REM sleep deprivation increases aggressiveness in male rats

The effect of REM-sleep disruption on affective processing: A systematic review of human and animal experimental studies

Evidence on the importance of rapid-eye-movement sleep (REMS) in processing emotions is accumulating. The focus of this systematic review is the outcomes of experimental REMS deprivation (REMSD), which is the most common method in animal models and human studies on REMSD. This review revealed that variations in the applied REMSD methods were substantial. Animal models used longer deprivation protocols compared with studies in humans, which mostly reported acute deprivation effects after one night. Studies on animal models showed that REMSD causes aggressive behavior, increased pain sensitivity, reduced sexual behavior, and compromised consolidation of fear memories. Animal models also revealed that REMSD during critical developmental periods elicits lasting consequences on affective-related behavior. The few human studies revealed increases in pain sensitivity and suggest stronger consolidation of emotional memories after REMSD. As pharmacological interventions (such as selective serotonin reuptake inhibitors [SSRIs]) may suppress REMS for long periods, there is a clear gap in knowledge regarding the effects and mechanisms of chronic REMS suppression in humans.

Crocin (bioactive compound of Crocus sativus L.) potently restores REM sleep deprivation-induced manic- and obsessive-compulsive-like behaviors in female rats

Rapid-eye movement (REM) sleep deprivation (SD) can induce manic-like behaviors including hyperlocomotion. On the other hand, crocin (one of the main compounds of Crocus sativus L. or Saffron) may be beneficial in the improvement of mental and cognitive dysfunctions. Also, crocin can restore the deleterious effects of SD on mental and cognitive processes. In this study, we investigated the effect of REM SD on female rats' behaviors including depression- and anxiety-like behaviors, locomotion, pain perception, and obsessive-compulsive-like behavior, and also, the potential effect of crocin on REM SD effects. We used female rats because evidence on the role of REM SD in modulating psychological and behavioral functions of female (but not male) rats is limited. REM SD was induced for 14 days (6h/day), and crocin (25, 50, and 75 mg/kg) was injected intraperitoneally. Open field test, forced swim test, hot plate test, and marble burying test were used to assess rats' behaviors. The results showed REM SD-induced manic-like behavior (hyperlocomotion). Also, REM SD rats showed decreased anxiety- and depression-like behavior, pain subthreshold (the duration it takes for the rat to feel pain), and showed obsessive compulsive-like behavior. However, crocin at all doses partially or fully reversed REM SD-induced behavioral changes. In conclusion, our results suggested the possible comorbidity of OCD and REM SD-induced manic-like behavior in female rats or the potential role of REM SD in the etiology of OCD, although more studies are needed. In contrast, crocin can be a possible therapeutic choice for decreasing manic-like behaviors.

Bipolar Chronobiology in Men and Mice: A Narrative Review

In patients with bipolar disorder, we do not only see a cycling of mood episodes, but also a shift in circadian rhythm. In the present overview, the circadian rhythm, the "internal clock", and their disruptions are briefly described. In addition, influences on circadian rhythms such as sleep, genetics, and environment are discussed. This description is conducted with a translational focus covering human patients as well as animal models. Concluding the current knowledge on chronobiology and bipolar disorder, implications for specificity and the course of bipolar disorder and treatment options are given at the end of this article. Taken together, circadian rhythm disruption and bipolar disorder are strongly correlated; the exact causation, however, is still unclear.

The Relation Between the Power of Prefrontal Gamma in Rest-state EEG Under Normal Sleep and Reactive Aggression Behaviour After Sleep Deprivation

Whether sleep deprivation affects aggressive behaviour is still under debate. The present study examined the influence of individual differences in reactive aggressive behaviour after sleep deprivation and preliminarily explored an electrophysiological marker to identify individuals with more aggressive behaviour after sleep deprivation. Thirty participants performed the Taylor Aggression Paradigm task under two sleep conditions: normal sleep (NS, one night of regular sleep) and total sleep deprivation (SD, 30 h of wakefulness), and 5-minute resting-state electroencephalogram (EEG) acquisition was completed under the NS condition. The results found that although sleep deprivation did not have significant effects on aggressive behaviour in the overall analysis, the participants can be classified as an increased group (n = 16) and a no-increased group (n = 14) by different changes in the two sleep conditions (SD-NS). In addition, prefrontal gamma (γ) power was significantly lower in the increased group than in the no-increased group, which may reflect the difference in ability on inhibition. Furthermore, more critical is that γ power was significantly negatively correlated with change in the reactive aggressive behaviour. These results indicate that the effect of SD on reactive aggression varies between individuals, and prefrontal γ power may be an effective electrophysiological marker for identifying people at risk of aggressive behaviour after SD.

The cyclic interaction between daytime behavior and the sleep behavior of laboratory dogs

Sleep deprivation has been found to negatively affect an individual´s physical and psychological health. Sleep loss affects activity patterns, increases anxiety-like behaviors, decreases cognitive performance and is associated with depressive states. The activity/rest cycle of dogs has been investigated before, but little is known about the effects of sleep loss on the behavior of the species. Dogs are polyphasic sleepers, meaning the behavior is most observed at night, but bouts are also present during the day. However, sleep can vary with ecological and biological factors, such as age, sex, fitness, and even human presence. In this study, kennelled laboratory adult dogs' sleep and diurnal behavior were recorded during 24-h, five-day assessment periods to investigate sleep quality and its effect on daily behavior. In total, 1560 h of data were analyzed, and sleep metrics and diurnal behavior were quantified. The relationship between sleeping patterns and behavior and the effect of age and sex were evaluated using non-parametric statistical tests and GLMM modelling. Dogs in our study slept substantially less than previously reported and presented a modified sleep architecture with fewer awakenings during the night and almost no sleep during the day. Sleep loss increased inactivity, decreased play and alert behaviors, while increased time spent eating during the day. Males appeared to be more affected by sleep fragmentation than females. Different age groups also experienced different effects of sleep loss. Overall, dogs appear to compensate for the lack of sleep during the night by remaining inactive during the day. With further investigations, the relationship between sleep loss and behavior has the potential to be used as a measure of animal welfare.

Sleep restriction alters reactive aggressive behavior and its relationship with sex hormones

Few studies have experimentally manipulated sleep to study its effect on aggressive behavior. The current study examined how reactive aggression was affected by having sleep restricted to 4-hours on a single night, a level of disruption commonly experienced. Both rested and sleep-restricted participants completed the Point Subtraction Aggression Paradigm (PSAP), a laboratory task in which participants seek to earn points, are provoked by a fictitious opponent stealing their points, and may choose to steal points in response. Logistic mixed-effect models were used to investigate the effect of sleep restriction and the role of sex hormones on the odds of choosing to steal. For men, and women in the luteal phase of the menstrual cycle, sleep restriction did not result in significant changes reactive aggression, although the patterns of aggressive behavior appeared less reactive and retaliatory in nature. For women in the follicular phase of the menstrual cycle, sleep restriction was associated with higher levels of reactive aggression. For both men and women in the luteal phase, sleep restriction disrupted an association between hormone change over the task (testosterone and estradiol, respectively) and reactive aggression that was observed in their control participants. In addition, higher testosterone before the PSAP in men was associated with maintaining a high level of stealing over the task. These results indicate a complex dynamic in which sex hormones and sleep interact to predict aggressive behavior in response to provocation.

Bipolar Disorder: Its Etiology and How to Model in Rodents

Characterized by the switch of manic and depressive phases, bipolar disorder was described as early as the fifth century BC. Nevertheless up to date, the underlying neurobiology is still largely unclear, assuming a multifactor genesis with both biological-genetic and psychosocial factors. Significant process has been achieved in recent years in researching the causes of bipolar disorder with modern molecular biological (e.g., genetic and epigenetic studies) and imaging techniques (e.g., positron emission tomography (PET) and functional magnetic resonance imaging (fMRI)). In this chapter we will first summarize our recent knowledge on the etiology of bipolar disorder. We then discuss how several factors observed to contribute to bipolar disorder in human patients can be manipulated to generate rodent models for bipolar disorder. Finally, we will give an overview on behavioral test that can be used to assess bipolar-disorder-like behavior in rodents.

Biological Clocks and Rhythms of Anger and Aggression

The body’s internal timekeeping system is an under-recognized but highly influential force in behaviors and emotions including anger and reactive aggression. Predictable cycles or rhythms in behavior are expressed on several different time scales such as circadian (circa diem, or approximately 24-h rhythms) and infradian (exceeding 24 h, such as monthly or seasonal cycles). The circadian timekeeping system underlying rhythmic behaviors in mammals is constituted by a network of clocks distributed throughout the brain and body, the activity of which synchronizes to a central pacemaker, or master clock. Our daily experiences with the external environment including social activity strongly influence the exact timing of this network. In the present review, we examine evidence from a number of species and propose that anger and reactive aggression interact in multiple ways with circadian clocks. Specifically, we argue that: (i) there are predictable rhythms in the expression of aggression and anger; (ii) disruptions of the normal functioning of the circadian system increase the likelihood of aggressive behaviors; and (iii) conversely, chronic expression of anger can disrupt normal rhythmic cycles of physiological activities and create conditions for pathologies such as cardiovascular disease to develop. Taken together, these observations suggest that a comprehensive perspective on anger and reactive aggression must incorporate an understanding of the role of the circadian timing system in these intense affective states.

Animal models for bipolar disorder: from bedside to the cage

Bipolar disorder is characterized by recurrent manic and depressive episodes. Patients suffering from this disorder experience dramatic mood swings with a wide variety of typical behavioral facets, affecting overall activity, energy, sexual behavior, sense of self, self-esteem, circadian rhythm, cognition, and increased risk for suicide. Effective treatment options are limited and diagnosis can be complicated. To overcome these obstacles, a better understanding of the neurobiology underlying bipolar disorder is needed. Animal models can be useful tools in understanding brain mechanisms associated with certain behavior. The following review discusses several pathological aspects of humans suffering from bipolar disorder and compares these findings with insights obtained from several animal models mimicking diverse facets of its symptomatology. Various sections of the review concentrate on specific topics that are relevant in human patients, namely circadian rhythms, neurotransmitters, focusing on the dopaminergic system, stressful environment, and the immune system. We then explain how these areas have been manipulated to create animal models for the disorder. Even though several approaches have been conducted, there is still a lack of adequate animal models for bipolar disorder. Specifically, most animal models mimic only mania or depression and only a few include the cyclical nature of the human condition. Future studies could therefore focus on modeling both episodes in the same animal model to also have the possibility to investigate the switch from mania-like behavior to depressive-like behavior and vice versa. The use of viral tools and a focus on circadian rhythms and the immune system might make the creation of such animal models possible.

Modeling mania in preclinical settings: A comprehensive review

The current pathophysiological understanding of mechanisms leading to onset and progression of bipolar manic episodes remains limited. At the same time, available animal models for mania have limited face, construct, and predictive validities. Additionally, these models fail to encompass recent pathophysiological frameworks of bipolar disorder (BD), e.g. neuroprogression. Therefore, there is a need to search for novel preclinical models for mania that could comprehensively address these limitations. Herein we review the history, validity, and caveats of currently available animal models for mania. We also review new genetic models for mania, namely knockout mice for genes involved in neurotransmission, synapse formation, and intracellular signaling pathways. Furthermore, we review recent trends in preclinical models for mania that may aid in the comprehension of mechanisms underlying the neuroprogressive and recurring nature of BD. In conclusion, the validity of animal models for mania remains limited. Nevertheless, novel (e.g. genetic) animal models as well as adaptation of existing paradigms hold promise.

Animal models of bipolar mania: The past, present and future

Bipolar disorder (BD) is the sixth leading cause of disability in the world according to the World Health Organization and affects nearly six million (∼2.5% of the population) adults in the United State alone each year. BD is primarily characterized by mood cycling of depressive (e.g., helplessness, reduced energy and activity, and anhedonia) and manic (e.g., increased energy and hyperactivity, reduced need for sleep, impulsivity, reduced anxiety and depression), episodes. The following review describes several animal models of bipolar mania with a focus on more recent findings using genetically modified mice, including several with the potential of investigating the mechanisms underlying 'mood' cycling (or behavioral switching in rodents). We discuss whether each of these models satisfy criteria of validity (i.e., face, predictive, and construct), while highlighting their strengths and limitations. Animal models are helping to address critical questions related to pathophysiology of bipolar mania, in an effort to more clearly define necessary targets of first-line medications, lithium and valproic acid, and to discover novel mechanisms with the hope of developing more effective therapeutics. Future studies will leverage new technologies and strategies for integrating animal and human data to reveal important insights into the etiology, pathophysiology, and treatment of BD.

Investigating the underlying mechanisms of aberrant behaviors in bipolar disorder from patients to models: Rodent and human studies

Psychiatric patients with bipolar disorder suffer from states of depression and mania, during which a variety of symptoms are present. Current treatments are limited and neurocognitive deficits in particular often remain untreated. Targeted therapies based on the biological mechanisms of bipolar disorder could fill this gap and benefit patients and their families. Developing targeted therapies would benefit from appropriate animal models which are challenging to establish, but remain a vital tool. In this review, we summarize approaches to create a valid model relevant to bipolar disorder. We focus on studies that use translational tests of multivariate exploratory behavior, sensorimotor gating, decision-making under risk, and attentional functioning to discover profiles that are consistent between patients and rodent models. Using this battery of translational tests, similar behavior profiles in bipolar mania patients and mice with reduced dopamine transporter activity have been identified. Future investigations should combine other animal models that are biologically relevant to the neuropsychiatric disorder with translational behavioral assessment as outlined here. This methodology can be utilized to develop novel targeted therapies that relieve symptoms for more patients without common side effects caused by current treatments.

Aggression in Young Adults — A Matter of Short Sleep and Social Jetlag?

Evening orientation and sleep duration have been linked with aggression and problematic behaviors, but no study has used an explicit aggression questionnaire. The present study used the Buss-Perry Aggression Questionnaire based on physical aggression, verbal aggression, anger, and hostility, as well as questionnaires on the timing of sleep and sleep duration to assess this relationship in young adult men. The Composite Scale of Morningness was used to assess circadian preference; sleep-wake variables (wake time and sleep onset time on weekdays and on weekend days) were used to calculate midpoint of sleep, social jetlag, and sleep duration. Results indicated that sleep duration correlated negatively with verbal aggression, physical aggression, and anger. Short sleepers were more aggressive. Using multivariate analysis of variance, shorter sleep duration was a significant predictor of verbal aggression and anger. Concerning physical aggression, social jetlag also contributed to the model. Morningness-eveningness was associated with the hostility scale with eveningness related to higher hostility. Men scored higher than women in physical and verbal aggression.

Rhythms, rhythmicity and aggression

The relationships between biological rhythms and human aggressive behavior are addressed and discussed in this article: First, circadian rhythms and aggression are considered. Studies of sleep/waking cycle disturbances in aggression are reported. Severe aggression is associated with profound changes in sleep architecture. Causal link is difficult to establish given that sleep disturbance and aggressive behavior could be the symptoms of the same disorder. Specific aggressive behavior developed during sleep is also described. In addition, hormonal circadian rhythm studies are reported. Thus, low cortisol levels, in particular low cortisol variability, are associated with aggressive behavior, suggesting an inhibitory role of cortisol. Testosterone has daily and seasonal fluctuations, but no link with aggression has been established. Neurophysiological underlying mechanisms are discussed in the last part of this article, with a focus on the relationship between brain rhythm and aggression. Increase of slow-wave EEG activities is observed in individuals with aggressive behavior. Epilepsy, as a disease of brain rhythm could be associated with aggressive behavior, in pre, post and inter ictal periodes. Incidence of aggression is not likely more prevalent in epileptic individuals compared to those with other neurological conditions. Ictal changes take the form of profound behavioral changes, including aggressive behavior which has been interpreted as the emergence of "archeical" or innate motor patterns. In this multidisciplinary approach, the main difficulty is the categorization of the differents types of aggression. Finally, taken together, these studies suggest that biological rhythms, especially circadian rhythms, could provide therapeutic benefits to human aggressive behavior. Biological rhythymicity seems to be a necessary permanent training offering interesting perspectives for the adaptation to changes in the field of aggression.

Sleep deprivation lowers reactive aggression and testosterone in men

The role of sleep deprivation in aggressive behavior has not been systematically investigated, despite a great deal of evidence to suggest a relationship. We investigated the impact of 33 h of sleep loss on endocrine function and reactive aggression using the Point Subtraction Aggression Paradigm (PSAP) task. PSAP performance was assessed in 24 young men and 25 women who were randomly assigned to a sleep deprivation or control condition. Sleep deprivation lowered reactive aggression and testosterone (but not cortisol) in men, and disrupted the positive relationship between a pre-post PSAP increase in testosterone and aggression that was evident in rested control men. While women increased aggression following provocation as expected, no influence of sleep deprivation was found. This is the first experimental study to demonstrate that sleep deprivation lowers reactive aggression in men. Testosterone, but not cortisol, played a role in the relationship between sleep and reactive aggression in men.

Predictive animal models of mania: hits, misses and future directions

Mania has long been recognized as aberrant behaviour indicative of mental illness. Manic states include a variety of complex and multifaceted symptoms that challenge clear clinical distinctions. Symptoms include over-activity, hypersexuality, irritability and reduced need for sleep, with cognitive deficits recently linked to functional outcome. Current treatments have arisen through serendipity or from other disorders. Hence, treatments are not efficacious for all patients, and there is an urgent need to develop targeted therapeutics. Part of the drug discovery process is the assessment of therapeutics in animal models. Here we review pharmacological, environmental and genetic manipulations developed to test the efficacy of therapeutics in animal models of mania. The merits of these models are discussed in terms of the manipulation used and the facet of mania measured. Moreover, the predictive validity of these models is discussed in the context of differentiating drugs that succeed or fail to meet criteria as approved mania treatments. The multifaceted symptomatology of mania has not been reflected in the majority of animal models, where locomotor activity remains the primary measure. This approach has resulted in numerous false positives for putative treatments. Recent work highlights the need to utilize multivariate strategies to enable comprehensive assessment of affective and cognitive dysfunction. Advances in therapeutic treatment may depend on novel models developed with an integrated approach that includes: (i) a comprehensive battery of tests for different aspects of mania, (ii) utilization of genetic information to establish aetiological validity and (iii) objective quantification of patient behaviour with translational cross-species paradigms.

Poor sleep as a potential causal factor in aggression and violence

Clinical observations suggest that sleep problems may be a causal factor in the development of reactive aggression and violence. In this review we give an overview of existing literature on the relation between poor sleep and aggression, irritability, and hostility. Correlational studies are supporting such a relationship. Although limited in number, some studies suggest that treatment of sleep disturbances reduces aggressiveness and problematic behavior. In line with this is the finding that sleep deprivation actually increases aggressive behavior in animals and angriness, short-temperedness, and the outward expression of aggressive impulses in humans. In most people poor sleep will not evoke actual physical aggression, but certain individuals, such as forensic psychiatric patients, may be particularly vulnerable to the emotional dysregulating effects of sleep disturbances. The relation between sleep problems and aggression may be mediated by the negative effect of sleep loss on prefrontal cortical functioning. This most likely contributes to loss of control over emotions, including loss of the regulation of aggressive impulses to context-appropriate behavior. Other potential contributing mechanisms connecting sleep problems to aggression and violence are most likely found within the central serotonergic and the hypothalamic-pituitary-adrenal-axis. Individual variation within these neurobiological systems may be responsible for amplified aggressive responses induced by sleep loss in certain individuals. It is of great importance to identify the individuals at risk, since recognition and adequate treatment of their sleep problems may reduce aggressive and violent incidents.

The neurobiology of the switch process in bipolar disorder: a review

OBJECTIVE

The singular phenomenon of switching from depression to its opposite state of mania or hypomania, and vice versa, distinguishes bipolar disorder from all other psychiatric disorders. Despite the fact that it is a core aspect of the clinical presentation of bipolar disorder, the neurobiology of the switch process is still poorly understood. In this review, we summarize the clinical evidence regarding somatic interventions associated with switching, with a particular focus on the biologic underpinnings presumably involved in the switch process.

DATA SOURCES

Literature for this review was obtained through a search of the MEDLINE database (1966-2008) using the following keywords and phrases: switch, bipolar disorder, bipolar depression, antidepressant, SSRIs, tricyclic antidepressants, norepinephrine, serotonin, treatment emergent affective switch, mania, hypomania, HPA-axis, glucocorticoids, amphetamine, dopamine, and sleep deprivation.

STUDY SELECTION

All English-language, peer-reviewed, published literature, including randomized controlled studies, naturalistic and open-label studies, and case reports, were eligible for inclusion.

DATA SYNTHESIS

Converging evidence suggests that certain pharmacologic and nonpharmacologic interventions with very different mechanisms of action, such as sleep deprivation, exogenous corticosteroids, and dopaminergic agonists, can trigger mood episode switches in patients with bipolar disorder. The switch-inducing potential of antidepressants is unclear, although tricyclic antidepressants, which confer higher risk of switching than other classes of antidepressants, are a possible exception. Several neurobiological factors appear to be associated with both spontaneous and treatment-emergent mood episode switches; these include abnormalities in catecholamine levels, up-regulation of neurotrophic and neuroplastic factors, hypothalamic-pituitary-adrenal axis hyperactivity, and circadian rhythms.

CONCLUSIONS

There is a clear need to improve our understanding of the neurobiology of the switch process; research in this field would benefit from the systematic and integrated assessment of variables associated with switching.

Cross-species assessments of motor and exploratory behavior related to bipolar disorder

Alterations in exploratory behavior are a fundamental feature of bipolar mania, typically characterized as motor hyperactivity and increased goal-directed behavior in response to environmental cues. In contrast, abnormal exploration associated with schizophrenia and depression can manifest as prominent withdrawal, limited motor activity, and inattention to the environment. While motor abnormalities are cited frequently as clinical manifestations of these disorders, relatively few empirical studies have quantified human exploratory behavior. This article reviews the literature characterizing motor and exploratory behavior associated with bipolar disorder and genetic and pharmacological animal models of the illness. Despite sophisticated assessment of exploratory behavior in rodents, objective quantification of human motor activity has been limited primarily to actigraphy studies with poor cross-species translational value. Furthermore, symptoms that reflect the cardinal features of bipolar disorder have proven difficult to establish in putative animal models of this illness. Recently, however, novel tools such as the human behavioral pattern monitor provide multivariate translational measures of motor and exploratory activity, enabling improved understanding of the neurobiology underlying psychiatric disorders.

Changes in cardiac variability after REM sleep deprivation in recurrent nightmares

STUDY OBJECTIVES

To assess whether dysfunctional autonomic regulation during REM sleep as indexed by heart rate variability (HRV) is a pathophysiological factor in frequent nightmares (NMs).

DESIGN

Monitoring with polysomnography (PSG) and electrocardiography (ECG) for 3 consecutive nights: Night 1 (N1), adaptation night; N2, administration of partial REM sleep deprivation; N3, recovery night. Differences between NM and control (CTL) groups assessed for ECG measures drawn from wakefulness, REM sleep, and Stage 2 sleep on both N1 and N3.

SETTING

Hospital-based sleep laboratory.

PARTICIPANTS

Sixteen subjects with frequent NMs (> or = 1 NM/week; mean age = 26.1 +/- 8.7 years) but no other medical or psychiatric disorders and 11 healthy comparison subjects ( < 1 NM/month; mean age = 27.1+/- 5.6 years).

RESULTS

NM and CTL groups differed on 2 REM sleep measures only on N1; the NM group had longer REM latencies and REM/NREM cycle durations than did the CTL group. No differences were found on time domain and absolute frequency domain ECG measures for either N1 or N3. However, altered HRV for the NM group was suggested by significantly higher LFnu, lower HFnu, and higher LF/HF ratio than for the CTL group.

CONCLUSIONS

Results are consistent with a higher than normal sympathetic drive among NM subjects which is unmasked by high REM sleep propensity. Results also support a growing literature linking anxiety disorders of several types (panic disorder, posttraumatic stress disorder (PTSD), generalized anxiety disorder) to altered HR variability.

REM sleep characteristics of nightmare sufferers before and after REM sleep deprivation

OBJECTIVES

To examine whether disrupted regulation of REM sleep propensity is implicated in nightmare (NM) pathophysiology.

BACKGROUND

Heightened REM propensity induced by REM sleep deprivation is belied by increases in REM %, REM density and the dream-like quality of dream mentation during post-deprivation recovery sleep. Compromised regulation of REM sleep propensity may be a contributing factor in the pathophysiology of frequent NMs.

METHODS

A preliminary study of 14 subjects with frequent NMs (> or = 1 NM/week; 27.6+/-9.9 years) and 11 healthy control subjects (<1 NM/month; 24.3+/-5.3 years) was undertaken. Subjects completed home sleep/dream logs and underwent three nights of polysomnographic recording with REM sleep deprivation on night 2. Group differences were assessed for a battery of REM sleep and dream measures on nights 1 and 3.

RESULTS

Several measures, including #skipped early-night REM periods, REM latency, REM/NREM cycle length, early/late REM density, REM rebound, late-night REM% and dream vividness, suggested that REM sleep propensity was abnormally low for the frequent NM group throughout the 3-day study.

CONCLUSIONS

Findings raise the possibility that REM anomalies recorded from NM sufferers sleeping in the laboratory environment reflect a disruption of one or more endogenous regulators of REM sleep propensity.

Assessment and treatment for insomnia and fatigue in the symptomatic menopausal woman with psychiatric comorbidity

Studies and treatments for the symptomatic menopausal woman with sleep complaints have been reviewed elsewhere. This article, as part of the clinical review series on the comorbid symptomatic menopausal woman, aims to examine the evidence for diagnosis and treatment of women who present with distressing sleep symptoms that they attribute to menopause. The etiology of these symptoms may be a psychiatric disorder, a pre- or co-existing problem with sleep, or a dynamic interaction among one of these and/or a symptomatic menopause. The relationship between sleep disturbance and cognitive complaints, mood problems, fatigue and low energy will be reviewed. The new research on sleep, clinical consequences of insomnia of various types, the impact of sleep disturbance on morbidity and functioning--in the context of the midlife woman in the menopausal transition--will be explored along with the evidence for different treatment strategies for these sleep problems.

A behavioural characterisation of the FVB/N mouse strain

The use of transgenic models in scientific research has made an enormous contribution to our understanding of the causes and symptoms of many diseases, including neurodegenerative conditions such as Alzheimer's Disease (AD) and Parkinson's Disease (PD). In the creation of transgenic models of neurodegenerative disease, effects of the background strain of the animal on the resulting genotype must be taken into consideration. This is particularly true for behavioural studies in which the background strain of the mouse may mask the phenotype of the genetic manipulation. Here, the behaviour of two mouse strains used in transgenic models, FVB/N and C57BL6/J, were compared. Studies of circadian wheel activity, cognition and aggression revealed considerable phenotypic differences between strains. These data also indicate that the FVB/N strain is not appropriate as a background strain in the behavioural assessment of transgenic mouse models.

Extracellular serotonin levels in the medullary reticular formation during normal sleep and after REM sleep deprivation

Rapid eye movement (REM) sleep is hypothesized to result from the activity of REM sleep-generating and REM sleep-inhibiting neurons. The serotoninergic (5-HT) neurons of the dorsal raphe nucleus (DRN) represents one such population of REM-sleep inhibiting neurons since they are silent during REM sleep. Consistent with the decrease in activity of 5-HT neurons, the brain extracellular levels of 5-HT are lower during REM sleep compared to wakefulness. It is not known whether serotonin release is also reduced as a consequence of REM sleep rebound. Using microdialysis sampling coupled to HPLC-ECD, we measured the extracellular levels of 5-HT and its metabolite (5-HIAA) in the medial medullary reticular formation (mMRF) of freely behaving rats during normal sleep, REM sleep deprivation as well as during REM sleep rebound. We found that the levels 5-HT and 5-HIAA were significantly decreased by REM sleep deprivation. The reduction of 5-HT release was maintained during REM sleep rebound but the extracellular level of its main metabolite was increased. In addition, even during REM sleep rebound, 5-HT release during sleep was low compared to wakefulness. Taken together these data support the permissive role of 5-HT neurotransmission for REM sleep expression.

How REM sleep deprivation and amantadine affects male rat sexual behavior

There are conflicting findings about the sexual effects of REM sleep deprivation (REMd). Otherwise, several studies show a dopaminergic hypersensitivity after REMd. The effect of REMd and amantadine (AMA) was studied for standard measures and temporal patterning in the first experiment, in four groups: normal with vehicle, normal with AMA (5.0 and 10 mg/kg), REMd with vehicle and REMd with AMA (5.0 and 10.0 mg/kg). REMd reduced mount latency (ML), intromission latency (IL) and mount number (MN) and increased copulatory efficiency (CE) and hit rate factor. REMd also reduced the mount bout number (MBN) and increased the sexual interaction (mount bout time, MBT) among male and female during copula. AMA stimulates initiation and hit rate factors and accelerates the temporal patterning of sexual behavior, evoking fewer and quicker mount bouts. In the experiments with combination of REMd and AMA administration, AMA did not increase behavior effects evoked by REM deprivation, probably due to a top or a bottom effect, depending on the measures considered. A second experiment studied the effects of AMA (1.25 to 5.0 mg/kg) and REMd on the sexual reflexes of nonimmobilized male rats. REMd enhanced the AMA effects upon the seminal emission reflex, but inhibited the penile erection reflex elicited by 1.25 mg/kg of AMA. Curiously, our results showed that REMd, like AMA, a dopaminergic agonist, causes similar effects of sexual behavior in the male rat, particularly those related to arousal mechanism and hit rate factor. The results are discussed and the effects of REMd probably involve dopaminergic hypersensitivity and increased sexual motivational response.

Effects of sleep deprivation on free-operant avoidance

Two studies examined effects of sleep deprivation on free-operant avoidance by rats. In Experiment 1, a 5-s shock-shock (SS) interval and 20-s response-shock (RS) interval produced baseline performances, which were reestablished after each experimental manipulation. Once baselines were established, animals were exposed to 24, 48, or 96 hr of sleep deprivation and equivalent periods of home cage and food restriction as a control condition. Compared to baseline, sleep deprivation increased response rates by increasing the proportion of brief interresponse times (IRTs); response rates changed little in the control conditions. Percentage of shocks avoided did not systematically change across conditions. In Experiment 2, the RS interval was manipulated (10, 20, and 40 s), while the SS interval (5 s) and level of sleep deprivation (48 hr) were held constant. Across RS intervals, sleep deprivation increased response rates via a shift toward brief IRTs. In addition, sleep deprivation increased the percentage of shocks avoided as an inverse function of RS intervals.

Neurotoxic N-methyl-D-aspartate lesion of the ventral midbrain and mesopontine junction alters sleep-wake organization

The dorsal regions of the midbrain and pons have been found to participate in sleep regulation. However, the physiological role of the ventral brainstem in sleep regulation remains unclear. We used N-methyl-D-aspartate-induced lesions of the ventral midbrain and pons to address this question. Unlike dorsal mesencephalic reticular formation lesions, which produce somnolence and electroencephalogram synchronization, we found that ventral midbrain lesions produce insomnia and hyperactivity. Marked increases in waking and decreases in slow wave sleep stage 1 (S1), stage 2 (S2) and rapid eye movement sleep were found immediately after the lesion. Sleep gradually increased, but never returned to baseline levels (baseline/month 1 post-lesion: waking, 30.6 +/- 4.58%/62.3 +/- 10.1%; S1, 5.1 +/- 0.74/3.9 +/- 1.91%; S2, 46.2 +/- 4.74%/23.1 +/- 5.47%; rapid eye movement sleep, 14.1 +/- 3.15%/7.2 +/- 5.42%). These changes are comparable in magnitude to those seen after basal forebrain lesions. Neuronal degeneration was found in the ventral rostral pons and midbrain, including the substantia nigra, ventral tegmental area, retrorubral nucleus, and ventral mesencephalic and rostroventral pontine reticular formation. We conclude that nuclei within the ventral mesencephalon and rostroventral pons play an important role in sleep regulation.

Dietary Tyrosine Protects Striatal Dopamine Receptors from the Adverse Effects of REM Sleep Deprivation

L-Tyrosine is a non-essential amino acid that is produced as an intermediary metabolite in the conversion of phenylalanine to 3,4-dihyroxyphenylalanine (DOPA), and is a precursor of the neurotransmitter dopamine. In previous studies, tyrosine pretreatment was shown to protect against the neurochemical and behavioral deficits of acute stress caused by tail shock or cold exposure in rodents. The present study addressed the hypothesis that tyrosine administration may be an effective counter-measure to dopamine-mediated behaviors induced by rapid eye-movement sleep deprivation (RSD). In order to test the hypothesis, Sprague-Dawley rats were divided into 9 treatment groups: RSD-treated rats on normal-protein diet (20% casein: 1% tyrosine, 1% valine); tank control (TC) rats on a normal diet; cage control (CC) rats on normal diet; RSD-treated rats on 4% tyrosine diet; TC rats on 4% tyrosine diet; CC rats on 4% tyrosine diet; RSD-treated rats on 4% valine diet; TC rats on 4% valine diet; CC rats on 4% valine diet. In the RSD group receiving tyrosine, there was no apparent change in Bmax for binding of the dopamine D2 receptor ligand [(3)H]YM-09151-2 in the striata as compared to the respective TC and CC groups; whereas RSD-treated rats maintained on the normal diet and valine supplementation demonstrated expected increases in Bmax for ligand binding. The TC group on the tyrosine diet showed attenuated catalepsy compared to the corresponding CC group, while the RSD group consuming tyrosine showed a catalepsy that was significantly increased, and similar to that of cage control animais on a control diet. These data suggest that the tyrosine-supplemented diet significantly attenuated RSD-induced changes in striatal dopamine D2 receptors, and the effect appeared sufficient to influence RSD-induced behaviors.

Stress-induced sleep deprivation modifies corticotropin releasing factor (CRF) levels and CRF binding in rat brain and pituitary

Electroencephalographic (EEG) studies have shown that corticotropin-releasing factor (CRF) administration induces EEG activation, decreases sleep time both in rats and humans and modifies the sleep pattern in sleep deprived rats. In the present study we have investigated whether CRF neuronal activity could be altered in a situation of disrupted sleep-wake cycle. Sleep deprivation (SD) was induced by keeping the rat for 72 h on a small platform (7 cm) surrounded by water. Immediately after the SD period rats were killed and CRF levels and CRF receptor binding were evaluated in different brain areas. A marked increase in CRF levels was present in the striatum (+224%), limbic areas (+144%) and pituitary (+42%) whereas the hypothalamic CRF content was reduced (-57%). A significant decrease in CRF binding was found in the striatum (-33%) and pituitary (-38%) of sleep deprived rats. These results indicate that CRF neuronal activity is stimulated by SD, suggesting that CRF might play an important role in the physiological regulation of the sleep-wake cycle and that an altered CRF neuronal activity might be involved in behavioral modifications related to sleep disturbances.

Effects of short- and long-term REM sleep deprivation on sexual behavior in male rats

The influence of selective REM sleep deprivation on masculine sexual behavior has been a matter of controversy. In the present study, the sexual behavior of male rats was analyzed in subjects deprived on REM sleep by the island technique for 24 or 16 h daily during 20 days. When compared to control rats, both groups displayed changes in sexual performance since the first day. The effects were: an increase in mount, intromission and ejaculation latencies and in mount frequency as well; a decrease of ejaculation frequency and of the Hit rate. The effects became stronger as REM sleep deprivation progressed. Rats deprived of REM sleep for 24 h were extremely debilitated after 12 days and some of them died, whereas the rats REM deprived for 16 h remained healthy during the 20 days. These data indicate that REM sleep deprivation interferes with the mechanisms that regulate male sexual behavior.

Dopamine D1 and opioid receptor binding changes in the limbic system of sleep deprived rats

Sleep deprivation induced by the platform technique is considered to be a heavy stressful situation in rats. At the end of the sleep deprivation period (72 h) the rat displayed particular behavior characterized by wakefulness, a high degree of motor and exploratory activity, increased alertness and reactivity to environmental stimuli. Our previous results indicated that this behavior was potently antagonized by the administration of the D1 selective antagonist SCH 23390 and by the opioid antagonist naloxone. In this paper we show that concomitantly to this behavior, an increased number of D1 receptors associated with an increased dopamine-stimulated adenylate cyclase activity is present in the limbic system but not in the striatum of these animals. On the contrary, a decreased Bmax of mu and delta opioid receptors was found in the same brain area. These data suggest an active role of limbic dopamine and opioid systems in the generation of arousal and insomnia related to sleep deprivation-induced stress.

Sleep deprivation in the rat: an animal model of mania

The model of sleep deprivation in rats by the platform method has been extensively studied in our laboratory as a possible animal model of mania. At the end of the period of sleep deprivation, the rat does not fall asleep as soon as it is returned to its home cage, but shows a period of wakefulness of about 30 min, during which the animal presents a cohort of symptoms that appear to mimic those present in idiopathic mania. In particular, during this period the animal displays insomnia, a high degree of hyperactivity, irritability, aggressiveness, hypersexuality and stereotypy. Haloperidol (0.2 mg/kg) was effective in reducing latency to sleep, while L-sulpiride was much weaker (< 50 mg/kg). The dopamine D1 receptor antagonist SCH 23390 exhibited an extremely high potency and efficacy in reducing sleep latency, a significant effect being observed with 3 micrograms/kg. The administration of the specific D1 receptor agonist SKF 38393 markedly prolonged the period of insomnia with the correlated behavioral syndrome. When lithium was added to the diet and consumed during the sleep deprivation period in adequate amounts to produce serum lithium levels of 0.7-1.0 mEq/l, sleep latency and locomotor activity were significantly reduced. The administration of naloxone (1-10 mg/kg) reduced the latency to sleep in a dose-related manner. By contrast, morphine (1 and 5 mg/kg, i.p.), beta-endorphin and [D-Ala2,D-Leu5]enkephalin (i.c.v., 2 and 1 micrograms, respectively) markedly prolonged the insomnia. The model not only represents a confirmation in the rat that sleep loss often precedes and may trigger a manic episode in man, but suggests that an opioid-dopamine interaction may play a pathogenetic role in mania.

Effects of paradoxical sleep deprivation and stress on the waking EEG of the rat

Effects of 72 h of paradoxical sleep deprivation (PSD) and stress on the waking EEG of rats were studied using the water tank technique. EEG was recorded at left and right parietal cortex and the spectrum was analyzed before PSD, after 24, 48, and 72 h of PSD, and 24 h after recovery. Absolute and relative power and interparietal correlation were obtained. The same analyses were performed on a larger platform group and on a cold water-stressed group. The following significant changes were observed on the waking EEG: PSD produced a decrease in interparietal correlation, an increase in absolute and relative power between 7.3 and 9.3 Hz, and a decrease in the delta band relative power. The PSD effect on relative power was less specific on absolute power; relative power between 7.3 and 9.3 Hz was also increased in the large platform control group. Interparietal correlation was also decreased in both control groups but in the water-stressed animals it followed a different time course. The present findings suggest that PSD may affect brain function by increasing the level of hippocampal arousal, whereas the combination of stress and PSD affects interhemispheric coupling.

Effects of rapid eye movement sleep deprivation on the properties of striatal dopaminergic system

Using the water tank procedure, we have examined the effects of rapid eye movement (REM) sleep deprivation and associated stress on the properties of striatal dopaminergic system. While stress decreased the number of D1 and D2 dopamine receptors, a combination of REM sleep deprivation attenuated the decrease. The ratio of D1 to D2 densities, however, increased on both the stress and REM sleep deprivation groups. In contrast, the number of dopamine uptake sites remained unchanged. The enhanced behavioral responses to dopaminergic stimulants after REM sleep deprivation are discussed.

Potentiation of metaphit-induced audiogenic seizures by REM sleep deprivation in rats

The possibility that REM sleep deprivation (REMD) induced increased susceptibility of rats to the convulsive effects of metaphit was investigated. Metaphit-induced audiogenic seizures were studied in three groups of animals: 1) caged controls; 2) large platform animals; and 3) small platform, REMD animals. After 48 h of confinement to their environments the rats from all three groups were injected with metaphit (10 mg kg-1, IP) and the procedures continued for the next 24 h. Immediately after removal from platforms and at 3-h intervals thereafter all rats were individually subjected to intense sound stimulation. Convulsive responses were recorded and analyzed with respect to incidence, intensity, and duration. The REMD rats were found to be more sensitive to the convulsive effects of metaphit compared to nondeprived rats. This was manifested in significantly shorter latencies to seizures, and significantly higher incidence, severity, and duration of seizures, especially of the most severe seizure component-tonic extensor convulsion. Inducing rats to convulse while they were being REM sleep deprived eliminated the REM sleep rebound observed in REMD rats that did not convulse. The occurrence of spontaneous EEG seizures during the undisturbed recovery period reduced REM sleep rebound. The results demonstrate a reciprocal relation between seizure behavior and REM sleep.

Dopamine and opioids interactions in sleep deprivation

1. Sleep deprivation induced by the platform technique is considered to be a heavy stressful situation in rats. At the end of the sleep deprivation period (72 hrs) the rat displayed particular behavior characterized by wakefulness, a high degree of motor and exploratory activity, increased alertness and reactivity to environmental stimuli. 2. Our results indicate that this behavior is potently antagonized by the administration of D1 antagonist SCH 23390 and by the opioid antagonist naloxone. 3. We also show that concomitantly to this behavior, an increased number of D1 receptors associated with an increased dopamine-stimulated adenylate cyclase activity is present in the limbic system but not in the striatum of these animals. On the contrary, a decreased Bmax of mu and delta opioid receptors was found in the same brain areas. 4. These data suggest an active role of limbic dopamine and opioid system in the generation of arousal and insomnia related to sleep deprivation-induced stress.

Magnetic fields mimic the behavioral effects of REM sleep deprivation in humans

The discovery of rapid eye movement (REM) sleep by Aserinsky and Kleitman in 1953 initiated the impetus for sleep research and specifically the investigations of the effects of REM sleep deprivation (RSD) on animal and human behavior. The behavioral effects of RSD include the enhancement of motivational and "drive"-related behaviors. In laboratory animals, RSD has been reported to increase appetite, sexual behavior, aggressiveness, and locomotor activity. Moreover, RSD reportedly improves mood in patients with endogenous depression and heightens appetite and sexual interest in normal subjects. Since "drive"-related behaviors are thought to involve activation of limbic dopaminergic reward sites, RSD may enhance motivational behaviors through an action on limbic dopaminergic functions. In the present communication, we present two patients (one with multiple sclerosis and the other with Parkinson's disease) in whom treatment with magnetic fields produced behavioral effects which paralleled those observed in REM-sleep-deprived animals and humans. We propose, therefore, that the behavioral and mental effects of treatment with magnetic fields may be mediated via RSD and, by inference, involve activation of limbic dopaminergic reward sites.

Sleep deprivation decreases mu and delta opioid receptor binding in the rat limbic system

Sleep deprivation induced by the platform technique is considered to be a heavy stressful situation in rats. At the end of the sleep deprivation period (72 h) the rat displayed particular behavior characterized by wakefulness, a high degree of motor and exploratory activity, increased alertness and reactivity to environmental stimuli. Our previous results indicated that this behavior was antagonized by the administration of the opioid receptor antagonist naloxone and increased by opioid agonists. In this paper we show that concomitantly with this behavior, a decreased Bmax of mu and delta opioid receptors is present in the limbic system of these animals. These data suggest an active role of limbic mu and delta receptors in the generation of arousal and insomnia related to sleep deprivation induced stress.

Sleep deprivation increases dopamine D1 receptor antagonist [3H]SCH 23390 binding and dopamine-stimulated adenylate cyclase in the rat limbic system

Sleep deprivation induced by the platform technique is considered to be a heavy stressful situation in rats. At the end of the sleep deprivation period (72 h) the rats displayed particular behaviour characterized by wakefulness, a high degree of motor and exploratory activity, increased alertness and reactivity to environmental stimuli. Our previous results indicated that this behaviour was potently antagonized by the administration of the D1-selective antagonist SCH 23390. In this paper we show that concomitantly to this behaviour, an increased number of D1 receptors associated with an increased dopamine-stimulated adenylate cyclase activity is present in the limbic system but not in the striatum of these animals. These data suggest an active role of limbic D1 receptors in the generation of arousal and insomnia related to sleep deprivation induced stress.

Changes in pontine unit activity with REM sleep deprivation

Short term rapid eye movement (REM) sleep deprivation produced a decrease in walking discharge rates of presumably noradrenergic pontine 'REM sleep-off' cells and an increase in waking discharge rates of pontine 'REM sleep-on' cells. These changes can be viewed as a correlate of increased REM sleep pressure. Slowing of REM sleep-off cells in waking is hypothesized to counteract the functional effects of REM sleep loss on noradrenergic receptor sensitivity. This slowing and the resulting reduction in norepinephrine release may contribute to the loss of vigilance seen with sleep deprivation.

Facilitation of the effect testosterone on male sexual behavior in rats deprived of REM sleep

The possibility of rapid eye movement sleep deprivation (REMd) altering the effect of testosterone on masculine sexual behavior was investigated. Adult castrated male Wistar rats with no sexual experience were randomly assigned to the following three groups: REMd (using the water tank technique) for 7 days, large platform control for 7 days, and undisturbed sleep control. All subjects were treated with 1 mg testosterone propionate daily for 14 days. Masculine sexual behavior was assessed 3 consecutive days prior to steroid administration and was evaluated daily during the treatment. Frequencies and latencies of mounts, intromissions, and ejaculations, as well as the postejaculatory refractory period were recorded. One hundred percent of the REMd subjects presented mounts, intromissions, and ejaculations sooner than the control group. In almost all parameters, a clear facilitation of sexual activity was observed in the REMd group.

Stress-induced insomnia: opioid-dopamine interactions

REM sleep deprivation induced by means of the platform technique (72 h) was followed by a period of latency to sleep characterized by a marked excitement in rats. The administration of naloxone at the end of the REM deprivation period reduced this latency to sleep while morphine, beta-endorphin and DADLE prolonged it. The dopamine D1 receptor antagonist SCH 23390 was extremely potent (0.003 mg/kg) to reduce the latency to sleep and the excitement while the D1 agonist SKF 38393 induced an opposite effect. The dopamine D2 receptor antagonist L-sulpiride was inactive up to a dose of 25 mg/kg. These data suggest that hyperactivity of the opioid and dopamine systems (specifically mediated through D1 receptors) is involved in such behaviour.

Electrophysiological evaluation of three paradoxical sleep deprivation techniques in rats

Three different techniques were used to study the effects of 72 hr deprivation of paradoxical sleep on percentages total sleep, light slow wave sleep, deep slow wave sleep and paradoxical sleep during deprivation and recovery periods in rats. The paradoxical sleep deprivation methods used were the classical platform, the pendulum and the multiple platform techniques. The different groups were continuously recorded over a base-line day, three deprivation days and four recovery days. All three groups showed clear suppression of paradoxical sleep throughout the deprivation period, although small differences between the pendulum and the multiple platform technique emerged. The distribution of sleep across the day and the amount of deep slow wave sleep were affected differently. Besides an exception immediately after deprivation, no important differences were detected on the recovery days. The recovery is characterized by an immediate rebound of paradoxical sleep, completed within two days, as well as rapid re-normalization of sleep percentages. A small rebound of deep slow wave sleep was recorded at the end of the dark period during the first three recovery days. Various sleep and non-sleep related variables of the PS deprivation techniques are discussed. It is improbable that the platform-pendulum controversy is due to differences in the amount of PS deprivation or the other sleep parameters measured here. Rather it looks as though non-specific platform effects override the effects of PS deprivation.

REM sleep deprivation facilitates the estrogen effect on heterotypical sexual behavior in male rats

Gonadectomized male rats were submitted to REM sleep deprivation (REMd) for 120 hr and their hetero and homotypical sexual response to estradiol benzoate (EB) was tested. Subjects (Ss) receiving 20 micrograms EB showed lordosis quotients (LQ) twice as high as those receiving 10 micrograms EB and at the same time the LQs in these groups were higher than in the non-REMd groups. Gonadectomized-adrenalectomized control Ss showed the highest levels of lordosis throughout the experiment. REMd by itself does not produce lordosis response. The results indicate that the brain structures underlying this behavior in males are probably similar to those in females, since REMd increases lordosis in both cases. The lack of homotypical sexual behavior normally observed in gonadectomized male rats does not seem to be affected by this treatment. The issue of adequate controls for REMd experiments is discussed.

REM-sleep deprivation, stress and emotional behavior in rats

Eighty-eight adult white rats were divided into 9 groups. Groups 1 and 2 served as controls. The rats of Group 3 were repeatedly aroused during 4 days at the very onset of each REM-sleep period by direct midbrain reticular formation stimulation. This deprivation decreased the daily amount of REM-sleep by 70%, while slow-wave sleep was reduced by 10% only. In Group 4, the animals were given food and water for 1 h a day only. Groups 5 and 6 were subjected to immobilization and cold stress, respectively. Groups 7, 8 and 9 were deprived of REM-sleep on platforms of 15, 11 and 6.5 cm in diameter, respectively. Stress was estimated by the classical Selye's triad: weight of adrenals and thymus and gastric ulceration. Emotionality was measured in the open-field and also by self-stimulation of the lateral hypothalamus. Neither emotional behavior disturbances nor Selye's stress features were found after REM-deprivation in Group 3. Moreover, arousal deprivation induced a slight, though significant, reduction in adrenal weight. Also, no changes in emotional behavior were noted in stress-exposed groups (5 and 6). Only the interplay between REM-sleep deprivation and stress on the platforms (Groups 7, 8 and especially 9) led to a considerable shift in emotionality.

The consolidation hypothesis for REM sleep function: stress and other confounding factors--a review

One commonly held hypothesis about the function of REM sleep (RS) concerns the consolidation of plastic processes, particularly those relating to learning and memory. The majority of the experimental data apparently supporting this hypothesis come from RS deprivation (RSD) studies. However, this review points out that: (i) there are several shortcomings with the methodology of animal RSD investigations, (ii) RSD seems to produce arousal and stereotyped behaviour which may interfere with learning etc., and consequently give artificial support to the hypothesis. The review then examines evidence outside the field of RSD, relating to the hypothesis, which seems further to confound or contradict it. Whilst the hypothesis is not rejected, these problems need to be addressed further by its supporters.

Evidence for REM sleep deprivation as the mechanism of action of antidepressant drugs

In the treatment of endogenous depression REM sleep deprivation and imipramine have similar efficacy. Across drugs, efficacy of antidepressant activity is directly related to capacity of drugs to produce large and sustained reductions of REM sleep. Endogenous depression unimproved by REM sleep deprivation is unimproved by imipramine. Endogenous depression improvement by REM sleep deprivation and by amitriptyline have the same biological correlate, viz, REM rebound. In animals REM sleep deprivation produces several behavioral changes (e.g., increased motor, sexual, aggressive, pleasure seeking, feeding activities) which are the reverse of behavioral changes of human endogenous depression.