Neuroethologic differences in sleep deprivation induced by the single- and multiple-platform methods

Electroacupuncture promotes the survival and synaptic plasticity of hippocampal neurons and improvement of sleep deprivation-induced spatial memory impairment

Aims

This study aimed to investigate whether electroacupuncture (EA) promotes the survival and synaptic plasticity of hippocampal neurons by activating brain‐derived neurotrophic factor (BDNF)/tyrosine receptor kinase (TrkB)/extracellular signal‐regulated kinase (Erk) signaling, thereby improving spatial memory deficits in rats under SD.

Methods

In vivo, Morris water maze (MWM) was used to detect the effect of EA on learning and memory, at the same time Western blotting (WB), immunofluorescence (IF), and transmission electron microscopy (TEM) were used to explore the plasticity of hippocampal neurons and synapses, and the expression of BDNF/TrkB/Erk signaling. In vitro, cultured hippocampal neurons were treated with exogenous BDNF and the TrkB inhibitor K252a to confirm the relationship between BDNF/TrkB/Erk signaling and synaptic plasticity.

Results

Our results showed that EA mitigated the loss of hippocampal neurons and synapses, stimulated hippocampal neurogenesis, and improved learning and memory of rats under SD accompanied by upregulation of BDNF and increased phosphorylation of TrkB and Erk. In cultured hippocampal neurons, exogenous BDNF enhanced the expression of synaptic proteins, the frequency of the postsynaptic currents, and the phosphorylation of TrkB and Erk; these effects were reversed by treatment with K252a.

Conclusions

Electroacupuncture alleviates SD‐induced spatial memory impairment by promoting hippocampal neurogenesis and synaptic plasticity via activation of BDNF/TrkB/Erk signaling, which provided evidence for EA as a therapeutic strategy for countering the adverse effects of SD on cognition.

A Tilted Axis: Maladaptive Inflammation and HPA Axis Dysfunction Contribute to Consequences of TBI

Each year approximately 1.7 million people sustain a traumatic brain injury (TBI) in the US alone. Associated with these head injuries is a high prevalence of neuropsychiatric symptoms including irritability, depression, and anxiety. Neuroinflammation, due in part to microglia, can worsen or even cause neuropsychiatric disorders after TBI. For example, mounting evidence demonstrates that microglia become “primed” or hyper-reactive with an exaggerated pro-inflammatory phenotype following multiple immune challenges. Microglial priming occurs after experimental TBI and correlates with the emergence of depressive-like behavior as well as cognitive dysfunction. Critically, immune challenges are various and include illness, aging, and stress. The collective influence of any combination of these immune challenges shapes the neuroimmune environment and the response to TBI. For example, stress reliably induces inflammation and could therefore be a gateway to altered neuropathology and behavioral decline following TBI. Given the increasing incidence of stress-related psychiatric disorders after TBI, the degree in which stress affects outcome is of particular interest. This review aims to highlight the role of the hypothalamic-pituitary-adrenal (HPA) axis as a key mediator of stress-immune pathway communication following TBI. We will first describe maladaptive neuroinflammation after TBI and how stress contributes to inflammation through both anti- and pro-inflammatory mechanisms. Clinical and experimental data describing HPA-axis dysfunction and consequences of altered stress responses after TBI will be discussed. Lastly, we will review common stress models used after TBI that could better elucidate the relationship between HPA axis dysfunction and maladaptive inflammation following TBI. Together, the studies described in this review suggest that HPA axis dysfunction after brain injury is prevalent and contributes to the dynamic nature of the neuroinflammatory response to brain injury. Experimental stressors that directly engage the HPA axis represent important areas for future research to better define the role of stress-immune pathways in mediating outcome following TBI.

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.

Neural Consequences of Chronic Short Sleep: Reversible or Lasting?

Approximately one-third of adolescents and adults in developed countries regularly experience insufficient sleep across the school and/or work week interspersed with weekend catch up sleep. This common practice of weekend recovery sleep reduces subjective sleepiness, yet recent studies demonstrate that one weekend of recovery sleep may not be sufficient in all persons to fully reverse all neurobehavioral impairments observed with chronic sleep loss, particularly vigilance. Moreover, recent studies in animal models demonstrate persistent injury to and loss of specific neuron types in response to chronic short sleep (CSS) with lasting effects on sleep/wake patterns. Here, we provide a comprehensive review of the effects of chronic sleep disruption on neurobehavioral performance and injury to neurons, astrocytes, microglia, and oligodendrocytes and discuss what is known and what is not yet established for reversibility of neural injury. Recent neurobehavioral findings in humans are integrated with animal model research examining long-term consequences of sleep loss on neurobehavioral performance, brain development, neurogenesis, neurodegeneration, and connectivity. While it is now clear that recovery of vigilance following short sleep requires longer than one weekend, less is known of the impact of CSS on cognitive function, mood, and brain health long term. From work performed in animal models, CSS in the young adult and short-term sleep loss in critical developmental windows can have lasting detrimental effects on neurobehavioral performance.

Short-term sleep deprivation stimulates hippocampal neurogenesis in rats following global cerebral ischemia/reperfusion

BACKGROUND

Sleep deprivation (SD) plays a complex role in central nervous system (CNS) diseases. Recent studies indicate that short-term SD can affect the extent of ischemic damage. The aim of this study was to investigate whether short-term SD could stimulate hippocampal neurogenesis in a rat model of global cerebral ischemia/reperfusion (GCIR).

METHODS

One hundred Sprague-Dawley rats were randomly divided into Sham, GCIR and short-term SD groups based on different durations of SD; the short-term SD group was randomly divided into three subgroups: the GCIR+6hSD*3d-treated, GCIR+12hSD-treated and GCIR+12hSD*3d-treated groups. The GCIR rat model was induced via the bilateral occlusion of the common carotid arteries and hemorrhagic hypotension. The rats were sleep-deprived starting at 48 h following GCIR. A Morris water maze test was used to assess learning and memory ability; cell proliferation and differentiation were analyzed via 5-bromodeoxyuridine (BrdU) and neuron-specific enolase (NSE), respectively, at 14 and 28 d; the expression of hippocampal BDNF was measured after 7 d.

RESULTS

The different durations of short-term SD designed in our experiment exhibited improvement in cognitive function as well as increased hippocampal BDNF expression. Additionally, the short-term SD groups also showed an increased number of BrdU- and BrdU/NSE-positive cells compared with the GCIR group. Of the three short-term SD groups, the GCIR+12hSD*3d-treated group experienced the most substantial beneficial effects.

CONCLUSIONS

Short-term SD, especially the GCIR+12hSD*3d-treated method, stimulates neurogenesis in the hippocampal dentate gyrus (DG) of rats that undergo GCIR, and BDNF may be an underlying mechanism in this process.

Evaluation of the effect of pentoxifylline on sleep-deprivation induced memory impairment

In this study, we examined the ability of Pentoxifylline (PTX) to prevent sleep deprivation induced memory impairment probably through decreasing oxidative stress. Sleep deprivation was chronically induced 8 h/day for 6 weeks in rats using modified multiple platform model. Concurrently, PTX (100 mg/kg) was administered to animals on daily basis. After 6 weeks of treatment, behavioral studies were conducted to test the spatial learning and memory using the Radial Arm Water Maze. Additionally, the hippocampus was dissected; and levels/activities of antioxidant defense biomarkers glutathione reduced (GSH), glutathione oxidized (GSSG), GSH/GSSG ratio, glutathione peroxidase (GPx), catalase, and superoxide dismutase (SOD), were assessed. The results show that chronic sleep deprivation impaired short- and long-term memories, which was prevented by chronic treatment with PTX. Additionally, PTX normalized sleep deprivation-induced reduction in the hippocampus GSH/GSSG ratio (P < 0.05), and activities of GPx, catalase, and SOD (P < 0.05). In conclusion, chronic sleep deprivation induces memory impairment, and treatment with PTX prevented this impairment probably through normalizing antioxidant mechanisms in the hippocampus.

Neurobiological consequences of sleep deprivation

Although the physiological function of sleep is not completely understood, it is well documented that it contributes significantly to the process of learning and memory. Ample evidence suggests that adequate sleep is essential for fostering connections among neuronal networks for memory consolidation in the hippocampus. Sleep deprivation studies are extremely valuable in understanding why we sleep and what are the consequences of sleep loss. Experimental sleep deprivation in animals allows us to gain insight into the mechanism of sleep at levels not possible to study in human subjects. Many useful approaches have been utilized to evaluate the effect of sleep loss on cognitive function, each with relative advantages and disadvantages. In this review we discuss sleep and the detrimental effects of sleep deprivation mostly in experimental animals. The negative effects of sleep deprivation on various aspects of brain function including learning and memory, synaptic plasticity and the state of cognition-related signaling molecules are discussed.

The neuroprotective effect of vitamin E on chronic sleep deprivation-induced memory impairment: the role of oxidative stress

Sleep deprivation induces oxidative stress and impairs learning and memory processes. Vitamin E, on the other hand, is a strong antioxidant that has neuroprotective effect on the brain. In this study, we examined the potential protective effect of chronic administration of vitamin E on chronic sleep deprivation-induced cognitive impairment. In addition, possible molecular targets for vitamin E effects on chronic sleep deprivation-induced cognitive impairment were determined. Sleep deprivation was induced in rats using modified multiple platform model. Vitamin E (100mg/kg) was administered to animals by oral gavage. Behavioral study was conducted to test the spatial learning and memory using the radial arm water maze (RAWM). In addition, the hippocampus was dissected out and antioxidant markers including glutathione (GSH), oxidized glutathione (GSSG) and GSH/GSSG, glutathione peroxidase (GPx), catalase, and superoxide dismutase (SOD) were assessed. The results of this project revealed that chronic sleep deprivation impaired both (short- and long-term) memories (P<0.05), while vitamin E treatment prevented such effect. Additionally, vitamin E normalized chronic sleep deprivation-induced reduction in the hippocampus GSH/GSSG ratio, and activity of catalase, SOD, and GPx. In conclusion, sleep deprivation induces memory impairment, and treatment with vitamin E prevented this impairment probably through its antioxidant action in the hippocampus.

Age-related changes during a paradigm of chronic sleep restriction

Fragmented and restricted sleep is a common problem for the human elderly. There is evidence that aging impairs sleep in animals as well. After sleep deprivation, older animals have less sleep rebound. Despite increasing complaints of reduced time for sleep in contemporary society, few studies have examined chronic sleep restriction protocols in animals. Therefore, the aim of the present study was to evaluate the effects of chronic sleep restriction on the sleep patterns of aged rats. Using the single platform method, 22-month-old male rats were submitted to 18 h of sleep restriction followed by 6 h of total sleep opportunity. The sleep-wake cycles of these rats were recorded for 6h/day throughout the 12-day procedure. The results showed that total sleep time and NREM sleep were reduced during the 12-day sleep restriction period. However, rebound REM sleep was only significant on day 6. A negative rebound was also seen, particularly during the last days of the chronic sleep restriction period. Furthermore, sleep latency and mean wake bout length progressively increased during the protocol. These findings indicate that older rats have an inability to restore their sleep patterns during extended sleep deprivation.

Comparison of the sleep pattern throughout a protocol of chronic sleep restriction induced by two methods of paradoxical sleep deprivation

The purpose of the present study was to evaluate the sleep homeostasis of rats submitted to a protocol of chronic sleep restriction by two methods and to evaluate the sleep characteristics during the recovery period. The sleep restriction protocol was accomplished by sleep depriving rats for 18 h everyday for 21 days, using the single platform method (SPM) or the modified multiple platform method (MMPM) of paradoxical sleep (PS) deprivation. Rats were allowed to sleep for 6 h (from 10:00 to 16:00; starting 3 h after lights on) in their individual home-cages, during which their sleep was recorded. At the end of the sleep restriction protocol, rats were recorded in their home-cages for 4 days, where they could sleep freely. Both methods used to induce chronic sleep restriction were effective, in sofar as they resulted in augmented sleep time during the 6h-sleep period, with very few bouts of wakening. Although comparison between the methods did not reveal differences, sleep restriction under MMPM produced a more consistent daily rebound, mainly of paradoxical sleep, with longer episodes. These results showed distinct sleep recovery patterns, suggesting a possible role of the waking experiences (i.e. immobilization stress, social interaction) acting on sleep consolidation.

Correlation between the fighting rates of REM sleep-deprived rats and susceptibility to the 'wild running' of audiogenic seizures

Sleep-deprived rats exhibit defensive fighting as well as explosive flights very similar to the wild-running of audiogenic seizures. In order to determine why sleep deprivation is a common factor that facilitates both panic and convulsive manifestations, the present study was undertaken to investigate whether rats that display sleep deprivation-induced fighting (SDIF) are the same as those that are susceptible to audiogenic wild-running (WR). Twenty-eight male adult Wistar rats were divided into two groups assigned to two experimental schemes. In the first, 18 subjects were submitted to REM-sleep deprivation for 5 days and had their SDIF evaluated in social grouping. After 1 week for recovery, their susceptibility to WR was tested in an acoustic stimulation trial (104 dB, 200 Hz, 60 s). Rats that did not present WR received a lactate infusion and were tested again by acoustic stimulation 40 min later. In the second experimental scheme, 10 subjects were initially evaluated for WR susceptibility and the number of SDIF was recorded in social grouping after 1 week. Three categories of WR-susceptibility were determined: WR-sensitive rats, intermediate WR-sensitive rats and WR-insensitive rats. The number of SDIF in each category was significantly different and there was a high positive correlation (r=0.89; Spearman test) between the number of SDIF and the level of WR-susceptibility. We conclude that the reasons why sleep deprivation exerts facilitatory effects on both panic and convulsive manifestations are due to overlappings of neural pathways responsible for both behavioral patterns and for the property of sleep deprivation to increase neuronal excitability.

Fighting by sleep-deprived rats as a possible manifestation of panic: effects of sodium lactate

Increased fighting is an effect of desynchronized sleep deprivation (DSD) in rats, and recently this behavior has been suggested to be spontaneous panic and equivalent to panic disorder. In the present study we tested this hypothesis by evaluating the effect of sodium lactate on this aggressiveness, because this substance is recognized to induce spontaneous panic attacks in patients. A total of 186 male albino Wistar rats, 250-350 g, 90-120 days of age, were submitted to DSD (multiple platform method) for 0, 4, or 5 days. At the end of the deprivation period the rats were divided into subgroups respectively injected intraperitoneally with 1.86, 2.98 and 3.72 g/kg of 1 M sodium lactate, or 1.86 and 3.72 g/kg of 2 M sodium lactate. The control animals were submitted to the same procedures but received equivalent injections of sodium chloride. Regardless of DSD time, sleep-deprived animals that received sodium lactate presented a significantly higher mean number of fights (0.13 +/- 0.02 fights/min) and a longer mean time spent in confrontation (2.43 +/- 0.66 s/min) than the controls (0.01 +/- 0.006 fights/min and 0.12 +/- 0.07 s/min, respectively; P<0.01, Student t-test). For the sodium lactate group, concentration of the solution and time of deprivation increased the number of fights, with the mean number of fights and mean duration of fighting episodes being greater with the 2.98 g/kg dose using 1 M lactate concentration. These results support the hypothesis that fighting induced by DSD is probably a spontaneous panic manifestation. However, additional investigations are necessary in order to accept this as a promising animal model for studies on panic disorder.