Wake-promoting and sleep-suppressing actions of hypocretin (orexin): basal forebrain sites of action.

The hypocretins (orexins) are a newly identified peptide family comprised of two peptides, hypocretin-1 and hypocretin-2. Recent observations suggest an involvement of these peptides in the regulation of behavioral state. For example, these peptides are found in a variety of brain regions associated with the regulation of forebrain neuronal and behavioral activity states. Furthermore, when infused into the lateral ventricles in awake animals, hypocretin-1 elicits increased duration of waking beyond that observed in vehicle-treated animals. Previous studies have been limited to an examination of the sleep-wake effects of hypocretin-1 in awake animals. Currently, the sleep-wake effects of hypocretin-2 and the extent to which hypocretins can initiate waking in the sleeping animal remain unclear. To better characterize the wake-promoting actions of the hypocretins, the current studies examined the sleep-wake effects of varying doses (0.007, 0.07 and 0.7 nmol) of hypocretin-1 and hypocretin-2 when administered into sleeping rats (e.g. remote-controlled infusions).Infusions of hypocretin-1 and hypocretin-2 into the lateral ventricles elicited a short latency (0.7 nmol hypocretin-1; 93+/-30 s from the start of the 120-s infusion) increase in electroencephalographic, electromyographic, and behavioral indices of waking. These infusions also produced substantial decreases in slow-wave and rapid-eye movement sleep. Hypocretin-1 was more potent than hypocretin-2 in these actions. Interestingly, hypocretin-1 infused into the fourth ventricle elicited less robust waking which occurred with a longer latency than infusions into the lateral ventricles. These latter observations suggest a forebrain site of action participates in hypocretin-1-induced waking.Within the forebrain, a variety of basal forebrain structures, including the medial preoptic area, the medial septal area and the substantia innominata, receive a moderate hypocretin innervation. Therefore, additional studies examined the sleep-wake effects of bilateral hypocretin-1 infusions into these basal forebrain structures. Robust increases in waking were observed following infusions into, but not outside, the medial septal area, the medial preoptic area and the substantia innominata.These results indicate a potentially prominent role of hypocretins in sleep-wake regulation via actions within certain basal forebrain structures and are consistent with studies indicating a prominent role of hypocretins in sleep/arousal disorders.     

Lesions of the suprachiasmatic nucleus eliminate the daily rhythm of hypocretin-1 release

STUDY OBJECTIVES: Hypocretins (orexins) are involved in the sleep disorder narcolepsy. While hypocretin-1 has a daily oscillation, little is known regarding the relative contribution of circadian and homeostatic components on hypocretin release. The effect of lesions of the suprachiasmatic nucleus (SCN) on hypocretin-1 in the cerebrospinal fluid (CSF) was examined. DESIGN: SCN-ablated (SCNx) and sham-operated control rats were implanted with activity-temperature transmitters. Animals were housed individually under 1 of 3 lighting conditions: 12-hour:12-hour light:dark cycle (LD), constant light (LL), and constant darkness (DD). Lesions were verified histologically and shown not to affect hypocretin-containing cells. Hypocretin-1 concentrations in the CSF were determined every 4 hours using radioimmunoassays. MEASUREMENTS AND RESULTS: Control animals displayed robust circadian (LL, DD) and diurnal (LD) fluctuations in CSF hypocretin-1, locomotor activity, and temperature. Peak CSF hypocretin-1 was at the end of the active period. Activity, temperature, and CSF hypocretin-1 were arrhythmic in SCNx animals in LL and DD. In LD, a weak but significant fluctuation in activity and temperature but not CSF hypocretin-1 was observed in SCNx animals. We also explored correlations between CSF hypocretin-1, CSF corticosterone, and locomotor activity occurring prior to CSF sampling in arrhythmic SCNx rats under constant conditions. Significant correlations between hypocretin-1 and activity were observed both across and within animals, suggesting that interindividual and time-of-the-day differences in activity have significant effects on hypocretin release in arrhythmic animals. No correlation was found between CSF hypocretin-1 and corticosterone. CONCLUSIONS: Hypocretin-1 release is under SCN control. Locomotor activity influences the activity of the hypocretin neurons.     

Locomotor-dependent and -independent components to hypocretin-1 (orexin A) regulation in sleep–wake consolidating monkeys

The hypocretin system is involved in the integration of hypothalamic functions with sleep and wake. Hypocretin-1 release peaks at the end of the active period in both diurnal and nocturnal species. A role for hypocretin-1 in the generation of locomotor activity has been suggested by electrophysiological and neurochemical studies in rodents, dogs and cats. These species, however, do not consolidate wake into a single, daily bout and manipulations of locomotion elicit changes in wakefulness, making it difficult to parse the relative contribution of these two factors. We have examined the relationship between locomotion and hypocretin-1 in a wake-consolidating animal, the squirrel monkey ( Saimiri sciureus ). Strikingly, we found that restricting locomotion to 17% of usual activity had no significant effect on the normal diurnal rise in cerebrospinal fluid (CSF) hypocretin-1, despite an associated increase in CSF cortisol. Increasing locomotion to greater than baseline activity did not significantly increase CSF hypocretin-1 concentrations, but did appear to have a positive modulatory effect on CSF hypocretin-1. In this wake-consolidating animal, locomotion is not necessary for CSF hypocretin-1 to increase throughout the daytime, but high levels of locomotion are likely to provide a small positive feedback onto the hypocretin system.     

Sleep-waking discharge patterns of neurons recorded in the rat perifornical lateral hypothalamic area

The perifornical lateral hypothalamic area (PF-LHA) has been implicated in the control of several waking behaviours, including feeding, motor activity and arousal. Several cell types are located in the PF-LHA, including projection neurons that contain the hypocretin peptides (also known as orexins). Recent findings suggest that hypocretin neurons are involved in sleep-wake regulation. Loss of hypocretin neurons in the human disorder narcolepsy is associated with excessive somnolence, cataplexy and increased propensity for rapid eye movement (REM) sleep. However, the relationship of PF-LHA neuronal activity to different arousal states is unknown. We recorded neuronal activity in the PF-LHA of rats during natural sleep and waking. Neuronal discharge rates were calculated during active waking (waking accompanied by movement), quiet waking, non-REM sleep and REM sleep. Fifty-six of 106 neurons (53 %) were classified as wake/REM-related. These neurons exhibited peak discharge rates during waking and REM sleep and reduced discharge rates during non-REM sleep. Wake-related neurons (38 %) exhibited reduced discharge rates during both non-REM and REM sleep when compared to that during waking. Wake-related neurons exhibited significantly higher discharge rates during active waking than during quiet waking. The discharge of wake-related neurons was positively correlated with muscle activity across all sleep-waking states. Recording sites were located within the hypocretin-immunoreactive neuronal field of the PF-LHA. Although the neurotransmitter phenotype of recorded cells was not determined, the prevalence of neurons with wake-related discharge patterns is consistent with the hypothesis that the PF-LHA participates in the regulation of arousal, muscle activity and sleep-waking states.     

Effects of lateral hypothalamic lesion with the neurotoxin hypocretin-2-saporin on sleep in Long-Evans rats

Narcolepsy, a disabling neurological disorder characterized by excessive daytime sleepiness, sleep attacks, sleep fragmentation, cataplexy, sleep-onset rapid eye movement sleep periods and hypnagogic hallucinations was recently linked to a loss of neurons containing the neuropeptide hypocretin. There is considerable variability in the severity of symptoms between narcoleptic patients, which could be related to the extent of neuronal loss in the lateral hypothalamus. To investigate this possibility, we administered two concentrations (90 ng or 490 ng in a volume of 0.5 microl) of the neurotoxin hypocretin-2-saporin, unconjugated saporin or saline directly to the lateral hypothalamus and monitored sleep, the entrained and free-running rhythm of core body temperature and activity. Neurons stained for hypocretin or for the neuronal specific marker were counted in the perifornical area, dorsomedial and ventromedial nucleus of the hypothalamus. More neuronal nuclei (NeuN) cells were destroyed by the higher concentration of hypocretin-2-saporin (-55%) compared with the lower concentration (-34%) in the perifornical area, although both concentrations lesioned the hypocretin neurons almost equally well (high concentration=91%; low concentration=88%). The high concentration of hypocretin-2-saporin also lesioned neurons in the dorsomedial nucleus of the hypothalamus and ventromedial nucleus of the hypothalamus. Narcoleptic-like sleep behavior was produced by both concentrations of the hypocretin-2-saporin. The high concentration produced a larger increase in non-rapid eye movement sleep amounts during the normally active night cycle than low concentration. Neither concentration of hypocretin-2-saporin disrupted the phase or period of the core temperature or activity rhythms. The low concentration of unconjugated saporin did not significantly lesion hypocretin or neurons and did not alter sleep. The high concentration of unconjugated saporin produced some loss of neuronal nuclei-immunoreactive (NeuN-ir) neurons and hypocretin immunoreactive neurons, but only a transient increase in non-rapid eye movement sleep. These results led us to conclude that the extent of hypocretin neuronal loss together with an accompanying loss of cells in the lateral hypothalamus may explain the differences in severity of symptoms seen in human narcolepsy.     

Hypocretin and melanin-concentrating hormone in patients with Huntington disease

Abstract To evaluate whether hypocretin-1 (orexin-A) and melanin-concentrating hormone (MCH) neurotransmission are affected in patients with Huntington disease (HD), we immunohistochemically stained hypocretin and MCH neurons and estimated their total numbers in the lateral hypothalamus of both HD patients and matched controls. In addition, hypocretin-1 levels were determined in prefrontal cortical tissue and post-mortem ventricular cerebrospinal fluid (CSF) using a radioimmunoassay. The total number of hypocretin-1 neurons was significantly reduced by 30% in HD brains (P = 0.015), while the total number of MCH neurons was not significantly altered (P = 0.100). Levels of hypocretin-1 were 33% lower in the prefrontal cortex of the HD patients (P = 0.025), but ventricular CSF levels were similar to the control values (P = 0.306). Neuronal intranuclear and cytoplasmic inclusions of mutant huntingtin were present in all HD hypothalami, although with a variable distribution across different hypothalamic structures. We found a specific reduction in hypocretin signaling in patients with HD as MCH cell number was not significantly affected. It remains to be shown whether the moderate decrease in hypocretin neurotransmission could contribute to clinical symptoms. As the number of MCH-expressing neurons was not affected, alterations in MCH signaling are unlikely to have clinical effects in HD patients.     

Neuronal mechanisms of active (rapid eye movement) sleep induced by microinjections of hypocretin into the nucleus pontis oralis of the cat

Hypocretinergic (orexinergic) neurons in the hypothalamus project to the nucleus pontis oralis, a nucleus which plays a crucial role in the generation of active (rapid eye movement) sleep. We recently reported that the microinjection of hypocretin into the nucleus pontis oralis of chronically-instrumented, unanesthetized cats induces a behavioral state that is comparable to naturally-occurring active sleep. The present study examined the intracellular signaling pathways underlying the active sleep-inducing effects of hypocretin. Accordingly, hypocretin-1, a protein kinase C inhibitor and a protein kinase A inhibitor were injected into the nucleus pontis oralis in selected combinations in order to determine their effects on sleep and waking states of chronically instrumented, unanesthetized cats. Microinjections of hypocretin-1 into the nucleus pontis oralis elicited active sleep with a short latency. However, a pre-injection of bisindolylmaleimide-I, a protein kinase C-specific inhibitor, completely blocked the active sleep-inducing effects of hypocretin-1. The combined injection of bisindolylmaleimide-I and hypocretin-1 significantly increased the latency to active sleep induced by hypocretin-1; it also abolished the increase in the time spent in active sleep induced by hypocretin-1. On the other hand, the injection of 2'5'-dideoxyadenosine, an adenylyl cyclase inhibitor, did not block the occurrence of active sleep by hypocretin-1. We conclude that the active sleep-inducing effect of hypocretin in the nucleus pontis oralis is mediated by intracellular signaling pathways that act via G-protein stimulation of protein kinase C.     

The wake-promoting effects of hypocretin-1 are attenuated in old rats

Disruption of sleep is a frequent complaint among elderly humans and is also evident in aged laboratory rodents. The neurobiological bases of age-related sleep/wake disruption are unknown. Given the critical role of the hypocretins in sleep/wake regulation, we sought to determine whether the wake-promoting effect of hypocretin changes with age in Wistar rats, a strain in which age-related changes in both sleep and hypocretin signaling have been reported. Intracerebroventricular infusions of hypocretin-1 (10 and 30 μg) significantly increased wake time relative to vehicle in both young (3 mos) and old (25 mos) Wistar rats. However, the magnitude and duration of the wake-promoting effects were attenuated with age. An increase of parameters associated with homeostatic sleep recovery after sleep deprivation, including non-rapid eye movement (NR) sleep time, NR delta power, the ratio of NR to rapid eye movement (REM) sleep, and NR consolidation, occurred subsequent to Hcrt-induced waking in young but not old rats. ICV infusions of hypocretin-2 (10 and 30 μg) produced fewer effects in both young and old rats. These data demonstrate that activation of a major sleep/wake regulatory pathway is attenuated in old rats.     

Synergistic sedative effects of noradrenergic alpha(1)- and beta-receptor blockade on forebrain electroencephalographic and behavioral indices

The locus coeruleus-noradrenergic system exerts an activating influence on forebrain neuronal and behavioral activity states. For example, in the anesthetized rat, unilateral locus coeruleus stimulation elicits bilateral activation of forebrain electroencephalographic activity. Pretreatment with a noradrenergic beta-antagonist blocks this effect, suggesting that beta-receptors play a critical role in locus coeruleus-dependent activation of the forebrain. Consistent with this, stimulation of beta-receptors located in certain basal forebrain structures evokes sustained periods of alert waking in the unanesthetized rat. Similar forebrain and behavioral activating effects are observed with alpha(1)-receptor stimulation within these basal forebrain regions. To assess the extent to which alpha(1)- and beta-receptors contribute to the maintenance of behavioral and forebrain activation, we examined the electroencephalographic and behavioral effects of alpha(1)-, beta- and combined alpha(1)/beta-receptor blockade in the unanesthetized rat. Rats were treated individually or in combination with either varying doses of the alpha(1)-antagonist, prazosin (intraperitoneally), and/or the beta-antagonist, timolol (intracerebroventricularly). Thirty minutes following treatment, animals were placed in a mildly-arousing novel environment, which has been demonstrated previously to elicit activation of central noradrenergic systems and sustained waking in vehicle-treated controls. Behavior and electroencephalographic activity were recorded and later scored. Electroencephalographic activity was analysed using power spectrum analysis.The following were observed: (i) beta-receptor blockade alone does not alter behavioral or electroencephalographic indices of alert waking; (ii) alpha(1)-receptor blockade alone increases high-voltage spindle activity in cortical electroencephalographic activity that was associated with decreased behavioral activity; (iii) combined alpha(1)- and beta-receptor blockade elicits a substantial increase in slow-wave activity (0.33-2.0Hz), also in association with decreased behavioral activity. All of these effects were dependent on the dose administered and time following initiation of testing. These results indicate that the combined actions of alpha(1)- and beta-receptors exert distinct and synergistic actions on cortical neuronal activity patterns that are essential elements of alert waking.     

Convergence of circadian and sleep regulatory mechanisms on hypocretin-1

Hypocretin is a potential regulator of sleep and wakefulness and its levels fluctuate with the day-night cycle with high levels during the animal's activity period. Whether the daily fluctuations are driven endogenously or by external light cycles is unknown. We investigated the circadian and homeostatic regulation of hypocretin in the absence of environmental light cycles. To this purpose we performed repetitive samplings of cerebrospinal fluid in rats through implanted microcannulas in the cisterna magna and determined hypocretin-1 levels by radioimmunoassay. These experiments were also performed in rats that received a lesion of the suprachiasmatic nucleus (SCN), a major pacemaker for circadian rhythms in mammals. The results showed sustained rhythmicity of hypocretin in constant dim red light in control animals. SCN-lesioned animals showed no circadian rhythms in hypocretin and mean hypocretin levels were remarkably low. The results indicate that the SCN is indispensable for rhythmicity in hypocretin and induces a daily increase in hypocretin levels during the animal's active phase. Additional sleep deprivation experiments were carried out to investigate homeostatic regulation of hypocretin. Hypocretin levels increased in response to sleep deprivation in both control and SCN-lesioned animals, demonstrating that sleep homeostatic control of hypocretin occurs independently from the SCN. Our data indicate that the circadian pacemaker of the SCN and sleep homeostatic mechanisms converge on one single sleep regulatory substance.     

Effects of IV and ICV hypocretin-1 (orexin A) in hypocretin receptor-2 gene mutated narcoleptic dogs and IV hypocretin-1 replacement therapy in a hypocretin-ligand-deficient narcoleptic dog

STUDY OBJECTIVES: Using two different canine models of narcolepsy, we evaluated the therapeutic effects of hypocretin-1 on cataplexy and sleep. MEASUREMENTS AND RESULTS: Intracerebroventricular administration of hypocretin-1 (10 and 30 nmol per dog) but not intravenous administration (up to 6 microg/kg) induced significant wakefulness in control dogs. However, hypocretin-1 had no effect on cataplexy or wakefulness in hypocretin receptor-2 gene (Hcrtr2) mutated narcoleptic Dobermans. Only very high intravenously doses of hypocretin-1 (96-384 microg/kg) penetrated the brain, to produce a short-lasting anticataplectic effect in a hypocretin-ligand-deficient animal. CONCLUSIONS: Hypocretin-1 administration, by central and systemic routes, does not improve narcoleptic symptoms in Hcrtr2 mutated Dobermans. Systemic hypocretin-1 hardly crosses the blood-brain barrier to produce therapeutic effects. The development of more centrally penetrable and longer lasting hypocretin analogs will be needed to further explore this therapeutic pathway in humans.     

The Injection of Hypocretin-1 into the Nucleus Pontis Oralis Induces either Active Sleep or Wakefulness Depending on the Behavioral State when it is Administered

Study Objectives:

We previously reported that the microinjection of hypocretin (orexin) into the nucleus pontis oralis (NPO) induces a behavioral state that is comparable to naturally occurring active (rapid eye movement) sleep. However, other laboratories have found that wakefulness occurs following injections of hypocretin into the NPO. The present study tested the hypothesis that the discrepancy in behavioral state responses to hypocretin injections is due to the fact that hypocretin was not administered during the same states of sleep or wakefulness.

Design:

Adult cats were implanted with electrodes to record sleep and waking states. Hypocretin-1 (0.25 μL, 500mM) was microinjected into the NPO while the animals were awake or in quiet (non-rapid eye movement) sleep.

Measurements and Results:

When hyprocretin-1 was microinjected into the NPO during quiet sleep, active sleep occurred with a short latency. In addition, there was a significant increase in the time spent in active sleep and in the number of episodes of this state. On the other hand, the injection of hyprocretin-1 during wakefulness resulted not only in a significant increase in wakefulness, but also in a decrease in the percentage and frequency of episodes of active sleep.

Conclusions:

The present data demonstrate that the behavioral state of the animal dictates whether active sleep or wakefulness is induced following the injection of hypocretin. Therefore, we suggest that hypocretin-1 enhances ongoing states of wakefulness and their accompanying patterns of physiologic activity and that hypocretin-1 is also capable of promoting active sleep and the changes in various processes that occur during this state.

Citation:

Xi M; Chase MH. The injection of hypocretin-1 into the nucleus pontis oralis induces either active sleep or wakefulness depending on the behavioral state when it is administered. SLEEP 2010;33(9):1236-1243.     

Modulatory effects of hypocretin-1/orexin-A with glutamate and gamma-aminobutyric acid on freshly isolated pyramidal neurons from the rat prefrontal cortex

It is widely known that hypocretins are essential for the regulation of wakefulness. Our recent reports have found that hypocretin-1 shows a direct postsynaptic excitatory effect on rat prefrontal cortex (PFC) pyramidal neurons. It remains unclear whether hypocretin-1 may interact with two classical neurotransmitter systems, glutamate and gamma-aminobutyric acid (GABA) in rat PFC. For this reason, we here investigated the modulatory actions of hypocretin-1 with these two transmitters on freshly isolated PFC pyramidal neurons using whole-cell patch-clamp recordings. We found that coadministration of hypocretin-1 and glutamate showed a synergistic effect on the recorded cells, and hypocretin-1 could excite the neurons even if GABA was present. Thus, our data suggest that there may be hypocretin-glutamate and hypocretin-GABA interactions in the PFC.     

CSF hypocretin-1 concentrations correlate with the level of fatigue in multiple sclerosis patients

Considering the multiplicity of symptoms associated with multiple sclerosis (MS), there is possibility that hypocretin system function might be involved in the pathogenesis of the disease. The current study aimed to investigate the hypocretin-1 levels in cerebrospinal fluid (CSF) of MS patients in relation to different neurological deficit measures including: Ambulation Index (AI), Expanded Disability Status Scale (EDSS), Fatigue Severity Scale (FSS), and Epworth Sleepiness Scale (ESS) in relapse-onset MS patients. 53 subjects were included into the study: 38 patients with a diagnosis of MS and 15 healthy controls. Among MS patients, 25 had relapsing-remitting and 13 secondary progressive MS. CSF hypocretin-1 levels did not differ between MS patients and healthy controls (p > 0.05). A positive correlation between hypocretin-1 level and fatigue level was found in MS patients (p < 0.05) and this effect was even stronger in the MS subgroup suffering from fatigue (p = 0.01). Hypocretin system seems to be generally unchanged in MS but a positive correlation between hypocretin-1 level and fatigue may indicate involvement of some compensatory mechanisms stimulating the production of the neuropeptide in MS patients.     

Hypocretin (orexin) loss in Alzheimer's disease

Sleep disturbances in Alzheimer's disease (AD) patients are associated with the severity of dementia and are often the primary reason for institutionalization. These sleep problems partly resemble core symptoms of narcolepsy, a sleep disorder caused by a general loss of the neurotransmitter hypocretin. AD is a neurodegenerative disorder targeting different brain areas and types of neurons. In this study, we assessed whether the neurodegenerative process of AD also affects hypothalamic hypocretin/orexin neurons. The total number of hypocretin-1 immunoreactive neurons was quantified in postmortem hypothalami of AD patients (n = 10) and matched controls (n = 10). In addition, the hypocretin-1 concentration was measured in postmortem ventricular cerebrospinal fluid of 24 AD patients and 25 controls (including the patients and controls in which the hypothalamic cell counts were performed). The number of hypocretin-1 immunoreactive neurons was significantly decreased by 40% in AD patients (median [25th-75th percentiles]); AD 12,935 neurons (9972-19,051); controls 21,002 neurons (16,439-25,765); p = 0.049). Lower cerebrospinal fluid (CSF) hypocretin-1 levels were found in AD patients compared with controls (AD: 275 pg/mL [197-317]; controls: 320 pg/mL [262-363]; p = 0.038). Two AD patients with documented excessive daytime sleepiness showed the lowest CSF hypocretin-1 concentrations (55 pg/mL and 76 pg/mL). We conclude that the hypocretin system is affected in advanced AD. This is reflected in a 40% decreased cell number, and 14% lower CSF hypocretin-1 levels.     

Intermediate hypocretin-1 cerebrospinal fluid levels and typical cataplexy: their significance in the diagnosis of narcolepsy type 1

Study ObjectivesThe diagnosis of narcolepsy type 1 (NT1) is based upon the presence of cataplexy and/or a cerebrospinal fluid (CSF) hypocretin-1/orexin-A level ≤ 110 pg/mL. We determined the clinical and diagnostic characteristics of patients with intermediate hypocretin-1 levels (111–200 pg/mL) and the diagnostic value of cataplexy characteristics in individuals with central disorders of hypersomnolence.MethodsRetrospective cross-sectional study of 355 people with known CSF hypocretin-1 levels who visited specialized Sleep-Wake Centers in the Netherlands. For n = 271, we had full data on cataplexy type (“typical” or “atypical” cataplexy).ResultsCompared to those with normal hypocretin-1 levels (>200 pg/mL), a higher percentage of individuals with intermediate hypocretin-1 levels had typical cataplexy (75% or 12/16 vs 9% or 8/88, p < .05), and/or met the diagnostic polysomnographic (PSG) and Multiple Sleep Latency Test (MSLT) criteria for narcolepsy (50 vs 6%, p < .001). Of those with typical cataplexy, 88% had low, 7% intermediate, and 5% normal hypocretin-1 levels (p < .001). Atypical cataplexy was also associated with hypocretin deficiency but to a lesser extent. A hypocretin-1 cutoff of 150 pg/mL best predicted the presence of typical cataplexy and/or positive PSG and MSLT findings.ConclusionIndividuals with intermediate hypocretin-1 levels or typical cataplexy more often have outcomes fitting the PSG and MSLT criteria for narcolepsy than those with normal levels or atypical cataplexy. In addition, typical cataplexy has a much stronger association with hypocretin-1 deficiency than atypical cataplexy. We suggest increasing the NT1 diagnostic hypocretin-1 cutoff and adding the presence of clearly defined typical cataplexy to the diagnostic criteria of NT1. Clinical trial information: This study is not registered in a clinical trial register, as it has a retrospective database design.     

Decreased hypocretin-1 (Orexin-A) levels in the cerebrospinal fluid of patients with myotonic dystrophy and excessive daytime sleepiness

STUDY OBJECTIVE: Myotonic dystrophy type 1 is a multisystem disorder with myotonia, muscle weakness, cataracts, endocrine dysfunction, and intellectual impairment. This disorder is caused by a CTG triplet expansion in the 3' untranslated region of the DMPK gene on 19q13. Myotonic dystrophy type 1 is frequently associated with excessive daytime sleepiness, sharing with narcolepsy a short sleep latency and the presence of sleep-onset rapid eye movement periods during the Multiple Sleep Latency Test. Since narcolepsy is characterized by a dysfunction of the hypothalamic hypocretin system, we investigated whether patients with myotonic dystrophy type 1 with excessive daytime sleepiness have abnormalities in the hypocretin system. DESIGN/PARTICIPANTS: Six patients with myotonic dystrophy type 1 complaining of excessive daytime sleepiness and 13 healthy controls without a sleep disorder were included. The patients with myotonic dystrophy type 1 were evaluated using clinical interviews, nocturnal polysomnograms, and Multiple Sleep Latency Tests. All patients had a confirmed genetic diagnosis for DM1 and were HLA typed. Cerebrospinal fluid hypocretin-1 levels were measured using a direct radioimmunoassay in patients and controls. Setting: University hospital sleep laboratory. INTERVENTIONS: N/A. MEASUREMENT AND RESULTS: The mean sleep latency on Multiple Sleep Latency Tests was abnormal in all patients (< 5 minutes in 2, < or = 8 in 4) and 2 sleep-onset rapid eye movement periods were observed in 2 subjects. All patients were HLA-DQB1*0602 negative. Hypocretin-1 levels were significantly lower in patients versus controls (p < 0.001); 1 case with 2 sleep-onset rapid eye movement periods had hypocretin-1 levels in the range generally observed in narcolepsy (< 110 pg/mL). Three cases had intermediate levels (110-200 pg/mL). Hypocretin-1 levels did not correlate clinically with disease severity or duration or with subjective or objective sleepiness reports. CONCLUSIONS: A dysfunction of the hypothalamic hypocretin system may mediate sleepiness and abnormal Multiple Sleep Latency Test results in patients with myotonic dystrophy type 1.     

Additive wake-promoting actions of medial basal forebrain noradrenergic alpha1- and beta-receptor stimulation

The locus coeruleus-noradrenergic system exerts an activating influence on forebrain neuronal and behavioral activity states, in part through the actions of noradrenergic beta-receptors in the medial septal (MS) and medial preoptic (MPOA) areas. MPOA alpha1-receptors exert similar wake-promoting actions. The current study examines the influence of alpha1-receptors located within MS on sleep-wake state. In addition, the extent to which alpha1- and beta-receptors located within MS and MPOA interact in the modulation of behavioral state was investigated by examining the effects of individual or combined infusion of alpha1- and beta-agonists into these regions. Results show that alpha1-receptors located within MS exert wake-promoting actions. Within both MS and MPOA, additive wake-promoting actions were observed with alpha1- and beta-receptor stimulation, the sum of which contributes to the overall arousal state of the animal.