Distinct lateral hypothalamic CaMKIIα neuronal populations regulate wakefulness and locomotor activity.

For nearly a century, evidence has accumulated indicating that the lateral hypothalamus (LH) contains neurons essential to sustain wakefulness. While lesion or inactivation of LH neurons produces a profound increase in sleep, stimulation of inhibitory LH neurons promotes wakefulness. To date, the primary wake-promoting cells that have been identified in the LH are the hypocretin/orexin (Hcrt) neurons, yet these neurons have little impact on total sleep or wake duration across the 24-h period. Recently, we and others have identified other LH populations that increase wakefulness. In the present study, we conducted microendoscopic calcium imaging in the LH concomitant with EEG and locomotor activity (LMA) recordings and found that a subset of LH neurons that express Ca2+/calmodulin-dependent protein kinase IIα (CaMKIIα) are preferentially active during wakefulness. Chemogenetic activation of these neurons induced sustained wakefulness and greatly increased LMA even in the absence of Hcrt signaling. Few LH CaMKIIα-expressing neurons are hypocretinergic or histaminergic while a small but significant proportion are GABAergic. Ablation of LH inhibitory neurons followed by activation of the remaining LH CaMKIIα neurons induced similar levels of wakefulness but blunted the LMA increase. Ablated animals showed no significant changes in sleep architecture but both spontaneous LMA and high theta (8 to 10 Hz) power during wakefulness were reduced. Together, these findings indicate the existence of two subpopulations of LH CaMKIIα neurons: an inhibitory population that promotes locomotion without affecting sleep architecture and an excitatory population that promotes prolonged wakefulness even in the absence of Hcrt signaling.

Orexin Facilitates the Peripheral Chemoreflex via Corticotropin-Releasing Hormone Neurons Projecting to the Nucleus of the Solitary Tract.

We previously showed that orexin neurons are activated by hypoxia and facilitate the peripheral chemoreflex (PCR)-mediated hypoxic ventilatory response (HVR), mostly by promoting the respiratory frequency response. Orexin neurons project to the nucleus of the solitary tract (nTS) and the paraventricular nucleus of the hypothalamus (PVN). The PVN contributes significantly to the PCR and contains nTS-projecting corticotropin-releasing hormone (CRH) neurons. We hypothesized that in male rats, orexin neurons contribute to the PCR by activating nTS-projecting CRH neurons. We used neuronal tract tracing and immunohistochemistry (IHC) to quantify the degree that hypoxia activates PVN-projecting orexin neurons. We coupled this with orexin receptor (OxR) blockade with suvorexant (Suvo, 20 mg/kg, i.p.) to assess the degree that orexin facilitates the hypoxia-induced activation of CRH neurons in the PVN, including those projecting to the nTS. In separate groups of rats, we measured the PCR following systemic orexin 1 receptor (Ox1R) blockade (SB-334867; 1 mg/kg) and specific Ox1R knockdown in PVN. OxR blockade with Suvo reduced the number of nTS and PVN neurons activated by hypoxia, including those CRH neurons projecting to nTS. Hypoxia increased the number of activated PVN-projecting orexin neurons but had no effect on the number of activated nTS-projecting orexin neurons. Global Ox1R blockade and partial Ox1R knockdown in the PVN significantly reduced the PCR. Ox1R knockdown also reduced the number of activated PVN neurons and the number of activated tyrosine hydroxylase neurons in the nTS. Our findings suggest orexin facilitates the PCR via nTS-projecting CRH neurons expressing Ox1R.

Inactivation of hypocretin receptor-2 signaling in dopaminergic neurons induces hyperarousal and enhanced cognition but impaired inhibitory control.

Hypocretin/Orexin (HCRT/OX) and dopamine (DA) are both key effectors of salience processing, reward and stress-related behaviors and motivational states, yet their respective roles and interactions are poorly delineated. We inactivated HCRT-to-DA connectivity by genetic disruption of Hypocretin receptor-1 (Hcrtr1), Hypocretin receptor-2 (Hcrtr2), or both receptors (Hcrtr1&2) in DA neurons and analyzed the consequences on vigilance states, brain oscillations and cognitive performance in freely behaving mice. Unexpectedly, loss of Hcrtr2, but not Hcrtr1 or Hcrtr1&2, induced a dramatic increase in theta (7-11 Hz) electroencephalographic (EEG) activity in both wakefulness and rapid-eye-movement sleep (REMS). DAHcrtr2-deficient mice spent more time in an active (or theta activity-enriched) substate of wakefulness, and exhibited prolonged REMS. Additionally, both wake and REMS displayed enhanced theta-gamma phase-amplitude coupling. The baseline waking EEG of DAHcrtr2-deficient mice exhibited diminished infra-theta, but increased theta power, two hallmarks of EEG hyperarousal, that were however uncoupled from locomotor activity. Upon exposure to novel, either rewarding or stress-inducing environments, DAHcrtr2-deficient mice featured more pronounced waking theta and fast-gamma (52-80 Hz) EEG activity surges compared to littermate controls, further suggesting increased alertness. Cognitive performance was evaluated in an operant conditioning paradigm, which revealed that DAHcrtr2-ablated mice manifest faster task acquisition and higher choice accuracy under increasingly demanding task contingencies. However, the mice concurrently displayed maladaptive patterns of reward-seeking, with behavioral indices of enhanced impulsivity and compulsivity. None of the EEG changes observed in DAHcrtr2-deficient mice were seen in DAHcrtr1-ablated mice, which tended to show opposite EEG phenotypes. Our findings establish a clear genetically-defined link between monosynaptic HCRT-to-DA neurotransmission and theta oscillations, with a differential and novel role of HCRTR2 in theta-gamma cross-frequency coupling, attentional processes, and executive functions, relevant to disorders including narcolepsy, attention-deficit/hyperactivity disorder, and Parkinson's disease.

In vivo photocontrol of orexin receptors with a nanomolar light-regulated analogue of orexin-B.

Orexinergic neurons are critically involved in regulating arousal, wakefulness, and appetite. Their dysfunction has been associated with sleeping disorders, and non-peptide drugs are currently being developed to treat insomnia and narcolepsy. Yet, no light-regulated agents are available to reversibly control their activity. To meet this need, a photoswitchable peptide analogue of the endogenous neuroexcitatory peptide orexin-B was designed, synthesized, and tested in vitro and in vivo. This compound - photorexin - is the first photo-reversible ligand reported for orexin receptors. It allows dynamic control of activity in vitro (including almost the same efficacy as orexin-B, high nanomolar potency, and subtype selectivity to human OX2 receptors) and in vivo in zebrafish larvae by direct application in water. Photorexin induces dose- and light-dependent changes in locomotion and a reduction in the successive induction reflex that is associated with sleep behavior. Molecular dynamics calculations indicate that trans and cis photorexin adopt similar bent conformations and that the only discriminant between their structures and activities is the positioning of the N-terminus. This, in the case of the more active trans isomer, points towards the OX2 N-terminus and extra-cellular loop 2, a region of the receptor known to be involved in ligand binding and recognition consistent with a "message-address" system. Thus, our approach could be extended to several important families of endogenous peptides, such as endothelins, nociceptin, and dynorphins among others, that bind to their cognate receptors through a similar mechanism: a "message" domain involved in receptor activation and signal transduction, and an "address" sequence for receptor occupation and improved binding affinity.

Sex-dependent effects of monomeric α-synuclein on calcium and cell death of lateral hypothalamic mouse neurons are altered by orexin.

Parkinson's Disease (PD) patients experience sleeping disorders in addition to the disease-defining symptomology of movement dysfunctions. The prevalence of PD is sex-based and presence of sleeping disorders in PD also shows sex bias with a stronger phenotype in males. In addition to loss of dopamine-containing neurons in the striatum, arousal-related, orexin-containing neurons in the lateral hypothalamus (LH) are lost in PD, which could contribute to state-related disorders. As orexin has been shown to be involved in sleeping disorders and to have neuroprotective effects, we asked whether orexin could protect sleep-related LH neurons from damage putatively from the protein α-synuclein (α-syn), which is found at high levels in the PD brain and that we have shown is associated with putatively excitotoxic rises in intracellular calcium in brainstem sleep-controlling nuclei, especially in males. Accordingly, we monitored intracellular calcium transients induced by α-syn and whether concurrent exposure to orexin affected those transients in LH cells of the mouse brain slice using calcium imaging. Further, we used an assay of cell death to determine whether LH cell viability was influenced when α-syn and orexin were co-applied when compared to exposure to α-syn alone. We found that excitatory calcium events induced by α-syn were reduced in amplitude and frequency when orexin was co-applied, and when data were evaluated by sex, this effect was found to be greater in females. In addition, α-syn exposure was associated with cell death that was higher in males, and interestingly, reduced cell death was noted when orexin was present, which did not show a sex bias. We interpret our findings to indicate that orexin is protective to α-syn-mediated damage to hypothalamic neurons, and the actions of orexin on α-syn-induced cellular effects differ between sexes, which could underlie sex-based differences in sleeping disorders in PD.

Orexin-A mediates glioblastoma proliferation inhibition by increasing ferroptosis triggered by unstable iron pools and GPX4 depletion.

Glioblastoma (GBM) represents a prevalent form of primary malignant tumours in the central nervous system, but the options for effective treatment are extremely limited. Ferroptosis, as the most enriched programmed cell death process in glioma, makes a critical difference in glioma progression. Consequently, inducing ferroptosis has become an appealing strategy for tackling gliomas. Through the utilization of multi-omics sequencing data analysis, flow cytometry, MDA detection and transmission electron microscopy, the impact of orexin-A on ferroptosis in GBM was assessed. In this report, we provide the first evidence that orexin-A exerts inhibitory effects on GBM proliferation via the induction of ferroptosis. This induction is achieved by instigating an unsustainable increase in iron levels and depletion of GPX4. Moreover, the regulation of TFRC, FTH1 and GPX4 expression through the targeting of NFE2L2 appears to be one of the potential mechanisms underlying orexin-A-induced ferroptosis.

Bi-allelic variants in HCRT cause autosomal recessive narcolepsy.

Narcolepsy with cataplexy is a complex disease with both genetic and environmental risk factors. To gain further insight into the homozygous HCRT-related narcolepsy, we present a case series of five patients from two consanguineous families, each harboring a novel homozygous variant of HCRT c.17_18del. All affected individuals exhibited severe cataplexy accompanied by narcolepsy symptoms during infancy. Additionally, cataplexy symptoms improved or disappeared in the majority of patients over time. Pathogenic variants in HCRT cause autosomal recessive narcolepsy with cataplexy. Genetic testing of the HCRT gene should be conducted in specific subgroups of narcolepsy, particularly those with early onset, familial cases, and a predominantly cataplexy phenotype.

Altered ventilatory responses to hypercapnia-hypoxia challenges in a preclinical SUDEP model involve orexin neurons.

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

Therapeutic effects of orexin-A in sepsis-associated encephalopathy in mice.

BACKGROUND: Sepsis-associated encephalopathy (SAE) causes acute and long-term cognitive deficits. However, information on the prevention and treatment of cognitive dysfunction after sepsis is limited. The neuropeptide orexin-A (OXA) has been shown to play a protective role against neurological diseases by modulating the inflammatory response through the activation of OXR1 and OXR2 receptors. However, the role of OXA in mediating the neuroprotective effects of SAE has not yet been reported. METHODS: A mouse model of SAE was induced using cecal ligation perforation (CLP) and treated via intranasal administration of exogenous OXA after surgery. Mouse survival, in addition to cognitive and anxiety behaviors, were assessed. Changes in neurons, cerebral edema, blood-brain barrier (BBB) permeability, and brain ultrastructure were monitored. Levels of pro-inflammatory factors (IL-1ß, TNF-α) and microglial activation were also measured. The underlying molecular mechanisms were investigated by proteomics analysis and western blotting. RESULTS: Intranasal OXA treatment reduced mortality, ameliorated cognitive and emotional deficits, and attenuated cerebral edema, BBB disruption, and ultrastructural brain damage in mice. In addition, OXA significantly reduced the expression of the pro-inflammatory factors IL-1ß and TNF-α, and inhibited microglial activation. In addition, OXA downregulated the expression of the Rras and RAS proteins, and reduced the phosphorylation of P-38 and JNK, thus inhibiting activation of the MAPK pathway. JNJ-10,397,049 (an OXR2 blocker) reversed the effect of OXA, whereas SB-334,867 (an OXR1 blocker) did not. CONCLUSION: This study demonstrated that the intranasal administration of moderate amounts of OXA protects the BBB and inhibits the activation of the OXR2/RAS/MAPK pathway to attenuate the outcome of SAE, suggesting that OXA may be a promising therapeutic approach for the management of SAE.

The role of orexin in Parkinson's disease.

Emerging evidence has implicated the orexin system in non-motor pathogenesis of Parkinson's disease. It has also been suggested the orexin system is involved in the modulation of motor control, further implicating the orexin system in Parkinson's disease. Parkinson's disease is the second most common neurodegenerative disease with millions of people suffering worldwide with motor and non-motor symptoms, significantly affecting their quality of life. Treatments are based solely on symptomatic management and no cure currently exists. The orexin system has the potential to be a treatment target in Parkinson's disease, particularly in the non-motor stage. In this review, the most current evidence on the orexin system in Parkinson's disease and its potential role in motor and non-motor symptoms of the disease is summarized. This review begins with a brief overview of Parkinson's disease, animal models of the disease, and the orexin system. This leads into discussion of the possible roles of orexin neurons in Parkinson's disease and levels of orexin in the cerebral spinal fluid and plasma in Parkinson's disease and animal models of the disease. The role of orexin is then discussed in relation to symptoms of the disease including motor control, sleep, cognitive impairment, psychological behaviors, and the gastrointestinal system. The neuroprotective effects of orexin are also summarized in preclinical models of the disease.

Single cell transcriptomics of cerebrospinal fluid cells from patients with recent-onset narcolepsy.

Narcolepsy is a rare cause of hypersomnolence and may be associated or not with cataplexy, i.e. sudden muscle weakness. These forms are designated narcolepsy-type 1 (NT1) and -type 2 (NT2), respectively. Notable characteristics of narcolepsy are that most patients carry the HLA-DQB1*06:02 allele and NT1-patients have strongly decreased levels of hypocretin-1 (synonym orexin-A) in the cerebrospinal fluid (CSF). The pathogenesis of narcolepsy is still not completely understood but the strong HLA-bias and increased frequencies of CD4+ T cells reactive to hypocretin in the peripheral blood suggest autoimmune processes in the hypothalamus. Here we analyzed the transcriptomes of CSF-cells from twelve NT1 and two NT2 patients by single cell RNAseq (scRNAseq). As controls, we used CSF cells from patients with multiple sclerosis, radiologically isolated syndrome, and idiopathic intracranial hypertension. From 27,255 CSF cells, we identified 20 clusters of different cell types and found significant differences in three CD4+ T cell and one monocyte clusters between narcolepsy and multiple sclerosis patients. Over 1000 genes were differentially regulated between patients with NT1 and other diseases. Surprisingly, the most strongly upregulated genes in narcolepsy patients as compared to controls were coding for the genome-encoded MTRNR2L12 and MTRNR2L8 peptides, which are homologous to the mitochondria-encoded HUMANIN peptide that is known playing a role in other neurological diseases including Alzheimer's disease.

Discovery and first-time disclosure of CVN766, an exquisitely selective orexin 1 receptor antagonist.

Modulators of orexin receptors are being developed for neurological illnesses such as sleep disorders, addictive behaviours and other psychiatric diseases. We herein describe the discovery of CVN766, a potent orexin 1 receptor antagonist that has greater than 1000-fold selectivity for the orexin 1 receptor over the orexin 2 receptor and demonstrates low off target hits in a diversity screen. In agreement with its in vitro ADME data, CVN766 demonstrated moderate in vivo clearance in rodents and displayed good brain permeability and target occupancy. This drug candidate is currently being investigated in clinical trials for schizophrenia and related psychiatric conditions.

Orexin B protects dopaminergic neurons from 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced neurotoxicity associated with reduced extracellular signal-regulated kinase phosphorylation.

BACKGROUND: The loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc) is a major pathological hallmark of Parkinson's disease (PD). Orexin B (OXB) has been reported to promote the growth of DA neurons. However, the roles of OXB in the degeneration of DA neurons still remained not fully clear. METHODS: An in vivo PD model was constructed by administrating 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in mice. Pole test was performed to investigate the motor function of mice and the number of DA neurons was detected by immunofluorescence (IF). A PD cell model was established by treating SH-SY5Y cells with 1-methyl-4-phenylpyridinium (MPP+). OXB was added to the culture medium 2 h after MPP + treatment. Microscopic analysis was carried out to investigate the function of OXB in the cell model of PD 24 h after MPP + challenge. RNA-Seq analysis of the PD cell model was performed to explore the possible mechanisms. Western blot was used to detect the phosphorylation levels of extracellular signal-regulated kinase (ERK). RESULTS: OXB significantly decreased the DA neurons death caused by MPTP, alleviated MPP+-induced neurotoxicity in SH-SY5Y cells, and robustly enhanced the weight and motor ability of PD mice. Besides, RNA-Seq analysis demonstrated that the mitogen-activated protein kinase (MAPK) pathway was involved in the pathology of PD. Furthermore, MPP + led to increased levels of phosphorylation of ERK (p-ERK), OXB treatment significantly decreased the levels of p-ERK in MPP+-treated SH-SY5Y cells. CONCLUSIONS: This study demonstrated that OXB exerts a neuroprotective role associated with reduced ERK phosphorylation in the PD model. This suggests that OXB may have therapeutic potential for treatment of PD.

Danavorexton (TAK-925): an orexin receptor 2 agonist as a new 'arousal' agent.

A preclinical study in animals has further characterised a new 'arousal' agent. Danavorexton (TAK-925) is an agonist for orexin receptor 2 where it promotes recovery from inhalational and i.v. anaesthesia and opioid sedation. Although danavorexton reverses opioid sedation, it does not compromise analgesia. This could be a useful addition to the postoperative drug cupboard.

Evaluating the efficacy of the selective orexin 1 receptor antagonist nivasorexant in an animal model of binge-eating disorder.

OBJECTIVE: Test the efficacy of the selective orexin 1 receptor (OX1R) antagonist (SO1RA) nivasorexant in an animal model of binge-eating disorder (BED) and study its dose-response relationship considering free brain concentrations and calculated OX1R occupancy. Compare nivasorexant's profile to that of other, structurally diverse SO1RAs. Gain understanding of potential changes in orexin-A (OXA) neuropeptide and deltaFosB (ΔFosB) protein expression possibly underlying the development of the binge-eating phenotype in the rat model used. METHOD: Binge-like eating of highly palatable food (HPF) in rats was induced through priming by intermittent, repeated periods of dieting and access to HPF, followed by an additional challenge with acute stress. Effects of nivasorexant were compared to the SO1RAs ACT-335827 and IDOR-1104-2408. OXA expression in neurons and neuronal fibers as well as ΔFosB and OXA-ΔFosB co-expression was studied in relevant brain regions using immuno- or immunofluorescent histochemistry. RESULTS: All SO1RAs dose-dependently reduced binge-like eating with effect sizes comparable to the positive control topiramate, at unbound drug concentrations selectively blocking brain OX1Rs. Nivasorexant's efficacy was maintained upon chronic dosing and under conditions involving more frequent stress exposure. Priming for binge-like eating or nivasorexant treatment resulted in only minor changes in OXA or ΔFosB expression in few brain areas. DISCUSSION: Selective OX1R blockade reduced binge-like eating in rats. Neither ΔFosB nor OXA expression proved to be a useful classifier for their binge-eating phenotype. The current results formed the basis for a clinical phase II trial in BED, in which nivasorexant was unfortunately not efficacious compared with placebo. PUBLIC SIGNIFICANCE: Nivasorexant is a new investigational drug for the treatment of binge-eating disorder (BED). It underwent clinical testing in a phase II proof of concept trial in humans but was not efficacious compared with placebo. The current manuscript investigated the drug's efficacy in reducing binge-like eating behavior of a highly palatable sweet and fat diet in a rat model of BED, which initially laid the foundation for the clinical trial.

The metabolism of the orexin-1 selective receptor antagonist nivasorexant.

Nivasorexant was the first orexin-1 selective receptor antagonist entering clinical development. Despite encouraging preclinical evidence in animal models, a proof-of-concept trial in binge-eating patients recently failed to demonstrate its clinical utility in this population.Across species, nivasorexant clearance was driven by metabolism along seven distinct pathways, five of which were hydroxylation reactions in various locations of the molecule. The exact sites of metabolism were identified by means of mass spectrometry, the use of deuterated analogues, and finally confirmed by chemical references.CYP3A4 was the main cytochrome P450 enzyme involved in nivasorexant metabolism in vitro and accounting for about 90% of turnover in liver microsomes. Minor roles were taken by CYP2C9 and CYP2C19 but individually did not exceed 3-7%.In the rat, nivasorexant was mostly excreted via the bile after extensive metabolism, while urinary excretion was negligible. Only traces of the parent drug were detected in urine, bile, or faeces.

Evaluating routine blood and cerebrospinal fluid samples in narcolepsy patients.

Cerebrospinal fluid hypocretin-1 is proven to be a precise diagnostic marker of narcolepsy Type 1 (NT1). However other characteristics of cerebrospinal fluid and blood parameters have not yet been described. The objective of this study was to evaluate the differences in routine blood and cerebrospinal fluid analyses between NT1 patients and patients suspected of hypersomnia. We collected retrospectively all measures of cerebrospinal fluid hypocretin-1 between 2019 and 2022. This yielded 612 patients out of which 146 were diagnosed with NT1 and the rest (466 patients) were used as a control group. We selected the most relevant routine samples from both blood, plasma and cerebrospinal fluid and compared the two groups. The only significantly different analytes were plasma lactate dehydrogenase and cerebrospinal fluid hypocretin-1. No other differences were found between the groups including thyroid markers, markers of neuroendocrine function, inflammatory markers in blood or cerebrospinal fluid, markers of permeability of the blood brain barrier or metabolic markers in blood samples. We found no significant differences in routine blood or cerebrospinal fluid components, neuroendocrine function, neuroinflammation and metabolic markers. The results reflect that the hypocretin system does not seem to play a chronic major role in regulation of these markers. None of the parameters routinely measured in blood in these patients could differentiate between NT1 and non-NT1 disorders besides CSF-hcrt-1.

Control of motivation for sucrose in the paraventricular hypothalamic nucleus by dynorphin peptides and the kappa opioid receptor.

The dynorphin peptides are the endogenous ligands for the kappa opioid receptor (KOR) and regulate food intake. Administration of dynorphin-A1-13 (DYN) in the paraventricular hypothalamic nucleus (PVN) increases palatable food intake, and this effect is blocked by co-administration of the orexin-A neuropeptide, which is co-released with DYN in PVN from neurons located in the lateral hypothalamus. While PVN administration of DYN increases palatable food intake, whether it increases food-seeking behaviors has yet to be examined. We tested the effects of DYN and norBNI (a KOR antagonist) on the seeking and consumption of sucrose using a progressive ratio (PR) and demand curve (DC) tasks. In PVN, DYN did not alter the sucrose breaking point (BP) in the PR task nor the elasticity or intensity of demand for sucrose in the DC task. Still, DYN reduced the delay in obtaining sucrose and increased licks during sucrose intake in the PR task, irrespective of the co-administration of orexin-A. In PVN, norBNI increased the delay in obtaining sucrose and reduced licks during sucrose intake in the PR task while increasing elasticity without altering intensity of demand in the DC task. However, subcutaneous norBNI reduced the BP for sucrose and increased the delay in obtaining sucrose in the PR task while reducing the elasticity of demand. Together, these data show different effects of systemic and PVN blockade of KOR on food-seeking, consummatory behaviors, and incentive motivation for sucrose and suggest that KOR activity in PVN is necessary but not sufficient to drive seeking behaviors for palatable food.

Sleep quality in patients with chronic spontaneous urticaria and relation with Orexin-A, leptin, and ghrelin.

Background: Sleep can be affected in patients with chronic spontaneous urticaria (CSU). The mechanisms of sleep regulation remain poorly understood. Orexin-A, a neuroexcitatory peptide, plays a role in coordinating sleep-wake states. Ghrelin and leptin are involved in sleep regulation through the orexin system. Objective: The effects of orexin-A, ghrelin, and leptin on sleep quality in patients with CSU have not been investigated. We aimed to determine the effects of CSU on sleep quality and the association between serum orexin-A, ghrelin, and leptin levels, and sleep quality in patients with CSU. Methods: Thirty-three patients with CSU and 34 sex- and age-matched controls were included in the study. Serum orexin-A, leptin, and ghrelin levels, and the Pittsburgh Sleep Quality Index (PSQI) and the Epworth Sleepiness Scale (ESS) scores were measured in patients with CSU and in the controls; also used were the chronic urticaria quality-of-life questionnaire score and the urticaria activity score used for 7 consecutive days. Results: Median (minimum-maximum) orexin-A, leptin, and ghrelin levels in patients were 385 pg/mL (90-495 pg/mL), 3.1 ng/mL (0-21.2 ng/mL), and 701.8 pg/mL (101.9-827.7 pg/mL), respectively. Median serum orexin-A and leptin levels were higher in the patients compared with the controls (p < 0.001 and p = 0.012, respectively), whereas the median serum ghrelin levels were similar to the controls (p = 0.616). The serum orexin-A level was positively correlated with ghrelin (r = 0.298, p = 0.014), PSQI sleep quality (r = 0.356, p = 0.003), and ESS (r = 0.357, p = 0.003). Conclusion: Serum orexin-A is associated with sleep quality in patients with CSU. Further studies are needed to elucidate the role of ghrelin and leptin on sleep quality in patients with CSU.

Effects of fasting and environmental factors on appetite regulators in pond loach Misgurnus anguillicaudatus.

The pond loach (Misgurnus anguillicaudatus) is an important aquaculture freshwater species, used as an ornamental fish, food source for humans and angling bait. Pond loaches are resistant to fasting and extreme environmental conditions, including temperature and low oxygen levels. Little is known about how these factors affect the feeding physiology and the endocrine regulation of feeding of loaches. In this study, we examined the effects of fasting, as well as increased temperature and decreased oxygen levels on food intake and transcript levels of appetite regulators. Fasted fish had lower blood glucose levels, and lower expression levels of intestine CCK and PYY, and brain CART1, but had higher levels of brain orexin and ghrelin than fed fish. Fish held at 30 °C had higher food intake, glucose levels, and mRNA levels of intestine CCK and PYY, and brain CART2, but lower brain orexin levels than fish at 20 °C. Fish held at low oxygen levels had a lower food intake, higher intestine CCKa and ghrelin, and brain orexin, CART2 and ghrelin mRNA expression levels than fish held at high O2 levels. Our results suggest that fasting and high temperatures increase the expression of orexigenic and anorexigenic factors respectively, whereas the increase in expression of both orexigenic and anorexigenic factors in low O2 environments might not be related to their role in feeding, but possibly to protection from tissue damage. The results of our study might shed new light on how pond loaches are able to cope with extreme environmental conditions such as low food availability, extreme temperatures and hypoxia.