Neural circuitry of stress-induced insomnia in rats

Decreased Cortical Sulcus Depth in Parkinson's Disease with Excessive Daytime Sleepiness

INTRODUCTION

Excessive daytime sleepiness (EDS), a prevalent non-motor symptom in Parkinson's disease (PD), significantly impacts the quality of life for PD patients and elevates the risks of injury. Our study is to investigate the altered cortical surface morphology characteristics in PD patients with EDS (PD-EDS).

METHODS

Clinical data and magnetic resonance imaging were obtained from the Parkinson's Progression Marker Initiative database, comprising 36 PD-EDS and 98 PD patients without EDS (PD-nEDS). The computational anatomy toolbox was utilized to derive sulcus depth (SD) and deep grey matter (GM) nuclei volumes.

RESULTS

PD-EDS patients exhibited significantly decreased SD values in the right caudal middle frontal gyrus, pars opercularis, and superior temporal cortex relative to PD-nEDS patients. However, no significant differences in deep GM nuclei volumes were identified. Receiver operating characteristic (ROC) curve analyses further revealed that these cortical SD values could potentially serve as a screening index for distinguishing PD-EDS from PD-nEDS. Additionally, although PD-EDS patients had a longer disease duration and poorer performance in motor function and depression compared to PD-nEDS patients, these factors were included as covariates in the neuroimaging analyses.

CONCLUSION

Our study findings demonstrated that decreased cortical SD values might induce sleep-wake state instability and contribute to the pathophysiological mechanisms of EDS in early-stage PD.

Sleep Fragmentation Modulates the Neurophysiological Correlates of Cognitive Fatigue

Cognitive fatigue (CF) is a critical factor affecting performance and well-being. It can be altered in suboptimal sleep quality conditions, e.g., in patients suffering from obstructive sleep apnea who experience both intermittent hypoxia and sleep fragmentation (SF). Understanding the neurophysiological basis of SF in healthy individuals can provide insights to improve cognitive functioning in disrupted sleep conditions. In this electroencephalographical (EEG) study, we investigated in 16 healthy young participants the impact of experimentally induced SF on the neurophysiological correlates of CF measured before, during, and after practice on the TloadDback, a working memory task tailored to each individual's maximal cognitive resources. The participants spent three consecutive nights in the laboratory two times, once in an undisrupted sleep (UdS) condition and once in an SF condition induced by non-awakening auditory stimulations, counterbalanced and performed the TloadDback task both in a high (HCL) and a low (LCL) cognitive load condition. EEG activity was recorded during wakefulness in the 5 min resting state immediately before and after, as well as during the 16 min of the TloadDback task practice. In the high cognitive load under a sleep-fragmentation (HCL/SF) condition, high beta power increased during the TloadDback, indicating heightened cognitive effort, and the beta and alpha power increased in the post- vs. pre-task resting state, suggesting a relaxation rebound. In the low cognitive load/undisturbed sleep (LCL/UdS) condition, low beta activity increased, suggesting a relaxed focus, as well as mid beta activity associated with active thinking. These findings highlight the dynamic impact of SF on the neurophysiological correlates of CF and underscore the importance of sleep quality and continuity to maintain optimal cognitive functioning.

The abnormalities of brain function in females with primary insomnia: a resting-state functional magnetic resonance imaging study

Background

The neuropathologic mechanism of primary insomnia (PI) of females remains unclear. This study aims to investigate the features of amplitude of low-frequency fluctuations (ALFF) and regional homogeneity (ReHo) in females with PI using functional magnetic resonance imaging (fMRI), and then explore the abnormalities of functional connectivity (FC).

Materials and methods

A total of 39 female PI patients and 31 female healthy controls (HC) were enrolled in the study. The sleep condition was assessed using the Pittsburgh Sleep Quality Index (PSQI), and Insomnia Severity Index (ISI), and their depressive symptom was evaluated using the Hamilton Depression Scale (HAMD-24). The rs-fMRI was once conducted for every subject. ReHo, ALFF, and ROI-based FC were used to analyze the changes of brain function.

Results

ALFF values were increased in the Cerebelum_4_5_L, as well as decreased ALFF in the bilateral Frontal_Sup_Medial (SFGmed), Angular_L (ANG.L), Parietal_Inf_R (IPL.R), SupraMarginal_R (SMG.R), and Postcentral_R (PoCG.R). ReHo values were increased in the Temporal_Pole_Mid_R (TPOsup.R), as well as decreased ReHo in the Insula_R (INS.R), Frontal_Inf_Oper_R (ORBinf.R), Putamen_R (PUT.R), Rolandic_Oper_R (ROL.R), bilateral Cingulum_Post (PCG), bilateral Frontal_Sup_Medial (SFGmed), bilateral anterior cingulate and paracingulate gyri (ACG), and the bilateral precuneus (PCUN). Across the entire brain, there was a decline in the FC between Angular_R and Frontal_Sup_Medial_L.

Conclusion

Alterations in brain regions of female patients with PI involved multiple functional networks, including the default mode network, the salience network, the central executive network, and the limbic network. Reduced coordination between functional networks may be an important mechanism for insomnia and may lead to reduced cognitive function and decision-making ability.

Cannabidiol Exerts Sedative and Hypnotic Effects in Normal and Insomnia Model Mice Through Activation of 5-HT1A Receptor

Cannabis sativa has been used for improving sleep for long history. Cannabidiol (CBD) has drown much attention as a non-addictive psychoactive component in Cannabis sativa extract. However, the effects of CBD on sleep architecture and it's acting mechanism remains unclear. In the present study, we evaluated the sedative-hypnotic effect of cannabidiol (CBD), assessed the effects of CBD on sleep using a wireless physiological telemetry system. We further explored the therapeutic effects of CBD using 4-chloro-dl-phenylalanine (PCPA) induced insomnia model and changes in sleep latency, sleep duration and intestinal flora were evaluated. CBD shortened sleep latency and increases sleep duration in both normal and insomnia mice, and those effects were blocked by 5-HT1A receptor antagonist WAY100635. We determined that CBD increases 5-HT1A receptors expression and 5-HT content in the hypothalamus of PCPA-pretreated mice and affects tryptophan metabolism in the intestinal flora. These results showed that activation of 5-HT1A receptors is one of the potential mechanisms underlying the sedative-hypnotic effect of CBD. This study validated the effects of CBD on sleep and evaluated its potential therapeutic effects on insomnia.

A midbrain GABAergic circuit constrains wakefulness in a mouse model of stress

Enhancement of wakefulness is a prerequisite for adaptive behaviors to cope with acute stress, but hyperarousal is associated with impaired behavioral performance. Although the neural circuitries promoting wakefulness in acute stress conditions have been extensively identified, less is known about the circuit mechanisms constraining wakefulness to prevent hyperarousal. Here, we found that chemogenetic or optogenetic activation of GAD2-positive GABAergic neurons in the midbrain dorsal raphe nucleus (DRNGAD2) decreased wakefulness, while inhibition or ablation of these neurons produced an increase in wakefulness along with hyperactivity. Surprisingly, DRNGAD2 neurons were paradoxically wakefulness-active and were further activated by acute stress. Bidirectional manipulations revealed that DRNGAD2 neurons constrained the increase of wakefulness and arousal level in a mouse model of stress. Circuit-specific investigations demonstrated that DRNGAD2 neurons constrained wakefulness via inhibition of the wakefulness-promoting paraventricular thalamus. Therefore, the present study identified a wakefulness-constraining role DRNGAD2 neurons in acute stress conditions.

Impact of single-trial avoidance learning on subsequent sleep

Both non-rapid eye movement (NonREM) sleep and rapid eye movement (REM) sleep, as well as sleep spindle and ripple oscillations, are important for memory formation. Through cortical EEG recordings of prefrontal cortex and hippocampus during and after an inhibitory avoidance task, we analysed the dynamic changes in the amounts of sleep, spindle and ripple oscillations related to memory formation. The total amount of NonREM sleep was reduced during the first hour after learning. Moreover, significant decrease of the total spindle and ripple counts was observed at the first hour after learning as well. In addition, foot shock alone, with no associated learning, produced little effect on the dynamics of sleep oscillations, indicating that the learning experience is necessary for these changes to occur.

Sleep: How stress keeps you up at night

Stress disrupts sleep, but the neural mechanisms underlying this relationship remain unclear. Novel findings in mice reveal a hypothalamic circuit that fragments sleep and promotes arousal after stress.

Regulation of stress-induced sleep fragmentation by preoptic glutamatergic neurons

Sleep disturbances are detrimental to our behavioral and emotional well-being. Stressful events disrupt sleep, in particular by inducing brief awakenings (microarousals, MAs), resulting in sleep fragmentation. The preoptic area of the hypothalamus (POA) is crucial for sleep control. However, how POA neurons contribute to the regulation of MAs and thereby impact sleep quality is unknown. Using fiber photometry in mice, we examine the activity of genetically defined POA subpopulations during sleep. We find that POA glutamatergic neurons are rhythmically activated in synchrony with an infraslow rhythm in the spindle band of the electroencephalogram during non-rapid eye movement sleep (NREMs) and are transiently activated during MAs. Optogenetic stimulation of these neurons promotes MAs and wakefulness. Exposure to acute social defeat stress fragments NREMs and significantly increases the number of transients in the calcium activity of POA glutamatergic neurons during NREMs. By reducing MAs, optogenetic inhibition during spontaneous sleep and after stress consolidates NREMs. Monosynaptically restricted rabies tracing reveals that POA glutamatergic neurons are innervated by brain regions regulating stress and sleep. In particular, presynaptic glutamatergic neurons in the lateral hypothalamus become activated after stress, and stimulating their projections to the POA promotes MAs and wakefulness. Our findings uncover a novel circuit mechanism by which POA excitatory neurons regulate sleep quality after stress.

Sex differences in body temperature and neural power spectra in response to repeated restraint stress

Repeated stress is associated with an increased risk of developing psychiatric illnesses such as post-traumatic stress disorder (PTSD), which is more common in women, yet the neurobiology behind this sex difference is unknown. Habituation to repeated stress is impaired in PTSD, and recent preclinical studies have shown that female rats do not habituate as fully as male rats to repeated stress, which leads to impairments in cognition and sleep. Further research should examine sex differences after repeated stress in other relevant measures, such as body temperature and neural activity. In this study, we analyzed core body temperature and EEG power spectra in adult male and female rats during restraint, as well as during sleep transitions following stress. We found that core body temperature of male rats habituated to repeated restraint more fully than female rats. Additionally, we found that females had a higher average beta band power than males on both days of restraint, indicating higher levels of arousal. Lastly, we observed that females had lower delta band power than males during sleep transitions on Day 1 of restraint, however, females demonstrated higher delta band power than males by Day 5 of restraint. This suggests that it may take females longer to initiate sleep recovery compared with males. These findings indicate that there are differences in the physiological and neural processes of males and females after repeated stress. Understanding the way that the stress response is regulated in both sexes can provide insight into individualized treatment for stress-related disorders.

Association of Sleep Characteristics with Tinnitus and Hearing Loss

Objective

The impact of poor sleep on tinnitus has been mainly attributed to central processes. There is an association between sleep disorders and hearing loss, but whether hearing levels mediate the association between sleep disorders and tinnitus is unknown. This study investigates the association between sleep characteristics, tinnitus, and hearing loss.

Study Design

Cross-sectional.

Setting

National Health and Nutrition Examination Survey (NHANES).

Methods

Study cohort includes 9693 adults (≥20 years) from the NHANES 2005 to 2018 who completed audiometric testing and questionnaires on tinnitus and sleep characteristics. Multivariable regression analyses were performed to quantify associations between sleep characteristics, tinnitus, and hearing loss.

Results

In this cohort, 29% (95% confidence interval [CI]: 28%-31%) reported trouble sleeping and 9% (95% CI: 8%-10%) reported being diagnosed with sleep disorders. Negative sleep characteristics (less hours of sleep, diagnosis of a sleep disorder, trouble sleeping, or OSA symptoms) were not associated with audiometry-measured hearing loss in multivariable models adjusted for demographics and comorbidities but were significantly associated with bothersome tinnitus. This association remained significant without substantial attenuation in multivariable models additionally adjusting for hearing levels: sleeping <8 h/day (vs ≥8) (odds ratio [OR]: 1.28 [95% CI: 1.08-1.52]), trouble sleeping (OR: 1.78 [95% CI: 1.45-2.19]), diagnosis of sleep disorders (OR: 1.57 [95% CI: 1.14-2.15]), and report of OSA symptoms (OR: 1.42 [95% CI: 1.08-1.88]).

Conclusion

Negative sleep characteristics were associated with tinnitus while there was no clinically meaningful association between sleep and hearing loss. Our findings suggest that the relationship between poor sleep and tinnitus is likely contributed by central processes without a major role of mediation via the peripheral auditory system.

Investigating the Role of BDNF in Insomnia: Current Insights

Insomnia is a common disorder defined as frequent and persistent difficulty initiating, maintaining, or going back to sleep. A hallmark symptom of this condition is a sense of nonrestorative sleep. It is frequently associated with other psychiatric disorders, such as depression, as well as somatic ones, including immunomediated diseases. BDNF is a neurotrophin primarily responsible for synaptic plasticity and proper functioning of neurons. Due to its role in the central nervous system, it might be connected to insomnia of multiple levels, from predisposing traits (neuroticism, genetic/epigenetic factors, etc.) through its influence on different modes of neurotransmission (histaminergic and GABAergic in particular), maintenance of circadian rhythm, and sleep architecture, and changes occurring in the course of mood disturbances, substance abuse, or dementia. Extensive and interdisciplinary evaluation of the role of BDNF could aid in charting new areas for research and further elucidate the molecular background of sleep disorder. In this review, we summarize knowledge on the role of BDNF in insomnia with a focus on currently relevant studies and discuss their implications for future projects.

Animal models of human insomnia

Insomnia disorder (chronic sleep continuity disturbance) is a debilitating condition affecting 5%-10% of the adult population worldwide. To date, researchers have attempted to model insomnia in animals through breeding strategies that create pathologically short-sleeping individuals or with drugs and environmental contexts that directly impose sleeplessness. While these approaches have been invaluable for identifying insomnia susceptibility genes and mapping the neural networks that underpin sleep-wake regulation, they fail to capture concurrently several of the core clinical diagnostic features of insomnia disorder in humans, where sleep continuity disturbance is self-perpetuating, occurs despite adequate sleep opportunity, and is often not accompanied by significant changes in sleep duration or architecture. In the present review, we discuss these issues and then outline ways animal models can be used to develop approaches that are more ecologically valid in their recapitulation of chronic insomnia's natural aetiology and pathophysiology. Conditioning of self-generated sleep loss with these methods promises to create a better understanding of the neuroadaptations that maintain insomnia, including potentially within the infralimbic cortex, a substrate at the crossroads of threat habituation and sleep.

Eurycoma longifolia (Tongkat Ali) enhances wakefulness during active periods but facilitates sleep during resting periods in C57BL/6 mice

The effects of the Eurycoma longifolia (also known as Tongkat Ali [TA]) on sleep and wakefulness was evaluated in C57BL/6 mice. While TA has been used as an aphrodisiac in males, it exhibits various pharmacological effects. The most notable effect observed with TA was wake-enhancement during the second half of the active period, accompanied by significant elevations in core body temperature (CBT). In contrast, sleep was enhanced during the resting period (i.e., increase in rapid eye movement [REM] sleep and delta electroencephalography [EEG] power in non-REM sleep) with significant declines in CBT. The transition of TA's effects between resting and active periods was rapid. The results of the experiments in constant darkness indicate that TA prolongs the circadian tau and that this transition is governed by circadian clock mechanisms rather than light exposure. TA did not demonstrate efficacy in aiding sleep in an acute stress-induced insomnia model; thus, TA may be more suitable as a wake-enhancing agent for daytime sleepiness, as sleep propensity tends to accumulate towards the end of active period. Since TA amplifies the rest-activity pattern, prolongs circadian tau and increases REM sleep, thereby reversing some common symptoms seen in elderly subjects, it may also hold promise as a rejuvenating medicine.

Acute or Chronic Exposure to Corticosterone Promotes Wakefulness in Mice

Elevated glucocorticoid levels triggered by stress potentially contribute to sleep disturbances in stress-induced depression. However, sleep changes in response to elevated corticosterone (CORT), the major glucocorticoid in rodents, remain unclear. Here, we investigated the effects of acute or chronic CORT administration on sleep using electroencephalogram (EEG) and electromyography (EMG) recordings in freely moving mice. Acute CORT exposure rapidly promoted wakefulness, marked by increased episodes and enhanced EEG delta power, while simultaneously suppressing rapid eye movement (REM) and non-rapid eye movement (NREM) sleep, with the latter marked by decreased mean duration and reduced delta power. Prolonged 28-day CORT exposure led to excessive wakefulness and REM sleep, characterized by higher episodes, and decreased NREM sleep, characterized by higher episodes and reduced mean duration. EEG theta activity during REM sleep and delta activity during NREM sleep were attenuated following 28-day CORT exposure. These effects persisted, except for REM sleep amounts, even 7 days after the drug withdrawal. Elevated plasma CORT levels and depressive phenotypes were identified and correlated with observed sleep changes during and after administration. Fos expression significantly increased in the lateral habenula, lateral hypothalamus, and ventral tegmental area following acute or chronic CORT treatment. Our findings demonstrate that CORT exposure enhanced wakefulness, suppressed and fragmented NREM sleep, and altered EEG activity across all stages. This study illuminates sleep alterations during short or extended periods of heightened CORT levels in mice, providing a neural link connecting insomnia and depression.

Control of Emotion and Wakefulness by Neurotensinergic Neurons in the Parabrachial Nucleus

The parabrachial nucleus (PBN) integrates interoceptive and exteroceptive information to control various behavioral and physiological processes including breathing, emotion, and sleep/wake regulation through the neural circuits that connect to the forebrain and the brainstem. However, the precise identity and function of distinct PBN subpopulations are still largely unknown. Here, we leveraged molecular characterization, retrograde tracing, optogenetics, chemogenetics, and electrocortical recording approaches to identify a small subpopulation of neurotensin-expressing neurons in the PBN that largely project to the emotional control regions in the forebrain, rather than the medulla. Their activation induces freezing and anxiety-like behaviors, which in turn result in tachypnea. In addition, optogenetic and chemogenetic manipulations of these neurons revealed their function in promoting wakefulness and maintaining sleep architecture. We propose that these neurons comprise a PBN subpopulation with specific gene expression, connectivity, and function, which play essential roles in behavioral and physiological regulation.

Co-occurring insomnia and anxiety: a randomized controlled trial of internet cognitive behavioral therapy for insomnia versus internet cognitive behavioral therapy for anxiety

STUDY OBJECTIVES

Insomnia and anxiety are highly prevalent and frequently co-occur. Given limited therapeutic resources and time constraints, the aim of this study was to compare which treatment-internet cognitive behavioral therapy (CBT) for insomnia or internet CBT for anxiety-leads to the best outcomes in individuals with comorbid insomnia and anxiety.

METHODS

120 participants with comorbid insomnia and clinical anxiety (as defined by scores above the clinical cutoff on the insomnia severity index (ISI) and the generalized anxiety disorder 7-item scale (GAD-7)) were randomized to receive internet-based cognitive behavioral therapy (iCBT) for insomnia or iCBT for anxiety. The primary outcome measures were the ISI and the generalized anxiety disorder 7-item scale. Primary outcome measures were assessed before treatment, at mid-treatment, at post-treatment, and 3 months after treatment. Secondary outcome measures assessed depression symptoms, distress, and sleep diary parameters.

RESULTS

Participants in both groups experienced large reductions in symptoms of insomnia, anxiety, depression, and distress, as well as improvements in sleep efficiency and total sleep time. Improvements were maintained at follow-up. Crucially, at the end of treatment, the insomnia treatment was more effective in reducing symptoms of insomnia than the anxiety treatment, and equally effective in reducing symptoms of anxiety. Treatment gains were maintained at 3-month follow-up, however, there were no differences between groups at that time point.

CONCLUSIONS

These results suggest that in the common case of a patient presenting with comorbid insomnia and anxiety, treatment for insomnia may be the most efficient treatment strategy.

TRIAL REGISTRATION

The trial was registered with the Australian and New Zealand Clinical Trials Registry, https://anzctr.org.au/Trial/Registration/TrialReview.aspx?ACTRN=12618001141235. Trial ID: ACTRN12618001141235. Trial name: a comparison of internet-based CBT for insomnia versus internet-based CBT for anxiety in a comorbid sample.

Altered functional connectivity of anterior cingulate cortex in chronic insomnia: A resting-state fMRI study

The aim of our present study was to explore the connectivity pattern change between the anterior cingulate cortex (ACC) and the voxels from the whole brain in chronic insomnia (CI). With region of interest (ROI)-based functional connectivity, a two-sample t-test was performed on individual FC correlation maps from two groups based on the resting-state fMRI data acquired from 57 CI patients and 46 healthy controls (GRF correction, voxel-level P < 0.001 and cluster-level P < 0.001). A correlation analysis was performed to evaluate the relationship between the clinical features and the abnormal FC. Compared to the healthy controls, the CI patients show increased connectivity between the ACC and the right middle frontal gyrus, with decreased connectivity between the ACC and the bilateral precuneus gyrus. Correlation analysis indicated that the decreased connectivity showed positive correlations with Self-Rating Anxiety Scale (SAS) scores. Our study shows the alterations of CI patients in the level of functional integration and may indicate the dysfunction of communication within brain regions of the default mode network (DMN). These changes and their correlation with negative emotions may provide additional evidence to understand the possible neural mechanisms of CI.

Connecting insufficient sleep and insomnia with metabolic dysfunction

The global epidemic of obesity and type 2 diabetes parallels the rampant state of sleep deprivation in our society. Epidemiological studies consistently show an association between insufficient sleep and metabolic dysfunction. Mechanistically, sleep and circadian rhythm exert considerable influences on hormones involved in appetite regulation and energy metabolism. As such, data from experimental sleep deprivation in humans demonstrate that insufficient sleep induces a positive energy balance with resultant weight gain, due to increased energy intake that far exceeds the additional energy expenditure of nocturnal wakefulness, and adversely impacts glucose metabolism. Conversely, animal models have found that sleep loss-induced energy expenditure exceeds caloric intake resulting in net weight loss. However, animal models have significant limitations, which may diminish the clinical relevance of their metabolic findings. Clinically, insomnia disorder and insomnia symptoms are associated with adverse glucose outcomes, though it remains challenging to isolate the effects of insomnia on metabolic outcomes independent of comorbidities and insufficient sleep durations. Furthermore, both pharmacological and behavioral interventions for insomnia may have direct metabolic effects. The goal of this review is to establish an updated framework for the causal links between insufficient sleep and insomnia and risks for type 2 diabetes and obesity.

Abnormal amygdala functional connectivity in MDD patients with insomnia complaints

BACKGROUND

Insomnia is one of the major symptom relevant factors in major depressive disorder (MDD), but the neurological mechanisms underlying the multiple effect between insomnia and depression have not been well interpreted. This study aimed at exploring the potential mechanisms between insomnia and depression based on amygdala-based resting-state functional connectivity (RSFC).

METHODS

In total 56 MDD patients with low insomnia (MDD-LI) patients, 46 MDD patients with high insomnia (MDD-HI) patients, and 57 healthy controls (HCs) were employed and underwent a resting-state functional magnetic resonance imaging (fMRI) scan. ANOVA test was performed on RSFC value for three groups. Correlation analysis was conducted to evaluate the relationship between abnormal RSFC values and clinical features.

RESULTS

We found that MDD-HI mainly showed increased RSFC in (bilateral superior temporal gyrus (STG), and decreased RSFC in left supplementary motor area (SMA) and bilateral postcentral gyrus (PoCG) compared with MDD-LI. Correlation analysis indicated that RSFC of the bilateral amygdala with STG were positively associated with the sleep disturbance score and adjust HAMD score.

CONCLUSION

Our findings suggest that RSFC in temporal lobe and other specifically activated regions may be associated with neural circuits involved with insomnia in MDD. These provide new evidence for understanding the potential mechanisms of major depression and insomnia from the perspective of functional connectivity.

Restraint stress induced anxiety and sleep in mice

In humans and animals, exposure to changes in internal or external environments causes acute stress, which changes sleep and enhances neurochemical, neuroendocrine, and sympathetic activities. Repeated stress responses play an essential role in the pathogenesis of psychiatric diseases and sleep disorders. However, the underlying mechanism of sleep changes and anxiety disorders in response to acute stress is not well established. In the current study, the effects of restraint stress (RS) on anxiety and sleep-wake cycles in mice were investigated. We found that after RS, the mice showed anxiety-like behavior after RS manipulation and increased the amounts of both non-rapid eye movement (NREM) and rapid eye movement (REM) sleep in the dark period. The increase in sleep time was mainly due to the increased number of episodes of NREM and REM sleep during the dark period. In addition, the mice showed an elevation of the EEG power spectrum of both NREM and REM sleep 2 h after RS manipulation. There was a significant reduction in the EEG power spectrum of both NREM and REM sleep during the darkperiod in the RS condition. The expression of the c-Fos protein was significantly increased in the parabrachial nucleus, bed nucleus of the stria terminalis, central amygdala, and paraventricular hypothalamus by RS manipulation. Altogether, the findings from the present study indicated that neural circuits from the parabrachial nucleus might regulate anxiety and sleep responses to acute stress, and suggest a potential therapeutic target for RS induced anxiety and sleep alterations.

Network pharmacology and pharmacological evaluation for deciphering novel indication of Sishen Wan in insomnia treatment

BACKGROUND

Insomnia is the most frequent sleep disorder worldwide and is a prominent risk factor for mental and physical health deterioration. The clinical application of common pharmacological treatments for insomnia is far from satisfactory due to their various adverse effects. In recent years, drugs developed from natural herbs have become potential alternative therapies for insomnia. Sishen Wan (SSW), a traditional Chinese medicine (TCM) used for centuries to treat diarrheal disease, consists of multiple neurologically active herbs with sleep-regulating potential that may have therapeutic effects on insomnia. However, its hypnotic and sleep-regulating effects have not been evaluated in clinical practice or laboratory experiments.

PURPOSE

To investigate the anti-insomnia effects of SSW and explore its possible mechanisms using preclinical models.

STUDY DESIGN AND METHODS

The sedative effect of the SSW formula was investigated using network pharmacology analysis that was validated using various pharmacological approaches, including the evaluation of locomotor activity (LMA), pentobarbital-induced sleep time, and electroencephalography/electromyogram (EEG/EMG)-based sleep profiling in normal rats. Several animal models of insomnia, including sleep deprivation, serotonin depletion, and cage-changing models, have been used to further assess the anti-insomnia effects of SSW. Furthermore, the potential underlying mechanisms of action of SSW were predicted using bioinformatics methods and verified using in vivo and in silico experiments.

RESULTS

The results showed that SSW reduced LMA and prolonged pentobarbital-induced sleep time in a dose-dependent manner, which was consistent with the increase in non-rapid eye movement (NREM) sleep in normal rats, indicating a solid sedative effect. In animal models of insomnia, SSW alleviated sleep disturbance by increasing NREM sleep time, shortening NREM sleep latency, and inhibiting sleep fragmentation, suggesting a possible curative effect of SSW on insomnia. Finally, through functional enrichment analysis and in vivo and in silico experiments, 5-HT_1A was identified as the key target of the anti-insomnia effect of SSW. Moreover, (S)-propranolol, nuciferine, zizyphusine, and N,N-dimethyl-5-methoxytryptamine may be the active compounds of SSW responsible for its anti-insomnia effect.

CONCLUSION

This study extended the possible indication scope for SSW, which provides a potential therapeutic TCM that may be used for insomnia treatment, as well as a reference scheme for the discovery of novel indications of TCM.

A paraventricular thalamus to central amygdala neural circuit modulates acute stress-induced heightened wakefulness

Heightened wakefulness in response to stressors is essential for survival but can also lead to sleep disorders like insomnia. The paraventricular thalamus (PVT) is both a critical thalamic area for wakefulness and a stress-sensitive brain region. However, whether the PVT and its neural circuitries are involved in controlling wakefulness in stress conditions remains unknown. Here, we find that PVT neurons projecting to the central amygdala (CeA) are activated by different stressors. These neurons are wakefulness-active and increase their activities upon sleep to wakefulness transitions. Optogenetic activation of the PVT-CeA circuit evokes transitions from sleep to wakefulness, whereas selectively silencing the activity of this circuit decreases time spent in wakefulness. Specifically, chemogenetic inhibition of CeA-projecting PVT neurons not only alleviates stress responses but also attenuates the acute stress-induced increase of wakefulness. Thus, our results demonstrate that the PVT-CeA circuit controls physiological wakefulness and modulates acute stress-induced heightened wakefulness.

A noradrenergic-hypothalamic neural substrate for stress-induced sleep disturbances

In our daily life, we are exposed to uncontrollable and stressful events that disrupt our sleep. However, the underlying neural mechanisms deteriorating the quality of non-rapid eye movement sleep (NREMs) and REM sleep are largely unknown. Here, we show in mice that acute psychosocial stress disrupts sleep by increasing brief arousals (microarousals [MAs]), reducing sleep spindles, and impairing infraslow oscillations in the spindle band of the electroencephalogram during NREMs, while reducing REMs. This poor sleep quality was reflected in an increased number of calcium transients in the activity of noradrenergic (NE) neurons in the locus coeruleus (LC) during NREMs. Opto- and chemogenetic LC-NE activation in naïve mice is sufficient to change the sleep microarchitecture similar to stress. Conversely, chemogenetically inhibiting LC-NE neurons reduced MAs during NREMs and normalized their number after stress. Specifically inhibiting LC-NE neurons projecting to the preoptic area of the hypothalamus (POA) decreased MAs and enhanced spindles and REMs after stress. Optrode recordings revealed that stimulating LC-NE fibers in the POA indeed suppressed the spiking activity of POA neurons that are activated during sleep spindles and REMs and inactivated during MAs. Our findings reveal that changes in the dynamics of the stress-regulatory LC-NE neurons during sleep negatively affect sleep quality, partially through their interaction with the POA.

Insomnia – Is it a Symptom or a Disorder?

Insomnia disorder is a common public health problem with a prevalence of approximately 2-5% of the population. It is of major importance to differentiate the insomnia disorder from the isolated symptoms and normal variants, and to define the secondary or associated conditions. Insomnia was mainly classified as acute and chronic insomnia disorder based on the 3rd edition of the International Classification of Sleep Disorders. Many models have been developed to explain the underlying mechanisms of insomnia, such as the Drosophila model, the cognitive model, the psychobiological inhibition model, the neurocognitive model, stimulus control model, hyperarousal model and the “3P model” (Spielman model). Optimizing the environmental conditions, lifestyle changes and elaborating the triggering factors are the first step in the management of insomnia disorders.

Multicomponent drug Neurexan mitigates acute stress-induced insomnia in rats

The aim of this study was to determine whether the multicomponent drug Neurexan could mitigate acute insomnia after exposure to a psychosocial stressor. We administered Neurexan orally to rats and examined stress-induced insomnia using the male rat dirty cage exchange method. The neurocircuitry and electrophysiological correlates of the model are characterised, and it represents various human insomnia conditions. Male rats were randomly assigned in a crossover design to six treatment groups and electroencephalography (EEG) electrodes attached. Three groups were exposed to a cage inhabited by another male rat for a week and the other three groups received a clean cage. Prior to cage change, rats were given either no drug, vehicle control or Neurexan. Non-rapid eye movement (NREM) sleep, REM sleep, and waking were assessed manually via EEG recordings. Group means were compared for sleep latency and for the 2 h after cage change for: time in each state, state-specific episode duration/frequency, in addition to NREM delta, gamma and REM theta EEG spectral power. Rats administered Neurexan fell asleep faster than vehicle-treated rats and spent less time awake with shorter, albeit more waking episodes and increased NREM episodes after dirty cage exposure. Neurexan-treated rats given dirty cages were not statistically different on any outcomes from Neurexan-treated rats given clean cages, thereby mitigating the stressor. In the EEG power spectra analysed, changes between treatment groups were not detected. This research confirms that Neurexan treatment has somnogenic effects and ameliorates psychological stressor-induced acute insomnia.

Vasopressin neurons in the paraventricular hypothalamus promote wakefulness via lateral hypothalamic orexin neurons

The sleep-wakefulness cycle is regulated by complicated neural networks that include many different populations of neurons throughout the brain. Arginine vasopressin neurons in the paraventricular nucleus of the hypothalamus (PVH^AVP) regulate various physiological events and behaviors, such as body-fluid homeostasis, blood pressure, stress response, social interaction, and feeding. Changes in arousal level often accompany these PVH^AVP-mediated adaptive responses. However, the contribution of PVH^AVP neurons to sleep-wakefulness regulation has remained unknown. Here, we report the involvement of PVH^AVP neurons in arousal promotion. Optogenetic stimulation of PVH^AVP neurons rapidly induced transitions to wakefulness from both NREM and REM sleep. This arousal effect was dependent on AVP expression in these neurons. Similarly, chemogenetic activation of PVH^AVP neurons increased wakefulness and reduced NREM and REM sleep, whereas chemogenetic inhibition of these neurons significantly reduced wakefulness and increased NREM sleep. We observed dense projections of PVH^AVP neurons in the lateral hypothalamus with potential connections to orexin/hypocretin (LH^Orx) neurons. Optogenetic stimulation of PVH^AVP neuronal fibers in the LH immediately induced wakefulness, whereas blocking orexin receptors attenuated the arousal effect of PVH^AVP neuronal activation drastically. Monosynaptic rabies-virus tracing revealed that PVH^AVP neurons receive inputs from multiple brain regions involved in sleep-wakefulness regulation, as well as those involved in stress response and energy metabolism. Moreover, PVH^AVP neurons mediated the arousal induced by novelty stress and a melanocortin receptor agonist melanotan-II. Thus, our data suggested that PVH^AVP neurons promote wakefulness via LH^Orx neurons in the basal sleep-wakefulness and some stressful conditions.

Activation of the Ventrolateral Preoptic Neurons Projecting to the Perifornical-Hypothalamic Area Promotes Sleep: DREADD Activation in Wild-Type Rats

The ventrolateral preoptic area (VLPO) predominantly contains sleep-active neurons and is involved in sleep regulation. The perifornical-hypothalamic area (PF-HA) is a wake-regulatory region and predominantly contains wake-active neurons. VLPO GABAergic/galaninergic neurons project to the PF-HA. Previously, the specific contribution of VLPO neurons projecting to the PF-HA (VLPO > PF-HAPRJ) in sleep regulation in rats could not be investigated due to the lack of tools that could selectively target these neurons. We determined the contribution of VLPO > PF-HAPRJ neurons in sleep regulation by selectively activating them using designer receptors exclusively activated by designer drugs (DREADDs) in wild-type Fischer-344 rats. We used a combination of two viral vectors to retrogradely deliver the Cre-recombinase gene, specifically, in VLPO > PF-HA neurons, and further express hM3Dq in those neurons to selectively activate them for delineating their specific contributions to sleep−wake functions. Compared to the control, in DREADD rats, clozapine-N-oxide (CNO) significantly increased fos-expression, a marker of neuronal activation, in VLPO > PF-HAPRJ neurons (2% vs. 20%, p < 0.01) during the dark phase. CNO treatment also increased nonREM sleep (27% vs. 40%, p < 0.01) during the first 3 h of the dark phase, when rats are typically awake, and after exposure to the novel environment (55% vs. 65%; p < 0.01), which induces acute arousal during the light phase. These results support a hypothesis that VLPO > PF-HAPRJ neurons constitute a critical component of the hypothalamic sleep−wake regulatory circuitry and promote sleep by suppressing wake-active PF-HA neurons.

Macroscale connections of the mouse lateral preoptic area and anterior lateral hypothalamic area

The macroscale neuronal connections of the lateral preoptic area (LPO) and the caudally adjacent lateral hypothalamic area anterior region (LHAa) were investigated in mice by anterograde and retrograde axonal tracing. Both hypothalamic regions are highly and diversely connected, with connections to >200 gray matter regions spanning the forebrain, midbrain, and rhombicbrain. Intrahypothalamic connections predominate, followed by connections with the cerebral cortex and cerebral nuclei. A similar overall pattern of LPO and LHAa connections contrasts with substantial differences between their input and output connections. Strongest connections include outputs to the lateral habenula, medial septal and diagonal band nuclei, and inputs from rostral and caudal lateral septal nuclei; however, numerous additional robust connections were also observed. The results are discussed in relation to a current model for the mammalian forebrain network that associates LPO and LHAa with a range of functional roles, including reward prediction, innate survival behaviors (including integrated somatomotor and physiological control), and affect. The present data suggest a broad and intricate role for LPO and LHAa in behavioral control, similar in that regard to previously investigated LHA regions, contributing to the finely tuned sensory‐motor integration that is necessary for behavioral guidance supporting survival and reproduction.

Effects of stress on endophenotypes of suicide across species: A role for ketamine in risk mitigation

Suicide is a leading cause of death and morbidity worldwide, yet few interventions are available to mitigate its risk. Barriers to effective treatments involve a limited understanding of factors that predict the onset of suicidal thoughts and behaviors. In the context of suicide risk, stress is a precipitating factor that is largely overlooked in the literature. Indeed, the pathophysiology of stress and suicide are heavily interconnected, underscoring the need to target the stress system in suicide prevention. In this review, we integrate findings from the preclinical and clinical literature that links stress and suicide. We focus specifically on the effects of stress on underlying biological functions and processes associated with suicide, allowing for the review of research using animal models. Owing to the rapid anti-suicidal effects of (R,S)-ketamine, we discuss its ability to modulate various stress-related endophenotypes of suicide, as well as its potential role in preventing suicide in those with a history of chronic life stress (e.g., early life adversity). We highlight future research directions that could advance our understanding of stress-related effects on suicide risk, advocating a dimensional, endophenotype approach to suicide research.

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Suicide and chronic stress pathophysiology are interconnected.

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Chronic stress has profound impacts on several endophenotypes of suicide.

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Animal and human research points to stress as a precipitating factor in suicide.

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Ketamine modulates specific biological processes associated with stress and suicide.

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Suicide research into endophenotypes can help inform risk-mitigation strategies.

When the Locus Coeruleus Speaks Up in Sleep: Recent Insights, Emerging Perspectives

For decades, numerous seminal studies have built our understanding of the locus coeruleus (LC), the vertebrate brain’s principal noradrenergic system. Containing a numerically small but broadly efferent cell population, the LC provides brain-wide noradrenergic modulation that optimizes network function in the context of attentive and flexible interaction with the sensory environment. This review turns attention to the LC’s roles during sleep. We show that these roles go beyond down-scaled versions of the ones in wakefulness. Novel dynamic assessments of noradrenaline signaling and LC activity uncover a rich diversity of activity patterns that establish the LC as an integral portion of sleep regulation and function. The LC could be involved in beneficial functions for the sleeping brain, and even minute alterations in its functionality may prove quintessential in sleep disorders.

Median preoptic GABA and glutamate neurons exert differential control over sleep behavior

Previous studies suggest that the median preoptic nucleus (MnPO) of the hypothalamus plays an important role in regulating the wake-sleep cycle and, in particular, homeostatic sleep drive. However, the precise cellular phenotypes, targets, and central mechanisms by which the MnPO neurons regulate the wake-sleep cycle remain unknown. Both excitatory and inhibitory MnPO neurons innervate brain regions implicated in sleep promotion and maintenance, suggesting that both cell types may participate in sleep control. Using genetically targeted approaches, we investigated the role of the MnPO GABAergic (MnPO^Vgat) and glutamatergic (MnPO^Vglut2) neurons in modulating wake-sleep behavior of mice. We found that both neuron populations differentially participate in wake-sleep control, with MnPO^Vgat neurons being involved in sleep homeostasis and MnPO^Vglut2 neurons facilitating sleep during allostatic (stressful) challenges.

Emotional Dysregulation, Anxiety Symptoms and Insomnia in Individuals with Alcohol Use Disorder

Alcohol craving is associated with insomnia symptoms, and insomnia is often reported as a reason for alcohol relapse. The current study examined associations between emotional regulation, anxiety, and insomnia among a group of 338 patients with alcohol use disorder (AUD). Because insomnia most often develops after stressful experiences, it was expected that anxiety symptoms would mediate the association between emotional dysregulation and insomnia severity. It was also expected that an insomnia diagnosis would moderate the association between emotional dysregulation and anxiety symptoms, namely that higher anxiety levels would be found in individuals with insomnia than in those without insomnia. Insomnia severity was assessed with a total score based on the Athens Insomnia Scale (AIS). Additionally, an eight-point cut-off score on the AIS was used to classify participants as with (n = 107) or without (n = 231) an insomnia diagnosis. Moreover, participants completed the Emotion Regulation Scale (DERS; total score) and the Brief Symptoms Inventory (BSI; anxiety). Individuals with insomnia did not differ from those without insomnia in age (p = 0.86), duration of problematic alcohol use (p < 0.34), mean days of abstinence (p = 0.17), nor years of education (p = 0.41). Yet, individuals with insomnia endorsed higher anxiety (p < 0.001) and higher emotional dysregulation (p < 0.001). Anxiety symptoms fully mediated the association between emotional dysregulation and insomnia severity (p < 0.001). Furthermore, insomnia diagnosis positively moderated the association between emotional dysregulation and anxiety (p < 0.001). Our results suggest that emotional dysregulation can lead to insomnia via anxiety symptoms. Treating anxiety symptoms and emotional dysregulation could help to prevent or alleviate symptoms of insomnia in people with AUD. Moreover, treating insomnia in people with AUD may also have a positive effect on anxiety symptoms.

Distinct Hypothalamic Paraventricular Nucleus Inputs to the Cingulate Cortex and Paraventricular Thalamic Nucleus Modulate Anxiety and Arousal

Insomnia and anxiety are two common clinical diseases that threaten people’s physical and mental health. Insomnia and anxiety may share some similar underlying neural circuit mechanisms in the brain. In this study, we combine techniques including chemo-fMRI, optogenetics, and chemogenetics to reveal that the glutamatergic neurons of the paraventricular hypothalamic nucleus (PVN) regulate both anxiety and arousal through two different downstream neural circuits. Optogenetic activation of the PVN-cingulate cortex (Cg) neural circuit triggers anxiety-like behaviors in mice without affecting the wakefulness, while optogenetic activation of the PVN-paraventricular thalamic nucleus (PVT) neural circuit promotes wakefulness in mice without affecting anxiety-like behaviors. Our research reveals that PVN is a key brain area for controlling anxiety and arousal behaviors. We also provide a neurological explanation for anxiety disorder and insomnia which may offer guidance for treatments including drugs or transcranial magnetic stimulation for the patients.

The Dynamic Relationship Between Alpha and Beta Power and Next-Day Suicidal Ideation in Individuals With Treatment-Resistant Depression

Background

Nocturnal wakefulness has emerged as a potential predictor of short-term suicide risk. This analysis used dynamic temporal patterns in alpha and beta power and global sleep metrics to explore the possible link between next-day suicidal ideation (NDSI) and wakefulness measures in unmedicated participants with treatment-resistant depression.

Methods

Thirty-three medication-free participants with treatment-resistant depression completed overnight polysomnography. Alpha and beta spectral power as functions over time were used to represent arousal-related components of the dynamic sleep process. A functional data analytic approach (multilevel functional principal component analysis [MFPCA]) was used to preserve the oscillatory nature of the data; MFPCA PC scores were then associated with NDSI. Associations between NDSI and polysomnography-defined wakefulness after sleep onset, sleep efficiency, and total sleep time were also evaluated.

Results

NDSI had the strongest relationship with the second beta PC score (slope = 0.09 [90% credible interval, 0.03 to 0.14]), which represented an oscillating pattern that reflected disturbed sleep. The first PCs from both alpha and beta MFPCAs represented the overall magnitude of power and were most closely associated with traditional polysomnography metrics but were not related to NDSI. Results were equivocal for wakefulness after sleep onset with NDSI and did not support a relationship between NDSI and either sleep efficiency or total sleep time, highlighting the value of information contained in oscillating electroencephalogram patterns for identifying physiological links between nocturnal wakefulness and NDSI.

Conclusions

This study leveraged the dynamic nature of wakefulness-related electroencephalogram frequencies and provides a potential electrophysiological link between suicidal ideation and wakefulness during sleep in individuals with treatment-resistant depression.

Longitudinal Analysis of Sleep-Wake States in Neonatal Rats Subjected to Hypoxia-Ischemia

OBJECTIVE

Sleep is necessary for brain maturation in infants. Perinatal hypoxic-ischemic encephalopathy (HIE) is a major cause of chronic neurological disease in infants. Although the developmental changes of electroencephalogram (EEG) in human newborns have been described, little is known about the EEG normal maturation characteristics in rodents and the changes in sleep-awake states caused by hypoxia-ischemia (HI). This study aimed to investigate the pathological response of sleep-wake states in neonatal rats with HIE.

METHODS

We constructed HIE and sham models on postnatal day (P) 3 rats and continuously monitored them using electroencephalography and electromyography for up to P12. The distribution of sleep-wake states was analyzed to estimate the effects of HIE.

RESULTS

Compared with the sham group, the HI group showed lower rapid eye movement (REM) sleep percentage, but wake percentage and frequency was higher during P4-P12. The frequency of REM and non-rapid eye movement (NREM) sleep increased and the duration of REM and NREM sleep decreased after HI induction. However, it gradually returned to the normal level with an increase in daytime.

CONCLUSION

HI damage alters the sleep-wake patterns during early neural development. The findings provide a comprehensive assessment of serial sleep-wake state recordings in neonatal rats from P4-P12.

Production of Lactobacillus brevis ProGA28 attenuates stress-related sleep disturbance and modulates the autonomic nervous system and the motor response in anxiety/depression behavioral tests in Wistar-Kyoto rats

AIMS

Many studies have reported that the production of Lactobacillus brevis is beneficial for sleep, but the underlying mechanism remains unclear. Other known beneficial effects of Lactobacillus brevis include improvement of anxious or depressive symptoms and better modulation of the autonomic nervous system, both of which impact sleep. In this study, we investigated whether the sleep benefit of Lactobacillus brevis was associated with the modulating effects on the autonomic nervous system and anxious/depressive symptoms.

MAIN METHODS

Wistar-Kyoto rats were fed the production of Lactobacillus brevis (ProGA28) for the last 2 weeks of treatment before being exposed to case exchange (stress-induced insomnia paradigm). Waking, quiet sleep, and paradoxical sleep states were defined based on polysomnographic measurements. Autonomic functioning was assessed by heart rate variability (HRV). A combined behavioral test was used to evaluate anxiety-like or depressive-like behaviors after the following 2 days.

KEY FINDINGS

In exposure to the dirty cage, the control group had significant prolongation of sleep latency, sleep loss during the first 2 h, and decreased parasympathetic activity and increased sympathetic activity during quiet sleep, which were significantly mitigated in the ProGA28 group. In behavioral tests, the ProGA28 group exhibited significantly less anxiety/depression-like motor responses in the elevated plus maze test, the forced swimming test, and the three-chamber social interaction test. Less initial sleep loss in the ProGA28 group was related to higher parasympathetic activity during quiet sleep, and shorter sleep latency in both groups was associated with longer time staying in the open arm in the elevated plus maze test.

SIGNIFICANCE

These findings suggest that L. brevis ProGA28 can attenuate stress-related sleep disturbance, which may be associated with increased parasympathetic activity and decreased anxiety-like behaviors.

Prenatally stress-exposed male rats present lower theta prefrontal activity during attention behaviors to receptive females

Prenatal stress affects brain functionality and sexual behavior. The medial prefrontal cortex (mPFC) participates in the integration and processing of sexual stimuli. Electroencephalographic (EEG) theta activity has been associated with attention as well as rewarding and sexually motivated states. Considering that the induction of sexual motivation requires attention to, and the adequate processing of, sexual stimuli, this study aimed to evaluate the effects of exposure to stress during the prenatal period on EEG activity in the mPFC during nose pokes in adulthood, actions which are indicators of attention to a receptive female. Eighteen sexually experienced male rats were used, nine stressed prenatally by immobilization during days 14-21 of gestation (stress-exposed group). The other nine formed the control group. All rats were implanted bilaterally in the mPFC (specifically in prelimbic areas) and were allowed one intromission with a receptive female to induce a sexually motivated state before the experimental session. During this session, both nose pokes and non-contact erections in the male rats were evaluated in the presence of an inaccessible receptive female. EEGs were recorded only during nose pokes. The stress-exposed group presented lower nose poke duration, fewer non-contact erections, and lower relative power of the theta band (4-7 Hz) in both prefrontal areas. Considering that the prevalence of this band is associated with attention and motivational processes, these data confirm the deleterious effect of prenatal stress on attention and sexual activation to sexually relevant stimuli in male rats during adulthood.

Abnormal functional connectivity of the salience network in insomnia

The salience network plays an important role in detecting stimuli related to behavior and integrating neural processes. The aim of this study was to investigate changes in functional connectivity of the salience network in insomnia patients. Independent component analysis combined with a dual regression approach was used to examine functional connectivity differences in the salience network between patients with insomnia (n = 33) and healthy controls (n = 33). Pearson correlation analysis was used to analyze the relationship between differences in functional connectivity and the clinical characteristics of insomnia patients. Compared to healthy controls, insomnia patients showed increased functional connectivity in the dorsal anterior cingulate cortex within the salience network, as well as greater connectivity between the salience network and other brain regions including the dorsolateral prefrontal cortex, superior frontal gyrus, sensorimotor area and brain stem. The correlation analysis showed that increased functional connectivity between the salience network and left dorsolateral prefrontal cortex was positively correlated with Pittsburgh Sleep Quality Index score. Increased functional connectivity between salience network and several brain regions may be related to hyperarousal in insomnia patients. The connectivity between salience network and dorsolateral prefrontal cortex may potentially be used as a neuroimaging biomarker of sleep quality.

Sex differences in stress-induced sleep deficits

Sleep disruptions are hallmarks in the pathophysiology of several stress-related disorders, including Major Depressive Disorder (MDD) and Post-Traumatic Stress Disorder (PTSD), both known to disproportionately affect female populations. Although previous studies have attempted to investigate disordered sleep in women, few studies have explored and compared how repeated stress affects sleep in both sexes in either human or animal models. We have previously shown that male rats exhibit behavioral and neuroendocrine habituation to 5 days of repeated restraint, whereas females do not; additional days of stress exposure are required to observe habituation in females. This study examined sex differences in sleep measures prior to, during, and after repeated restraint stress in adult male and female rats. Our data reveal that repeated stress increased time spent awake and decreased slow-wave sleep (SWS) and REM sleep (REMS) in females, and these effects persisted over 2 days of recovery. In contrast, the effects of stress on males were transient. These insomnia-like symptoms were accompanied by a greater number of exaggerated motor responses to waking from REMS in females, a phenotype similar to trauma-related nightmares. In sum, these data demonstrate that repeated stress produces disruptions in sleep that persist days after the stress is terminated in female rats. These disruptions in sleep produced by 5 days of repeated restraint may be due to their lack of habituation.

Centrally Projecting Edinger-Westphal Nucleus in the Control of Sympathetic Outflow and Energy Homeostasis

The centrally projecting Edinger-Westphal nucleus (EWcp) is a midbrain neuronal group, adjacent but segregated from the preganglionic Edinger-Westphal nucleus that projects to the ciliary ganglion. The EWcp plays a crucial role in stress responses and in maintaining energy homeostasis under conditions that require an adjustment of energy expenditure, by virtue of modulating heart rate and blood pressure, thermogenesis, food intake, and fat and glucose metabolism. This modulation is ultimately mediated by changes in the sympathetic outflow to several effector organs, including the adrenal gland, heart, kidneys, brown and white adipose tissues and pancreas, in response to environmental conditions and the animal's energy state, providing for appropriate energy utilization. Classic neuroanatomical studies have shown that the EWcp receives inputs from forebrain regions involved in these functions and projects to presympathetic neuronal populations in the brainstem. Transneuronal tracing with pseudorabies virus has demonstrated that the EWcp is connected polysynaptically with central circuits that provide sympathetic innervation to all these effector organs that are critical for stress responses and energy homeostasis. We propose that EWcp integrates multimodal signals (stress, thermal, metabolic, endocrine, etc.) and modulates the sympathetic output simultaneously to multiple effector organs to maintain energy homeostasis under different conditions that require adjustments of energy demands.

Effects of Electroacupuncture on Sleep via the Dopamine System of the HPA Axis in Rats after Cage Change

Background

Insomnia is often related to stressful events. The hypothalamus-pituitary-adrenal (HPA) axis is related to stress, and dopamine (DA) and DA receptors are involved in the regulation of HPA axis. Electroacupuncture (EA) can improve sleep in individuals with insomnia, but the mechanism is unclear. We demonstrated that EA can improve sleep in rats after cage change through DA and the DA receptors in the HPA axis.

Methods

A rat model of insomnia was established by cage change to a dirty cage. The rats in treatment groups were intervened by EA and D1R (or D2R) antagonists. Electroencephalography (EEG) and electromyogram (EMG) were recorded to compare the changes in sleep. The DA, corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH), and cortisol (CORT) levels in the plasma and hypothalamus were measured by ELISAs, and the D1R and D2R levels were measured by RT-PCR and immunohistochemistry.

Results

The dirty group showed a significant increase in the amount of wakefulness and decrease in the amount of NREM sleep, with decreased numbers of long NREM sleep bouts and REM sleep bouts and increased mean duration of wakefulness during the light period. EA and D1R (or D2R) antagonists intervention could improve sleep disturbance by decreasing wakefulness in the light period after cage change, EA and D1R (or D2R) antagonists could increase the hypothalamus DA, CRH, ACTH, CORT level, and the D1R and D2R mRNA levels in the HPA axis, and the effect of EA plus D1R (or D2R) antagonist was not superior to that of EA or D1R (or D2R) antagonists alone.

Conclusions

EA can improve the sleep of rats after cage change, and the mechanism may be related to the regulation of DA and D1R or D2R in the HPA axis.

Left superior temporal sulcus morphometry mediates the impact of anxiety and depressive symptoms on sleep quality in healthy adults

Anxiety and depressive symptoms may predispose individuals to sleep disturbance. Understanding how these emotional symptoms affect sleep quality, especially the underlying neural basis, could support the development of effective treatment. The aims of the present study were therefore to investigate potential changes in brain morphometry associated with poor sleep quality and whether this structure played a mediating role between the emotional symptoms and sleep quality. One hundred and forty-one healthy adults (69 women, mean age = 26.06 years, SD = 6.36 years) were recruited. A structural magnetic resonance imaging investigation was performed, and self-reported measures of anxiety, depressive symptoms and sleep quality were obtained for each participant. Whole-brain regression analysis revealed that worse sleep quality was associated with thinner cortex in left superior temporal sulcus (STS). Furthermore, the thickness of left STS mediated the association between the emotional symptoms and sleep quality. A subsequent commonality analysis showed that physiological component of the depressive symptoms had the greatest influence on sleep quality. In conclusion, thinner cortex in left STS may represent a neural substrate for the association between anxiety and depressive symptoms and poor sleep quality and may thus serve as a potential target for neuromodulatory treatment of sleep problems.

Convergent and divergent functional connectivityalterations of hippocampal subregions between short-term and chronic insomnia disorder

Insomnia disorder (ID) is reclassified into short-term and chronic subtypes based on recent etiological advances, however, neural mechanisms underlying the subtypes are rarely examined. In this study, we investigated gray matter volume and resting-state functional connectivity (RSFC) alterations of hippocampal subregions in short-term and chronic ID using multimodal MRI. We found convergent and divergent alterations between both ID groups in specific hippocampal subregions [right cornu ammonis 1 (CA1), subicular complex (Subc), and caudal hippocampus, (cHipp)] with prefrontal cortex [bilateral medial prefrontal cortex (MPFC), and right middle frontal gyrus] and limbic/paralimbic regions (bilateral middle cingulate cortex and left parahippocampal gyrus). Intriguingly, the RSFC of the right CA1/cHipp, particularly the intersection between these two subregions, with bilateral MPFC exhibited gradual increases from healthy controls to short-term ID and from short-term ID to chronic ID. Moreover, a negative correlation between the right CA1-left parahippocampal gyrus RSFC and Epworth Sleepiness Scale scores, and a positive correlation between the right CA1-bilateral MPFC RSFC and Insomnia Severity Index scores were found in the chronic ID group (P < 0.05). Our findings suggest convergent and divergent RSFC alterations of specific hippocampal subregions with the prefrontal cortex and limbic/paralimbic regions between short-term and chronic ID. These findings suggest that the hippocampus is a key node in establishing diagnostic and categorical biomarkers in ID and developing more effective treatment strategies.

Functional connectivity density abnormalities and anxiety in primary insomnia patients

Primary insomnia (PI) is strongly associated with emotional dysregulation. However, the neurobiological pathology of the association between PI and emotional dysregulation is limited. Previous studies have indicated an impact of PI on the emotional regulatory system, but the specificity of this finding remains to be confirmed. A sample of 27 primary insomnia patients (PIs) and 32 matched healthy controls (HCs) was recruited for this study. The functional connectivity density (FCD) was used to assess the spontaneous functional brain organization in PIs. Then, we identified whether the local (lFCD) and global FCD (gFCD) abnormalities can be the potential biomarker for emotion level in PIs. Our findings suggested that PIs exhibited higher levels of anxiety and depression, and the levels of anxiety and depression is associated with the insomnia severity. We also found that PIs showed both lower lFCD and gFCD in several regions (i.e. thalamus, anterior cingulate cortex (ACC), insula). Furthermore, the lower gFCD values of left ACC and right insula were associated with their anxiety level in PIs, which demonstrated their potential biomarker for anxiety in PIs. Our results demonstrated that the relationship between the insomnia severity and the anxiety level could be partially mediated by gFCD of the ACC and insula. The current study improved our understanding of the anxiety in PIs and provided helpful information for future therapeutic development for PIs.

Sleep-wake regulation in preterm and term infants

Study Objectives

In adults, wakefulness can be markedly prolonged at the expense of sleep, e.g. to stay vigilant in the presence of a stressor. These extra-long wake bouts result in a heavy-tailed distribution (highly right-skewed) of wake but not sleep durations. In infants, the relative importance of wakefulness and sleep are reversed, as sleep is necessary for brain maturation. Here, we tested whether these developmental pressures are associated with the unique regulation of sleep–wake states.

Methods

In 175 infants of 28–40 weeks postmenstrual age (PMA), we monitored sleep–wake states using electroencephalography and behavior. We constructed survival models of sleep–wake bout durations and the effect of PMA and other factors, including stress (salivary cortisol), and examined whether sleep is resilient to nociceptive perturbations (a clinically necessary heel lance).

Results

Wake durations followed a heavy-tailed distribution as in adults and lengthened with PMA and stress. However, differently from adults, active sleep durations also had a heavy-tailed distribution, and with PMA, these shortened and became vulnerable to nociception-associated awakenings.

Conclusions

Sleep bouts are differently regulated in infants, with especially long active sleep durations that could consolidate this state’s maturational functions. Curtailment of sleep by stress and nociception may be disadvantageous, especially for preterm infants given the limited value of wakefulness at this age. This could be addressed by environmental interventions in the future.

Consistent altered internal capsule white matter microstructure in insomnia disorder

STUDY OBJECTIVES

Suggested neural correlates of insomnia disorder have been hard to replicate. Even the most consistent finding, altered white matter microstructure in the anterior limb of the internal capsule, is based on handful studies. The urge for replicable targets to understand the underlying mechanisms of insomnia made us study white matter fractional anisotropy (FA) across three samples of cases and controls.

METHODS

3-Tesla MRI diffusion tensor imaging data of three independent samples were combined for analysis, resulting in n = 137 participants, of whom 73 were diagnosed with insomnia disorder and 64 were matched controls without sleep complaints. Insomnia severity was measured with the Insomnia Severity Index (ISI). White matter microstructure was assessed with FA. White matter tracts were skeletonized and analyzed using tract-based spatial statistics. We performed a region-of-interest analysis using linear mixed-effect models to evaluate case-control differences in internal capsule FA as well as associations between internal capsule FA and insomnia severity.

RESULTS

FA in the right limb of the anterior internal capsule was lower in insomnia disorder than in controls (β = -9.76e-3; SE = 4.17e-3, p = .034). In the entire sample, a higher ISI score was associated with a lower FA value of the right internal capsule (β = -8.05e- 4 FA/ISI point, SE = 2.60e- 4, p = .008). Ancillary whole brain voxel-wise analyses showed no significant group difference or association with insomnia severity after correction for multiple comparisons.

CONCLUSIONS

The internal capsule shows small but consistent insomnia-related alterations. The findings support a circuit-based approach to underlying mechanisms since this tract connects many brain areas previously implicated in insomnia.

The Dual Orexin Receptor Antagonist DORA-22 Improves Mild Stress-induced Sleep Disruption During the Natural Sleep Phase of Nocturnal Rats

Dual orexinergic antagonists (DORAs) have been recently developed as a pharmacotherapy alternative to established hypnotics. Hypnotics are largely evaluated in preclinical rodent models in the dark/active period yet should be ideally evaluated in the light/inactive period, analogous to when sleep disruption occurs in humans. We describe here the hypnotic efficacy of DORA-22 in rodent models of sleep disturbance produced by cage changes in the light/inactive period. Rats were administered DORA-22 or the GABA receptor-targeting hypnotic eszopiclone early in the light period, then exposed to six hourly clean cage changes with measurements of NREM sleep onset latency. Both compounds initially promoted sleep (hours 1 and 2), with DORA-22 exhibiting a more rapid hypnotic onset; and exhibited extended efficacy, evident six hours after administration in a sleep latencies test. A common complaint concerning hypnotic use is lingering hypersomnolence, and this is a concern in pharmacotherapy of the elderly. A second study was designed to determine a minimal dose of DORA-22 which would initially promote sleep but exhibit minimal extended hypnotic effect.Animals were administered DORA-22, then exposed for six hours to a single cage previously dirtied by a conspecific, followed by return to home cage. EEG measures indicated that all DORA-22 doses largely promoted sleep in the first hour. The lowest dose (1 mg/kg) did not decrease sleep onset latency at the six-hour timepoint, suggesting no residual hypersomnolence. We described here DORA-22 hypnotic efficacy during the normal sleep period of nocturnal rats, and demonstrate that well-chosen (low) hypnotic doses of DORA-22 may be hypnotically effective yet have minimal lingering effects.