The pendulum technique for paradoxical sleep deprivation in rats

A new technique for paradoxical sleep (PS) deprivation in rats is presented. Animals are prevented from entering into PS by allowing them to sleep for only brief periods of time. This is accomplished by an apparatus which moves the animals' cages backwards and forwards like a pendulum. At the extremes of the motion postural imbalance is produced in the animals forcing them to walk downwards to the other side of their cages. A minimal amount of PS and a moderate amount of slow wave sleep (SWS) were detected during a deprivation period of 72 hrs. Following the deprivation treatment the recovery of sleep was monitored for 3 hrs; at the beginning of the light period for one group and at the beginning of the dark period for a second group. The sleep-waking patterns of two baseline groups were established at the time when the recovery sleep was examined in the deprivation groups. The deprivation treatment resulted in a significant increase in the amount of PS and a significant decrease in the amount of SWS. The extent of PS increase was similar in both deprivation groups, in spite of a large difference in the amount of SWS. The decrease of SWS mainly occurred during recovery sleep in the light. It was observed that sleep in the dark differs from sleep in the light in behavioural aspects.     

Photically evoked potentials in the visual cortex following paradoxical sleep deprivation in rats

Immediately following 72 hr of paradoxical sleep (PS) deprivation, the P3-N3 amplitude of the photically evoked response in the visual cortex was measured in waking rats. PS deprivation was achieved instrumentally by one of three different techniques: the classical platform, the multiple platform, or the pendulum technique. For each of the techniques a control condition was run additionally. The PS deprivation effect consisted of a decrement in the P3-N3 amplitude, which was interpreted as indicating an increase in tonic arousal having a depressing influence on cortical excitability. Concomitantly, a relatively large technique effect occurred, in which the difference between the two platform techniques on the one hand, and the pendulum technique on the other, was most apparent. The same factors did not influence behavioural activity taking place during the presentation of photic stimulation, but did during the preceding 5 min adaptation period. Although the present findings are in contrast with previous reports in animals, they may not be inconsistent with the basic idea of the neural excitability hypothesis of PS.     

Effects of age on recovery of body weight following REM sleep deprivation of rats

Chronically enforced rapid eye (paradoxical) movement sleep deprivation (REM-SD) of rats leads to a host of pathologies, of which hyperphagia and loss of body weight are among the most readily observed. In recent years, the etiology of many REM-SD-associated pathologies have been elucidated, but one unexplored area is whether age affects outcomes. In this study, male Sprague-Dawley rats at 2, 6, and 12 months of age were REM sleep-deprived with the platform (flowerpot) method for 10-12 days. Two-month-old rats resided on 7-cm platforms, while 10-cm platforms were used for 6- and 12-month-old rats; rats on 15-cm platforms served as tank controls (TCs). Daily changes in food consumption (g/kg(0.67)) and body weight (g) during baseline, REM-SD or TCs, and post-experiment recovery in home cages were determined. Compared to TCs, REM-SD resulted in higher food intake and decreases in body weight. When returned to home cages, food intake rapidly declined to baseline levels. Of primary interest was that rates of body weight gain during recovery differed between the age groups. Two-month-old rats rapidly restored body weight to pre-REM-SD mass within 5 days; 6-month-old rats were extrapolated by linear regression to have taken about 10 days, and for 12-month-old rats, the estimate was about 35 days. The observation that restoration of body weight following its loss during REM-SD may be age-dependent is in general agreement with the literature on aging effects on how mammals respond to stress.     

Intracranial self-stimulation after paradoxical sleep deprivation induced by the platform method in rats

Lateral hypothalamic intracranial self-stimulation was studied before and after paradoxical sleep deprivation (PSD) induced by the platform method. Rats were assigned to two counterbalanced groups where the sequence order of experimental (small platform) and control (large platform) treatments was permuted. In contrast with previous findings significant changes in the response rates for intracranial self-stimulation were not observed after PSD. Ineffectiveness and nonspecific effects of the treatment are ruled out as the cause for our findings. An hypothesis is suggested that the effect of PSD upon intracranial self-stimulation could be dependent of the brain electrode location.     

REM sleep deprivation impairs muscle regeneration in rats

Introduction: The aim was observe the influence of sleep deprivation (SD) and sleep recovery on muscle regeneration process in rats submitted to cryolesion.

Methods: Thirty-two Wistar rats were randomly allocated in four groups: control (CTL), SD for 96?h (SD96), control plus sleep recovery period (CTL?+?R) and SD96h plus 96?h of sleep recovery (SD96?+?R). The animals were submitted to muscle injury by cryolesioning, after to SD and sleep recovery.

Results: The major outcomes of this study were the reduction of muscular IGF-1 in both legs (injured and uninjured) and a delay in muscle regeneration process of animals submitted to SD compared to animals that slept, with increase connective tissue, inflammatory infiltrate and minor muscle fibers.

Conclusions: SD impairs muscle regeneration in rats, moreover reduces muscular IGF-1 and sleep recovery was able to restore it to basal levels, but it was not enough to normalize the muscle regeneration.     

REM sleep deprivation diminishes fear in rats.

To test the hypothesis that REM sleep deprivation decreases fear, the behavior of 44 rats was measured in an open-field test. Prior to this test, the animals were exposed to 4 days to one of four treatments, i.e., either a dry environment control, a wet environment control, a 2-day REM deprivation period, or a 4-day REM deprivation period. During the test both exploration and three parameters of emotionality were recorded. The results offered convincing evidence in support of the hypothesis.     

REM sleep deprivation and food competition in male rats

As a test of the hypothesis that REM deprivation lowers the threshold for “motivational” behaviors, 17 male rats that had been REM deprived were tested against 17 non-deprived male rats in three series of food competition tests, i.e., an immediate, a 3 hr, and a 48 hr series of posttreatment tests. The results provide support for the hypothesis that REM deprivation generally activates “motivational” behaviors, in that the REM deprived animals won more frequently as had been predicted. However, the response gradients of the two groups over the course of the postteatment test series did not conform to prediction. These data are discussed together with the results of other studies which suggest that perhaps the list of behaviors which have been subsumed under the category—“motivational behaviors” is too broad to be of real scientific value.     

REM sleep deprivation increases aggressiveness in male rats.

As a test of the hypothesis that REM deprivation increases aggressiveness in rats, the effects of two and four days of REM deprivation were measured on the frequency and latency with which male rats attack mice. The results showed that REM deprivation increased the frequency of attacks, the muricide rate, and the latency to first attack in a “dose-related” fashion. To a degree these behaviors persisted through a 21-day recovery period.     

Effects of paradoxical sleep deprivation on two-way avoidance acquisition

Immediately following 72 hrs of paradoxical sleep (PS) deprivation, Wistar rats were given a shuttle-box avoidance task consisting of 50 trials. At an interval of 6 days retention was assessed through a reacquisition session of 20 trials. In a first experiment, the pendulum technique was employed for PS deprivation and its effects were compared with those produced by the conventional watertank technique. The first technique consists of arousing animals from sleep before PS can arise, by swinging their cages in a way that produces postural imbalance at regular intervals. A moving pendulum just not causing imbalance in the animals served as control for this technique. As control for the watertank technique the large platform was chosen. Shuttle-box avoidance was greatly impaired during the second half of the acquisition session in both platform conditions as compared to both pendulum conditions. A relatively small deficit was found toward the end of the session in both PS deprivation conditions as compared to both control conditions. No differences in avoidance were established during retention testing, suggesting that performance rather than learning deficits occurred during acquisition. In a second experiment, the multiple platform was used for PS deprivation. This modified version of the watertank technique also disrupted performance during shuttle-box avoidance acquisition. However, this effect appeared to be less pronounced than the effect found in the classical platform condition of Experiment 1. It is concluded that the performance deficit induced by both the classical and the multiple platform condition was mainly due to nonspecific effects.     

Cocaine-induced genital reflexes during paradoxical sleep deprivation and recovery

Paradoxical sleep deprivation (PSD) for 96 h together with cocaine administration elicits genital reflexes (penile erection [PE] and ejaculation [EJ]) in rats. Our objective was to examine genital reflexes after periods of 24, 48, 72, 96, 120, and 144 h of PSD and during a 4-day recovery period in acute cocaine-administered rats. After 24 h of PSD followed by cocaine administration, animals started to display PE and EJ, peaking in the 96th h of PSD, whereas PE and EJ were absent in control animals. The effects of more than 96 h of PSD decrease genital reflexes as observed after 120 and 144 h. Genital reflexes were present in the recovery periods but diminished gradually during the period evaluated. Even short periods of PSD probably cause supersensitivity of dopamine (DA) receptors and exacerbate the effects of cocaine on dopaminergic pathways to induce frequent PE and EJ.     

Short-term homeostasis of REM sleep assessed in an intermittent REM sleep deprivation protocol in the rat

An intermittent rapid eye movement (REM) sleep deprivation protocol was applied to determine whether an increase in REM sleep propensity occurs throughout an interval without REM sleep comparable with the spontaneous sleep cycle of the rat. Seven chronically implanted rats under a 12 : 12 light-dark schedule were subjected to an intermittent REM sleep deprivation protocol that started at hour 6 after lights-on and lasted for 3 h. It consisted of six instances of a 10-min REM sleep permission window alternating with a 20-min REM sleep deprivation window. REM sleep increased throughout the protocol, so that total REM sleep in the two REM sleep permission windows of the third hour became comparable with that expected in the corresponding baseline hour. Attempted REM sleep transitions were already increased in the second deprivation window. Attempted transitions to REM sleep were more frequent in the second than in the first half of any 20-min deprivation window. From one deprivation window to the next, transitions to REM sleep changed in correspondence to the amount of REM sleep in the permission window in-between. Our results suggest that: (i) REM sleep pressure increases throughout a time segment similar in duration to a spontaneous interval without REM sleep; (ii) it diminishes during REM sleep occurrence; and (iii) that drop is proportional to the intervening amount of REM sleep. These results are consistent with a homeostatic REM sleep regulatory mechanism that operates in the time scale of spontaneous sleep cycle.     

Reversal of paradoxical sleep deprivation by amygdaloid stimulation during learning

Rats were subjected to a partial, selective paradoxical sleep (PS) deprivation. Two groups were trained in a shuttle avoidance task, one receiving posttraining amygdaloid stimulations (AS). A third group received AS, but was not trained. Levels of PS in the AS trained group were higher than in the AS non-trained controls, while the reverse was true for the slow wave sleep (SWS) measure. Both AS groups had levels of PS and SWS superior to the non-AS trained rats. In a second experiment, a group of normally rested AS animals was trained in the same task with a non-AS control group. These groups did not differ in terms of learning performance. Results were believed to support the hypothesis of a close relationship between sleep and learning.     

A multinational study of sleep disorders during female mid-life

Background

Although sleep disturbances are common during female mid-life, few studies have described in detail the prevalence of this problem and related risk factors.

Objective

To determine the prevalence of sleep disturbances in mid-aged women using validated tools. Assessment of determinants capable of influencing the prevalence of insomnia and poor sleep quality was also performed.

Methods

A total of 6079 women aged 40–59 of 11 Latin American countries were invited to fill out the Athens Insomnia Scale (AIS), the Pittsburgh Sleep Quality Index (PSQI), the Goldberg Anxiety and Depression Scale, the Menopause Rating Scale (MRS), the Brief Scale of Abnormal Drinking and a general socio-demographic questionnaire.

Results

Overall, 56.6% of surveyed women suffered of either insomnia, poor sleep quality, or both. Specifically, 43.6% and 46.2% presented insomnia and poor sleep quality in accordance to the AIS and the PSQI respectively. The prevalence of insomnia increased with female age (from 39.7% in those aged 40–44 to 45.2% in those aged 55–59, p < 0.0001) and menopausal stage (from 39.5% in premenopausal aged 40–44 to 46.3% in late postmenopausal ones, p < 0.0001). “Awakening during the night” (AIS: Item 2) was the most highly rated of all items and contributing in a higher degree (mean 16%) to the total score of the scale in all menopausal phases. Sleep quality also worsened with age and menopausal status, impairment particularly affecting sleep efficiency and latency and the increased use of hypnotics. Vasomotor symptoms (VMS), depressive mood and anxiety were associated to sleep disturbances. Women presenting sleep disturbances displayed a 2-fold increase in the severity of menopausal symptoms (higher total MRS scores) which was translated into a 6–8 times higher risk of impaired quality of life. Logistic regression analysis determined that female age, the presence of chronic disease, troublesome drinking, anxiety, depression, VMS, drug use (hypnotics and hormone therapy) were significant risk factors related to the presence of sleep disturbances. Higher educational level related to less insomnia and better sleep quality.

Conclusion

Insomnia and poor sleep quality were highly prevalent in this mid-aged female sample in which the influence of age and the menopause was only modest and rather linked to menopausal symptoms already occurring since the premenopause.     

REM sleep deprivation increases preference for novelty in rats.

As a further test of the hypothesis that REM deprivation decreases fear, the behavior of 40 male rats was measured in a Y-maze adapted to test for preference for novelty. Prior to this test, the animals were exposed for 4 days to one of four treatments, i.e., either a dry environment control, a wet environment control, a 2-day REM deprivation period or a 4-day REM deprivation period. During the test both number of grid crossing in the novel and non-novel arms of the Y-maze and three indices of emotionality were recorded. The results were congruent with data we had reported earlier and offered convincing evidence in support of the hypothesis.     

Selective deprivation of paradoxical sleep and consolidation of shuttle-box avoidance.

Investigated whether paradoxical sleep is implicated in the storage of information acquired during shuttle-box avoidance. Wistar rats were given 5 brief training sessions distributed over the light period of the diurnal cycle. During the intervals between sessions the animals were selectively deprived of paradoxical sleep by awakening them every time they showed this type of sleep. The onset of paradoxical sleep was identified when hippocampal theta rhythm occurred during behavioural sleep. Yoked control animals got the same treatment irrespective of their sleep-waking behaviour, whereas free sleep rats were allowed to sleep undisturbed. In spite of large differences in the amount of paradoxical sleep during the intersession intervals no differences in learning performances were found among the groups. A tendency toward more intertrial crossings was noted in the paradoxical sleep deprived group at the end of training. It is concluded that storage of information acquired during distributed shuttle-box avoidance is not dependent on the presence of paradoxical sleep immediately following learning. Some possibilities are considered that paradoxical sleep may still be involved in memory storage processes.     

Effect of light deprivation on sleep in the rat

The sleep-wake cycles of 24- and 30- day-old rats reared in darkness from 48 hr after birth (E) were polygraphically recorded in 3 3-hr sessions (0900–1200 hr; 1230–1530 hr; 1600–1900 hr) and compared to normally reared controls (C). The total amount of paradoxical sleep (PS) over the 3 3-hr sessions of the light-deprived rats (E₂₄ and E₃₀) was significantly less than in the controls (C₂₄, and C₃₀). The distribution of PS over the 3 sessions was different for the control groups: C₂₄ showed a significantly greater amount of PS and SWS during 1230–1530 hr, and C₃₀ during 1230–1530 and 16–19 hr. Light-deprived groups showed no significant variations neither in PS nor in SWS or W within the three sessions. These data fail to support the hypothesis that PS functions as a compensatory stimulation under conditions of low stimulation.     

Short-term REM sleep deprivation increases acetylcholinesterase activity in the medulla of rats

Involvement of cholinergic ponto-medullary brainstem mechanism regulating rapid eye movement (REM) sleep is known. Recently it was found that though short term REM deprivation influenced brainstem neuronal excitability, the activity of the brainstem acetylcholinesterase was not affected until after 96 h deprivation. Therefore, it was hypothesized that short-term REM deprivation might influence acetylcholinesterase in a restricted brainstem region. Results of this study show that the enzyme activity increased only in the medulla after 24 and 48 h REM deprivation. The flower pot technique was used for depriving the experimental rats of REM sleep. Suitable control experiments were conducted to rule out the possibility of non-specific effects. Thus, the medullary cholinergic mechanism probably is more important for REM.     

Effects of REM deprivation on the lordosis response induced by gonadal steroids in ovariectomized rats

Ovariectomized rats were submitted to REM sleep deprivation (REMd) using the water tank technique and their behavioral responsiveness (lordosis) to gonadal steroids was tested. In Experiment 1, animals received 2 micrograms of estradiol benzoate (EB) followed by 2 mg of progesterone (P) 44 hours later. Several REMd periods (12, 72, 96 and 120 hr) were applied, all ending four hr after P. REMd animals showed significantly lower lordosis quotients (LQ) than undisturbed sleep animals regardless of the duration of the deprivation period. In Experiment 2, animals received a single dose of EB (2 micrograms) and were REMd for 120 hours. Animals were tested daily to evaluate their LQ. EB, at this dose level, failed to elicit significant lordosis behavior in undisturbed sleep rats. REMd rats gradually increased their LQ values reaching maximal levels at 72 hours. Adrenalectomized control groups receiving the same hormonal treatment responded similarly to the experimental groups, thus discarding the participation of adrenal steroids in these effects. The present results show that REMd differentially affects the response to E and P in ovariectomized rats, enhancing the former and inhibiting the latter.     

Non-REM sleep as a source of learning deficits induced by REM sleep deprivation.

Procedures that deprive animal subjects of rapid eye movement sleep have often been associated with learning impairments. Previously, the conclusion has been drawn that these learning impairments are due to the absence of some positive function of rapid eye movement sleep. The present research indicates more precisely that typical impairments associated with the deprivation procedures may be due to isolated periods of non-REM sleep, rather than due to the simple absence of rapid eye movement sleep. Mice were tested for acquistion of a complex maze task, and subjected to post-trial rapid eye movement sleep deprivation by the pedestal method. Only animals demonstrating (non-REM) sleep behaviors during deprivation gave evidence of learning deficits.     

Differential effect of paradoxical sleep deprivation on acquisition and retrieval of conditioned taste aversion in rats.

Paradoxical sleep deprivation (PSD) was used to interfere with acquisition or retrieval of conditioned taste aversion (CTA). PSD was achieved by confining rats to small pedestals placed on an electrified grid floor. Fifteen-min access to 0.1% sodium saccharin (conditioned stimulus-CS) by water deprived rats was followed 30–120 min later by intraperitoneal injection of lithium chloride (unconditioned stimulus-US, 0.15 M, 2% to 4% body weight). Retention was tested 1 to 5 days later by offering the animal saccharin again. A 24-hr PSD preceding saccharin drinking prevented CTA acquisition. CTA disruption was diminished by a 2-hr, and completely abolished by an 8-hr interval of home cage recovery inserted between the 24-hr PSD and saccharin presentation. CTA was slightly facilitated by 2-hr PSD in the CS-US interval. The 24-hr PSD preceding CS caused the same CTA disruption when followed by free sleep opportunity or by continued PSD in the 2-hr CS-US interval. Twenty-four-hr PSD preceding retention testing slightly improved retrieval of well established CTA. It is concluded that PSD interferes with the formation of the short-term gustatory trace of CTA but does not affect retrieval of CTA engrams. Gradual compensation for the PSD effect on CTA learning by pre-acquisition sleep suggests that the processes responsible for CTA disruption and recovery correspond to depletion and repletion of the same neurotransmitter stores.