Sleep deprivation decreases neuronal excitability and responsiveness in rats both in vivo and ex vivo

The Endogenous Pain Modulatory System as a Healing Mechanism: A Proposal on How to Measure and Modulate It

BACKGROUND

Chronic pain is highly burdening and multifactorial in etiology. The endogenous-pain-healing system restores body tissue to a non-painful state after an injury leading to pain, and its disruption could represent a relevant mechanism, especially for nursing interventions.

AIM

To review the literature and summarize the results that support this hypothesis.

METHODS

We hypothesized that the mechanism behind this system mainly depends on the endogenous pain modulatory system (EPMS), which is responsible for inhibiting pain after tissue healing is complete and facilitating it when tissue damage is still present. Different biomarkers can quantify EPMS functioning. We reviewed the literature and included relevant information regarding this hypothesis.

RESULTS

First, conditioned pain modulation (CPM) measures pain inhibition and is a possible predictor for pain chronification. Second, motor cortex excitability measures the cortical control of the EPMS, which can be assessed through transcranial magnetic stimulation (using intracortical inhibition) or electroencephalography. Modifiable factors disrupt its functioning, such as sleep deprivation, medication overuse, and mental health status, but could be protective, such as exercise, certain medications, mind-body techniques, and non-invasive neuromodulation therapies. The acquisition of neurophysiological knowledge of how the chronicity of pain occurs and the EPMS involvement in this process may allow for better management of these patients.

CONCLUSIONS

We raised the hypothesis that the impairment of the EPMS (altered cortical excitability and descendent pain modulation pathways) seems to be related to the disruption of the pain healing process and its chronicity. Further longitudinal studies evaluating the relationship between these biomarkers and chronic pain development are necessary.

Sleep- and sleep deprivation-related changes of vertex auditory evoked potentials during the estrus cycle in female rats

The estrus cycle in female rodents has been shown to affect a variety of physiological functions. However, little is known about its presumably thorough effect on auditory processing during the sleep-wake cycle and sleep deprivation. Vertex auditory evoked potentials (vAEPs) were evoked by single click tone stimulation and recorded during different stages of the estrus cycle and sleep deprivation performed in metestrus and proestrus in female rats. vAEPs showed a strong sleep-dependency, with the largest amplitudes present during slow wave sleep while the smallest ones during wakefulness. Higher amplitudes and longer latencies were seen in the light phase during all vigilance stages. The largest amplitudes were found during proestrus (light phase) while the shortest latencies were seen during estrus (dark phase) compared to the 2nd day diestrus baseline. High-amplitude responses without latency changes were also seen during metestrus with increased homeostatic sleep drive. More intense and faster processing of auditory information during proestrus and estrus suggesting a more effective perception of relevant environmental cues presumably in preparation for sexual receptivity. A 4-h sleep deprivation resulted in more pronounced sleep recovery in metestrus compared to proestrus without difference in delta power replacement suggesting a better tolerance of sleep deprivation in proestrus. Sleep deprivation decreased neuronal excitability and responsiveness in a similar manner both during metestrus and proestrus, suggesting that the negative consequences of sleep deprivation on auditory processing may have a limited correlation with the estrus cycle stage.

Making migraine easier to stomach: the role of the gut-brain-immune axis in headache disorders

BACKGROUND AND PURPOSE

Headache disorders place a significant burden on the healthcare system, being the leading cause of disability in those under 50 years. Novel studies have interrogated the relationship between headache disorders and gastrointestinal dysfunction, suggesting a link between the gut-brain-immune (GBI) axis and headache pathogenesis. Although the exact mechanisms driving the complex relationship between the GBI axis and headache disorders remain unclear, there is a growing appreciation that a healthy and diverse microbiome is necessary for optimal brain health.

METHODS

A literature search was performed through multiple reputable databases in search of Q1 journals within the field of headache disorders and gut microbiome research and were critically and appropriately evaluated to investigate and explore the following; the role of the GBI axis in dietary triggers of headache disorders and the evidence indicating that diet can be used to alleviate headache severity and frequency. The relationship between the GBI axis and post-traumatic headache is then synthesized. Finally, the scarcity of literature regarding paediatric headache disorders and the role that the GBI axis plays in mediating the relationship between sex hormones and headache disorders are highlighted.

CONCLUSIONS

There is potential for novel therapeutic targets for headache disorders if understanding of the GBI axis in their aetiology, pathogenesis and recovery is increased.

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.

Ketamine affects homeostatic sleep regulation in the absence of the circadian sleep-regulating component in freely moving rats

Pharmacological effects of ketamine may affect homeostatic sleep regulation via slow wave related mechanisms. In the present study effects of ketamine applied at anesthetic dose (80 mg/kg) were tested on neocortical electric activity for 24 h in freely moving rats. Ketamine effects were compared to changes during control (saline) injections and after 6 h gentle handling sleep deprivation (SD). As circadian factors may mask drug effects, an illumination protocol consisting of short light-dark cycles was applied. Ketamine application induced a short hypnotic stage with characteristic slow cortical rhythm followed by a long-lasting hyperactive waking resulting pharmacological SD. Coherence analysis indicated an increased level of local synchronization in broad local field potential frequency ranges during hyperactive waking but not during natural- or SD-evoked waking. Both slow wave sleep and rapid eye movement sleep were replaced after the termination of the ketamine effect. Our results show that both ketamine-induced hypnotic state and hyperactive waking can induce homeostatic sleep pressure with comparable intensity as 6 h SD, but ketamine-induced waking was different compared to the SD-evoked one. Both types of waking stages were different compared to spontaneous waking but all three types of wakefulness can engage the homeostatic sleep regulating machinery to generate sleep pressure dissipated by subsequent sleep. Current-source density analysis of the slow waves showed that cortical transmembrane currents were stronger during ketamine-induced hypnotic stage compared to both sleep replacement after SD and ketamine application, but intracortical activation patterns showed only quantitative differences. These findings may hold some translational value for human medical ketamine applications aiming the treatment of depression-associated sleep problems, which can be alleviated by the homeostatic sleep effect of the drug without the need for an intact circadian regulation.

Relationship between sleep quality, mood state, and performance of elite air-rifle shooters

Background

To evaluate the impact of pre-competition sleep quality on the mood and performance of elite air-rifle shooters.

Methods

Elite shooters who participated in an air-rifle shooting-competition from April 2019 to October 2019 were evaluated using actigraphy, including Total Sleep Time (TST), Sleep Efficiency (SE), Sleep Latency (SL), Wake-time after Sleep Onset (WASO). Sleep quality was assessed by Pittsburgh sleep quality index (PSQI) and Profile of Mood State (POMS). Mood state was assessed by Competitive State Anxiety Inventory-2.

Results

Study included 23 shooters, of them 13 male and 10 female with the mean age 23.11 ± 4.82 years. The average time to fall asleep was 20.6 ± 14.9 min, TST was 7.0 ± 0.8 h and SE was 85.9 ± 5.3%. Average sleep quality was 5.2 ± 2.2 and tended to decrease as the competition progressed. Pre-competition sleep time in female athletes was significantly higher compared to the competition day (P = 0.05). Pre-competition SL was significantly longer in women than in men (P = 0.021). During training and pre-competition, the tension, fatigue, depression, and emotional disturbance were significantly lower in athletes with good sleep quality. Athletes with good sleep quality had significantly more energy. The PSQI total score positively correlated with cognitive anxiety (r = 0.471, P < 0.01), and somatic anxiety (r = 0.585, P < 0.01), and negatively correlated with energy (− 0.504, P < 0.01) and self-confidence scores (r = − 0.523, P < 0.01).

Conclusion

Poor sleep quality negatively impacted the mood of athletes; however, sleep indices and competition performance of athletes during competitions were not significantly correlated.

Flavonoid-Like Components of Peanut Stem and Leaf Extract Promote Sleep by Decreasing Neuronal Excitability

SCOPE

Peanut stem and leaf (PSL), a traditional Chinese medicine, is widely used as a dietary supplement to improve sleep quality; however, the underlying mechanism is unclear. Here, the study aims to determine whether active compounds in PSL extract exert their effects by mediating neuronal excitability.

METHODS AND RESULTS

Aqueous PSL extract (500 mg kg^-1 BW) increases the duration of total sleep (TS), slow wave sleep (SWS) and rapid eye movement sleep (REMS) in BALB/c mice after 7 and 14 continuous days of intragastric administration. Two PSL extract components with flavonoid-like structures: 4',7-di-O-methylnaringenin (DMN, 61 µg kg^-1 BW) and 2'-O-methylisoliquiritigenin (MIL, 12 µg kg^-1 BW), show similar effects on sleep in BALB/c mice. Moreover, incubation with DMN (50 µM) and MIL (50 µM) acutely reduces voltage-gated sodium and potassium currents and suppresses the firing of evoked action potential in mouse cortical neurons, indicating the inhibition on neuronal excitability. Meanwhile, RNA-seq analysis predicts the potential regulation of voltage-gated channels, which is according with the molecular docking simulation that both MIL and DMN can bind to voltage gated sodium channels 1.2 (Na_v 1.2).

CONCLUSIONS

DMN and MIL are the active ingredients of PSL that improve sleep quality, suggesting that PSL promotes sleep by regulating the excitability of neurons.

Integrated metabolomics and proteomics analysis reveals energy metabolism disorders in the livers of sleep-deprived mice

Sleep deprivation (SD) has been linked to impaired mental and physical health, obesity, and various diseases. However, the molecular mechanism underlying the effects of SD in the liver is still unclear. To investigate the metabolome and proteome alterations in the liver, an in vivo model of SD was established based on automated random motion platform techniques by applying a strategy of 10 consecutive days of 20 h of sleep deprivation +4 h of resting. The liver's altered metabolites and proteins were detected by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and data analyses were performed with MetaboAnalyst 5.0. This study found 15 differential metabolites, including 12 upregulated- metabolites and 3 downregulated- metabolites. A total of 493 proteins were differentially regulated, including 377 upregulated- proteins and 116 downregulated- proteins. The glutathione metabolism, fructose and mannose metabolism, and pyruvate metabolism pathways had significant effects on the sleep-deprived mouse livers. These three active pathways cause energy metabolism disorder and may induce obesity. In conclusion, this study demonstrates that SD could change the metabolism of glucose, and specific fatty acids, amino acids, and critical enzymes in the liver, providing a reference for the health effects of insufficient sleep. SIGNIFICANCE STATEMENT: So far, little is known about the changes in metabolites and proteins in the liver of individuals who suffer from SD. Metabolites and proteins in serum, urine and hypothalamus do not entirely reflect the effects of sleep deprivation on the whole body. In addition, many SD-induced models used the multiplatform water environment method, which causes mice to fall into the water frequently. Under this condition, the physical exertion of mice is extremely high, and it is not suitable for long-term sleep deprivation. The SD induction process has caused some influence on the model. Finally, few studies have elucidated the imbalance of energy metabolism caused by SD to induce obesity from the molecular mechanism. This study used a rotary table deprivation apparatus to trigger SD. This method will not cause excessive consumption and stimulation of mice. Furthermore, this study analyzed the metabolic and proteomic changes in the liver and enriched the range and means of metabolic and proteomic changes in sleep deprived mice. Finally, this research provides reference for elucidating the molecular mechanism of sleep deprivation causing energy metabolism disorders in the liver of mice.

Homeostatic sleep regulation in the absence of the circadian sleep-regulating component: effect of short light-dark cycles on sleep-wake stages and slow waves

BACKGROUND

Aside from the homeostatic and circadian components, light has itself an important, direct as well as indirect role in sleep regulation. Light exerts indirect sleep effect by modulating the circadian rhythms. Exposure to short light-dark cycle (LD 1:1, 1:1 h light - dark) eliminates the circadian sleep regulatory component but direct sleep effect of light could prevail. The aim of the present study was to examine the interaction between the light and the homeostatic influences regarding sleep regulation in a rat model.

METHODS

Spontaneous sleep-wake and homeostatic sleep regulation by sleep deprivation (SD) and analysis of slow waves (SW) were examined in Wistar rats exposed to LD1:1 condition using LD12:12 regime as control.

RESULTS

Slow wave sleep (SWS) and REM sleep were both enhanced, while wakefulness (W) was attenuated in LD1:1. SWS recovery after 6-h total SD was more intense in LD1:1 compared to LD12:12 and SWS compensation was augmented in the bright hours. Delta power increment during recovery was caused by the increase of SW number in both cases. More SW was seen during baseline in the second half of the day in LD1:1 and after SD compared to the LD12:12. Increase of SW number was greater in the bright hours compared to the dark ones after SD in LD1:1. Lights ON evoked immediate increase in W and decrease in both SWS and REM sleep during baseline LD1:1 condition, while these changes ceased after SD. Moreover, the initial decrease seen in SWS after lights ON, turned to an increase in the next 6-min bin and this increase was stronger after SD. These alterations were caused by the change of the epoch number in W, but not in case of SWS or REM sleep. Lights OFF did not alter sleep-wake times immediately, except W, which was increased by lights OFF after SD.

CONCLUSIONS

Present results show the complex interaction between light and homeostatic sleep regulation in the absence of the circadian component and indicate the decoupling of SW from the homeostatic sleep drive in LD1:1 lighting condition.

Sleep deprivation and its association with diseases- a review

Sleep deprivation, a consequence of multiple health problems or a cause of many major health risks, is a significant public health concern in this era. In the recent years, numerous reports have been added to the literature to provide explanation and to answer previously unanswered questions on this important topic but comprehensive updates and reviews in this aspect remain scarce. The present study identified 135 papers that investigated the association between sleep deprivation and health risks, including cardiovascular, respiratory, neurological, gastrointestinal, immunology, dermatology, endocrine, and reproductive health. In this review, we aimed to provide insight into the association between sleep deprivation and the development of diseases. We reviewed the latest updates available in the literature and particular attention was paid to reports that detailed all possible causal relationships involving both extrinsic and intrinsic factors that may be relevant to this topic. Various mechanisms by which sleep deprivation may affect health were presented and discussed, and this review hopes to serve as a platform for ideas generation for future research.

Complete sleep and local field potential analysis regarding estrus cycle, pregnancy, postpartum and post-weaning periods and homeostatic sleep regulation in female rats

Sleep and local field potential (LFP) characteristics were addressed during the reproductive cycle in female rats using long-term (60-70 days) recordings. Changes in homeostatic sleep regulation was tested by sleep deprivation (SDep). The effect of mother-pup separation on sleep was also investigated during the postpartum (PP) period. First half of the pregnancy and early PP period showed increased wakefulness (W) and higher arousal indicated by elevated beta and gamma activity. Slow wave sleep (SWS) recovery was suppressed while REM sleep replacement was complete after SDep in the PP period. Pup separation decreased maternal W during early-, but increased during middle PP while did not affect during late PP. More W, less SWS, higher light phase beta activity but lower gamma activity was seen during the post-weaning estrus cycle compared to the virgin one. Maternal sleep can be governed by the fetuses/pups needs and their presence, which elevate W of mothers. Complete REM sleep- and incomplete SWS replacement after SDep in the PP period may reflect the necessity of maternal REM sleep for the offspring while SWS increase may compete with W essential for maternal care. Maternal experience may cause sleep and LFP changes in the post-weaning estrus cycle.

Changes in Physiological and Pathological Behaviours Produced by Deep Microelectrode Implantation Surgery in Rats: A Temporal Analysis

Physiological behaviours such as the sleep-wake cycle and exploratory behaviours are important parameters in intact and sham-operated animals and are usually thought to be unaffected by experimental protocols in which neurosurgery is performed. However, there is insufficient evidence in the literature on the behavioural and cognitive effects observed after deep microelectrode implantation surgery in animal models of neurological diseases. Similarly, in studies that utilize animal models of neurological diseases, the impact of surgery on the pathological phenomena being studied is often minimized. Based on these considerations, we performed a temporal analysis of the effects of deep microelectrode implantation surgery in the hippocampus of rats on quiet wakefulness, sleep, and exploratory activity and the pathological behaviours such as convulsive seizures according to the Racine scale. Male Wistar rats (210-300 g) were used and grouped in sham and epileptic animals. Single doses of pilocarpine hydrochloride (2.4 mg/2 μl; i.c.v.) were administered to the animals to generate spontaneous and recurrent seizures. Deep microelectrode implantation surgeries in both groups and analysis of Fast ripples were performed. Physiological and pathological behaviours were recorded through direct video monitoring of animals (24/7). Our principal findings showed that in epileptic animals, one of the main behaviours affected by surgery is sleep; as a consequence of this behavioural change, a decrease in exploratory activity was also found as well as the mean time spent daily in seizures of scale 4 and the number of seizure events of scales 4 and 5 was increased after surgery. No significant correlations between the occurrence of FR and seizure events of scale 4 (rho 0.63, p value 0.25) or 5 (rho -0.7, p value 0.18) were observed. In conclusion, microelectrode implantation surgeries modified some physiological and pathological behaviours; therefore, it is important to consider this fact when it is working with animal models.

Genetic variant rs3750625 in the 3'UTR of ADRA2A affects the sleep quality of patients in the ICU by promoting miR‑34a binding to ADRA2A

Poor sleep is very common in patients in the ICU and hence, sleep quality is considered an important aspect of intensive care; however, the underlying mechanisms of poor sleep in patients in the ICU remain unknown. In this study, we aimed to explore the role of rs3750625, which is located in the 3'UTR of adrenoceptor alpha 2A (ADRA2A), in sleep quality. For this purpose, luciferase assay was conducted to investigate the association between miR‑34a and ADRA2A, and the effect of rs3750625 on the binding affinity between miR‑34a and ADRA2A was examined. RT‑qPCR and western blot analysis were carried out to examine the regulatory association between miR‑34a and ADRA2A. The differences in sleep time and efficiency were compared between groups carrying the AC and CC genotypes of rs3750625, respectively. According to the results from an online search, miR‑34a could directly bind to the 3'UTR of ADRA2A, and such binding was confirmed by the observation that miR‑34a inhibited the luciferase activity of major or minor ADRA2A 3'UTR in a dose‑dependent manner in HCN‑1A and U251 cells. In addition, the ADRA2A protein and mRNA levels in the HCN‑1A and U251 cells were evidently decreased following transfection with miR‑34a precursors. Notably, patients in the AC group exhibited a similar level of miR‑34a mRNA expression compared with patients in the CC group; however, the ADRA2A mRNA and protein levels in the CC group were significantly increased in comparison with those in the AC group. In addition, the sleep time and sleep efficiency in the CC group were much higher than those in the AC group. Furthermore, the mean arterial pressure (MAP) values in both the AC and CC groups remained stable from 22:00 to 08:00, and the respiratory rates in both groups were quite similar. However, the heart rate of patients in the CC group was much lower than that of patients in the AC group. On the whole, the findings of this study suggest that the genetic variant rs3750625 in the 3'UTR of ADRA2A affects the sleep quality of patients in the ICU by promoting the binding of miR‑34a to ADRA2A, and hence it may serve as a novel biomarker for the prediction of the sleep quality of patients in the ICU.

Analysis of Propagation of Slow Rhythmic Activity Induced in Ex Vivo Rat Brain Slices

Slow wave oscillation is a synchronous oscillatory mechanism that is a characteristic wave type of the cerebral cortex during physiological deep sleep or anesthesia. It may play an important role in cortical analysis of sensory input. Our goal was (1) to develop optimal conditions for the induction of this slow rhythmic activity in adult rat cortical slices, (2) to identify connections through which the activity propagates between coupled cortical regions, and (3) to study the pattern of horizontal and vertical flow of activity developed spontaneously in cortical slices. Experiments were performed on intact or differently incised rat cortical slices. According to our results, spontaneous cortical activity develops reliably in slightly modified artificial cerebrospinal fluid, first in the entorhinal cortical region of horizontally cut slices and then it spreads directly to the perirhinal (PRh) cortex. The activity readily generated in layer 2/3 of the entorhinal cortex then quickly spreads vertically to upper layer 2-3 in the same area and to the neighboring regions, that is, to the PRh cortex. Synchronization of activity in neighboring cortical areas occurs through both callosal connections and layer 2-3 intrinsic network, which are important in the propagation of spontaneous, inherent cortical slow wave activity.