Narcolepsy: genetic predisposition and neuropharmacological mechanisms. REVIEW ARTICLE

The role of orexinergic system in the regulation of cataplexy

Loss of orexin/hypocretin causes serious sleep disorder; narcolepsy. Cataplexy is the most striking symptom of narcolepsy, characterized by abrupt muscle paralysis induced by emotional stimuli, and has been considered pathological activation of REM sleep atonia system. Clinical treatments for cataplexy/narcolepsy and early pharmacological studies in narcoleptic dogs tell us about the involvement of monoaminergic and cholinergic systems in the control of cataplexy/narcolepsy. Muscle atonia may be induced by activation of REM sleep-atonia generating system in the brainstem. Emotional stimuli may be processed in the limbic systems including the amygdala, nucleus accumbens, and medial prefrontal cortex. It is now considered that orexin/hypocretin prevents cataplexy by modulating the activity of different points of cataplexy-inducing circuit, including monoaminergic/cholinergic systems, muscle atonia-generating systems, and emotion-related systems. This review will describe the recent advances in understanding the neural mechanisms controlling cataplexy, with a focus on the involvement of orexin/hypocretin system, and will discuss future experimental strategies that will lead to further understanding and treatment of this disease.

Narcolepsy in Children: Sleep disorders in children, A rapidly evolving field seeking consensus

Narcolepsy is a life-long sleep disorder with two distinct subtypes, narcolepsy type I and narcolepsy type II. It is now well recognized that the loss of hypocretin neurons underlies the pathogenesis of narcolepsy type I, however, the pathogenesis of narcolepsy type II is currently unknown. Both genetic and environmental factors play an important role in the pathogenesis of narcolepsy. There is increasing evidence that autoimmune processes may play a critical role in the loss of hypocretin neurons. Infections especially streptococcus and influenza have been proposed as a potential trigger for the autoimmune-mediated mechanism. Several recent studies have shown increased cases of pediatric narcolepsy following the 2009 H1N1 pandemic. The increased cases in Europe seem to be related to a specific type of H1N1 influenza vaccination (Pandemrix), while the increased cases in China are related to influenza infection. Children with narcolepsy can have an unusual presentation at disease onset including complex motor movements which may lead to delayed diagnosis. All classic narcolepsy tetrads are present in only a small proportion of children. The diagnosis of narcolepsy is confirmed by either obtaining cerebrospinal fluid hypocretin or overnight sleep study with the multiple sleep latency test (MSLT). There are limitations of using MSLT in young children such that a negative MSLT test cannot exclude narcolepsy. HLA markers have limited utility in narcolepsy, but it may be useful in young children with clinical suspicion of narcolepsy. For management, both pharmacologic and non-pharmacologic treatments are important in the management of narcolepsy. Pharmacotherapy is primarily aimed to address excessive daytime sleepiness and REM-related symptoms such as cataplexy. In addition to pharmacotherapy, routine screening of behavioral and psychosocial issues is warranted to identify patients who would benefit from bio-behavior intervention.

The Genetics of Sleep Disorders in Children: A Narrative Review

Sleep is a universal, highly preserved process, essential for human and animal life, whose complete functions are yet to be unravelled. Familial recurrence is acknowledged for some sleep disorders, but definite data are lacking for many of them. Genetic studies on sleep disorders have progressed from twin and family studies to candidate gene approaches to culminate in genome-wide association studies (GWAS). Several works disclosed that sleep-wake characteristics, in addition to electroencephalographic (EEG) sleep patterns, have a certain degree of heritability. Notwithstanding, it is rare for sleep disorders to be attributed to single gene defects because of the complexity of the brain network/pathways involved. Besides, the advancing insights in epigenetic gene-environment interactions add further complexity to understanding the genetic control of sleep and its disorders. This narrative review explores the current genetic knowledge in sleep disorders in children, following the International Classification of Sleep Disorders-Third Edition (ICSD-3) categorisation.

Polysomnographic nighttime features of narcolepsy: A systematic review and meta-analysis

Polysomnographic studies have been conducted to explore nighttime sleep features in narcolepsy, but their relationship to narcolepsy is still imperfectly understood. We conducted a systematic review of the literature exploring polysomnographic differences between narcolepsy patients and healthy controls (HCs) in EMBASE, MEDLINE, All EBM databases, CINAHL, and PsycINFO. 108 studies were identified for this review, 105 of which were used for meta-analysis. Meta-analyses revealed significant reductions in sleep latency, sleep efficiency, slow wave sleep percentage, rapid eye movement sleep (REM) latency, cyclic alternating pattern rate, and increases in total sleep time, wake time after sleep onset (WASO), awakening numbers (AWN) per hour, stage shift (SS) per hour, N1 percentage, apnea hypopnea index, and periodic limb movement index in narcolepsy patients compared with HCs. Furthermore, narcolepsy type 1 patients showed more disturbed nighttime sleep compared with narcolepsy type 2 patients. Children and adolescent narcolepsy patients show increased WASO, AWN, and SS compared with adult patients. Macro- and micro-structurally, our study suggests that narcolepsy patients have poor nighttime sleep. Sex, age, body mass index, disease duration, disease type, medication status, and adaptation night are demographic, clinical and methodological factors that contribute to heterogeneity between studies.

Orexin-A/Hypocretin-1 Controls the VTA-NAc Mesolimbic Pathway via Endocannabinoid-Mediated Disinhibition of Dopaminergic Neurons in Obese Mice

Disinhibition of orexin-A/hypocretin-1 (OX-A) release occurs to several output areas of the lateral hypothalamus (LH) in the brain of leptin knockout obese ob/ob mice. In this study, we have investigated whether a similar increase of OX-A release occurs to the ventral tegmental area (VTA), an orexinergic LH output area with functional effects on dopaminergic signaling at the mesolimbic circuit. By confocal and correlative light and electron microscopy (CLEM) morphological studies coupled to molecular, biochemical, and pharmacological approaches, we investigated OX-A-mediated dopaminergic signaling at the LH-VTA-nucleus accumbens (NAc) pathway in obese ob/ob mice compared to wild-type (wt) lean littermates. We found an elevation of OX-A trafficking and release to the VTA of ob/ob mice and consequent orexin receptor-1 (OX1R)-mediated over-activation of dopaminergic (DA) neurons via phospholipase C (PLC)/diacylglycerol lipase (DAGL-α)-induced biosynthesis of the endocannabinoid 2-arachidonoylglycerol (2-AG). In fact, by retrograde signaling to cannabinoid receptor type 1 (CB1R) at inhibitory inputs to DA neurons, 2-AG inhibited GABA release thus inducing an increase in DA concentration in the VTA and NAc of ob/ob mice. This effect was prevented by the OX1R antagonist SB-334867 (30 mg/Kg, i.p.), or the CB1R antagonist AM251 (10 mg/Kg, i.p.) and mimicked by OX-A injection (40 μg/Kg, i.p.) in wt lean mice. Enhanced DA signaling to the NAc in ob/ob mice, or in OX-A-injected wt mice, was accompanied by β-arrestin2-mediated desensitization of dopamine D2 receptor (D2R) in a manner prevented by SB-334867 or the D2R antagonist L741 (1.5 mg/Kg, i.p.). These results further support the role of OX-A signaling in the control of neuroadaptive responses, such as compulsive reward-seeking behavior or binge-like consumption of high palatable food, and suggest that aberrant OX-A trafficking to the DA neurons in the VTA of ob/ob mice influences the D2R response at NAc, a main target area of the mesolimbic pathway, via 2-AG/CB1-mediated retrograde signaling.

Early detection of Niemann-pick disease type C with cataplexy and orexin levels: continuous observation with and without Miglustat

Study objectives

Niemann-Pick type C (NPC) is an autosomal recessive and congenital neurological disorder characterized by the accumulation of cholesterol and glycosphingolipids. Symptoms include hepatosplenomegaly, vertical supranuclear saccadic palsy, ataxia, dystonia, and dementia. Some cases frequently display narcolepsy-like symptoms, including cataplexy which was reported in 26% of all NPC patients and was more often recorded among late-infantile onset (50%) and juvenile onset (38%) patients. In this current study, we examined CSF orexin levels in the 10 patients of NPC with and without cataplexy, which supports previous findings.

Methods

Ten patients with NPC were included in the study (5 males and 5 females). NPC diagnosis was biochemically confirmed in all 10 patients, from which 8 patients with NPC1 gene were identified. We compared CSF orexin levels among NPC, narcoleptic and idiopathic hypersomnia patients.

Results

Six NPC patients with cataplexy had low or intermediate orexin levels. In 4 cases without cataplexy, their orexin levels were normal. In 5 cases with Miglustat treatment, their symptoms stabilized or improved. For cases without Miglustat treatment, their conditions worsened generally. The CSF orexin levels of NPC patients were significantly higher than those of patients with narcolepsy-cataplexy and lower than those of patients with idiopathic hypersomnia, which was considered as the control group with normal CSF orexin levels.

Discussion

Our study indicates that orexin level measurements can be an early alert of potential NPC. Low or intermediate orexin levels could further decrease due to reduction in the neuronal function in the orexin system, accelerating the patients’ NPC pathophysiology. However with Miglustat treatment, the orexin levels stabilized or improved, along with other general symptoms. Although the circuitry is unclear, this supports that orexin system is indeed involved in narcolepsy-cataplexy in NPC patients.

Conclusion

The NPC patients with cataplexy had low or intermediate orexin levels. In the cases without cataplexy, their orexin levels were normal. Our study suggests that orexin measurements can serve as an early alert for potential NPC; furthermore, they could be a marker of therapy monitoring during a treatment.

Isolated Central Hypothyroidism in an Adolescent With Narcolepsy

Isolated central hypothyroidism (ICH) and narcolepsy are conditions rarely seen in the pediatric population which are usually characterized by delayed diagnosis and treatment due to their variable presentation and subclinical onset. We describe an unusual case of an adolescent male diagnosed with narcolepsy and central hypothyroidism. A 15-year-old obese boy presented with the complaint of excessive daytime sleepiness, fatigue, and snoring. Obstructive sleep apnea (OSA) was initially suspected as the underlying cause, but the sleep study was negative for OSA. However, the multiple sleep latency test was consistent with narcolepsy without cataplexy. He was then started on modafinil, but his symptoms persisted. Thyroid function tests were performed that were consistent with ICH. Thyroid replacement therapy was initiated with subsequent improvement in symptoms. A theoretical association exists between narcolepsy and ICH due to the involvement of the hypothalamus and pituitary gland. Nevertheless, clinical association, as seen in our case, is rare. Central hypothyroidism is a known etiology leading to fatigue and sleepiness. Narcolepsy without cataplexy can have overlapping symptoms with hypothyroidism, as seen in our patient. The presence of narcolepsy should prompt screening for hypothyroidism in appropriate clinical settings.

Constructing gene network for type 1 narcolepsy based on genome-wide association study and differential gene expression analysis (STROBE)

Although many genes that affect narcolepsy risk have been identified, the interactions among these genes are still unclear. Moreover, there is a lack of research on the construction of the genetic network of narcolepsy. To screen candidate genes related to the onset of narcolepsy type 1, the function and distribution of important genes related to narcolepsy type 1 were studied and a gene network was constructed to study the pathogenesis of narcolepsy type 1.A case-control study (observational study) of 1075 Chinese narcoleptic patients and 1997 controls was conducted. The gene-sequencing data was analyzed using genome-wide association analysis. The candidate genes related to narcolepsy were identified by differential gene expression analysis and literature research. Then, the 28 candidate genes were input into the KEGG database and 32 pathway data related to candidate genes were obtained. A gene network, with the pathways as links and the genes as nodes, was constructed. According to our results, TNF, MHC II, NFATC2, and CXCL8 were the top genes in the gene network.TNF, MHC II, NFATC2, and CXCL8 are closely related to narcolepsy type I and require further study. By analyzing the pathways of disease-related genes and the network of gene interaction, we can provide an outlinefor the study of specific mechanisms of and treatments for narcolepsy.

Utility of the sleep stage sequence preceding sleep onset REM periods for the diagnosis of narcolepsy: a study in a Japanese cohort

BACKGROUND

The minimum narcolepsy criteria "mean sleep latency (MSL) ≤8 min and ≥2 sleep onset rapid eye movement (REM) periods (SOREMPs) on polysomnography (PSG) and the multiple sleep latency test (MSLT)," according to The International Classification of Sleep Disorders, Third Edition (ICSD-3), are not specific to narcolepsy. Recently, the characteristic sleep stage sequences preceding SOREMPs in narcolepsy have received attention, but their diagnostic utility remains unclear.

METHODS

We retrospectively reviewed PSG/MSLT records and chart data for 102 Japanese patients with hypersomnia and at least one SOREMP. We examined the sporadic rates of two sleep stage sequences preceding the SOREMPs-wakefulness or stage 1 to REM (W/S1→R) and stage 2 to REM (S2→R)-comparing these between patient groups with narcolepsy type 1 (N = 28), narcolepsy type 2 (N = 19), and other hypersomnia (N = 55). We also examined the utility of three simple indices using the occurrence of W/S1→R SOREMPs for distinguishing between narcolepsy and other hypersomnia in patients who satisfied the minimum narcolepsy criteria.

RESULTS

W/S1→R SOREMPs were significantly more frequent in narcolepsy than in other hypersomnia, and this tendency was also observed even in the patients who satisfied the minimum narcolepsy criteria. The three indices had moderate sensitivities and specificities for distinguishing between narcolepsy and other hypersomnia in patients satisfying the minimum narcolepsy criteria.

CONCLUSIONS

The W/S1→R pattern was observed significantly more frequently in narcolepsy than in other hypersomnia, suggesting it may help with differentiating narcolepsy from other hypersomnia in patients demonstrating the narcolepsy criteria, although its ability to do so may be modest.

A randomized study of solriamfetol for excessive sleepiness in narcolepsy

Objective

Solriamfetol (JZP‐110) is a selective dopamine and norepinephrine reuptake inhibitor with wake‐promoting effects. This phase 3 study (NCT02348593) evaluated the safety and efficacy of solriamfetol in narcolepsy.

Methods

Patients with narcolepsy with mean sleep latency <25 minutes on the Maintenance of Wakefulness Test (MWT), Epworth Sleepiness Scale (ESS) score ≥10, and usual nightly sleep ≥6 hours were randomized to solriamfetol 75, 150, or 300 mg, or placebo for 12 weeks. Coprimary endpoints were change from baseline to week 12 in MWT and ESS. Improvement on the Patient Global Impression of Change (PGI‐C) was the key secondary endpoint.

Results

Safety and modified intention‐to‐treat populations included 236 and 231 patients, respectively. Solriamfetol 300 and 150 mg were positive on both coprimary endpoints. Least squares mean (standard error [SE]) changes from baseline were 12.3 (SE = 1.4) and 9.8 (SE = 1.3) minutes for solriamfetol 300 and 150 mg on the MWT, respectively, versus 2.1 (SE = 1.3) minutes for placebo, and −6.4 (SE = 0.7) for 300 mg and −5.4 (SE = 0.7) for 150 mg on the ESS versus −1.6 (SE = 0.7) for placebo (all p < 0.0001). At week 12, higher percentages of patients treated with solriamfetol 150 mg (78.2%) and 300 mg (84.7%) reported PGI‐C improvement relative to placebo (39.7%; both p < 0.0001). Adverse events ≥5% across all solriamfetol doses included headache (21.5%), nausea (10.7%), decreased appetite (10.7%), nasopharyngitis (9.0%), dry mouth (7.3%), and anxiety (5.1%).

Interpretation

Solriamfetol has the potential to be an important therapeutic option for the treatment of impaired wakefulness and excessive sleepiness in patients with narcolepsy. ANN NEUROL 2019;85:359–370.

Epidemiology and Pathophysiology of Childhood Narcolepsy

It is now recognized that there are two types of narcolepsy. Narcolepsy type I or Narcolepsy with cataplexy is caused by the loss of hypocretin or orexin neurons. Narcolepsy type II or narcolepsy without cataplexy has normal hypocretin and the etiology is unknown. Hypocretin is a neuropeptide produced by neurons in the lateral hypothalamus. Both genetic and environmental factors play a crucial role in the pathogenesis of narcolepsy. Most patients with narcolepsy type I and half of patients with narcolepsy type II carry HLA-DQB1*0602. HLA-DQB1*0602 forms a heterodimer with HLA-DQA1*0102 and may act as an antigen presenter to the T cell receptors, resulting in narcolepsy susceptibility. In addition, narcolepsy has been shown to be linked to polymorphisms in other non-HLA genes that may affect immune regulatory function, leading to speculation that autoimmune processes may play a crucial role in the loss of hypocretin neurons. Infections have been proposed as a potential trigger for the autoimmune-mediated mechanism. Several recent studies have shown increased cases of narcolepsy, especially in children and adolescents in relation with H1N1 influenza. The increased cases in Europe seems to be related to a specific type of H1N1 influenza vaccination (Pandemrix), while the increased cases in China are related to influenza infection. The data from the Pediatric Working Group of the Sleep Research Network have shown similar increases of early onset narcolepsy in the United States.

Wake-promoting effects of ONO-4127Na, a prostaglandin DP1 receptor antagonist, in hypocretin/orexin deficient narcoleptic mice

Prostaglandin (PG)D2 is an endogenous sleep substance, and a series of animal studies reported that PGD2 or PGD2 receptor (DP1) agonists promote sleep, while DP1 antagonists promote wakefulness. This suggests the possibility of use of PG DP1 antagonists as wake-promoting compounds. We therefore evaluated the wake-promoting effects of ONO-4127Na, a DP1 antagonist, in a mouse model of narcolepsy (i.e., orexin/ataxin-3 transgenic mice) and compared those to effects of modafinil. ONO-4127Na perfused in the basal forebrain (BF) area potently promoted wakefulness in both wild type and narcoleptic mice, and the wake-promoting effects of ONO-4127Na at 2.93 × 10(-4) M roughly corresponded to those of modafinil at 100 mg/kg (p.o.). The wake promoting effects of ONO-4127Na was observed both during light and dark periods, and much larger effects were seen during the light period when mice slept most of the time. ONO-4127Na, when perfused in the hypothalamic area, had no effects on sleep. We further demonstrated that wake-promoting effects of ONO-4127Na were abolished in DP1 KO mice, confirming that the wake-promoting effect of ONO-4127Na is mediated by blockade of the PG DP1 receptors located in the BF area. ONO-4127Na reduced DREM, an EEG/EMG assessment of behavioral cataplexy in narcoleptic mice, suggesting that ONO-4127Na is likely to have anticataplectic effects. DP1 antagonists may be a new class of compounds for the treatment of narcolepsy-cataplexy, and further studies are warranted.

Effect of Oral JZP-110 (ADX-N05) on Wakefulness and Sleepiness in Adults with Narcolepsy: A Phase 2b Study

STUDY OBJECTIVES

To evaluate the efficacy and safety of oral JZP-110, a second-generation wake-promoting agent with dopaminergic and noradrenergic activity, for treatment of impaired wakefulness and excessive sleepiness in adults with narcolepsy.

METHODS

This was a phase 2b, randomized, double-blind, placebo-controlled, parallel-group trial conducted at 28 centers in the United States. Patients were adults with narcolepsy who had baseline scores ≥ 10 on the Epworth Sleepiness Scale (ESS) and baseline sleep latency ≤ 10 min on the Maintenance of Wakefulness Test (MWT). Patients received a daily placebo (n = 49) or JZP-110 (n = 44) 150 mg/day weeks 1-4 and 300 mg/day weeks 5-12. Primary efficacy endpoints were change from baseline in average MWT sleep latency, and the Clinical Global Impression-Change (CGI-C); secondary endpoints were change from baseline in ESS score and Patient Global Impression-Change.

RESULTS

Improvements were significantly greater with JZP-110 versus placebo on mean MWT sleep latency (4 w, 9.5 versus 1.4 min, P < 0.0001; 12 w, 12.8 versus 2.1 min, P < 0.0001), percentage of patients with CGI-C improvement (4 w, 80% versus 51%, P = 0.0066; 12 w, 86% versus 38%, P < 0.0001), and mean change in ESS (4 w, -5.6 versus -2.4, P = 0.0038; 12 w, -8.5 versus -2.5, P < 0.0001). Three JZP-110-treated patients (6.8%) discontinued due to adverse events (AEs). The most common AEs with JZP-110 versus placebo were insomnia (23% versus 8%), headache (16% versus 10%), nausea (14% versus 6%), diarrhea (11% versus 6%), decreased appetite (14% versus 0%), and anxiety (11% versus 0%).

CONCLUSIONS

At doses of 150-300 mg/day, JZP-110 was well tolerated and significantly improved the ability to stay awake and subjective symptoms of excessive sleepiness in adults with narcolepsy.

CLINICAL TRIALS REGISTRATION

Clinicaltrials.gov identifier NCT01681121.

Can the success of structured therapy for giggle incontinence be predicted?

Introduction:

To evaluate possible factors that can guide the clinician to predict potential cases refractoriness to medical treatment for giggle incontinence (GI) and to examine the effectiveness of different treatment modalities.

Material and methods:

The data of 48 children referred to pediatric urology outpatient clinic between 2000 and 2013 diagnosed as GI were reviewed. Mean age, follow-up, GI frequency, associated symptoms, medical and family history were noted. Incontinence frequency differed between several per day to less than once weekly. Children were evaluated with uroflowmetry-electromyography and post-void residual urine. Clinical success was characterized as a full or partial response, or nonresponse as defined by the International Children's Continence Society. Univariate analysis was used to find potential factors including age, sex, familial history, GI frequency, treatment modality and dysfunctional voiding to predict children who would possibly not respond to treatment.

Results:

Mean age of the patients was 8.4 years (range 5 to 16). Mean follow-up time and mean duration of asymptomatic period were noted as 6.7±1.4 years and 14.2±2.3 months respectively. While 12 patients were treated with only behavioral urotherapy (Group-1), 11 patients were treated with alpha-adrenergic blockers and behavioral urotherapy (Group-2) and 18 patients with methylphenidate and behavioral urotherapy (Group-3). Giggle incontinence was refractory to eight children in-group 1; six children in-group 2 and eight children in-group 3. Daily GI frequency and dysfunctional voiding diagnosed on uroflowmetry-EMG were found as outstanding predictive factors for resistance to treatment modalities.

Conclusions:

A variety of therapies for GI have more than 50% failure rate and a standard treatment for GI has not been established. The use of medications to treat these patients would not be recommended, as they appear to add no benefit to symptoms and may introduce severe adverse effects.

Brain imaging and cognition in young narcoleptic patients

The relationship between functional brain images and performances in narcoleptic patients and controls is a new field of investigation. We studied 71 young, type 1 narcoleptic patients and 20 sex- and age-matched control individuals using brain positron emission tomography (PET) images and neurocognitive testing. Clinical investigation was carried out using sleep-wake evaluation questionnaires; a sleep-wake study was conducted with actigraphy, polysomnography, multiple sleep latency test (MSLT), and blood tests (with human leukocyte antigen typing). The continuous performance test (CPT) and Wisconsin card sorting test (WCST) were administered on the same day as the PET study. PET data were analyzed using Statistical Parametric Mapping (version 8) software. Correlation of brain imaging and neurocognitive function was performed by Pearson's correlation. Statistical analyses (Student's t-test) were conducted with SPSS version-18. Seventy-one narcoleptic patients (mean age: 16.15 years, 41 boys (57.7%)) and 20 controls (mean age: 15.1 years, 12 boys (60%)) were studied. Results from the CPT and WCST showed significantly worse scores in narcoleptic patients than in controls (P < 0.05). Compared to controls, narcoleptic patients presented with hypometabolism in the right mid-frontal lobe and angular gyrus (P < 0.05) and significant hypermetabolism in the olfactory lobe, hippocampus, parahippocampus, amygdala, fusiform, left inferior parietal lobe, left superior temporal lobe, striatum, basal ganglia and thalamus, right hypothalamus, and pons (P < 0.05) in the PET study. Changes in brain metabolic activity in narcoleptic patients were positively correlated with results from the sleepiness scales and performance tests. Young, type 1 narcoleptic patients face a continuous cognitive handicap. Our imaging cognitive test protocol can be useful for investigating the effects of treatment trials in these patients.

Role of the Histamine H3 Receptor in the Central Nervous System

The G_i/o protein-coupled histamine H₃ receptor is distributed throughout the central nervous system including areas like cerebral cortex, hippocampus and striatum with the density being highest in the posterior hypothalamus, i.e. the area in which the histaminergic cell bodies are located. In contrast to the other histamine receptor subtypes (H₁, H₂ and H₄), the H₃ receptor is located presynaptically and shows a constitutive activity. In detail, H₃ receptors are involved in the inhibition of histamine release (presynaptic autoreceptor), impulse flow along the histaminergic neurones (somadendritic autoreceptor) and histamine synthesis. Moreover, they occur as inhibitory presynaptic heteroreceptors on serotoninergic, noradrenergic, dopaminergic, glutamatergic, GABAergic and perhaps cholinergic neurones. This review shows for four functions of the brain that the H₃ receptor represents a brake against the wake-promoting, anticonvulsant and anorectic effect of histamine (via postsynaptic H₁ receptors) and its procognitive activity (via postsynaptic H₁ and H₂ receptors). Indeed, H₁ agonists and H₃ inverse agonists elicit essentially the same effects, at least in rodents; these effects are opposite in direction to those elicited by brain-penetrating H₁ receptor antagonists in humans. Although the benefit for H₃ inverse agonists for the symptomatic treatment of dementias is inconclusive, several members of this group have shown a marked potential for the treatment of disorders associated with excessive daytime sleepiness. In March 2016, the European Commission granted a marketing authorisation for pitolisant (Wakix^R) (as the first representative of the H₃ inverse agonists) for the treatment of narcolepsy.

Suvorexant for the treatment of insomnia

Suvorexant (Belsorma(®)) is the first orexin receptor antagonist approved by the US FDA (August 2014) for insomnia treatment. Following comprehensive Phase II/III studies, with up to 12 months of treatment in adult and elderly patients, there is little doubt that suvorexant induces and maintains sleep. However, the FDA and sponsor disagreed about effective versus safe doses (November 2012). The FDA considered that 5-15 mg were efficient and probably safe, whereas the sponsors had proposed 15-40 mg. The final approved doses are 5, 10, 15 and 20 mg. The major issues are next-morning somnolence and safety as seen in driving tests, with possible signs of muscle weakness, weird dreams, sleep walking, other nighttime behaviors and suicidal ideation. Despite its limitations, suvorexant's market entry offers a truly novel treatment for insomnia, paving the way for follow-up compounds and opening therapeutic avenues in other disorders for orexin receptor modulating compounds.

Perifornical orexinergic neurons modulate REM sleep by influencing locus coeruleus neurons in rats

Activation of the orexin (OX)-ergic neurons in the perifornical (PeF) area has been reported to induce waking and reduce rapid eye movement sleep (REMS). The activities of OX-ergic neurons are maximum during active waking and they progressively reduce during non-REMS (NREMS) and REMS. Apparently, the locus coeruleus (LC) neurons also behave in a comparable manner as that of the OX-ergic neurons particularly in relation to waking and REMS. Further, as PeF OX-ergic neurons send dense projections to LC, we argued that the former could drive the LC neurons to modulate waking and REMS. Studies in freely moving normally behaving animals where simultaneously neuro-chemo-anatomo-physio-behavioral information could be deciphered would significantly strengthen our understanding on the regulation of REMS. Therefore, in this study in freely behaving chronically prepared rats we stimulated the PeF neurons without or with simultaneous blocking of specific subtypes of OX-ergic receptors in the LC while electrophysiological recording characterizing sleep-waking was continued. Single dose of glutamate stimulation as well as sustained mild electrical stimulation of PeF (both bilateral) significantly increased waking and reduced REMS as compared to baseline. Simultaneous application of OX-receptor1 (OX1R) antagonist bilaterally into the LC prevented PeF stimulation-induced REMS suppression. Also, the effect of electrical stimulation of the PeF was long lasting as compared to that of the glutamate stimulation. Further, sustained electrical stimulation significantly decreased both REMS duration as well as REMS frequency, while glutamate stimulation decreased REMS duration only.

Orexin in sleep, addiction and more: is the perfect insomnia drug at hand?

Orexins A and B (hypocretins 1 and 2) and their two receptors (OX1R and OX2R) were discovered in 1998 by two different groups. Orexin A and B are derived from the differential processing of a common precursor, the prepro-orexin peptide. The neuropeptides are expressed in a few thousand cells located in the lateral hypothalamus (LH), but their projections and receptor distribution are widespread throughout the brain. Remarkably, prepro peptide and double (OX1R/OX2R) receptor knock out (KO) mice reproduce a sleep phenotype known in humans and dogs as narcolepsy/cataplexy. In humans, this disease is characterized by the absence of orexin producing cells in the LH, and severely depleted levels of orexin the cerebrospinal fluid. Null mutation of the individual OX1R or OX2R in mice substantially ameliorates the narcolepsy/cataplexy phenotype compared to the OX1R/OX2R KO, and highlights specific roles of the individual receptors in sleep architecture, the OX1R KO demonstrating an a attenuated sleep phenotype relative to the OX2R KO. It has therefore been suggested that orexin is a master regulator of the sleep-wake cycle, with high activity of the LH orexin cells during wake and almost none during sleep. Less than 10years later, the first orexin antagonist, almorexant, a dual orexin receptor antagonist (DORA), was reported to be effective in inducing sleep in volunteers and insomnia patients. Although development was stopped for almorexant and for Glaxo's DORA SB-649868, no less than 4 orexin receptor antagonists have reached phase II for insomnia, including Filorexant (MK-6096) and Suvorexant (MK-4305) from Merck. Suvorexant has since progressed to Phase III and dossier submission to the FDA. These four compounds are reported as DORAs, however, they equilibrate very slowly at one and/or the other orexin receptor, and thus at equilibrium may show more or less selectivity for OX1R or OX2R. The appropriate balance of antagonism of the two receptors for sleep is a point of debate, although in rodent models OX2R antagonism alone appears sufficient to induce sleep, whereas OX1R antagonism is largely devoid of this effect. Orexin is involved in a number of other functions including reward and feeding, where OX1R (possibly OX2R) antagonists display anti-addictive properties in rodent models of alcohol, smoking, and drug self-administration. However, despite early findings in feeding and appetite control, orexin receptor antagonists have not produced the anticipated effects in models of increased food intake or obesity in rodents, nor have they shown marked effects on weight in the existing clinical trials. The role of orexin in a number of other domains such as pain, mood, anxiety, migraine and neurodegenerative diseases is an active area of research. The progress of the orexin field is thus extraordinary, and the community awaits the clinical testing of more receptor selective antagonists in sleep and other disorders, as well as that of orexin agonists, with the latter expected to produce positive outcomes in narcolepsy/cataplexy and other conditions.

Greatly increased numbers of histamine cells in human narcolepsy with cataplexy

OBJECTIVE

To determine whether histamine cells are altered in human narcolepsy with cataplexy and in animal models of this disease.

METHODS

Immunohistochemistry for histidine decarboxylase (HDC) and quantitative microscopy were used to detect histamine cells in human narcoleptics, hypocretin (Hcrt) receptor-2 mutant dogs, and 3 mouse narcolepsy models: Hcrt (orexin) knockouts, ataxin-3-orexin, and doxycycline-controlled-diphtheria-toxin-A-orexin.

RESULTS

We found an average 64% increase in the number of histamine neurons in human narcolepsy with cataplexy, with no overlap between narcoleptics and controls. However, we did not see altered numbers of HDC cells in any of the animal models of narcolepsy.

INTERPRETATION

Changes in histamine cell numbers are not required for the major symptoms of narcolepsy, because all animal models have these symptoms. The histamine cell changes we saw in humans did not occur in the 4 animal models of Hcrt dysfunction we examined. Therefore, the loss of Hcrt receptor-2, of the Hcrt peptide, or of Hcrt cells is not sufficient to produce these changes. We speculate that the increased histamine cell numbers we see in human narcolepsy may instead be related to the process causing the human disorder. Although research has focused on possible antigens within the Hcrt cells that might trigger their autoimmune destruction, the present findings suggest that the triggering events of human narcolepsy may involve a proliferation of histamine-containing cells. We discuss this and other explanations of the difference between human narcoleptics and animal models of narcolepsy, including therapeutic drug use and species differences.

Increased plasma level of tumor necrosis factor α in patients with narcolepsy in Taiwan

BACKGROUND

Narcolepsy is a neuropsychiatric disorder characterized by excessive daytime sleepiness, cataplexy, hypnagogic hallucinations, and abnormal rapid eye movement (REM) sleep. Tumor necrosis factor α (TNF α) and its cognate receptors have been reported to be involved in the pathophysiology of narcolepsy in addition to the HLA antigen system. Our study aimed to determine if the TNF-α system was associated with narcolepsy in our patients.

METHODS

We first measured the plasma level of TNF α in 56 narcoleptic patients and 53 control subjects using a highly sensitive enzyme-linked immunosorbent assay. We next determined the genotype of three single nucleotide polymorphisms (SNPs) (T-1031C, C-863A, and C-857T) at the promoter region of the TNF-α gene and one missense SNP (T587G, M196R) at the exon 6 of the tumor necrosis factor receptor 2 gene, TNFR2, in a sample of 75 narcoleptic patients and 201 control subjects by direct sequencing analysis.

RESULTS

We found a significant elevation of plasma level of TNF α in patients with narcolepsy compared with the control subjects (4.64pg/mL vs 1.06pg/mL; P=.0013). However, we did not find significant differences between these two groups in the allelic and genotypic distributions of the investigated polymorphisms.

CONCLUSIONS

Our study suggests that an increased TNF-α level was associated with narcolepsy in our patients, and that chronic inflammation due to various factors might have led to the increased TNF-α levels found in our patients.

Association analysis of the major histocompatibility complex, class II, DQ β1 gene, HLA-DQB1, with narcolepsy in Han Chinese patients from Taiwan

BACKGROUND

Narcolepsy is a rare, chronic, disabling neuropsychiatric disorder characterized by excessive daytime sleepiness, cataplexy, hypnagogic hallucinations, sleep paralysis, and abnormal rapid eye movement sleep. It is strongly associated with the HLA-DQB1(∗)06:02 allele in various ethnic groups. Our study aimed to investigate the allelic spectrum of HLA-DQB1 in a sample of Han Chinese patients with narcolepsy and control subjects from Taiwan.

METHODS

We determined the genotype of the major histocompatibility complex, class II, DQ β1 gene, HLA-DQB1, in 72 narcolepsy subjects (44 men, 28 women), including 52 narcolepsy subjects with cataplexy (narcolepsy+cataplexy), 20 narcolepsy subjects without cataplexy (narcolepsy-cataplexy), and 194 control subjects (94 men, 100 women) using a sequence-specific oligonucleotide-probe hybridization technique.

RESULTS

We found a strong HLA-DQB1(∗)06:02 association in narcolepsy+cataplexy subjects (odds ratio [OR], 321.4 [95% confidence interval {CI}, 70.7-1461.4]). The association was less prominent in narcolepsy-cataplexy subjects (OR, 6.9 [95% CI, 2.4-20.1]). In addition to the DQB1(∗)06:02, we found that (∗)03:01 also was a predisposing allele (OR, 2.0 [95% CI, 1.1-3.7]) in narcolepsy+cataplexy subjects, though the (∗)06:01 was a predisposing allele (OR, 2.8 [95% CI, 1.2-6.7]) in narcolepsy-cataplexy subjects. Furthermore, we found a significant overrepresentation of DQB1(∗)06:02 homozygotes in narcolepsy+cataplexy subjects.

CONCLUSIONS

Our data add further support to the strong association of the HLA-DQB1(∗)06:02 allele with narcolepsy, especially in narcolepsy+cataplexy patients. Our study also indicates additional HLA-DQB1 alleles may modify the presentation of narcolepsy+cataplexy patients, such as DQB1(∗)03:01 and DQB1(∗)06:01 in our study. Our results are limited by the small sample size and can only be considered as preliminary findings.

Efficacy and safety of adjunctive modafinil treatment on residual excessive daytime sleepiness among nasal continuous positive airway pressure-treated japanese patients with obstructive sleep apnea syndrome: a double-blind placebo-controlled study

STUDY OBJECTIVES

This double-blind study evaluated the efficacy and safety of modafinil for treating excessive daytime sleepiness in Japanese patients with obstructive sleep apnea syndrome (OSAS).

METHODS

Patients with residual excessive sleepiness (Epworth Sleepiness Scale [ESS] ≥ 11) on optimal nasal continuous positive airway pressure (nCPAP) therapy (apnea-hypopnea index ≤ 10) were randomized to either 200 mg modafinil (n = 52) or placebo (n = 62) once daily for 4 weeks. Outcomes included baseline-week 4 changes in ESS total score, sleep latency on maintenance of wakefulness test (SL-MWT), nocturnal polysomnography, Pittsburgh Sleep Quality Index (PSQI), and safety.

RESULTS

All 114 randomized patients completed the study. Mean change in ESS total score (-6.6 vs -2.4, p < 0.001) and SL-MWT (+2.8 vs -0.4 minutes, p = 0.009) were significantly greater with modafinil than with placebo. ESS total score decreased from > 11 to < 11 at the final assessment in 69.2% of modafinil-treated patients and 30.6% of placebo-treated patients (p < 0.001). Corresponding rates at week 1 were 57.7% and 33.9% (p = 0.014). Changes in nocturnal polysomnography, PSQI, and apnea-hypopnea index from baseline to the final assessment were similar in both groups. Adverse drug reactions occurred in 36.5% and 22.6% of patients in the modafinil and placebo groups, respectively (p = 0.146).

CONCLUSIONS

Once-daily modafinil was effective and well tolerated for managing residual daytime sleepiness in Japanese OSAS patients with residual excessive daytime sleepiness on optimal nCPAP therapy.

Orexin deficiency and narcolepsy

Orexin deficiency results in the sleep disorder narcolepsy in many mammalian species, including mice, dogs, and humans, suggesting that the orexin system is particularly important for normal regulation of sleep/wakefulness states, and especially for maintenance of wakefulness. This review discusses animal models of narcolepsy; the contribution of each orexin receptor subtype to the narcoleptic phenotypes; and the etiology of orexin neuronal death. It also raises the possibility of novel therapies targeting the orexin system for sleep disorders including insomia and narcolepsy-cataplexy.

Orexin: a potential role in the process of obstructive sleep apnea

Obstructive sleep apnea (OSA) is a complicated disease with an unrecognized mechanism. Obesity, sex, age, and smoking have been found to be independent correlates of OSA. Orexin (also named hypocretin) mainly secreted by lateral hypothalamus neurons has a wide array of biological functions like regulating sleep, energy levels and breathing. Several clinical studies found ties between orexin and OSA. Because of the close correlation between orexin and obesity, sex, age and smoking (which are the key risk factors for OSA patients), we hypothesize that orexin may play a key role in the pathogenesis of OSA.

Hypocretins and the neurobiology of sleep-wake mechanisms

In 1998, our group discovered a cDNA that encoded the precursor of two putative neuropeptides that we called hypocretins for their hypothalamic expression and their similarity to the secretin family of neuropeptides. In the past 15 years, numerous studies have placed the hypocretin system as an integrator of homeostatic functions with a crucial, nonredundant function as an arousal stabilizer. Here, we discuss some of the data that have accumulated over the years on the integrating capacity of these hypothalamic neurons and their role on sleep-to-wake transitions.

Clinical and urodynamic effect of methylphenidate for the treatment of giggle incontinence (enuresis risoria)

AIMS

We retrospectively investigated the efficacy of methylphenidate (MPH) in giggle incontinence (GI), and the relationship between GI and urodynamic parameters.

METHODS

Nine (n = 9) female GI patients underwent 1 year of treatment with 5 mg MPH. Three questionnaires, voiding diaries, and UDS were conducted before and after treatment. The severity of GI was classified into mild, moderate, and severe. Clinical success was characterized as: full response, response, partial response, and non-response.

RESULTS

The mean age of all patients was 16.2 ± 2.3 years. Five patients had mild, one had moderate, and three had severe grade incontinent. All patients reported complete cessation of wetting after MPH treatment. The mean duration of asymptomatic period was 7 ± 3.2 months. There were no statistically significant score changes in all three questionnaires: Urgency Perception Scale (UPS), Overactive Bladder Symptom Score (OABSS) and Primary Overactive Symptom Questionnaire (POSQ), and voiding diaries (P > 0.05). In UDS, there were no statistically significant altered parameters, except maximum urethral closure pressure (MUCP) and maximum urethral pressure (MUP). After treatment, the mean MUCP was increased from 52.2 ± 6.8 to 73.0 ± 5.4 cmH(2) O (P < 0.05), and the mean MUP was increased from 48.6 ± 7.3 to 70.2 ± 5.0 cmH(2) O (P < 0.05).

CONCLUSIONS

MPH can be a viable option for the primary treatment of GI, and it may be related to increasing urethral closure pressure. It was not possible to establish if a relationship between GI and detrusor overactivity exists.

Narcolepsy: a review

Narcolepsy is a lifelong sleep disorder characterized by a classic tetrad of excessive daytime sleepiness with irresistible sleep attacks, cataplexy (sudden bilateral loss of muscle tone), hypnagogic hallucination, and sleep paralysis. There are two distinct groups of patients, ie, those having narcolepsy with cataplexy and those having narcolepsy without cataplexy. Narcolepsy affects 0.05% of the population. It has a negative effect on the quality of life of its sufferers and can restrict them from certain careers and activities. There have been advances in the understanding of the pathogenesis of narcolepsy. It is thought that narcolepsy with cataplexy is secondary to loss of hypothalamic hypocretin neurons in those genetically predisposed to the disorder by possession of human leukocyte antigen DQB1*0602. The diagnostic criteria for narcolepsy are based on symptoms, laboratory sleep tests, and serum levels of hypocretin. There is no cure for narcolepsy, and the present mainstay of treatment is pharmacological treatment along with lifestyle changes. Some novel treatments are also being developed and tried. This article critically appraises the evidence for diagnosis and treatment of narcolepsy.

Expert opinion on pharmacotherapy of narcolepsy

IMPORTANCE TO THE FIELD

Narcolepsy is a neurodegenerative disorder resulting in the instability of the sleep-wake cycle and marked by low levels of hypocretin in cerebrospinal fluid. Sleep instability is marked by brisk, sleep-onset REM periods and sleep fragmentation, while the waking state is interrupted by the intrusion of REM sleep and sometimes accompanied by cataplectic attacks.

AREAS COVERED IN THIS REVIEW

Current pharmacologic interventions that aim to address three primary features of this disorder; excessive daytime sleepiness (EDS), cataplexy and automatic behaviors, and sleep fragmentation. We review and compare the use of traditional and new stimulants in the treatment of EDS. For the treatment of cataplexy and automatic behaviors, serotonergic and noradrenergic agents are considered. The role of gamma-hydroxybutyrate (GHB) is also explored in its ability to reduce daytime sleepiness and catapletic attacks and to consolidate sleep. Findings are based on a PubMed literature search of clinical and basic science research papers spanning 1977-2009.

WHAT THE READER WILL GAIN

A comprehensive understanding of the various existing and promising future treatments for narcolepsy. For each of these treatments, we evaluate risks versus benefits of treatment, and proposed pharmacologic mechanisms of action. We conclude with a review of new treatment approaches, including thyrotropin-releasing hormone (TRH), histamine agonists, immunotherapy and hypocretin replacement therapies.

TAKE HOME MESSAGE

Narcolepsy is an autoimmune, neurodegenerative disorder that results in significant sleep-wake instability with or without cataplectic attacks. Current treatments aim symptomatically to reconsolidate the sleep and waking states and to reduce daytime attacks of cataplexy. Future treatments aim primarily towards correcting the causal deficiency of hypocretin or preventing the autoimmune response that results in the loss of hypocretin cells.

Chemistry and biology of orexin signaling

The orexins are neurohormones that, in concert with their cognate receptors, regulate a number of important physiological processes, including feeding, sleep, reward seeking and energy homeostasis. The orexin receptors have recently emerged as important drug targets. This review provides an overview of recent development in deciphering the biology of orexin signaling as well as efforts to manipulate orexin signaling pharmacologically.

[Narcolepsy with and without cataplexy: an uncommon disabling and unrecognized disease]

Although narcolepsy is a relatively uncommon condition, its impact on a child's life can be dramatic and disabling. Narcolepsy is characterized by excessive daytime sleepiness (EDS), with brief "sleep attacks" at very unusual times and usually associated with cataplexy (sudden loss of muscle control while awake, resulting in a fall, triggered by laughter). Other symptoms frequently reported are sleep paralysis (feeling of being unable to move or speak, even totally aware), hypnagogic hallucinations (vivid dreamlike experiences difficult to distinguish from reality) or disturbed night time sleep. Some children also experience depression or overweight-obesity. Although narcolepsy has been thoroughly studied, the exact cause is unknown. It appears to be a disorder of cerebral pathways that control sleep and wakefulness, involving dorsolateral hypothalamus and hypocretin. A genetic factor has been suggested, but narcolepsy in relatives is rare. Researchers have suggested that a set of genes combines with additional factors in a person's life to cause narcolepsy. The effective treatment of narcolepsy requires not only medication (usually stimulants, antidepressants and sodium oxybate), but also adjustments in life-style (scheduled naps). Management of this condition in children demands a comprehensive approach to the patient, that includes a correct diagnosis, pharmacological and non-pharmacological treatment and adjustments in the environment. These strategies can improve the child's self-esteem and ability to obtain a good education.

Differential effects of acute and repeat dosing with the H3 antagonist GSK189254 on the sleep-wake cycle and narcoleptic episodes in Ox-/- mice

BACKGROUND AND PURPOSE

Histamine H3 receptor antagonists are currently being evaluated in clinical trials for a number of central nervous system disorders including narcolepsy. These agents can increase wakefulness (W) in cats and rodents following acute administration, but their effects after repeat dosing have not been reported previously.

EXPERIMENTAL APPROACH

EEG and EMG recordings were used to investigate the effects of acute and repeat administration of the novel H3 antagonist GSK189254 on the sleep-wake cycle in wild-type (Ox+/+) and orexin knockout (Ox-/-) mice, the latter being genetically susceptible to narcoleptic episodes. In addition, we investigated H3 and H1 receptor expression in this model using radioligand binding and autoradiography.

KEY RESULTS

In Ox+/+ and Ox-/- mice, acute administration of GSK189254 (3 and 10 mg x kg(-1) p.o.) increased W and decreased slow wave and paradoxical sleep to a similar degree to modafinil (64 mg x kg(-1)), while it reduced narcoleptic episodes in Ox-/- mice. After twice daily dosing for 8 days, the effect of GSK189254 (10 mg x kg(-1)) on W in both Ox+/+ and Ox-/- mice was significantly reduced, while the effect on narcoleptic episodes in Ox-/- mice was significantly increased. Binding studies revealed no significant differences in H3 or H1 receptor expression between Ox+/+ and Ox-/- mice.

CONCLUSIONS AND IMPLICATIONS

These studies provide further evidence to support the potential use of H3 antagonists in the treatment of narcolepsy and excessive daytime sleepiness. Moreover, the differential effects observed on W and narcoleptic episodes following repeat dosing could have important implications in clinical studies.

Pediatric narcolepsy

Narcolepsy is a disabling disease with a prevalence of 0.05%. It is characterized by excessive daytime sleepiness, cataplexy, sleep paralysis, hypnogogic hallucinations, automatic behavior, and disrupted nocturnal sleep. The presentation can be very variable, making diagnosis difficult. Loss of hypocretin containing neurons in the lateral hypothalamus has been noted in autopsy studies, and the cerebrospinal fluid level of hypocretin is reduced in patients with narcolepsy with cataplexy. New treatment options are available for the many symptoms of this disease. Early recognition and treatment can greatly improve the quality of life of patients with narcolepsy. A detail review of the epidemiology, pathophysiology, and management of narcolepsy in children is presented.

Management of narcolepsy

BACKGROUND

Narcolepsy is a rare chronic sleep disorder classically characterized by excessive daytime sleepiness. Other symptoms of the disease, including cataplexy, sleep paralysis, hypnagogic hallucinations and disturbed nocturnal sleep, may follow later. The disease can be incapacitating and frequently results in impaired psychosocial interaction. In the absence of a cure for narcolepsy, medical therapy is directed at symptom control.

OBJECTIVES

The aim of this study was to review the current approach to the treatment of narcolepsy.

METHODS

A search of three bibliographic databases (MEDLINE/PubMed, EMBASE and the Cochrane Library Database) was conducted from 1966 to January 2008 using the National Library of Medicine MeSH search terms narcolepsy and cataplexy. Relevant studies, case reports, review articles, editorials, short communications and chapters from selected textbooks were then extracted and manually cross-referenced.

RESULTS/CONCLUSIONS

Traditionally, stimulants have been used to improve the symptoms of excessive daytime sleepiness. However, the treatment of narcolepsy has evolved recently with the widespread use of newer drugs, including modafinil for daytime sleepiness, newer antidepressants for cataplexy and gamma-hydroxybutyrate (sodium oxybate) for both excessive daytime sleepiness and cataplexy.

Antidepressant drugs for narcolepsy

BACKGROUND

Narcolepsy is a disorder of the central nervous system, the main symptoms of which are excessive daytime sleepiness (EDS) and cataplexy (an abrupt and reversible decrease in or loss of muscle tone, affecting the limbs or trunk or both, elicited by emotional stimuli). Narcolepsy has an adverse impact on people's quality of life. Together with stimulant drugs (used to control EDS), antidepressants are usually recommended to counteract cataplexy. In addition, some antidepressants are also reported to improve EDS.

OBJECTIVES

To evaluate the effects of antidepressant drugs on EDS, cataplexy, quality of life, and their side effects in people with narcolepsy.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 2, 2007), MEDLINE (1966 to 2007), EMBASE (1980 to 2007), PsycINFO (1872 to 2007), and CINAHL (1981 to 2007). Bibliographies of identified articles were reviewed to find additional references. Unpublished randomised trials were searched for by consulting governmental and non-governmental clinical trial registers, disease-specific websites, investigators and experts in the field, pharmaceutical companies/manufacturers.

SELECTION CRITERIA

Parallel or cross-over randomised or quasi-randomised controlled trials testing the treatment of narcolepsy with any type of antidepressant drug versus no treatment, placebo, or another antidepressant drug.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data.

MAIN RESULTS

Three cross-over and two parallel trials were included with a total of 246 participants. The methodological quality of all studies was unclear. As the trials tested different comparisons, or had a different design or dealt with different outcome measures, meta-analysis was not performed. In one cross-over trial (10 participants) femoxetine had no significant effect in eliminating or reducing EDS but significantly reduced cataplexy. Mild and transient side effects were reported in the femoxetine treatment period by two participants. In a second cross-over trial (56 participants) viloxazine significantly reduced EDS and cataplexy. In a third cross-over trial the authors inappropriately treated the trial design as a parallel study and no conclusions can be reached in favour of either drug. Two more trials with parallel design tested ritanserin versus placebo without finding differences of effectiveness in reducing EDS or cataplexy.

AUTHORS' CONCLUSIONS

There was no good quality evidence that antidepressants are effective for narcolepsy or improve quality of life. Despite the clinical consensus recommending antidepressants for cataplexy there is scarce evidence that antidepressants have a positive effect on this symptom. There is a clear need for well-designed randomised controlled trials to assess the effect of antidepressants on narcolepsy.

Effects of rapid eye movement sleep deprivation on hypocretin neurons in the hypothalamus of a rat model of depression

Hypocretin (Hcrt, also known as orexin) is a hypothalamic neuropeptide linked to narcolepsy, a disorder diagnosed by the appearance of rapid eye-movement sleep (REMS)-state characteristics during waking. Major targets of Hcrt-containing fibers include the locus coeruleus and the raphe nucleus, areas with important roles in regulation of mood and sleep. A relationship between REMS and mood is suggested by studies demonstrating that REMS-deprivation (REMSD) ameliorates depressive symptoms in humans. Additional support is found in animal studies where antidepressants and REMSD have similar effects on monoamiergic systems thought to be involved in major depression. Recently, we have reported that Wistar-Kyoto (WKY) rats, an animal model of depression, have reduced number and size of hypothalamic cells expressing Hcrt-immunoractivity compared to the parent, Wistar (WIS) strain, suggesting the possibility that the depressive-like attributes of the WKY rat may be determined by this relative reduction in Hcrt cells [Allard, J.S., Tizabi, Y., Shaffery, J.P., Trouth, C.O., Manaye, K., 2004. Stereological analysis of the hypothalamic hypocretin/orexin neurons in an animal model of depression. Neuropeptides 38, 311-315]. In this study, we sought to test the hypothesis that REMSD would result in a greater increase in the number and/or size of hypothalamic, Hcrt-immunoreactive (Hcrt-ir) neurons in WKY, compared to WIS rats. The effect of REMSD, using the multiple-small-platforms-over-water (SPRD) method, on size and number of Hcrt-ir cells were compared within and across strains of rats that experienced multiple-large-platforms-over-water (LPC) as well as to those in a normal, home-cage-control (CC) setting. In accord with previous findings, the number of Hcrt-ir cells was larger in all three WIS groups compared to the respective WKY groups. REMSD produced a 20% increase (p<0.02) in the number of hypothalamic Hcrt-ir neurons in WKY rats compared to cage control WKY (WKY-CC) animals. However, an unexpected higher increase in number of Hcrt-ir cells was also observed in the WKY-LPC group compared to both WKY-CC (31%, p<0.001) and WKY-SPRD (20%, p<0.002) rats. A similar, smaller, but non-significant, pattern of change was noted in WIS-LPC group. Overall the data indicate a differential response to environmental manipulations where WKY rats appear to be more reactive than WIS rats. Moreover, the findings do not support direct antidepressant-like activity for REMSD on hypothalamic Hcrt neurons in WKY rats.

REM sleep characteristics in narcolepsy and REM sleep behavior disorder

STUDY OBJECTIVES

To assess the presence of polysomnographic characteristics of REM sleep behavior disorder (RBD) in narcolepsy; and to quantify REM sleep parameters in patients with narcolepsy, in patients with "idiopathic" RBD, and in normal controls.

DESIGN

Sleep laboratory study

PARTICIPANTS

Sixteen patients with narcolepsy and cataplexy matched for age and sex with 16 patients with "idiopathic" RBD and with 16 normal controls were studied.

MEASUREMENTS AND RESULTS

Higher percentages of REM sleep without atonia, phasic electromyographic (EMG) activity, and REM density were found in patients with narcolepsy than normal controls. In contrast, RBD patients had a higher percentage of REM sleep without atonia but a lower REM density than patients with narcolepsy and normal controls. Based on a threshold of 80% for percentage of REM sleep with atonia, 50% of narcoleptics and 87.5% of RBD patients had abnormal REM sleep muscle activity. No significant behavioral manifestation in REM sleep was noted in either narcoleptics or controls. We also found a higher frequency of periodic leg movements during wake (PLMW) and during sleep (PLMS) in narcoleptic patients compared to controls.

CONCLUSIONS

The present study demonstrates abnormalities in REM sleep motor regulation with an increased frequency of REM sleep without atonia, phasic EMG events and PLMS in narcoleptic patients when compared to controls. These abnormalities were seen more prominently in patients with RBD than in narcoleptics, with the exception of the PLMS index. We proposed that dysfunctions in hypocretin/dopaminergic system may lead to motor dyscontrol in REM sleep that results in dissociated sleep/wake states.

Periodic leg movements during sleep and wakefulness in narcolepsy

The objectives of the study were to measure the prevalence of periodic leg movements during NREM and REM sleep (PLMS) and while awake (PLMW) and to assess the impact of PLMS on nocturnal sleep and daytime functioning in patients with narcolepsy. One hundred and sixty-nine patients with narcolepsy and 116 normal controls matched for age and gender were included. Narcoleptics with high and low PLMS indices were compared to assess the impact of PLMS on sleep and Multiple Sleep Latency Test (MSLT) variables. More narcoleptics than controls had a PLMS index greater than 5 per hour of sleep (67% versus 37%) and an index greater than 10 (53% versus 21%). PLMS indices were higher both in NREM and REM sleep in narcoleptic patients, but the between-group difference was greater for REM sleep. A significant increase of PLMS index was also found with aging in both narcoleptic patients and controls. PLMW indices were also significantly higher in narcoleptic patients. Patients with an elevated index of PLMS had a higher percentage of stage 1 sleep, a lower percentage of REM sleep, a lower REM efficiency and a shorter MSLT latency. The present study demonstrates a high frequency of PLMS and PLMW in narcolepsy, an association between the presence of PLMS and measures of REM sleep and daytime functioning disruption. These results suggest that PLMS represent an intrinsic feature of narcolepsy.

The hypothalamic peptidergic system, hypocretin/orexin and vigilance control

Using forward and reverse genetics, the genes (hypocretin/orexin ligand and its receptor) involved in the pathogenesis of the sleep disorder, narcolepsy, in animals, have been identified. Mutations in hypocretin related-genes are extremely rare in humans, but hypocretin-ligand deficiency is found in most narcolepsy-cataplexy cases. Hypocretin deficiency in humans can be clinically detected by CSF hypocretin-1 measures, and undetectably low CSF hypocretin-1 is now included in the revised international diagnostic criteria of narcolepsy. Since hypocretin-ligand deficiency is the major pathophysiology in human narcolepsy, hypocretin replacements (using hypocretin agonists or gene therapy) are promising future therapeutic options. New insights into the roles of hypocretin system on sleep physiology have also rapidly increased. Hypocretins are involved in various fundamental hypothalamic functions such as feeding, energy homeostasis and neuroendocrine regulation. Hypocretin neurons project to most ascending arousal systems (including monoaminergic and cholinergic systems), and generally exhibit excitatory inputs. Together with the recent finding of the sleep promoting system in the hypothalamus (especially in the GABA/galanin ventrolateral preoptic area which exhibits inhibitory inputs to these ascending systems), the hypothalamus is now recognized as the most important brain site for the sleep switch, and other peptidergic systems may also participate in this regulation. Meanwhile, narcolepsy now appears to be a more complex condition than previously thought. The pathophysiology of the disease is involved in the abnormalities of sleep and various hypothalamic functions due to hypocretin deficiency, such as the changes in energy homeostasis, stress reactions and rewarding. Narcolepsy is therefore, an important model to study the link between sleep regulation and other fundamental hypothalamic functions.

Histamine H3 receptor antagonists: From target identification to drug leads

The successful cloning and functional expression of the histamine H(3) receptor in the late 1990 s has greatly facilitated our efforts to identify small molecule, non-imidazole based compounds to permit the evaluation of H(3) antagonists in models of CNS disorders. High-throughput screening identified several series of lead compounds, including a series of imidazopyridines, which led to JNJ-6379490, a compound with high affinity for the human H(3) receptor. Analysis of structural features common to several series of non-imidazole H(3) receptor ligands resulted in a pharmacophore model. This model led to the design of JNJ-5207852, a diamine-based H(3) antagonist with good in vitro and in vivo efficacy but with an undesirable long half-life. However, further modifications of the template provided an understanding of the effect of structural modifications on pharmacokinetic properties, ultimately affording several additional series of compounds including JNJ-10181457, a compound with an improved pharmacokinetic profile. These compounds allowed in vivo pharmacological evaluation to show that H(3) antagonists promote wakefulness, but unlike modafinil and classical psychostimultants, they do not increase locomotor activity or produce any alteration of the EEG power spectral activity in rats. H(3) antagonists also increase extracellular acetylcholine and norepinephrine but not dopamine in rat frontal cortex and show efficacy in various models of learning-memory deficit. In addition, cFos immunoreactivity studies show H(3) antagonists activate neuronal cells in restricted rat brain regions in contrast to widespread activation after modafinil or amphetamine treatment. Therefore, H(3) antagonists are promising clinical candidates for the treatment of excessive day time sleepiness and/or cognitive disorders.