Sleep deprivation impairs spatial memory and decreases extracellular signal-regulated kinase phosphorylation in the hippocampus

Sleep deprivation and memory consolidation in rats: A meta-analysis of experimental studies

Sleep deprivation (SD) continues to be used today to examine the role of sleep across diverse cognitive domains. Extensive research has been conducted to investigate the impact of SD on memory, though findings across studies have been inconsistent. This meta-analysis systematically assessed the effects of SD on memory performance in rats and identified the factors that may moderate these effects. PubMed, PsychInfo, Google scholar, and Scopus databases were used to search for studies. Out of 128 identified studies, 25 studies with 78 reports were included in the final analysis. A random effects meta-analysis was performed, along with subgroup analysis and meta-regression. The results showed that overall, SD has a negative impact on memory in rats. Additionally, sex, memory response type, and number of learning trials for spatial tasks can act as moderators of the relationship between SD and memory. The type of memory task and assessment method used contributed to variability in observed outcomes, with hippocampus-dependent tasks showing the most pronounced memory impairments. The number of learning trials for spatial tasks also moderated the effects, with more trials mitigating the impact of SD. These findings reinforce the role of sleep in memory, particularly for hippocampus-dependent tasks.

Could sleep be a brain/cognitive/neural reserve-builder factor? A systematic review on the cognitive effects of sleep modulation in animal models

The brain/cognitive/neural reserve concept suggests that lifelong experiences, from early life through adulthood, make the brain more resilient to neuronal damage. Modifiable lifestyle factors, such as sleep, can support the development and enhance such a reserve, helping to counteract age- or disease-related brain changes and their impact on cognition. Sleep plays a crucial role in cognitive functioning, and disruptions or disorders may increase neurodegenerative risks. This systematic review aims to explore how functional and disturbed sleep impacts cognitive functions and neuromorphological mechanisms in rodents, aiming to better understand its role in brain/cognitive/neural reserve development. This systematic review, registered on PROSPERO (ID: CRD42023423901) and conducted according to PRISMA-P guidelines, searched PubMed, Scopus, Web of Science, and Embase databases for studies up to June 2022, with terms related to sleep, rodents, and cognitive functions. Of the 28,666 articles identified, 142 met the inclusion criteria. Main results showed significant cognitive decline after sleep deprivation, especially in memory performance. These findings supports the importance of sleep as a critical factor in modulating brain/cognitive/neural reserve.

Cognitive disorders: Potential astrocyte-based mechanism

Cognitive disorders are a common clinical manifestation, including a deterioration in the patient's memory ability, attention, executive power, language, and other functions. The contributing factors of cognitive disorders are numerous and diverse in nature, including organic diseases and other mental disorders. Neurodegenerative diseases are a common type of organic disease related to the pathology of neuronal death and disruption of glial cell balance, ultimately accompanied with cognitive impairment. Thus, cognitive disorder frequently serves as an extremely critical indicator of neurodegenerative disorders. Cognitive impairments negatively affect patients' daily lives. However, our understanding of the precise pathogenic pathways of cognitive defects remains incomplete. The most prevalent kind of glial cells in the central nervous system are called astrocytes. They have a unique significance in cerebral function because of their wide range of functions in maintaining homeostasis in the central nervous system, regulating synaptic plasticity, and so on. Dysfunction of astrocytes is intimately linked to cognitive disorders, and we are attempting to understand this phenomenon predominantly from those perspectives: neuroinflammation, astrocytic senescence, connexin, Ca2 + signaling, mitochondrial dysfunction, and the glymphatic system.

Exploring β-caryophyllene: a non-psychotropic cannabinoid's potential in mitigating cognitive impairment induced by sleep deprivation

Sleep deprivation or sleep loss, a prevalent issue in modern society, is linked to cognitive impairment, leading to heightened risks of errors and accidents. Chronic sleep deprivation affects various cognitive functions, including memory, attention, and decision-making, and is associated with an increased risk of neurodegenerative diseases, cardiovascular issues, and metabolic disorders. This review examines the potential of β-caryophyllene, a dietary non-psychotropic cannabinoid, and FDA-approved flavoring agent, as a therapeutic solution for sleep loss-induced cognitive impairment. It highlights β-caryophyllene's ability to mitigate key contributors to sleep loss-induced cognitive impairment, such as inflammation, oxidative stress, neuronal death, and reduced neuroplasticity, by modulating various signaling pathways, including TLR4/NF-κB/NLRP3, MAPK, Nrf2/HO-1, PI3K/Akt, and cAMP/PKA/CREB. As a naturally occurring, non-psychotropic compound with low toxicity, β-caryophyllene emerges as a promising candidate for further investigation. The review underscores the therapeutic potential of β-caryophyllene for sleep loss-induced cognitive impairment and provides mechanistic insights into its action on crucial pathways, suggesting that β-caryophyllene could be a valuable addition to strategies aimed at combating cognitive impairment and other health issues due to sleep loss.

Sleep disturbance in rodent models and its sex-specific implications

Sleep disturbances, encompassing altered sleep physiology or disorders like insomnia and sleep apnea, profoundly impact physiological functions and elevate disease risk. Despite extensive research, the underlying mechanisms and sex-specific differences in sleep disorders remain elusive. While polysomnography serves as a cornerstone for human sleep studies, animal models provide invaluable insights into sleep mechanisms. However, the availability of animal models of sleep disorders is limited, with each model often representing a specific sleep issue or mechanism. Therefore, selecting appropriate animal models for sleep research is critical. Given the significant sex differences in sleep patterns and disorders, incorporating both male and female subjects in studies is essential for uncovering sex-specific mechanisms with clinical relevance. This review provides a comprehensive overview of various rodent models of sleep disturbance, including sleep deprivation, sleep fragmentation, and circadian rhythm dysfunction. We evaluate the advantages and disadvantages of each model and discuss sex differences in sleep and sleep disorders, along with potential mechanisms. We aim to advance our understanding of sleep disorders and facilitate sex-specific interventions.

Vitamin D injection into the dorsal-CA1 hippocampus improves short-term sleep deprivation induced cognitive impairment in male rats

This study was conducted with aim of investigating the consequences of sleep deprivation (SD) on cognitive functions. For this purpose, adult male rats were subjected to SD protocol for 5 h. The SD and the control rats were trained in the Morris water maze (MWM) to assess spatial behavioral deficits due to the SD protocol. To determine the role of astrocytes in spatial navigation deficits associated with SD, an inhibitor of astrocyte activation, fluorocitrate (FC), or a suppressor of astrocyte activation, vitamin D, was injected into the dorsal-CA1 hippocampus before subjecting rats to the SD protocol and the effects of these compounds on spatial navigation deficits associated with SD in the MWM were assessed. As expected, 5 h of SD impaired the Morris water navigation task in rats. FC injection into the dorsal-CA1 hippocampus before the SD protocol did not prevent the SD-induced cognitive deficits. Interestingly, injection of vitamin D into the dorsal-CA1 hippocampus prior to the SD protocol alleviated the SD-induced severe spatial navigation deficit in the MWM. Sequential injection of FC and vitamin D prior to the SD protocol did not reduce the SD-induced spatial memory impairment, suggesting a role for astrocytes. In sum, vitamin D can improve cognitive dysfunction associated with sleep deprivation, possibly dependent on astrocyte function. The results show that maintaining adequate levels of vitamin D offers a promising avenue to improve cognitive function in sleep-deprived conditions.

The role of sleep in the link between cannabis use and memory function: evidence from a cross-sectional study

Background: It is known that cannabis use affects memory and sleep problems independently. However, to date, how memory and sleep problems may interact as a result of cannabis use remains unknown.Objectives: We performed a secondary analysis of existing data to determine whether sleep quality mediates the association between cannabis use and memory and whether sex moderated these effects.Methods: A total of 141 adults with cannabis use disorder (CUD) (83 men) and 87 without CUD (39 men) participated in this study. Outcome measures included self-reported sleep problems from the past 7 days (Marijuana Withdrawal Checklist), learning and memory performance via the short visual object learning task (sVOLT), short visual object learning task delayed (sVOLTd), and verbal memory via the N-back. Bootstrapped mediation and moderated mediation analyses were run to test if sleep quality mediated the association between cannabis use and memory outcomes and whether sex moderated these effects, respectively.Results: Sleep quality mediated the effect of group (i.e. adults with and without CUD) on sVOLT efficiency scores (indirect effect ß = -.08, 95% CI [-0.14, -0.04]) and sVOLTd efficiency scores (indirect effect ß = -.09, 95% CI [-0.14, -0.04]), where greater sleep difficulties was associated with poorer memory performance (decreased efficiency scores). Sex did not moderate these relationships.Conclusion: These initial findings of a mediating role of sleep in the association between CUD and visual learning memory highlight potential critical downstream effects of disrupted sleep in those with CUD and suggest the importance of investigating sleep in CUD.

Sleep and memory: The impact of sleep deprivation on transcription, translational control, and protein synthesis in the brain

In countries around the world, sleep deprivation represents a widespread problem affecting school-age children, teenagers, and adults. Acute sleep deprivation and more chronic sleep restriction adversely affect individual health, impairing memory and cognitive performance as well as increasing the risk and progression of numerous diseases. In mammals, the hippocampus and hippocampus-dependent memory are vulnerable to the effects of acute sleep deprivation. Sleep deprivation induces changes in molecular signaling, gene expression and may cause changes in dendritic structure in neurons. Genome wide studies have shown that acute sleep deprivation alters gene transcription, although the pool of genes affected varies between brain regions. More recently, advances in research have drawn attention to differences in gene regulation between the level of the transcriptome compared with the pool of mRNA associated with ribosomes for protein translation following sleep deprivation. Thus, in addition to transcriptional changes, sleep deprivation also affects downstream processes to alter protein translation. In this review, we focus on the multiple levels through which acute sleep deprivation impacts gene regulation, highlighting potential post-transcriptional and translational processes that may be affected by sleep deprivation. Understanding the multiple levels of gene regulation impacted by sleep deprivation is essential for future development of therapeutics that may mitigate the effects of sleep loss.

Precise timing of ERK phosphorylation/dephosphorylation determines the outcome of trial repetition during long-term memory formation

Two-trial learning in Aplysia reveals nonlinear interactions between training trials: A single trial has no effect, but two precisely spaced trials induce long-term memory. Extracellularly regulated kinase (ERK) activity is essential for intertrial interactions, but the mechanism remains unresolved. A combination of immunochemical and optogenetic tools reveals unexpected complexity of ERK signaling during the induction of long-term synaptic facilitation by two spaced pulses of serotonin (5-hydroxytryptamine, 5HT). Specifically, dual ERK phosphorylation at its activating TxY motif is accompanied by dephosphorylation at the pT position, leading to a buildup of inactive, singly phosphorylated pY-ERK. Phosphorylation and dephosphorylation occur concurrently but scale differently with varying 5HT concentrations, predicting that mixed two-trial protocols involving both "strong" and "weak" 5HT pulses should be sensitive to the precise order and timing of trials. Indeed, long-term synaptic facilitation is induced only when weak pulses precede strong, not vice versa. This may represent a physiological mechanism to prioritize memory of escalating threats.

Environmental Enrichment Reverses Maternal Sleep Deprivation-Induced Anxiety-Like Behavior and Cognitive Impairment in CD-1 Mice

Preclinical studies have clearly indicated that offspring of mothers who suffered sleep deprivation during pregnancy exhibit anxiety, depression-like behaviors, and cognitive deficits. The cognitive impairment induced by maternal sleep deprivation (MSD) is currently poorly treated. Growing evidence indicates that an enriched environment (EE) improves cognition function in models of Alzheimer’s disease, schizophrenia, and lipopolysaccharide. However, the effects of EE on hippocampal-dependent learning and memory, as well as synaptic plasticity markers changes induced by MSD, are unclear. In the present study, pregnant CD-1 mice were randomly divided into a control group, MSD group, and MSD+EE group. Two different living environments, including standard environment and EE, were prepared. When male and female offspring were 2 months, the open field test and elevated plus maze were used to assess anxiety-like behavior, and the Morris water maze was used to evaluate hippocampal learning and memory. Western blotting and real-time fluorescence quantitative polymerase chain reaction were used to detect the expression of brain-derived neurotrophic factor and Synaptotagmin-1 in the hippocampus of offspring. The results revealed that MSD-induced offspring showed anxiety-like behaviors and cognitive impairment, while EE alleviated anxiety-like behavior and cognitive impairment in offspring of the MSD+EE group. The cognitive impairment induced by MSD was associated with a decreased brain-derived neurotrophic factor and an increased Synaptotagmin-1, while EE increased and decreased brain-derived neurotrophic factor and Synaptotagmin-1 in the hippocampus of mice from the MSD+EE group, respectively. Taken together, we can conclude that EE has beneficial effects on MSD-induced synaptic plasticity markers changes and can alleviate anxiety-like behaviors and cognitive impairment.

Sleep Disturbance and Alzheimer's Disease: The Glial Connection

Poor quality and quantity of sleep are very common in elderly people throughout the world. Growing evidence has suggested that sleep disturbances could accelerate the process of neurodegeneration. Recent reports have shown a positive correlation between sleep deprivation and amyloid-β (Aβ)/tau aggregation in the brain of Alzheimer's patients. Glial cells have long been implicated in the progression of Alzheimer's disease (AD) and recent findings have also suggested their role in regulating sleep homeostasis. However, how glial cells control the sleep-wake balance and exactly how disturbed sleep may act as a trigger for Alzheimer's or other neurological disorders have recently gotten attention. In an attempt to connect the dots, the present review has highlighted the role of glia-derived sleep regulatory molecules in AD pathogenesis. Role of glia in sleep disturbance and Alzheimer's progression.

Evaluating the effect of selenium on spatial memory impairment induced by sleep deprivation

Sleep deprivation (SD) impairs memory due to disturbing oxidative stress parameters. Selenium is a main component of several antioxidant enzymes and provides a neuroprotective effect. The present study aimed to investigate the potential neuroprotective effect of chronic selenium administration on cognitive impairments induced by chronic SD. Adult male Wister rats were randomly assigned into five groups (n = 12/group). The SD was induced in rats using modified multiple platform model. Selenium (6 µg/kg of animal's body weight) was administered to rats via oral gavage for 6 weeks. The spatial learning and memory were assessed using the radial arm water maze (RAWM). Moreover, we measured the levels of reduced glutathione (GSH), oxidized glutathione (GSSG) and GSH/GSSG, catalase, glutathione peroxidase (GPx), superoxide dismutase (SOD), thiobarbituric acid reactive substances (TBARS) and brain derived neurotrophic factor (BDNF) in the hippocampus. The results indicate that short- and long-term memory were impaired by chronic sleep deprivation (P < 0.05), while selenium administration prevented this effect. Moreover, selenium normalized antioxidants activities which were reduced by SD such as: catalase (P < 0.05), and SOD (P < 0.05), and significantly enhanced the ratio of GSH/GSSG in sleep-deprived rats (P < 0.05), without significant alteration of BDNF (P > 0.05), GSH (P > 0.05), or TBARS levels (P > 0.05). In conclusion, chronic SD induced memory impairment, and chronic treatment with selenium prevented this impairment by normalizing antioxidant enzymes activities in the hippocampus.

Sleep Disruption Worsens Seizures: Neuroinflammation as a Potential Mechanistic Link

Sleep disturbances, such as insomnia, obstructive sleep apnea, and daytime sleepiness, are common in people diagnosed with epilepsy. These disturbances can be attributed to nocturnal seizures, psychosocial factors, and/or the use of anti-epileptic drugs with sleep-modifying side effects. Epilepsy patients with poor sleep quality have intensified seizure frequency and disease progression compared to their well-rested counterparts. A better understanding of the complex relationship between sleep and epilepsy is needed, since approximately 20% of seizures and more than 90% of sudden unexpected deaths in epilepsy occur during sleep. Emerging studies suggest that neuroinflammation, (e.g., the CNS immune response characterized by the change in expression of inflammatory mediators and glial activation) may be a potential link between sleep deprivation and seizures. Here, we review the mechanisms by which sleep deprivation induces neuroinflammation and propose that neuroinflammation synergizes with seizure activity to worsen neurodegeneration in the epileptic brain. Additionally, we highlight the relevance of sleep interventions, often overlooked by physicians, to manage seizures, prevent epilepsy-related mortality, and improve quality of life.

Altered hippocampal transcriptome dynamics following sleep deprivation

Widespread sleep deprivation is a continuing public health problem in the United States and worldwide affecting adolescents and adults. Acute sleep deprivation results in decrements in spatial memory and cognitive impairments. The hippocampus is vulnerable to acute sleep deprivation with changes in gene expression, cell signaling, and protein synthesis. Sleep deprivation also has long lasting effects on memory and performance that persist after recovery sleep, as seen in behavioral studies from invertebrates to humans. Although previous research has shown that acute sleep deprivation impacts gene expression, the extent to which sleep deprivation affects gene regulation remains unknown. Using an unbiased deep RNA sequencing approach, we investigated the effects of acute sleep deprivation on gene expression in the hippocampus. We identified 1,146 genes that were significantly dysregulated following sleep deprivation with 507 genes upregulated and 639 genes downregulated, including protein coding genes and long non-coding RNAs not previously identified as impacted by sleep deprivation. Notably, genes significantly upregulated after sleep deprivation were associated with RNA splicing and the nucleus. In contrast, downregulated genes were associated with cell adhesion, dendritic localization, the synapse, and postsynaptic membrane. Furthermore, we found through independent experiments analyzing a subset of genes that three hours of recovery sleep following acute sleep deprivation was sufficient to normalize mRNA abundance for most genes, although exceptions occurred for some genes that may affect RNA splicing or transcription. These results clearly demonstrate that sleep deprivation differentially regulates gene expression on multiple transcriptomic levels to impact hippocampal function.

Sericin protects against acute sleep deprivation-induced memory impairment via enhancement of hippocampal synaptic protein levels and inhibition of oxidative stress and neuroinflammation in mice

Sleep deprivation (SD) induces learning and memory deficits via inflammatory responses and oxidative stress. On the other hand, sericin (Ser) possesses potent antioxidant and neuroprotective effects. We investigated the effect of different doses of Ser on the SD-induced cognitive impairment. Ser (100, 200, and 300 mg/kg) was administered to animals via oral gavage for 8 days, 5 days before to SD, and during SD. SD was induced in mice using a modified multiple platform model, starting on the 6th day for 72 h. Spatial learning and memory were assessed using the Lashley III maze. Serum corticosterone level, and hippocampal malondialdehyde (MDA), total antioxidant capacity (TAC), and the activity of superoxide dismutase (SOD) and glutathione peroxidase (GPx) enzymes were evaluated. The expression of growth-associated protein 43 (GAP-43), post-synaptic density-95 (PSD-95), synapsin 1 (SYN-1), and synaptophysin (SYP), and inflammation markers were detected by western blotting. SD caused cognitive impairment, while Ser pretreatment prevented such an effect. Serum corticosterone also increased with SD, but its levels were suppressed in SD mice receiving Ser. Furthermore, Ser normalized SD-induced reduction in the hippocampus activity of SOD and GPx, increased TAC, and decreased MDA levels. Besides, Ser pretreatment increased GAP-34, SYP, SYN-I, and PSD-95 and reduced IL1-β and TNF-α in the hippocampus. SD induced memory impairment and pretreatment with Ser improved memory via its antioxidant, anti-inflammation, and up-regulation of synaptic proteins in the hippocampus.

A conserved role for sleep in supporting Spatial Learning in Drosophila

Sleep loss and aging impair hippocampus-dependent Spatial Learning in mammalian systems. Here we use the fly Drosophila melanogaster to investigate the relationship between sleep and Spatial Learning in healthy and impaired flies. The Spatial Learning assay is modeled after the Morris Water Maze. The assay uses a "thermal maze" consisting of a 5 × 5 grid of Peltier plates maintained at 36-37°C and a visual panorama. The first trial begins when a single tile that is associated with a specific visual cue is cooled to 25°C. For subsequent trials, the cold tile is heated, the visual panorama is rotated and the flies must find the new cold tile by remembering its association with the visual cue. Significant learning was observed with two different wild-type strains-Cs and 2U, validating our design. Sleep deprivation prior to training impaired Spatial Learning. Learning was also impaired in the classic learning mutant rutabaga (rut); enhancing sleep restored learning to rut mutants. Further, we found that flies exhibited a dramatic age-dependent cognitive decline in Spatial Learning starting at 20-24 days of age. These impairments could be reversed by enhancing sleep. Finally, we find that Spatial Learning requires dopaminergic signaling and that enhancing dopaminergic signaling in aged flies restored learning. Our results are consistent with the impairments seen in rodents and humans. These results thus demonstrate a critical conserved role for sleep in supporting Spatial Learning, and suggest potential avenues for therapeutic intervention during aging.

Rapid eye movement sleep deprivation impairs neuronal plasticity and reduces hippocampal neuronal arborization in male albino rats: Noradrenaline is involved in the process

Rapid eye movement sleep (REMS) favors brain development and memory, while it is decreased in neurodegenerative diseases. REMS deprivation (REMSD) affects several physiological processes including memory consolidation; however, its detailed mechanism(s) of action was unknown. REMS reduces, while REMSD elevates noradrenaline (NA) level in the brain; the latter induces several deficiencies and disorders, including changes in neuronal cytomorphology and apoptosis. Therefore, we proposed that REMS- and REMSD-associated modulation of NA level might affect neuronal plasticity and affect brain functions. Male albino rats were REMS deprived by flower-pot method for 6 days, and its effects were compared with home cage and large platform controls as well as post-REMSD recovered and REMS-deprived prazosin (α1-adrenoceptor antagonist)-treated rats. We observed that REMSD reduced CA1 and CA3 neuronal dendritic length, branching, arborization, and spine density, while length of active zone and expressions of pre- as well as post-synaptic proteins were increased as compared to controls; interestingly, prazosin prevented most of the effects in vivo. Studies on primary culture of neurons from chick embryo brain confirmed that NA at lower concentration(s) induced neuronal branching and arborization, while higher doses were destructive. The findings support our contention that REMSD adversely affects neuronal plasticity, branching, and synaptic scaffold, which explain the underlying cytoarchitectural basis of REMSD-associated patho-physio-behavioral changes. Consolidation of findings of this study along with that of our previous reports suggest that the neuronal disintegration could be due to either withdrawal of direct protective and proliferative role of low dose of NA or indirect effect of high dose of NA or both.

Sleep Deprivation Aggravates Cognitive Impairment by the Alteration of Hippocampal Neuronal Activity and the Density of Dendritic Spine in Isoflurane-Exposed Mice

Isoflurane contributes to cognitive deficits when used as a general anesthetic, and so does sleep deprivation (SD). Patients usually suffer from insomnia before an operation due to anxiety, fear, and other factors. It remains unclear whether preoperative SD exacerbates cognitive impairment induced by isoflurane. In this study, we observed the effects of pretreated 24-h SD in adult isoflurane-exposed mice on the cognitive behaviors, the Ca²⁺ signals of dorsal hippocampal CA1 (dCA1) neurons in vivo with fiber photometry, and the density of dendritic spines in hippocampal neurons. Our results showed that in cognitive behavior tasks, short-term memory damages were more severe with SD followed by isoflurane exposure than that with SD or isoflurane exposure separately, and interestingly, severe long-term memory deficits were induced only by SD followed by isoflurane exposure. Only the treatment of SD followed by isoflurane exposure could reversibly decrease the amplitude of Ca²⁺ signals when mice were freely moving and increase the duration of Ca²⁺ signals during the long-term memory behavior test. The density of dendritic spines with both SD and isoflurane exposure was lower than that with SD alone. This study suggests that SD should be avoided preoperatively in patients undergoing elective surgery under isoflurane anesthesia.

Short-term sleep deprivation immediately after contextual conditioning inhibits BDNF signaling and disrupts memory consolidation in predator odor trauma mice model of PTSD

Post-traumatic stress disorder (PTSD) is a debilitating neuropsychiatric illness affecting > 7 million people every year in the US. Recently, we have shown that the mouse model of predator odor trauma (POT) displayed contextual conditioning and core features of PTSD including sleep disturbances (hyperarousal) and retrieval of traumatic memories following exposure to objective reminders (re-experiencing). PTSD is a disorder of memory function. Since memory consolidation requires the expression of BDNF along with an activation of MAPK/pERK signaling pathway in limbic brain structures (hippocampus and amygdala) and sleep favors memory consolidation, we hypothesized that short-term sleep deprivation (SD, 3 h), immediately after contextual conditioning will attenuate molecular correlates of memory consolidation, sleep disturbances, and memory consolidation. We performed two experiments in adult male C57BL/6J mice to test our hypothesis. Experiment 1 determined the effects of SD on contextual conditioning and changes in sleep wakefulness. Experiment 2 determined the effects of SD on contextual conditioning-induced changes in the expression of BDNF and pERK in hippocampus and amygdala. SD immediately after contextual conditioning (POT + SD group) significantly attenuated sleep disturbances, memory retrieval, and expression of pERK and BDNF in the hippocampus and amygdala as compared to POT-SD group (no SD after contextual conditioning). No significant differences were observed between POT + SD, NOC-SD (no contextual conditioning + no SD), and NOC + SD (no contextual conditioning + SD) groups. Memory consolidation requires sleep and the expression of pERK and BDNF in hippocampus and amygdala immediately after contextual conditioning in POT model of PTSD in mice.

Cognitive Impairments of Sleep-Deprived Ovariectomized (OVX) Female Rats by Voluntary Exercise

Introduction:

Previous studies demonstrated that forced and voluntary exercise had ameliorative effects on behavioral tasks followed by Sleep Deprivation (SD) in intact female rats. The main goal of this research was evaluating the impact of voluntary exercise on cognitive functions while SD and ovariectomization is induced in female wistar rats.

Methods:

The rats were anesthesized combining dosage of ketamine and xylazine. Then, both ovaries were eliminated and 3 weeks after surgery the animals entered the study. The exercise protocol took 4 weeks of voluntary exercise in a wheel which was connected to home cage. For inducing a 72 hours deprivation the multiple platforms was applied. The cognitive functions were studied by exploiting the Morris Water Maze (MWM) and Novel object recognition tests. Anxiety was evaluated by open field test and corticostrone measurement was carried out by ELISA method. One-way and two-way ANOVA and repeated measures were utilized for data analysis and P<0.05 was considered statistically significant.

Results:

We observed significant spatial and recognition learning and memory impairments in OVX sleep-deprived rats compared to the control group and voluntary exercise alleviated the SD-induced learning and memory defects.

Conclusion:

We concluded that voluntary exercise can improve cognitive impairments followed by SD in OVX female rats.

Effect of sleep loss on executive function and plasma corticosterone levels in an arctic-breeding songbird, the Lapland longspur (Calcarius lapponicus)

Sleep is a fundamental component of vertebrate life, although its exact functions remain unclear. Animals deprived of sleep typically show reduced neurobiological performance, health, and in some cases, survival. However, a number of vertebrate taxa exhibit adaptations that permit normal activities even when sleep is reduced. Lapland longspurs (Calcarius lapponicus), arctic-breeding passerine birds, exhibit around-the-clock activity during their short breeding season, with an inactive period of ca. 4 h/day. Whether behavioral or physiological costs occur from sleep loss (SL) in this species is unknown. To assess the effects of SL, wild-caught male longspurs were placed in captivity (12L:12D) and trained for one month to successfully learn color association and spatial memory tasks. Birds were then placed in automated sleep fragmentation cages that utilize a moving wire to force movement every 1 min (60 arousals/h) during 12D (inactive period) or control conditions (during 12L; active period). After SL (or control) treatment, birds were presented with color association and spatial memory tasks a final time to assess executive function. Baseline plasma corticosterone concentration, body mass, and satiety were also measured. SL significantly elevated corticosterone levels and increased accuracy during color association recall but did not affect the overall time required to complete the task. SL had no effect upon spatial memory, body mass, or satiety. Taken together, these results suggest that Lapland longspurs exhibit a degree of behavioral, but not physiological, insensitivity to acute SL. Whether elevated plasma concentrations of corticosterone play a direct role in ameliorating cognitive deficits from SL require additional study.

Modulation of hippocampal dopamine and synapse-related proteins by electroacupuncture improves memory deficit caused by sleep deprivation

BACKGROUND

Sleep is crucial for proper functioning of the brain, whereas lack of sleep is very common in modern society and can cause memory impairment. Hence, it is of great significance to find effective methods to intervene in the pathogenesis of memory impairment.

OBJECTIVE

We designed this study to explore the mechanism underlying the therapeutic effects of electroacupuncture (EA) on the deficits caused by sleep deprivation (SD).

METHODS

In this study, we first utilized the modified multiple platform method (MMPM) to establish a rat model of SD, which was followed by use of the Y-maze and Morris water maze (MWM) to assess the performance of rats following EA treatment.

RESULTS

We found that EA at GV20 and ST36 significantly decreased the number of error reactions, increased the number of active avoidance responses in the Y-maze and shortened the latency of finding the platform in the MWM test in SD + EA versus untreated SD groups. Moreover, EA treatment partially restored SD-induced reductions in hippocampal dopamine (DA) content and significantly increased the levels of phosphorylated (p) synapsin I, calcium/calmodulin-dependent protein kinase (CaMK) II, and tyrosine hydroxylase, which are related to the synthesis and release of DA.

CONCLUSIONS

In summary, we it appears that EA at GV20 and ST36 may improve SD-induced memory deficits by restoring the quantity of DA in the hippocampus, which is related to activation of CaMK II, synapsin I, and tyrosine hydroxylase. EA may have potential as an alternative therapy for SD and could improve learning and memory deficits among those suffering from sleep deficiency, although this needs verification by prospective clinical studies.

Role of Glia in the Regulation of Sleep in Health and Disease

Sleep is a naturally occurring physiological state that is required to sustain physical and mental health. Traditionally viewed as strictly regulated by top-down control mechanisms, sleep is now known to also originate locally. Glial cells are emerging as important contributors to the regulation of sleep-wake cycles, locally and among dedicated neural circuits. A few pioneering studies revealed that astrocytes and microglia may influence sleep pressure, duration as well as intensity, but the precise involvement of these two glial cells in the regulation of sleep remains to be fully addressed, across contexts of health and disease. In this overview article, we will first summarize the literature pertaining to the role of astrocytes and microglia in the regulation of sleep under normal physiological conditions. Afterward, we will discuss the beneficial and deleterious consequences of glia-mediated neuroinflammation, whether it is acute, or chronic and associated with brain diseases, on the regulation of sleep. Sleep disturbances are a main comorbidity in neurodegenerative diseases, and in several brain diseases that include pain, epilepsy, and cancer. Identifying the relationships between glia-mediated neuroinflammation, sleep-wake rhythm disruption and brain diseases may have important implications for the treatment of several disorders. © 2020 American Physiological Society. Compr Physiol 10:687-712, 2020.

The protective effect of edaravone on memory impairment induced by chronic sleep deprivation

Sleep plays a critical role in body health maintenance, whereas sleep deprivation (SD) negatively affects cognitive function. Cognitive defects mainly memory impairment resulting from sleep deprivation were related to an increase in the level of oxidative stress in the body, including the brain hippocampus region. Edaravone is a potent free radical scavenger having antioxidant effect. In the current study, edaravone's ability to prevent SD induced cognitive impairment was tested in rats. Animals were sleep deprived 8 h/day for 4 weeks. Concurrently, edaravone was administrated intraperitoneally for four weeks. Animals performance during cognitive testing was evaluated to display if edaravone has a role in the prevention of sleep deprivation induced memory impairment. Additionally, the role of antioxidant biomarkers glutathione peroxidase (GPx), catalase, glutathione (GSH), oxidized glutathione (GSSG), GSH/GSSG in this effect was investigated. The results showed that SD impaired both short- and long- term memories, and chronic edaravone administration prevented such effect. Additionally, edaravone prevented decreases in hippocampal GPx, catalase, GSH/GSSG ratio and normalized increases in GSSG levels, which were impaired by SD model. In conclusion, current result showed a protective effect of edaravone administration against SD induction that could be related to edaravone's ability to normalizing mechanisms related to oxidative balance.

Effects of CDP-choline administration on learning and memory in REM sleep-deprived rats

Cytidine 5-diphosphocholine (CDP-choline) administration has been shown to improve learning and memory deficits in different models of brain disorders. In this study, effects of CDP-choline on the well known negative effects of Rapid Eye Movements (REM) sleep deprivation on learning and memory were investigated. Sleep deprivation was induced by placing adult male Wistar albino rats on 6.5 cm diameter platforms individually for 96 h according to flower pot method. Learning and memory performances were evaluated using Morris Water Maze (MWM) test during the same period of time. Saline or CDP-choline (100 µmol/kg, 300 µmol/kg or 600 µmol/kg) was administered intraperitoneally 30 min prior to the onset of MWM experiments. On completion of behavioral tests, rats were decapitated and hippocampi were assayed for total and phosphorylated Ca²⁺/calmodulin-dependent protein kinase II (tCaMKII and pCaMKII, respectively) and total antioxidant capacity. We observed that while REM sleep deprivation had no effect on learning, it diminished the memory function, which was associated with decreased levels of pCaMKII and total antioxidant capacity in the hippocampus. CDP-choline treatment blocked the impairment in memory function of sleep-deprived rats and, increased pCaMKII levels and total antioxidant capacity. These data suggest that CDP-choline reduces REM sleep deprivation-induced impairment in memory, at least in part, by counteracting the disturbances in biochemical and molecular biological parameters.

The p75 Neurotrophin Receptor Is an Essential Mediator of Impairments in Hippocampal-Dependent Associative Plasticity and Memory Induced by Sleep Deprivation

Sleep deprivation (SD) interferes with hippocampal structural and functional plasticity, formation of long-term memory and cognitive function. The molecular mechanisms underlying these effects are incompletely understood. Here, we show that SD impaired synaptic tagging and capture and behavioral tagging, two major mechanisms of associative learning and memory. Strikingly, mutant male mice lacking the p75 neurotrophin receptor (p75NTR) were resistant to the detrimental effects of SD on hippocampal plasticity at both cellular and behavioral levels. Mechanistically, SD increased p75NTR expression and its interaction with phosphodiesterase. p75NTR deletion preserved hippocampal structural and functional plasticity by preventing SD-mediated effects on hippocampal cAMP-CREB-BDNF, cAMP-PKA-LIMK1-cofilin, and RhoA-ROCK2 pathways. Our study identifies p75NTR as an important mediator of hippocampal structural and functional changes associated with SD, and suggests that targeting p75NTR could be a promising strategy to limit the memory and cognitive deficits that accompany sleep loss.SIGNIFICANCE STATEMENT The lack of sufficient sleep is a major health concern in today's world. Sleep deprivation (SD) affects cognitive functions such as memory. We have investigated how associative memory mechanisms, synaptic tagging and capture (STC), was impaired in SD mice at cellular and behavioral level. Interestingly, mutant male mice that lacked the p75 neurotrophin receptor (p75NTR) were seen to be resistant to the SD-induced impairments in hippocampal synaptic plasticity and STC. Additionally, we elucidated the molecular pathways responsible for this rescue of plasticity in the mutant mice. Our study has thus identified p75NTR as a promising target to limit the cognitive deficits associated with SD.

Microglia-Mediated Synapse Loss in Alzheimer's Disease

Microglia are emerging as key players in neurodegenerative diseases, such as Alzheimer's disease (AD). Thus far, microglia have rather been known as modulator of neurodegeneration with functions limited to neuroinflammation and release of neurotoxic molecules. However, several recent studies have demonstrated a direct role of microglia in "neuro" degeneration observed in AD by promoting phagocytosis of neuronal, in particular, synaptic structures. While some of the studies address the involvement of the β-amyloid peptides in the process, studies also indicate that this could occur independent of amyloid, further elevating the importance of microglia in AD. Here we review these recent studies and also speculate about the possible cellular mechanisms, and how they could be regulated by risk genes and sleep. Finally, we deliberate on possible avenues for targeting microglia-mediated synapse loss for therapy and prevention.Dual Perspectives Companion Paper: Alzheimer's Disease and Sleep-Wake Disturbances: Amyloid, Astrocytes, and Animal Models by William M. Vanderheyden, Miranda M. Lim, Erik S. Musiek, and Jason R. Gerstner.

Voluntary exercise reduces plasma cortisol levels and improves transitory memory impairment in young and aged Octodon degus

Sleep deprivation (SD) has been reported to induce transient cognitive impairment in functional domains commonly affected in dementia, including memory. Indeed, sleep disturbance has been proposed as an early marker for Alzheimer's disease (AD). SD emulates many aging-related modifications, including important memory dysfunctions possibly caused by triggers of stress such as cortisol. Although exercise is widely assumed to be beneficial for overall health, only recently has the research community focused its attention on its possible effects on brain functions such as cognition. Octodon degus (O. degus) is a recent rodent model considered suitable for the study of neurodegenerative diseases, since it spontaneously develops several histopathological hallmarks observed in AD. We aimed to uncover the interaction between stress, exercise, age and transient memory impairments after SD insult. In this study, animals had free individual access to wheels to practice voluntary exercise. The Barnes Maze (BM) task was conducted with young and aged O. degus animals after combining voluntary exercise and either normal sleep or SD. Plasma cortisol levels were measured after each condition. SD impaired hippocampus-dependent memory in both young and old animals, while cortisol levels did not significantly differ between non-SD and SD animals. However, voluntary exercise for 45 days improved the cognitive impairment caused by SD compared with the control condition. Moreover, voluntary exercise decreased plasma cortisol levels in both conditions, independently of the age.

Sleep deprivation, oxidative stress and inflammation

Adequate sleep is essential for normal brain function, especially during early life developmental stages as postnatal brain maturation occurs during the critical period of childhood and adolescence. Therefore, sleep disturbance and/or deficit during this period can have detrimental consequences. Many epidemiological and clinical studies have linked early life sleep disturbance with occurrence of later life behavioral and cognitive impairments. Role of oxidative stress and inflammation has been implicated in sleep deprivation-related impairments. This review article presents a detailed description of the current state of the literature on the subject.

Self-regulation and social behavior during sleep deprivation

An emerging literature is specifically focusing on the effects of sleep deprivation on aspects of social functioning and underlying neural changes. Two critical facets of social behavior emerge that are negatively impacted by sleep deprivation-self-regulation, which includes behavioral and emotional regulation, and social monitoring, which includes perceiving and interpreting cues relating to self and others. Sleep deprived individuals performing tasks with social components show altered brain activity in areas of the prefrontal cortex implicated in self-control, inhibition, evaluation, and decision-making, in proximity to mesocorticolimbic pathways to reward and emotional processing areas. These cognitive changes lead to increased reward seeking and behaviors that promote negative health outcomes (such as increased consumption of indulgence foods). These changes also lead to emotional disinhibition and increased responses to negative stimuli, leading to reductions in trust, empathy, and humor. Concomitant attentional instability leads to impaired social information processing, impairing individual and team performance and increasing likelihood of error, incident, and injury. Together, changes to reward seeking, the foundational components of social interaction, and interpretation of social cues, can result in unpleasant or deviant behavior. These behaviors are perceived and negatively responded to by others, leading to a cycle of conflict and withdrawal. Further studies are necessary and timely. Educational and behavioral interventions are required to reduce health-damaging behaviors, and to reduce emotionally-laden negative interpretation of sleep-deprived exchanges. This may assist with health, and with team cohesion (and improved performance and safety) in the workplace and the home.

Stem-leaf saponins from Panax notoginseng counteract aberrant autophagy and apoptosis in hippocampal neurons of mice with cognitive impairment induced by sleep deprivation

Backgroud

Sleep deprivation (SD) impairs learning and memory by inhibiting hippocampal functioning at molecular and cellular levels. Abnormal autophagy and apoptosis are closely associated with neurodegeneration in the central nervous system. This study is aimed to explore the alleviative effect and the underlying molecular mechanism of stem–leaf saponins of Panax notoginseng (SLSP) on the abnormal neuronal autophagy and apoptosis in hippocampus of mice with impaired learning and memory induced by SD.

Methods

Mouse spatial learning and memory were assessed by Morris water maze test. Neuronal morphological changes were observed by Nissl staining. Autophagosome formation was examined by transmission electron microscopy, immunofluorescent staining, acridine orange staining, and transient transfection of the tf-LC3 plasmid. Apoptotic event was analyzed by flow cytometry after PI/annexin V staining. The expression or activation of autophagy and apoptosis-related proteins were detected by Western blotting assay.

Results

SLSP was shown to improve the spatial learning and memory of mice after SD for 48 h, accomanied with restrained excessive autophage and apoptosis, whereas enhanced activation of phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin signaling pathway in hippocampal neurons. Meanwhile, it improved the aberrant autophagy and apoptosis induced by rapamycin and re-activated phosphoinositide 3-kinase/Akt/mammalian target of rapamycin signaling transduction in HT-22 cells, a hippocampal neuronal cell line.

Conclusion

SLSP could alleviate cognitive impairment induced by SD, which was achieved probably through suppressing the abnormal autophagy and apoptosis of hippocampal neurons. The findings may contribute to the clinical application of SLSP in the prevention or therapy of neurological disorders associated with SD.

Protective role of hydroalcoholic extract of Cajanus cajan Linn leaves against memory impairment in sleep deprived experimental rats

Background

The plant Cajanus cajan had earlier shown protective effect against hypoxic-ischemic brain damage in rats.

Objective

Hence, hydroalcoholic extract of C. cajan Linn leaves (HECC) was evaluated for its protective role against memory impairment in sleep-deprived Sprague Dawley rats.

Materials and methods

Adult rats were divided into five groups each consisting of 5 rats (n = 5). Groups I, II, III, IV and V received 1 mL/kg 1% CMC, 1 mL/kg 1% CMC, 200 mg/kg HECC, 400 mg/kg HECC and 200 mg/kg piracetam respectively as per b.wt. orally everyday for 14 days. Animals of every groups except group-I were subjected to sleep-deprivation from 15th to 19th day for induction of memory impairment. Behavioral activities i.e., elevated plus maze test and locomotor activity were evaluated. Afterwards, brain was isolated from the sacrificed animals for biochemical investigation of acetylcholinesterase (AChE); antioxidant activities i.e., catalase (CAT), superoxide dismutase (SOD), lipid peroxide; and histopathological changes.

Results

The percent number of entries, number of entries in open arm, AChE activity, lipid peroxide activity of HECC-treated group-III and group-IV were significantly (p < 0.01) decreased while, their CAT and SOD activities were significantly (p < 0.01) increased in dose-dependent manner as compared to sleep-deprived group-II. The activities of group-IV were almost significantly equivalent to that of piracetam-treated group-V. Protective effect of HECC was well supported with brain's histopathology.

Conclusion

HECC possesses a protective effect against memory impairment indicating its therapeutic efficacy against memory loss as in Alzheimer's disease. Probable underlying mechanisms may be brain's AChE inhibition and increased antioxidant potential by HECC.

Tau Pathology of Alzheimer Disease: Possible Role of Sleep Deprivation

Sleep deprivation is a common complaint in modern societies. Insufficient sleep has increased the risk of catching neurodegenerative diseases such as Alzheimer’s. Several studies have indicated that restricted sleep increases the level of deposition of β-amyloid and formation of neurofibrillary tangles, the major brain microstructural hallmarks for Alzheimer disease. The mechanisms by which sleep deprivation affects the pathology of Alzheimer disease has not yet been fully and definitively identified. However, risk factors like apolipoprotein E risk alleles, kinases and phosphatases dysregulation, reactive oxygen species, endoplasmic reticulum damages, glymphatic system dysfunctions and orexinergic system inefficacy have been identified as the most important factors which mediates between the two conditions. In this review, these factors are briefly discussed.

Neuroprotective Effects of Nicotine on Hippocampal Long-Term Potentiation in Brain Disorders

Long-term potentiation (LTP) is commonly considered the cellular correlate of learning and memory. In learning and memory impairments, LTP is invariably diminished in the hippocampus, the brain region responsible for memory formation. LTP is measured electrophysiologically in various areas of the hippocampus. Two mechanistically distinct phases of LTP have been identified: early phase LTP, related to short-term memory; and late-phase LTP, related to long-term memory. These two forms can be severely reduced in a variety of conditions but can be rescued by treatment with nicotine. This report reviews the literature on the beneficial effect of nicotine on LTP in conditions that compromise learning and memory.

Dietary polyphenols promote resilience against sleep deprivation-induced cognitive impairment by activating protein translation

Previous evidence has suggested that dietary supplementation with a bioactive dietary polyphenol preparation (BDPP) rescues impairment of hippocampus-dependent memory in a mouse model of sleep deprivation (SD). In the current study, we extend our previous evidence and demonstrate that a mechanism by which dietary BDPP protects against SD-mediated cognitive impairment is via mechanisms that involve phosphorylation of the mammalian target of rapamycin complex 1 and its direct downstream targets, including the eukaryotic translation initiation factor 4E (eIF4E)-binding protein 1 (4E-BP1) and the ribosomal protein S6 kinase β-1 (p70S6K). In additional mechanistic studies in vitro, we identified the brain bioavailable phenolic metabolites derived from the metabolism of dietary BDPP that are responsible for the attenuation of SD-mediated memory impairments. On the basis of high-throughput bioavailability studies of brain bioavailable metabolites after dietary BDPP treatment, we found that select polyphenol metabolites [ e.g., cyanidin-3'- O-glucoside and 3-(3'-hydroxyphenyl) propionic acid] were able to rescue mTOR and p70S6K phosphorylation in primary cortico-hippocampal neuronal cultures, as well as rescue 4E-BP1 phosphorylation in response to treatment with 4EGI-1, a specific inhibitor of eIF4E-eIF4G interaction. Our findings reveal a previously unknown role for dietary polyphenols in the rescue of SD-mediated memory impairments via mechanisms involving the promotion of protein translation.-Frolinger, T., Smith, C., Cobo, C. F., Sims, S., Brathwaite, J., de Boer, S., Huang, J., Pasinetti, G. M. Dietary polyphenols promote resilience against sleep deprivation-induced cognitive impairment by activating protein translation.

Deletion of the endogenous TrkB.T1 receptor isoform restores the number of hippocampal CA1 parvalbumin-positive neurons and rescues long-term potentiation in pre-symptomatic mSOD1(G93A) ALS mice

Amyotrophic lateral sclerosis (ALS) causes rapidly progressive paralysis and death within 5 years from diagnosis due to degeneration of the motor circuits. However, a significant population of ALS patients also shows cognitive impairments and progressive hippocampal pathology. Likewise, the mutant SOD1(G93A) mouse model of ALS (mSOD1), in addition to loss of spinal motor neurons, displays altered spatial behavior and hippocampal abnormalities including loss of parvalbumin-positive interneurons (PVi) and enhanced long-term potentiation (LTP). However, the cellular and molecular mechanisms underlying these morpho-functional features are not well understood. Since removal of TrkB.T1, a receptor isoform of the brain-derived neurotrophic factor, can partially rescue the phenotype of the mSOD1 mice, here we tested whether removal of TrkB.T1 can normalize the number of PVi and the LTP in this model. Stereological analysis of hippocampal PVi in control, TrkB.T1^-/-, mSOD1, and mSOD1 mice deficient for TrkB.T1 (mSOD1/T1^-/-) showed that deletion of TrkB.T1 restored the number of PVi to physiological level in the mSOD1 hippocampus. The rescue of PVi neuron number is paralleled by a normalization of high-frequency stimulation-induced LTP in the pre-symptomatic mSOD1/T1^-/- mice. Our experiments identified TrkB.T1 as a cellular player involved in the homeostasis of parvalbumin expressing interneurons and, in the context of murine ALS, show that TrkB.T1 is involved in the mechanism underlying structural and functional hippocampal degeneration. These findings have potential implications for hippocampal degeneration and cognitive impairments reported in ALS patients at early stages of the disease.

Sleep deprivation impairs synaptic tagging in mouse hippocampal slices

Metaplasticity refers to the ability of experience to alter synaptic plasticity, or modulate the strength of neuronal connections. Sleep deprivation has been shown to have a negative impact on synaptic plasticity, but it is unknown whether sleep deprivation also influences processes of metaplasticity. Therefore, we tested whether 5 h of total sleep deprivation (SD) in mice would impair hippocampal synaptic tagging and capture (STC), a form of heterosynaptic metaplasticity in which combining strong stimulation in one synaptic input with weak stimulation at another input allows the weak input to induce long-lasting synaptic strengthening. STC in stratum radiatum of area CA1 occurred normally in control mice, but was impaired following SD. After SD, potentiation at the weakly stimulated synapses decayed back to baseline within 2 h. Thus, sleep deprivation disrupts a prominent form of metaplasticity in which two independent inputs interact to generate long-lasting LTP.

Frontal cortical mitochondrial dysfunction and mitochondria-related β-amyloid accumulation by chronic sleep restriction in mice

Mitochondrial dysfunction induced by mitochondria-related β-amyloid (Aβ) accumulation is increasingly being considered a novel risk factor for sporadic Alzheimer’s disease pathophysiology. The close relationship between chronic sleep restriction (CSR) and cortical Aβ elevation was confirmed recently. By assessing frontal cortical mitochondrial function (electron microscopy manifestation, cytochrome C oxidase concentration, ATP level, and mitochondrial membrane potential) and the levels of mitochondria-related Aβ in 9-month-old adult male C57BL/6J mice subjected to CSR and as an environmental control (CO) group, we aimed to evaluate the association of CSR with mitochondrial dysfunction and mitochondria-related Aβ accumulation. In this study, frontal cortical mitochondrial dysfunction was significantly more severe in CSR mice compared with CO animals. Furthermore, CSR mice showed higher mitochondria-associated Aβ, total Aβ, and mitochondria-related β-amyloid protein precursor (AβPP) levels compared with CO mice. In the CSR model, mouse frontal cortical mitochondrial dysfunction was correlated with mitochondria-associated Aβ and mitochondria-related AβPP levels. However, frontal cortical mitochondria-associated Aβ levels showed no significant association with cortical total Aβ and mitochondrial AβPP concentrations. These findings indicated that CSR-induced frontal cortical mitochondrial dysfunction and mitochondria-related Aβ accumulation, which was closely related to mitochondrial dysfunction under CSR.

Morin hydrate mitigates rapid eye movement sleep deprivation-induced neurobehavioural impairments and loss of viable neurons in the hippocampus of mice

Rapid eye movement sleep deprivation distorts the body's homeostasis and results in oxidative breakdown which may be responsible for a variety of neurological disorders. Some naturally occurring compounds of plant origin with antioxidant and neuroprotective properties are known to attenuate the detrimental effects of REM sleep deprivation. Morin hydrate, a flavonoid from Mulberry has demonstrated antioxidant and neuroprotective activities but its effect in sleep disturbed mice is unknown. The study was designed to explore the neuroprotective effect of Morin hydrate on 48 h. REM sleep deprivation-induced behavioural impairments and neuronal damage in mice. Mice were allotted into six treatment groups (n = 6): groups 1 and 2 received vehicle (10 ml/kg normal saline), groups 3-5 received Morin hydrate (5, 10, 20 mg/kg i.p) while group 6 received ginseng (25 mg/kg) which served as the reference drug. Treatment was performed daily for 5 days and animals were sleep-deprived on the last 48 h. Various behavioural tests (Elevated plus maze, Y-maze, locomotor activity) followed by oxidative parameters (malondialdehyde, nitric oxide, reduced glutathione) and histolopathological changes in the Cornu ammonis 1 (CA1) region of the hippocampus were assessed. Data were analysed using ANOVA at α_0.05. Morin hydrate (5, 10, 20 mg/kg) significantly enhanced memory performance, improves anxiolytic-like behaviour, reverses hyperlocomotion, restored depleted reduced glutathione, attenuated raised malondialdehyde and nitric oxide levels as compared to control animals and protects against loss of hippocampal neurons. Results of this present study suggest that Morin hydrate possess neuroprotective effects against sleep deprivation-induced behavioural impairments, oxidative stress and neuronal damage.

Neuropeptide S overcomes short term memory deficit induced by sleep restriction by increasing prefrontal cortex activity

Sleep restriction (SR) impairs short term memory (STM) that might be related to different processes. Neuropeptide S (NPS), an endogenous neuropeptide that improves short term memory, activates arousal and decreases anxiety is likely to counteract the SR-induced impairment of STM. The objective of the present study was to find common cerebral pathways in sleep restriction and NPS action in order to ultimately antagonize SR effect on memory. The STM was assessed using a spontaneous spatial alternation task in a T-maze. C57-Bl/6J male mice were distributed in 4 groups according to treatment (0.1nmol of NPS or vehicle intracerebroventricular injection) and to 20h-SR. Immediately after behavioural testing, regional c-fos immunohistochemistry was performed and used as a neural activation marker for spatial short term memory (prefrontal cortex, dorsal hippocampus) and emotional reactivity (basolateral amygdala and ventral hippocampus). Anxiety-like behaviour was assessed using elevated-plus maze task. Results showed that SR impaired short term memory performance and decreased neuronal activation in cingular cortex.NPS injection overcame SR-induced STM deficits and increased neuronal activation in infralimbic cortex. SR spared anxiety-like behavior in the elevated-plus maze. Neural activation in basolateral nucleus of amygdala and ventral hippocampus were not changed after SR.In conclusion, the present study shows that NPS overcomes SR-induced STM deficits by increasing prefrontal cortex activation independently of anxiety-like behaviour.

Cellular and Molecular Mechanisms of REM Sleep Homeostatic Drive: A Plausible Component for Behavioral Plasticity

Homeostatic regulation of REM sleep drive, as measured by an increase in the number of REM sleep transitions, plays a key role in neuronal and behavioral plasticity (i.e., learning and memory). Deficits in REM sleep homeostatic drive (RSHD) are implicated in the development of many neuropsychiatric disorders. Yet, the cellular and molecular mechanisms underlying this RSHD remain to be incomplete. To further our understanding of this mechanism, the current study was performed on freely moving rats to test a hypothesis that a positive interaction between extracellular-signal-regulated kinase 1 and 2 (ERK1/2) activity and brain-derived neurotrophic factor (BDNF) signaling in the pedunculopontine tegmentum (PPT) is a causal factor for the development of RSHD. Behavioral results of this study demonstrated that a short period (<90 min) of selective REM sleep restriction (RSR) exhibited a strong RSHD. Molecular analyses revealed that this increased RSHD increased phosphorylation and activation of ERK1/2 and BDNF expression in the PPT. Additionally, pharmacological results demonstrated that the application of the ERK1/2 activation inhibitor U0126 into the PPT prevented RSHD and suppressed BDNF expression in the PPT. These results, for the first time, suggest that the positive interaction between ERK1/2 and BDNF in the PPT is a casual factor for the development of RSHD. These findings provide a novel direction in understanding how RSHD-associated specific molecular changes can facilitate neuronal plasticity and memory processing.