Modafinil prevents inhibitory avoidance memory deficit induced by sleep deprivation in rats

REM sleep deprivation induced by the modified multi-platform method has detrimental effects on memory: A systematic review and meta-analysis

The modified multi-platform method (MMPM) is used to induce animal models of paradoxical sleep deprivation and impairs memory in rodents. However, variations in MMPM protocols have contributed to inconsistent conclusions across studies. This meta-analysis aimed to assess the variations of the MMPM and their effects on memory in rats and mice. A comprehensive search identified 60 studies, and 50 were included in our meta-analysis. Overall, the meta-analysis showed that the MMPM significantly reduced the percentage of time spent in target quadrants (I2 = 54 %, 95 % confidence interval [CI] = [-1.83, -1.18]) and the number of platform-area crossings (I2 = 26 %, 95 % CI = [-1.71, -1.07]) in the Morris water maze (MWM) and shortened the latency to entering the dark compartment in the passive avoidance task (I2 = 68 %, 95 % CI = [-1.36, -0.57]), but it increased the number of errors in the radial arm water maze (RAWM) (I2 = 59 %, 95 % CI = [1.29, 2.07]). Additionally, mice performed worse on the MWM, whereas rats performed worse on the passive avoidance task. More significant memory deficits were found in cross-learning and post-learning MMPM in the MWM and RAWM, respectively. This study provided evidence that the MMPM can be used in preclinical studies of memory deficits induced by paradoxical sleep deprivation.

Targeting microbiota to alleviate the harm caused by sleep deprivation

Sleep deprivation has become a common health hazard, affecting 37-58% of the population and promoting the occurrence and development of many diseases. To date, effective treatment strategies are still elusive. Accumulating evidence indicates that modulating the intestinal microbiota harbors significant potential for alleviating the deleterious impacts of sleep deprivation. This paper first reviews the effects of sleep deprivation on gastrointestinal diseases, metabolic diseases, and neuropsychiatric diseases, discussing its specific mechanisms of influence. We then focus on summarizing existing interventions, including probiotics, melatonin, prebiotics, diet, and fecal microbiota transplantation (FMT). Finally, we have discussed the advantages and limitations of each strategy. Compared with other strategies, probiotics showed a high potential in alleviating sleep deprivation-related hazards due to their reduced risk and high security. We suggest that future research should focus on the specific mechanisms by which probiotics mitigate the harms of sleep deprivation, such insights may unveil novel pathways for treating diseases exacerbated by insufficient sleep.

Exogenous growth hormone administration during total sleep deprivation changed the microRNA-9 and dopamine D2 receptor expressions followed by improvement in the hippocampal synaptic potential, spatial cognition, and inflammation in rats

RATIONALE

Disorders caused by total sleep deprivation can be modulated by the administration of growth hormone, which could affect the expression of microRNA-9 and dopamine D2 receptor expressions followed by improvement in the hippocampal synaptic potential, spatial cognition, and inflammation in rats.

OBJECTIVES

The present study aimed to elucidate the putative effects of exogenous growth hormone (GH) against total sleep deprivation (TSD)-induced learning and memory dysfunctions and possible involved mechanisms.

METHODS

To induce TSD, rats were housed in homemade special cages equipped with stainless steel wire conductors to induce general and inconsistent TSD. They received a mild repetitive electric shock to their paws every 10 min for 21 days. GH (1 mg/kg, sc) was administered to adult young male rats once daily for 21-day-duration induction of TSD. Spatial learning and memory performance, inflammatory status, microRNA-9 (miR-9) expression, dopamine D2 receptor (DRD2) protein level, and hippocampal histological changes were assayed at scheduled times after TSD.

RESULTS

The results indicated that TSD impaired spatial cognition, increased TNF-α, decreased level of miR-9, and increased DRD2 levels. Treatment with exogenous GH improved spatial cognition, decreased TNF-α, increased level of miR-9, and decreased DRD2 levels after TSD.

CONCLUSIONS

Our findings suggest that GH may play a key role in the modulation of learning and memory disorders as well as the ameliorating abnormal DRD2-related functional disorders associated with miR-9 in TSD.

Inhibition of Histone Deacetylase Reinstates Hippocampus-Dependent Long-Term Synaptic Plasticity and Associative Memory in Sleep-Deprived Mice

Sleep plays an important role in the establishment of long-term memory; as such, lack of sleep severely impacts domains of our health including cognitive function. Epigenetic mechanisms regulate gene transcription and protein synthesis, playing a critical role in the modulation of long-term synaptic plasticity and memory. Recent evidences indicate that transcriptional dysregulation as a result of sleep deprivation (SD) may contribute to deficits in plasticity and memory function. The histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA), also known as Vorinostat, a clinically approved drug for human use, has been shown to ameliorate cognitive deficits in several neurological disease models. To further explore the therapeutic effect of SAHA, we have examined its potential role in improving the SD-mediated impairments in long-term plasticity, associative plasticity, and associative memory. Here we show that SAHA preserves long-term plasticity, associative plasticity, and associative memory in SD hippocampus. Furthermore, we find that SAHA prevents SD-mediated epigenetic changes by upregulating histone acetylation, hence preserving the ERK-cAMP-responsive element-binding protein (CREB)/CREB-binding protein-brain-derived neurotrophic factor pathway in the hippocampus. These data demonstrate that modifying epigenetic mechanisms via SAHA can prevent or reverse impairments in long-term plasticity and memory that result from sleep loss. Thus, SAHA could be a potential therapeutic agent in improving SD-related memory deficits.

Modafinil protects hippocampal neurons by suppressing excessive autophagy and apoptosis in mice with sleep deprivation

BACKGROUND AND PURPOSE

Sleep deprivation compromises learning and memory in both humans and animals, and can be reversed by administration of modafinil, a drug promoting wakefulness. Dysfunctional autophagy increases activation of apoptotic cascades, ultimately leading to increased neuronal death, which can be alleviated by autophagy inhibitors. This study aimed to investigate the alleviative effect and mechanism of modafinil on the excessive autophagy occurring in the hippocampus of mice with deficiency of learning and memory induced by sleep deprivation.

EXPERIMENTAL APPROACH

The Morris water maze was used to assess the effects of modafinil on male C57BL/6Slac mice after 48-hr sleep deprivation. The HT-22 hippocampal neuronal cell line was also used. Nissl staining, transmission electron microscope, immunofluorescence, Western blot, transient transfection, and autophagy inducer were used to study the effect and mechanism of modafinil on hippocampal neurons with excessive autophagy and apoptosis.

KEY RESULTS

Modafinil improved learning and memory in sleep-deprived mice, associated with the inhibition of excessive autophage and apoptosis and an enhanced activation of the PI3K/Akt/mTOR/P70S6K signalling pathway in hippocampal neurons. These effects of modafinil were abolished by rapamycin. In addition, modafinil suppressed the aberrant autophagy and apoptosis induced by rapamycin and reactivated PI3K/Akt/mTOR/P70S6K signals in HT-22 cells.

CONCLUSIONS AND IMPLICATIONS

These results suggested that modafinil alleviated impaired learning and memory of sleep-deprived mice potentially by suppressing excessive autophagy and apoptosis of hippocampal neurons. This novel mechanism may add to our knowledge of modafinil in the clinical treatment of impaired memory caused by sleep loss.

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.

Cognitive and hippocampus biochemical changes following sleep deprivation in the adult male rat

Sleep deprivation (SD) influences physiological processes such as cognitive function. The balance of oxidant and antioxidant markers, neurotrophic factors and magnesium are affected by sleep deprivation but there is no difference between pre and post training sleep deprivation. This study was designed to investigate memory retrieval and biochemical factors such as oxidant and antioxidant enzyme, brain-derived neurotrophic factor (BDNF) and magnesium levels in the hippocampus following pre and post-training sleep deprivation. Male Wistar rats (weighing 200 ± 20 g) in below groups were used: control 1, 24, 48 and 72 h SD before training groups, control2, 24 h SD1 after training (being evaluated 24 h after training) and SD2 24 after training (being evaluated 48 h after training). Memory was evaluated 90 min, 24 h or 48 h after training by step-through passive avoidance apparatus. Multiple platforms method was used to induce SD. Oxidant and antioxidant markers including glutathione (GSH), glutathione reductase (GPx), malonedialdehyde (MDA), Total antioxidant concentration, catalase, superoxide dismutase (SOD), magnesium and BDNF were assessed in the hippocampus or/and brain. 72 h pre-training SD impaired short and long-term memory significantly. There was no significant difference in hippocampus oxidant and antioxidant markers compared to control. Hippocampal BDNF and magnesium did not show any changes in all SD groups. Lack of correlation between memory impairment and levels of BDNF, magnesium and/or oxidant and antioxidant balance in the hippocampus is likely to be related to animal locomotor activity in the multiple platforms method. More research is needed to clarify the role of neurochemical systems.

Distinct behavioral and brain changes after different durations of the modified multiple platform method on rats: An animal model of central fatigue

The modified multiple platform method (MMPM) is a classical sleep deprivation model. It has been widely used in behavioral and brain research, due to its effects on physical and mental functions. However, different MMPM protocols can promote distinct effects in rats. Although the MMPM has been proved to induce central fatigue, the effects of different durations of subjection to the MMPM remain undetermined. This study aims to investigate the changes in behavior, N-Methyl-d-Aspartate receptor 1 (NR1) and 2A (NR2A), as well as the ultrastructural alteration in the hippocampus after different MMPM modelling, to compare the central fatigue effect induced by dynamic MMPM. Rats were randomly divided into four groups: 5-, 14- and 21- day MMPM groups, and a control group. Each MMPM group underwent a 14-hour daily MMPM modelling. After each training session, open field and elevated plus maze tests were performed. Corticosterone levels were detected by ELISA, and the hippocampal NR1 and NR2A were measured by RT-PCR and Western blot analysis. In addition, ultrastructural changes in the hippocampal cornu ammonis 1(CA1) region were determined by transmission electron microscopy (TEM). The findings showed that the 5 and 14 days of MMPM induced a high-stress state, while the 21 days of MMPM induced anxiety and degenerative alteration in the hippocampal morphology. Additionally, hippocampal NR1 and NR2A gene expression decreased in all MMPM groups, whereas the protein expression only decreased in the 21-day group. Overall, different durations of MMPM caused distinct behavioral and brain changes, and the 21 days of MMPM could induce central fatigue.

Effects of sleep deprivation on different phases of memory in the rat: dissociation between contextual and tone fear conditioning tasks

Numerous studies show that sleep deprivation (SD) impacts negatively on cognitive processes, including learning and memory. Memory formation encompasses distinct phases of which acquisition, consolidation and retrieval are better known. Previous studies with pre-training SD induced by the platform method have shown impairment in fear conditioning tasks. Nonetheless, pre-training manipulations do not allow the distinction between effects on acquisition and/or consolidation, interfering, ultimately, on recall of/performance in the task. In the present study, animals were first trained in contextual and tone fear conditioning (TFC) tasks and then submitted to SD with the purpose to evaluate the effect of this manipulation on different stages of the learning process, e.g., in the uptake of (new) information during learning, its encoding and stabilization, and the recall of stored memories. Besides, we also investigated the effect of SD in the extinction of fear memory and a possible state-dependent learning induced by this manipulation. For each task (contextual or TFC), animals were trained and then distributed into control, not sleep-deprived (CTL) and SD groups, the latter being submitted to the modified multiple platform paradigm for 96 h. Subsets of eight rats in each group/experiment were submitted to the test of the tasks, either immediately or at different time intervals after SD. The results indicated that (a) pre- but not post-training SD impaired recall in the contextual and TFC; (b) this impairment was not state-dependent; and (c) in the contextual fear conditioning (CFC), pre-test SD prevented extinction of the learned task. Overall, these results suggest that SD interferes with acquisition, recall and extinction, but not necessarily with consolidation of emotional memory.

Predictive validity of a MK-801-induced cognitive impairment model in mice: implications on the potential limitations and challenges of modeling cognitive impairment associated with schizophrenia preclinically

Cognitive impairment associated with schizophrenia (CIAS) is a major and disabling symptom domain of the disease that is generally unresponsive to current pharmacotherapies. Critically important to the discovery of novel therapeutics for CIAS is the utilization of preclinical models with robust predictive validity. We investigated the predictive validity of MK-801-induced memory impairments in mouse inhibitory avoidance (MK-IA) as a preclinical model for CIAS by investigating compounds that have been tested in humans, including antipsychotics, sodium channel blocker mood stabilizers, and putative cognitive enhancers. The atypical antipsychotic clozapine, as well as risperidone and olanzapine (see Brown et al., 2013), had no effect on MK-801-induced memory impairments. For sodium channel blockers, carbamazepine significantly attenuated memory impairments induced by MK-801, whereas lamotrigine had no effect. Nicotine, donepezil, modafinil, and xanomeline all significantly attenuated MK-801-induced memory impairments, but the magnitude of effects and the dose-responses observed varied across compounds. Clinically, only acute administration of nicotine has demonstrated consistent positive effects on CIAS, while inconsistent results have been reported for lamotrigine, donepezil, and modafinil; atypical antipsychotics produce only moderate improvements at best. A positive clinical signal has been observed with xanomeline, but only in a small pilot trial. The results presented here suggest that the MK-IA model lacks robust predictive validity for CIAS as the model is likely permissive and may indicate false positive signals for compounds and mechanisms that lack clear clinical efficacy for CIAS. Our findings also highlight the potential limitations and challenges of using NMDA receptor antagonists in rodents to model CIAS.

Experimental sleep deprivation as a tool to test memory deficits in rodents

Paradigms of sleep deprivation (SD) and memory testing in rodents (laboratory rats and mice) are here reviewed. The vast majority of these studies have been aimed at understanding the contribution of sleep to cognition, and in particular to memory. Relatively little attention, instead, has been devoted to SD as a challenge to induce a transient memory impairment, and therefore as a tool to test cognitive enhancers in drug discovery. Studies that have accurately described methodological aspects of the SD protocol are first reviewed, followed by procedures to investigate SD-induced impairment of learning and memory consolidation in order to propose SD protocols that could be employed as cognitive challenge. Thus, a platform of knowledge is provided for laboratory protocols that could be used to assess the efficacy of drugs designed to improve memory performance in rodents, including rodent models of neurodegenerative diseases that cause cognitive deficits, and Alzheimer's disease in particular. Issues in the interpretation of such preclinical data and their predictive value for clinical translation are also discussed.

Lithium prevents REM sleep deprivation-induced impairments on memory consolidation

BACKGROUND

Pre-training rapid eye movement sleep (REMS) deprivation affects memory acquisition and/or consolidation. It also produces major REMS rebound at the cost of waking and slow wave sleep (SWS). Given that both SWS and REMS appear to be important for memory processes, REMS rebound after training may disrupt the organization of sleep cycles, i.e., excessive amount of REMS and/or little SWS after training could be harmful for memory formation.

OBJECTIVE

To examine whether lithium, a drug known to increase SWS and reduce REMS, could prevent the memory impairment induced by pre-training sleep deprivation.

DESIGN

Animals were divided in 2 groups: cage control (CC) and REMS-deprived (REMSDep), and then subdivided into 4 subgroups, treated either with vehicle or 1 of 3 doses of lithium (50, 100, and 150 mg/kg) 2 h before training on the multiple trial inhibitory avoidance task. Animals were tested 48 h later to make sure that the drug had been already metabolized and eliminated. Another set of animals was implanted with electrodes and submitted to the same experimental protocol for assessment of drug-induced sleep-wake changes.

SUBJECTS

Wistar male rats weighing 300-400 g.

RESULTS

Sleep deprived rats required more trials to learn the task and still showed a performance deficit during test, except from those treated with 150 mg/kg of lithium, which also reduced the time spent in REM sleep during sleep recovery.

CONCLUSION

Lithium reduced rapid eye movement sleep and prevented memory impairment induced by sleep deprivation. These results indicate that these phenomena may be related, but cause-effect relationship cannot be ascertained.

The impact of sleep loss on hippocampal function

Hippocampal cellular and molecular processes critical for memory consolidation are affected by the amount and quality of sleep attained. Questions remain with regard to how sleep enhances memory, what parameters of sleep after learning are optimal for memory consolidation, and what underlying hippocampal molecular players are targeted by sleep deprivation to impair memory consolidation and plasticity. In this review, we address these topics with a focus on the detrimental effects of post-learning sleep deprivation on memory consolidation. Obtaining adequate sleep is challenging in a society that values "work around the clock." Therefore, the development of interventions to combat the negative cognitive effects of sleep deprivation is key. However, there are a limited number of therapeutics that are able to enhance cognition in the face of insufficient sleep. The identification of molecular pathways implicated in the deleterious effects of sleep deprivation on memory could potentially yield new targets for the development of more effective drugs.

Differential effects of modafinil on memory in naïve and memory-impaired rats

Modafinil is a wake-promoting drug and has been approved for the treatment of excessive daytime sleepiness in narcolepsy and obstructive sleep apnea. Modafinil was shown to improve learning and memory in rodents, and to reverse memory deficits induced by sleep deprivation or stress. However, depending on the memory paradigm used, modafinil might also impair memory. We aimed to investigate the effects of modafinil on memory consolidation and retrieval for object recognition and inhibitory avoidance in naïve adult rats. We also investigated whether acute or chronic administration of modafinil would reverse memory deficits induced by iron overload, a model of memory impairment related to neurodegenerative disorders. Adult naïve rats received modafinil (0.0, 0.75, 7.5 or 75 mg/kg) either immediately after training or 1 h prior to testing in object recognition or inhibitory avoidance. Iron-treated rats received modafinil immediately after training in object recognition. In order to investigate the effects of chronic modafinil, iron-treated rats received daily injections of modafinil for 17 days, and 24 h later they were trained in object recognition or inhibitory avoidance. Acute modafinil does not affect memory consolidation or retrieval in naive rats. A single injection of modafinil at the highest dose was able to recover recognition memory in iron-treated rats. Chronic modafinil completely recovered iron-induced recognition memory and emotional memory deficits. Additional preclinical and clinical studies are necessary in order to support the applicability of modafinil in recovering memory impairment associated with neurodegenerative disorders.

Inhibitory effects of modafinil on emotional memory in mice

Modafinil (MOD), a psychostimulant used to treat narcolepsy, excessive daytime sleepiness, and sleepiness due to obstructive sleep apnea, appears to promote a possible facilitatory effect on cognitive function. In the present study, we investigated the effects of the acute administration of MOD on the different steps of emotional memory formation and usage (acquisition, consolidation and retrieval) as well as the possible participation of the state-dependency phenomenon on the cognitive effects of this compound. Mice were acutely treated with 32, 64 or 128 mg/kg MOD before training or testing or immediately after training and were subjected to the plus-maze discriminative avoidance task. The results showed that although pre-training MOD administration did not exert any effects on learning, the doses of 32 or 64 mg/kg induced emotional memory deficits during testing. Still, the post-training acute administration of the higher doses of MOD (64 and 128 mg/kg) impaired associative memory consolidation. When the drug was administered pre-test, only the 32 mg/kg dose impaired the task retrieval. Importantly, the cognitive impairing effects induced by 32 mg/kg MOD were not related to the phenomenon of state-dependency. In all, our findings provide pre-clinical evidence of potential emotional memory amnesia induced by MOD. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

Modafinil treatment prevents REM sleep deprivation-induced brain function impairment by increasing MMP-9 expression

Previous work showed that sleep deprivation (SD) impairs hippocampal-dependent cognitive function and synaptic plasticity, and a novel wake-promoting agent modafinil prevents SD-induced memory impairment in rat. However, the mechanisms by which modafinil prevented REM-SD-induced impairment of brain function remain poorly understood. In the present study, rats were sleep-deprived by using the modified multiple platform method and brain function was detected. The results showed that modafinil treatment prevented REM-SD-induced impairment of cognitive function. Modafinil significantly reduced the number of errors compared to placebo and upregulated synapsin I expression in the dorsal hippocampal CA3 region. A synaptic plasticity-related gene, MMP-9 expression was also upregulated in modafinil-treated rats. Importantly, downregulation of MMP-9 expression by special siRNA decreased synapsin I protein levels and synapse numbers. Therefore, we demonstrated that modafinil increased cognition function and synaptic plasticity, at least in part by increasing MMP-9 expression in REM-SD rats.