Alteration of motor control during REM sleep has been extensively described in sleep disorders, in particular in isolated REM sleep behavior disorder (iRBD) and narcolepsy type 1 (NT1). NT1 is caused by the loss of orexin/hypocretin (ORX) neurons. Unlike in iRBD, the RBD comorbid symptoms of NT1 is not associated with alpha-synucleinopathies. To determine whether the chronic absence of ORX neuropeptides is sufficient to induce RBD symptoms, we analyzed during REM sleep the EMG signal of the prepro-hypocretin knockout mice (ORX-/-), a recognized mouse model of NT1. Then, we evaluated the severity of motor alterations by comparing EMG data of ORX-/- mice to those of mice with a targeted suppression of the sublaterodorsal glutamatergic neurotransmission, a recognized rodent model of iRBD. We found a significant alteration of tonic and phasic components of EMG during REM sleep in ORX-/- mice, with more phasic events and more REM sleep episodes without atonia compared to the control wild-type mice. However, these phasic events were fewer, shorter and less complex in ORX-/- mice compared to the RBD-like ORX-/- mice. We thus show that ORX-deficiency, as seen in NT1, is sufficient to impair muscle atonia during REM sleep with a moderate severity of alteration as compared to isolated RBD mice. As described in NT1 patients, we report a major inter-individual variability in the severity and the frequency of RBD symptoms in ORX-deficient mice.

OBJECTIVE: This Phase 3 double-blind, placebo-controlled study evaluated the efficacy and safety of daridorexant in Japanese patients with insomnia disorder.
METHODS: 490 patients with insomnia disorder from 95 sites in Japan were randomized to daridorexant 50 mg (n = 163), 25 mg (n = 163) or placebo (n = 164) for 4 weeks, followed by a 7-day placebo run-out and a 30-day safety follow-up. The primary efficacy endpoints, in hierarchical order, were change from baseline at Week 4 in subjective total sleep time (sTST) and subjective latency to sleep onset (sLSO), for daridorexant 50 mg vs placebo. sTST and sLSO were also evaluated (secondary endpoints) for daridorexant 25 mg vs placebo. Safety endpoints included adverse events and next-morning sleepiness (Visual Analog Scale, VAS).
RESULTS: Daridorexant 50 mg significantly increased sTST and decreased sLSO versus placebo at Week 4 (least-squares mean difference [LSMD]: sTST 20.3 min [95 % CI 11.4, 29.2] p < 0.001; sLSO -10.7 min [-15.8, -5.5] p < 0.001). Daridorexant 25 mg also significantly improved both endpoints versus placebo (LSMD: sTST 9.2 min [0.3, 18.1] p = 0.042; sLSO -7.2 min [-12.3, -2.0] p = 0.006). Overall incidence of adverse events was similar across groups (50 mg: 22 %; 25 mg: 18 %; placebo 23 %); somnolence, the most common event, increased with increasing dose (50 mg: 6.8 %; 25 mg: 3.7 %; placebo 1.8 %). However, daridorexant did not increase VAS next-morning sleepiness. No rebound or withdrawal-related symptoms were observed after treatment discontinuation.
CONCLUSIONS: In Japanese patients with insomnia disorder, daridorexant (25 and 50 mg) was well tolerated and significantly improved subjective sleep outcomes, with no evidence of residual effects.

Orexin is exclusively produced in neurons localized within the lateral hypothalamic area (LHA) and perifornical area (PFA). Orexin has been identified as a key promotor of arousal. The selective loss of orexinergic neurons results in narcolepsy. It is known that the intrinsic electrophysiological properties are critical for neurons to perform their functions in corresponding brain regions. In addition to hypothalamic orexin, other brain nuclei are involved in the regulation of sleep and wakefulness. Quite a lot of studies focus on elucidating orexin-induced regulation of sleep-wake states and modulation of neuronal electrophysiological properties in several brain regions. Here, we summarize that the orexinergic neurons exhibit spontaneous firing activity which is associated with the states of sleep-wake cycle. Orexin mainly exerts postsynaptic excitatory effects on multiple brain nuclei associated with the process of sleep and wakefulness. This review may provide a background to guide future research about the cellular mechanisms of orexin-induced maintaining of arousal.

Narcolepsy with cataplexy (NT1) is a rare hypothalamic disorder that presents with a dysregulation of the sleep-wake cycle (i.e., excessive daytime sleepiness and sleep and cataplectic attacks) and other motor, cognitive, psychiatric, metabolic, and autonomic disturbances, with putative autoimmune pathogenesis. Pediatric acute-onset neuropsychiatric syndrome (PANS) is a clinically heterogeneous disorder that presents with acute-onset obsessive-compulsive symptoms and/or a severe eating restriction, with concomitant cognitive, behavioral, or affective symptoms caused by infections and other environmental triggers provoking an inflammatory brain response, which evolves into a chronic or progressive neuroimmune disorder. In this study, we present the case of a 13-year-old boy with vocal tics and syncopal-like episodes, eventually diagnosed as NT1 and PANS, and from this we discuss the hypothesis that both NT1 and PANS might belong to the same immunological spectrum, resulting in comparable imbalances in key neurotransmitter axes (i.e., orexinergic and dopaminergic), with conceptual and operational implications, especially with regards to the pharmacological tretament.

The orexinergic system and its receptors are involved in many physiological processes. Their functions in energy homeostasis, arousal, cognition, stress processing, endocrine functions, and pain modulation have been investigated. Many studies have shown that the orexinergic system cooperates with the dopaminergic system in the addiction process. Emerging evidence suggests that the orexinergic system can be effective in the induction of drug dependence and tolerance. Therefore, several researches have been conducted on the effect of orexin receptor (OXR) antagonists on reducing tolerance and dependence caused by drug abuse. Due to the significant growth of the studies on the orexinergic system, the current literature was conducted to collect the findings of previous studies on orexin and its receptors in the induction of drug addiction. In addition, cellular and molecular mechanisms of the possible role of orexin in drug tolerance and dependence are discussed. The findings indicate that the administration of OXR antagonists reduces drug dependence. OXR blockers seem to counteract the addictive effects of drugs through multiple mechanisms, such as preventing neuronal adaptation. This review proposes the potential clinical use of OXR antagonists in the treatment of drug dependence.

β-amyloid42 (Aβ42) in Alzheimer\'s disease (AD) and orexin in narcolepsy are considered crucial biomarkers for diagnosis and therapeutic targets. Recently, orexin and Aβ cerebral dynamics have been studied in both pathologies, but how they interact with each other remains further to be known. In this study, we investigated the reliability of using the correlation between orexin-A and Aβ42 CSF levels as a candidate marker to explain the chain of events leading to narcolepsy or AD pathology. In order to test the correlation between these biomarkers, patients diagnosed with AD (n = 76), narcolepsy type 1 (NT1, n = 17), narcolepsy type 2 (NT2, n = 23) and healthy subjects (n = 91) were examined. Patients and healthy subjects underwent lumbar puncture between 8:00 and 10:00 am at the Neurology Unit of the University Hospital of Rome \"Tor Vergata\". CSF levels of Aβ42, total-tau, phosphorylated-tau, and orexin-A were assessed. The results showed that CSF levels of Aβ42 were significantly lower (p < 0.001) in AD (332.28 ± 237.36 pg/mL) compared to NT1 (569.88 ± 187.00 pg/mL), NT2 (691.00 ± 292.63 pg/mL) and healthy subjects (943.68 ± 198.12 pg/mL). CSF orexin-A levels were statistically different (p < 0.001) between AD (148.01 ± 29.49 pg/mL), NT1 (45.94 ± 13.63 pg/mL), NT2 (104.92 ± 25.55 pg/mL) and healthy subjects (145.18 ± 27.01 pg/mL). Moderate-severe AD patients (mini mental state examination < 21) showed the highest CSF orexin-A levels, whereas NT1 patients showed the lowest CSF orexin-A levels. Correlation between CSF levels of Aβ42 and orexin-A was found only in healthy subjects (r = 0.26; p = 0.01), and not in narcolepsy or AD patients. This lack of correlation in both diseases may be explained by the pathology itself since the correlation between these two biomarkers is evident only in the healthy subjects. This study adds to the present literature by further documenting the interplay between orexinergic neurotransmission and cerebral Aβ dynamics, possibly sustained by sleep.

OBJECTIVE: Sleep disturbances are amongst most frequent non-motor symptoms of Parkinson\'s Disease (PD), and they are similarly frequently reported in other alpha-syncleinopathies, such as Dementia with Lewy Bodies (DLB) and Multiple System Atrophy (MSA). More recently, the orexin system has been implicated in control of arousal based on salient environmental set points, and its dysregulation in sleep issues in alpha-synucleinopathies suggested by the findings from the translational animal models. However, its role in the patients with alpha-synucleinopathies remains unclear. We thus set to systematically review, and to critically assess, contemporary evidence on the association of the orexinergic system and sleep disturbances in alpha-synucleinopathies. In this systematic review, studies investigating orexin and sleep in alpha-synucleinopathies (Rapid Eye Movement (REM) Behaviour Disorder (RBD), Parkinson\'s Disease (PD), Dementia with Lewy Bodies (DLB), Multiple System Atrophy (MSA)) were identified using electronic database searches of PubMed, Web of Science and PsychINFO using MeSH terms, keywords, and title words such as \"Alpha-synucleinopathies\" AND \"Orexin\" AND \"Sleep Disturbances\".
RESULTS: 17 studies were included in this systemic review, of which 2 studies on RBD, 10 on PD, 4 on DLB, and 1 on MSA patients. Taken together, RBD and PD studies suggest a potential adaptive increase in orexin levels in early stages of the neurodegenerative process, with reduced levels more often reported for later, more advanced stages of illness. To date, no differences in orexin levels were demonstrated between MSA patients and healthy controls. There is a dearth of studies on the role of orexin levels in alpha-synucleinopathies. Moreover, significant methodologic limitations in the current body of work, including use of non-standardised research protocols and lack of prospective, multi-centre studies, disallow for any finite conclusion in regards to underlying pathomechanisms. Nonetheless, a picture of a complex, multifaceted relationship between the dysregulation of the orexinergic pathway and sleep disturbances in alpha-synucleinopathies is emerging. Hence, future studies disentangling orexinergic pathomechanisms of alpha-syncleinopathies are urgently needed to obtain a more comprehensive account of the role of orexinergic pathway in alpha-synucleinopathies. Pharmacological manipulations of orexins may have multiple therapeutic applications in treatment strategies, disease diagnosis, and might be effective for treating both motor and non-motor symptoms.

Failure to recover from repeated hypercapnia and hypoxemia (HH) challenges caused by severe GCS and postictal apneas may contribute to sudden unexpected death in epilepsy (SUDEP). Our previous studies found orexinergic dysfunction contributes to respiratory abnormalities in a preclinical model of SUDEP, Kcna1-/- mice. Here, we developed two gas challenges consisting of repeated HH exposures and used whole body plethysmography to determine whether Kcna1-/- mice have detrimental ventilatory responses. Kcna1-/- mice exhibited an elevated ventilatory response to a mild repeated hypercapnia-hypoxia (HH) challenge compared to WT. Moreover, 71% of Kcna1-/- mice failed to survive a severe repeated HH challenge, whereas all WT mice recovered. We next determined whether orexin was involved in these differences. Pretreating Kcna1-/- mice with a dual orexin receptor antagonist rescued the ventilatory response during the mild challenge and all subjects survived the severe challenge. In ex vivo extracellular recordings in the lateral hypothalamus of coronal brain slices, we found reducing pH either inhibits or stimulates putative orexin neurons similar to other chemosensitive neurons; however, a significantly greater percentage of putative orexin neurons from Kcna1-/-mice were stimulated and the magnitude of stimulation was increased resulting in augmentation of the calculated chemosensitivity index relative to WT. Collectively, our data suggest that increased chemosensitive activity of orexin neurons may be pathologic in the Kcna1-/- mouse model of SUDEP, and contribute to elevated ventilatory responses. Our preclinical data suggest that those at high risk for SUDEP may be more sensitive to HH challenges, whether induced by seizures or other means; and the depth and length of the HH exposure could dictate the probability of survival.

The Maintenance of Wakefulness Test (MWT) is a widely accepted objective test used to evaluate daytime somnolence and is commonly used in clinical studies evaluating novel therapeutics for excessive daytime sleepiness. In the latter, sleep onset latency (SOL) is typically the sole MWT endpoint. Here, we explored microsleeps, sleep probability measures derived from automated sleep scoring, and quantitative electroencephalography (qEEG) features as additional MWT biomarkers of daytime sleepiness, using data from a phase 1B trial of the selective orexin receptor 2 agonist danavorexton (TAK-925) in people with narcolepsy type 1 (NT1) or type 2 (NT2). Danavorexton treatment reduced the rate and duration of microsleeps during the MWT in NT1 (days 1 and 7; p ≤ 0.005) and microsleep rate in NT2 (days 1 and 7; p < 0.0001). Use of an EEG-sleep-staging-derived measure to determine the probability of wakefulness for each minute revealed a novel metric to track changes in daytime sleepiness, which were consistent with the θ/α ratio, a known biomarker of drowsiness. The slopes of line-fits to both the log-transformed sleepiness score or log-transformed θ/α ratio correlated well to (inverse) MWT SOL for NT1 (R = 0.93 and R = 0.83, respectively) and NT2 (R = 0.97 and R = 0.84, respectively), suggesting that individuals with narcolepsy have increased sleepiness immediately after lights-off. These analyses demonstrate that novel EEG-based biomarkers can augment SOL as predictors of sleepiness and its response to treatment and provide a novel framework for the analysis of wake EEG in hypersomnia disorders.

Introduction: Premenstrual dysphoric disorder (PMDD), a severe form of premenstrual syndrome (PMS), is a serious health disorder that affects patient moods. It is caused by cyclic psychological symptoms and its pathogenesis is still unclear. Abnormalities in the basolateral amygdala (BLA) orexin system, which are important causes of the development of depressive mood, have not been reported in PMDD, so exploring its intrinsic mechanisms is meaningful for enriching the pathomechanisms of PMDD. Methods: High performance liquid chromatography was used for the determination of the active ingredients of Jingqianshu granules. Developing a rat model of premenstrual depression using the forced swimming test (FST). The experiment consisted of two parts. In Part 1, the rats were divided into the control group, the model group, the model + Jingqianshu group, and the model + fluoxetine group. The FST, open field test, and elevated plus maze test, were used to assess the behavior of the rats as well as to evaluate the effect of drug intervention. Immunofluorescence and RT-qPCR were used to detect the expression of orexin and its receptors OX1R and OX2R genes and proteins. The expression of Toll-like receptor 4, nuclear factor kappa-B, tumor necrosis factor-α, interleukin 6, and interleukin-1β in the BLA brain region was detected by Western-Blot. In part 2, the rats were injected intracerebrally with orexin-A. Observe the behavioral activities of rats in the control group, model group, and model+orexin-A group. Immunofluorescence was used to detect microglia in the BLA area of rats, and the expression levels of the above inflammatory factors were detected by Western-Blot. Results: The five components of Jingqianshu granules are: paeoniflorin, erulic acid, liquiritin, hesperidin, and paeonol. During the estrous cycle, rats exhibited depressive-like behavior during the non-receptive phase of the behavioral test, which disappeared during the receptive phase. Immunofluorescence and RT-qPCR showed reduced gene and protein expression of orexin, OX1R, and OX2R in the BLA region of rats in the model group.WB showed elevated levels of inflammatory factors. All returned to control levels after drug treatment. In part 2, injection of orexin-A into the BLA brain region of model rats resulted in reduced immunoreactivity of microglia and decreased expression levels of inflammatory factors. Discussion: Jianqianshu granules can achieve the purpose of treating premenstrual depression by regulating orexin-mediated inflammatory factors, which provides a new idea for further research on the pathogenesis of PMDD. However, the current study is still preliminary and the pathogenesis of PMDD is complex. Therefore, more in-depth exploration is needed.