was found in the cerebral hemispheres after the rebound of REM sleep following its deprivation, and after the recovery sleep following the stress. A significant increase of AMPS was found in the brain stem of rats allowed to recuperate after REM deprivation or stress as compared with the stressed and REM deprived animals. Recovery sleep induced a significant increase of AMPS in the cerebellum in previously stressed rats, while previously REM deprived rats exhibited a further decrease of AMPS from control values. The possible functional meaning of these results is discussed in relation to the role of REM sleep in protein synthesis and learning and memory processes. Intriguing, well-controlled positive findings and the fact that no experimental design is known where stress is minimal while REM deprivation is 100 per cent, justify and encourage continued efforts in studying the biochemical state of the brain during sleep and/or its alterations.     

Rapid changes in glutamate levels in the posterior hypothalamus across sleep-wake states in freely behaving rats

The histamine-containing posterior hypothalamic region (PH-TMN) plays a key role in sleep-wake regulation. We investigated rapid changes in glutamate release in the PH-TMN across the sleep-wake cycle with a glutamate biosensor that allows the measurement of glutamate levels at 1- to 4-s resolution. In the PH-TMN, glutamate levels increased in active waking (AW) and rapid eye movement (REM) sleep compared with quiet waking and nonrapid eye movement (NREM) sleep. There was a rapid (0.6 +/- 1.8 s) and progressive increase in glutamate levels at REM sleep onset. A reduction in glutamate levels consistently preceded the offset of REM sleep by 8 +/- 3 s. Short-duration sleep deprivation resulted in a progressive increase in glutamate levels in the PH-TMN, perifornical-lateral hypothalamus (PF-LH), and cortex. We found that in the PF-LH, glutamate levels took a longer time to return to basal values compared with the time it took for glutamate levels to increase to peak values during AW onset. This is in contrast to other regions we studied in which the return to baseline values after AW was quicker than their rise with waking onset. In summary, we demonstrated an increase in glutamate levels in the PH-TMN with REM/AW onset and a drop in glutamate levels before the offset of REM. High temporal resolution measurement of glutamate levels reveals dynamic changes in release linked to the initiation and termination of REM sleep.     

Control of REM sleep: an aspect of the regulation of physiological homeostasis.

Since REM sleep is characterized by a suspension of the hypothalamic integration of homeostatic regulations, it has been assumed that the duration of both REM sleep episodes and of the time interval between the end of one episode and the beginning of the following episode may be regulated according to sleep related processes and the homeostatic needs of the organism. A series of studies performed on the rat has shown that REM sleep episodes occur as two basic types: single REM sleep episodes, that are separated by intervals > 3 min and sequential episodes, that are separated by intervals < or = 3 min and appear in a cluster. Moreover, it has been observed that, in this species, a change in REM sleep occurrence is caused by a modification in the number of episodes and not in their duration. With respect to this, sleep deprivation and recovery are characterized by a decrease and an increase, respectively, in the number of sequential REM sleep episodes, but the number of single episodes tends to be kept constant. The central aspects of this kind of regulation have been examined biochemically in the preoptic-anterior hypothalamus, an area involved in the control of autonomic and sleep related processes. The results show that the accumulation of adenosine 3':5'-cyclic monophosphate (cAMP) is impaired, in this region, during sleep deprivation and appears to return to the control levels, during the recovery, with a rate inversely related to the degree of the previous deprivation. Moreover, it has been observed that the systemic administration of DL-propranolol and LiCl reduces cAMP accumulation mainly in the preoptic-anterior hypothalamus; this condition is concomitant with a reduction in REM sleep occurrence.     

Serotonin Turnover in Discrete Regions of Young Rat Brain After 24 h REM Sleep Deprivation

The present study has attempted to elucidate the alteration of serotonin turnover after 24 h REM sleep deprivation in different regions in brain of young rat. Sleep deprivation was induced by the inverted flowerpot technique. Results of this study show increased serotonin turnover after 24 h REM sleep deprivation in all the brain regions except in the hypothalamus. The decreased 5-HT ratio shows increased serotonin in the hypothalamus after 24 h sleep deprivation. This study indicates increased activity of serotonergic neurons in the hypothalamus after 24 h sleep deprivation. This also indicates that the hypothalamus plays a role in the immediate compensatory mechanism during 24 h REM sleep deprivation in young rats.     

Chronic REM Sleep Restriction in Juvenile Male Rats Induces Anxiety-Like Behavior and Alters Monoamine Systems in the Amygdala and Hippocampus

Adolescence is marked by major physiological changes, including those in the sleep-wake cycle, such as phase delay, which may result in reduced sleep hours. Sleep restriction and/or deprivation in adult rats activate stress response and seem to be a risk factor for triggering emotional disorders. In the present study, we sought to evaluate the behavioral and neurobiological consequences of prolonged REM sleep restriction in juvenile male rats. Immediately after weaning, on postnatal day 21, three males from each litter were submitted to REM sleep deprivation and the other three animals were maintained in their home-cages. REM sleep restriction (REMSR) was accomplished by placing the animals in the modified multiple platform method for 18 h and 6 h in the home-cage, where they could sleep freely; the sleep restriction lasted 21 consecutive days, during which all animals were measured and weighed every 3 days. After the end of this period, all animals were allowed to sleep freely for 2 days, and then the behavioral tests were performed for evaluation of depressive and anxiety-like profiles (sucrose negative contrast test and elevated plus maze, EPM). Blood sampling was performed 5 min before and 30 and 60 min after the EPM for determination of corticosterone plasma levels. The adrenals were weighed and brains collected and dissected for monoamine levels and receptor protein expression. REMSR impaired the physical development of adolescents, persisting for a further week. Animals submitted to REMSR exhibited higher basal corticosterone levels and a greater anxiety index in the EPM, characteristic of an anxious profile. These animals also exhibited higher noradrenaline levels in the amygdala and ventral hippocampus, without any change in the expression of β1-adrenergic receptors, as well as higher serotonin and reduced turnover in the dorsal hippocampus, with diminished expression of 5-HT1_A. Finally, greater concentration of BDNF was observed in the dorsal hippocampus in chronically sleep-restricted animals. Chronic REMSR during puberty impaired physical development and induced anxiety-like behavior, attributed to increased noradrenaline and serotonin levels in the amygdala and hippocampus.     

The features of sleep homeostasis in pregnant rats

To investigate the effects of short-term sleep deprivation on the sleep pattern during pregnancy, cortical and hippocampal EEG and locomotor activity were recorded within 24-hours in a "disk-over-water" paradigm in 18 Wistar rats. Rats were adapted to experimental situation and were able to move across the rotating disk without falling in water. Then a polysomnogram was recorded for 3 sequential days in the control group 1 (n = 12) without disk rotation. On the next day non-pregnant rats (experimental group 1, n = 6) were subjected to the sleep deprivation procedure with a pre-set program of disk rotation from 11:00 to 14:00 during 3 sequential days. Other 6 rats (experimental group 2) were subjected to sleep deprivation on the 5-7th day of pregnancy. EEG and locomotor activity were also constantly recorded during the sleep deprivation procedure. In control group 2 (n = 6, without sleep deprivation), a polysomnogram was recorded on the 5-7th day of pregnancy. As compared to non-pregnant rats, sleep intensity of pregnant rats increased during the first hours after the deprivation, and a considerable rebound of REM sleep took place. Sleep pattern during the off-light 12 hours remained unchanged. The results suggest that homeostatic compensation of sleep deprivation effects in rats on the first week of pregnancy is more efficient than in control non-pregnant animals.     

Noradrenaline acting on alpha1-adrenoceptor mediates REM sleep deprivation-induced increased membrane potential in rat brain synaptosomes

We hypothesized that one of the functions of REM sleep is to maintain brain excitability and therefore, REM sleep deprivation is likely to modulate neuronal transmembrane potential; however, so far there was no direct evidence to support the claim. In this study a cationic dye, 3,3'-diethylthiacarbocyanine iodide was used to estimate the potential in synaptosomal samples prepared from control and REM sleep deprived rat brains. The activity of Na-K-ATPase that maintains the transmembrane potential was also estimated in the same sample. Further, the roles of noradrenaline and alpha1-adrenoceptor in mediating the responses were studied both in vivo as well as in vitro. Rats were REM sleep deprived for 4 days by the classical flower-pot method; large platform and recovery controls were carried out in addition to free-moving control. The fluorescence intensity increased in samples prepared from REM sleep deprived rat brain as compared to control, which reflected synaptosomal depolarization after deprivation. The Na-K-ATPase activity also increased in the same deprived sample. Furthermore, both the effects were mediated by noradrenaline acting on alpha1-adrenoceptors in the brain. This is the first direct evidence showing that REM sleep deprivation indeed increased neuronal depolarization, which is the likely cause for increased brain excitability, thus supporting our hypothesis and the effect was mediated by noradrenaline acting through the alpha1-adrenoceptor.     

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.     

Preoptic hypothalamic warming suppresses laryngeal dilator activity during sleep

Upper airway dilator activity during sleep appears to be diminished under conditions of enhanced sleep propensity, such as after sleep deprivation, leading to worsening of obstructive sleep apnea (OSA). Non-rapid eye movement (NREM) sleep propensity originates in sleep-active neurons of the preoptic area (POA) of the hypothalamus and is facilitated by activation of POA warm-sensitive neurons (WSNs). We hypothesized that activation of WSNs by local POA warming would inhibit activity of the posterior cricoarytenoid (PCA) muscle, an airway dilator, during NREM sleep. In chronically prepared unrestrained cats, the PCA exhibited inspiratory bursts in approximate synchrony with inspiratory diaphragmatic activity during waking, NREM, and REM. Integrated inspiratory PCA activity (IA), peak activity (PA), and the lead time (LT) of the onset of inspiratory activity in PCA relative to diaphragm were significantly reduced in NREM sleep and further reduced during REM sleep compared with waking. Mild bilateral local POA warming (0.5-1.2 degrees C) significantly reduced IA, PA, and LT during NREM sleep compared with a prewarming NREM baseline. In some animals, effects of POA warming on PCA activity were found during waking or REM. Because POA WSN activity is increased during spontaneous NREM sleep and regulates sleep propensity, we hypothesize that this activation contributes to reduction of airway dilator activity in patients with OSA.     

Maternal stress induces adult reduced REM sleep and melatonin level

We have previously reported that neonatal maternal deprivation (MD) resulted in a decrease of total sleep and an increase of orexin A in adult rats. Now, we characterized features of sleep, activity, and melatonin levels in rats neonatally treated with MD and control (MC) procedures. Adult male Sprague-Dawley rats were treated with either MD or MC procedures for 10 days starting at postnatal day 4. At 3 months of age, sleep was recorded for 48 h in one set of MD and MC rats, while another set of MD and MC rats was measured for locomotor activity (under LD = 12:12). Melatonin levels in the blood, pineal gland, and hypothalamus were measured as well as clock protein level in the hypothalamus. Compared to the MC rats, REM sleep in the MD rats was significantly reduced in the light periods but not in the dark periods. Both quiet wake and total wake in the MD rats were significantly increased during the light period compared to the MC rats. The weight of the pineal gland of the MD rats was significantly smaller than in MC rats. Melatonin levels of the MD group were significantly reduced in the pineal gland and hypothalamus compared to the MC group. No significant difference was identified between groups in the expression of the clock protein in the hypothalamus. Neonatal MD resulted in reduced REM sleep and melatonin levels, without changes of circadian cycle of locomotor activity and levels of clock protein.