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Carpi M, Palagini L, Fernandes M, Calvello C, Geoffroy PA, Miniati M, Pini S, Gemignani A, Mercuri NB, Liguori C. Clinical usefulness of dual orexin receptor antagonism beyond insomnia: Neurological and psychiatric comorbidities. Neuropharmacology 2024; 245:109815. [PMID: 38114045 DOI: 10.1016/j.neuropharm.2023.109815] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Revised: 12/11/2023] [Accepted: 12/12/2023] [Indexed: 12/21/2023]
Abstract
Orexin is a neurotransmitter produced by a small group of hypothalamic neurons. Besides its well-known role in the regulation of the sleep-wake cycle, the orexin system was shown to be relevant in several physiological functions including cognition, mood and emotion modulation, and energy homeostasis. Indeed, the implication of orexin neurotransmission in neurological and psychiatric diseases has been hypothesized via a direct effect exerted by the projections of orexin neurons to several brain areas, and via an indirect effect through orexin-mediated modulation of sleep and wake. Along with the growing evidence concerning the use of dual orexin receptor antagonists (DORAs) in the treatment of insomnia, studies assessing their efficacy in insomnia comorbid with psychiatric and neurological diseases have been set in order to investigate the potential impact of DORAs on both sleep-related symptoms and disease-specific manifestations. This narrative review aimed at summarizing the current evidence on the use of DORAs in neurological and psychiatric conditions comorbid with insomnia, also discussing the possible implication of modulating the orexin system for improving the burden of symptoms and the pathological mechanisms of these disorders. Target searches were performed on PubMed/MEDLINE and Scopus databases and ongoing studies registered on Clinicaltrials.gov were reviewed. Despite some contradictory findings, preclinical studies seemingly support the possible beneficial role of orexin antagonism in the management of the most common neurological and psychiatric diseases with sleep-related comorbidities. However, clinical research is still limited and further studies are needed for corroborating these promising preliminary results.
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Affiliation(s)
- Matteo Carpi
- Sleep and Epilepsy Centre, Neurology Unit, University Hospital Tor Vergata, Rome, Italy.
| | - Laura Palagini
- Department of Clinical and Experimental Medicine, Unit of Psychiatry, Azienda Ospedaliero Universitaria Pisana AUOP, Pisa, Italy.
| | - Mariana Fernandes
- Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.
| | - Carmen Calvello
- Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.
| | - Pierre Alexis Geoffroy
- Département de Psychiatrie et D'addictologie, AP-HP, GHU Paris Nord, DMU Neurosciences, Hopital Bichat - Claude Bernard, F-75018, Paris, France; GHU Paris - Psychiatry & Neurosciences, Paris, France; Université de Paris, NeuroDiderot, Inserm, FHU I2-D2, F-75019, Paris, France.
| | - Mario Miniati
- Department of Clinical and Experimental Medicine, Unit of Psychiatry, Azienda Ospedaliero Universitaria Pisana AUOP, Pisa, Italy.
| | - Stefano Pini
- Department of Clinical and Experimental Medicine, Unit of Psychiatry, Azienda Ospedaliero Universitaria Pisana AUOP, Pisa, Italy.
| | - Angelo Gemignani
- Unit of Psychology, Department of Surgical, Medical and Molecular Pathology and Critical Care Medicine, University of Pisa, Azienda Ospedaliero Universitaria Pisana AUOP, Pisa, Italy.
| | | | - Claudio Liguori
- Sleep and Epilepsy Centre, Neurology Unit, University Hospital Tor Vergata, Rome, Italy; Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.
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Atacan Yaşgüçlükal M, Ayça S, Demirbilek V, Saltık S, Yalçınkaya C, Erdoğan Döventaş Y, Çokar Ö. Serum Levels of Neuropeptides in Epileptic Encephalopathy With Spike-and-Wave Activation in Sleep. Pediatr Neurol 2023; 144:110-114. [PMID: 37229878 DOI: 10.1016/j.pediatrneurol.2023.04.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 03/13/2023] [Accepted: 04/21/2023] [Indexed: 05/27/2023]
Abstract
BACKGROUND Epileptic encephalopathy with spike-and-wave activation in sleep (EE-SWAS) is a syndrome of childhood, characterized by diffuse or generalized spike-wave activity in electroencephalography during non-rapid eye movement sleep. Neuropeptides have been demonstrated in several studies to function in the sleep-wake cycle and display convulsant and anticonvulsant features. In this study, we aimed to investigate the relationship between EE-SWAS and neuropeptides such as dynorphin, galanin, ghrelin, leptin, melatonin, and orexin. METHODS This multicenter study was conducted from July 2019 to January 2021. There were three groups: Group 1 contained patients with EE-SWAS. Group 2 consisted of patients with self-limited focal epilepsy of childhood (SeLFE), and group 3 was the control group. Levels of neuropeptides were compared in the sera of these three groups. RESULTS There were 59 children aged between four and 15 years. Group 1 contained 14 children, group 2 contained 24 children, and group 3 contained 21 children. The level of leptin is higher and the level of melatonin is lower in group 1 than in group 3 (P = 0.01 and P = 0.005, respectively). In group 3, the level of orexin was lower than in both groups 2 and 3 (P = 0.01 and P = 0.01). CONCLUSIONS These data show that the level of leptin was higher and the level of melatonin was lower in patients with EE-SWAS than in the control group. Furthermore, patients with EE-SWAS had lower orexin levels than both the control group and patients with SeLFE. Further research is required to understand the potential role of these neuropeptides in the pathophysiology of EE-SWAS.
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Affiliation(s)
- Miray Atacan Yaşgüçlükal
- Neurology Department, University of Health Sciences Haseki Education and Research Hospital, Istanbul, Turkey.
| | - Senem Ayça
- Department of Pediatric Neurology, University of Health Sciences Haseki Education and Research Hospital, Istanbul, Turkey
| | - Veysi Demirbilek
- Cerrahpaşa Medical Faculty, Neurology Department, İstanbul University-Cerrahpaşa, Istanbul, Turkey
| | - Sema Saltık
- Cerrahpaşa Medical Faculty, Department of Pediatric Neurology, İstanbul University-Cerrahpaşa, Istanbul, Turkey
| | - Cengiz Yalçınkaya
- Cerrahpaşa Medical Faculty, Neurology Department, İstanbul University-Cerrahpaşa, Istanbul, Turkey
| | - Yasemin Erdoğan Döventaş
- Department of Medical Biochemistry, University of Health Sciences Haseki Education and Research Hospital, Istanbul, Turkey
| | - Özlem Çokar
- Neurology Department, University of Health Sciences Haseki Education and Research Hospital, Istanbul, Turkey
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Sheibani M, Shayan M, Khalilzadeh M, Ghasemi M, Dehpour AR. Orexin receptor antagonists in the pathophysiology and treatment of sleep disorders and epilepsy. Neuropeptides 2023; 99:102335. [PMID: 37003137 DOI: 10.1016/j.npep.2023.102335] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2023] [Revised: 03/20/2023] [Accepted: 03/23/2023] [Indexed: 03/29/2023]
Abstract
The correlation between sleep and epilepsy has been argued over the past decades among scientists. Although the similarities and contrasts between sleep and epilepsy had been considered, their intertwined nature was not revealed until the nineteenth century. Sleep is recognized as a recurring state of mind and body through alternating brain electrical activities. It is documented that sleep disorders are associated with epilepsy. The origin, suppression, and spread of seizures are affected by sleep. As such, in patients with epilepsy, sleep disorders are a frequent comorbidity. Meanwhile, orexin, a wake-promoting neuropeptide, provides a bidirectional effect on both sleep and epilepsy. Orexin and its cognate receptors, orexin receptor type 1 (OX1R) and type 2 (OX2R), orchestrate their effects by activating various downstream signaling pathways. Although orexin was considered a therapeutic target in insomnia shortly after its discovery, its potential usefulness for psychiatric disorders and epileptic seizures has been suggested in the pre-clinical studies. This review aimed to discuss whether the relationship between sleep, epilepsy, and orexin is clearly reciprocal.
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Affiliation(s)
- Mohammad Sheibani
- Department of Pharmacology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran; Razi Drug Research Center, School of Medicine, Iran University of Medical Sciences, Tehran, Iran
| | - Maryam Shayan
- Experimental Medicine Research Centre, Tehran University of Medical Sciences, Tehran, Iran; Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Mina Khalilzadeh
- Experimental Medicine Research Centre, Tehran University of Medical Sciences, Tehran, Iran; Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Mehdi Ghasemi
- Department of Neurology, University of Massachusetts Chan Medical School, Worcester, MA 01655, USA.
| | - Ahmad Reza Dehpour
- Experimental Medicine Research Centre, Tehran University of Medical Sciences, Tehran, Iran; Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
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Relation Between Orexin A and Epileptic Seizures. Epilepsy Res 2022; 184:106972. [DOI: 10.1016/j.eplepsyres.2022.106972] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 02/23/2022] [Accepted: 06/22/2022] [Indexed: 11/19/2022]
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Elahdadi Salmani M, Sarfi M, Goudarzi I. Hippocampal orexin receptors: Localization and function. VITAMINS AND HORMONES 2022; 118:393-421. [PMID: 35180935 DOI: 10.1016/bs.vh.2021.12.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Orexin (hypocretin) is secreted from the perifornical/lateral hypothalamus and is well known for sleep regulation. Orexin has two, orexin A and B, transcripts and two receptors, type 1 and 2 (OX1R and OX2R), located in the plasma membrane of neurons in different brain areas, including the hippocampus involved in learning, memory, seizures, and epilepsy, as physiologic and pathologic phenomena. OX1R is expressed in the dentate gyrus and CA1 and the OX2R in the CA3 areas. Orexin enhances learning and memory as well as reward, stress, seizures, and epilepsy, partly through OX1Rs, while either aggravating or alleviating those phenomena via OX2Rs. OX1Rs activation induces long-term changes of synaptic responses in the hippocampus, an age and concentration-dependent manner. Briefly, we will review the localization and functions of hippocampal orexin receptors, their role in learning, memory, stress, reward, seizures, epilepsy, and hippocampal synaptic plasticity.
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Affiliation(s)
| | | | - Iran Goudarzi
- School of Biology, Damghan University, Damghan, Iran
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Razavi BM, Farivar O, Etemad L, Hosseinzadeh H. Suvorexant, a Dual Orexin Receptor Antagonist, Protected Seizure through Interaction with GABA A and Glutamate Receptors. IRANIAN JOURNAL OF PHARMACEUTICAL RESEARCH : IJPR 2020; 19:383-390. [PMID: 33224245 PMCID: PMC7667563 DOI: 10.22037/ijpr.2019.14688.12584] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Orexin can increase neuronal excitability and induce epileptic activity. In this study, the effects of suvorexant (orexin receptor antagonist) on pentylenetetrazol (PTZ) and maximal electroshock (MES)-induced seizure were investigated. Mice were divided into 5 groups of six animals each including normal saline (10 mL/kg), diazepam (2 mg/kg), and suvorexant (50, 100 and 200 mg/kg) groups. In PTZ test, the latency to first minimal clonic seizure (MCS), latency to the first generalized tonic–clonic seizures (GTCS), total duration of seizure and also protection against mortality were evaluated. In MES, the hind limb tonic extension (HLTE) and the protection against mortality were recorded. In order to evaluate the role of GABAA in anticonvulsant effect of suvorexant, flumazenil was used and to investigate the role of glutamate, the protein levels of AMPAR and NMDAR were measured in hippocampus by western blotting. In PTZ model, suvorexant (200mg/kg) increased MCS and GTCS latencies. Suvorexant (100 and 200 mg/kg) decreased total duration of seizure compared to control group. In PTZ model, flumazenil inhibited the prolongation of seizure latency induced by suvorexant. In MES, the HLTE was decreased by suvorexant (100 and 200 mg/kg) and suvorexant was protected against mortality by 83.3%. Moreover, the protein levels of NMDAR and AMPAR were decreased by suvorexant. Suvorexant exerted anticonvulsant activity and in addition to its inhibitory effect on orexin receptors, this effect may be mediated, at least partly, through interaction with GABAA and glutamate receptors.
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Affiliation(s)
- Bibi Marjan Razavi
- Targeted Drug Delivery Research Center, Pharmaceutical Technology Institute, Mashhad University of Medical Sciences, Mashhad, Iran.,Department of Pharmacodynamics and Toxicology, School of Pharmacy, Mashhad University of Mdical sciences,Mashhad,Iran
| | - Omid Farivar
- Department of Pharmacodynamics and Toxicology, School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Leila Etemad
- Pharmaceutical Research Center, Pharmaceutical Technology Institute, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Hossein Hosseinzadeh
- Department of Pharmacodynamics and Toxicology, School of Pharmacy, Mashhad University of Mdical sciences,Mashhad,Iran.,Pharmaceutical Research Center, Pharmaceutical Technology Institute, Mashhad University of Medical Sciences, Mashhad, Iran
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Samzadeh M, Papuć E, Furtak-Niczyporuk M, Rejdak K. Decreased Cerebrospinal Fluid Orexin-A (Hypocretin-1) Concentrations in Patients after Generalized Convulsive Status Epilepticus. J Clin Med 2020; 9:jcm9103354. [PMID: 33086714 PMCID: PMC7589455 DOI: 10.3390/jcm9103354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 10/10/2020] [Accepted: 10/13/2020] [Indexed: 11/16/2022] Open
Abstract
The effects of status epilepticus on the orexin/hypocretin system have yet to be investigated. The present study aimed to assay orexin-A/hypocretin-1 in the cerebrospinal fluid (CSF) of patients after generalized convulsive status epilepticus (GCSE). The study groups included 20 GCSE patients, 24 patients diagnosed with epilepsy but remaining in remission (ER), and 25 normal controls (CTR). Diagnostic lumbar puncture was performed in GCSE patients within 3–10 days of seizure cessation, as well as in the ER and to CTR subjects. Among all GCSE patients, the outcome was graded according to the modified Rankin Scale (mRS) at 1-month follow-up. Orexin-A levels were measured in unextracted CSF samples, using a commercial radioimmunoassay. There was a significant overall difference in median CSF orexin-A concentrations between GCSE, RE, and CTR patients (p < 0.001). The lowest concentrations were noted in the GCSE group compared to ER (p < 0.001) or CTR (p < 0.001). CSF orexin-A levels in GCSE patients inversely correlated with clinical outcome as assessed on the mRS at 1-month follow-up (r = −0.55; p = 0.1). In conclusion, CSF orexin-A levels may serve as a biomarker of increased turn-over of the peptide or post-SE neuronal damage, and implicates the orexin system in the pathogenesis of SE.
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Affiliation(s)
- Mojdeh Samzadeh
- Department of Neurology, Medical University of Lublin, 20-954 Lublin, Poland; (M.S.); (E.P.)
| | - Ewa Papuć
- Department of Neurology, Medical University of Lublin, 20-954 Lublin, Poland; (M.S.); (E.P.)
| | | | - Konrad Rejdak
- Department of Neurology, Medical University of Lublin, 20-954 Lublin, Poland; (M.S.); (E.P.)
- Correspondence:
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Çikriklar HI, Kotan D, Yücel M, Ceylan M, Çiftçi GG, Bayraktutan ÖF, Çiftçi IH. The role of Orexin-A levels in epileptic seizure. Neurosci Lett 2020; 734:135097. [PMID: 32485288 DOI: 10.1016/j.neulet.2020.135097] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2019] [Revised: 03/16/2020] [Accepted: 05/23/2020] [Indexed: 02/06/2023]
Abstract
BACKGROUND The aim of this study is to determine the usefulness of Orexin-A levels in differentiating between epileptic seizures and psychogenic non-epileptic seizures in patients presenting to the emergency service with epileptic seizure-type symptoms. METHODS A total of 80 individuals were included in this study, including 59 who presented to the emergency service within the first four hours of having been diagnosed with generalized tonic-clonic seizures (39 with epileptic seizures (ES) and 20 with pseudoseizures (PNES) and 21 controls. Orexin-A levels were measured in venous blood samples. RESULTS The mean Orexin-A levels were 5.16 ng/mL in the control group, 7.17 ng/mL in the PNES group, and 11.08 ng/mL in the ES group (Table 1). The mean Orexin-A level of the ES group was significantly different from both the control group and the PNES group (Table 1, p < 0.001); the difference between the control group and the PNES group was not significant (p > 0.05). CONCLUSIONS Results of this study suggest that blood Orexin-A may be an effective biomarker in the differential diagnosis of epileptic seizures/psychogenic non-epileptic seizures in patients presenting to the emergency service with an epileptic seizure-type clinical picture.
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Affiliation(s)
| | - Dilcan Kotan
- Altinsehir Mahallesi 326. Sokak No:7 Daire:20, NILÜFER, Bursa, Turkey
| | - Murat Yücel
- Altinsehir Mahallesi 326. Sokak No:7 Daire:20, NILÜFER, Bursa, Turkey
| | - Mustafa Ceylan
- Altinsehir Mahallesi 326. Sokak No:7 Daire:20, NILÜFER, Bursa, Turkey
| | - Gönül G Çiftçi
- Altinsehir Mahallesi 326. Sokak No:7 Daire:20, NILÜFER, Bursa, Turkey
| | | | - Ihsan H Çiftçi
- Altinsehir Mahallesi 326. Sokak No:7 Daire:20, NILÜFER, Bursa, Turkey
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Orexins role in neurodegenerative diseases: From pathogenesis to treatment. Pharmacol Biochem Behav 2020; 194:172929. [PMID: 32315694 DOI: 10.1016/j.pbb.2020.172929] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 04/07/2020] [Accepted: 04/08/2020] [Indexed: 12/12/2022]
Abstract
Orexin is a neurotransmitter that mainly regulates sleep/wake cycle. In addition to its sleep cycle regulatory role, it is involved in regulation of attention, energy homeostasis, neurogenesis and cognition. Several evidences has shown the involvement of orexin in narcolepsy, but there are also growing evidences that shows the disturbance in orexin system in neurodegenerative diseases including Alzheimer's, Parkinson's, Epilepsy, Huntington's diseases and Amyotrophic lateral sclerosis. Pathogenesis and clinical symptoms of these disorders can be partly attributed from orexin system imbalance. However, there are controversial reports on the exact relationship between orexin and these neurodegenerative diseases. Therefore, the aim of this review is to summarize the current evidences regarding the role of orexin in these neurodegenerative diseases.
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10
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Hayatdavoudi P, Sadeghnia HR, Mohamadian-Roshan N, Hadjzadeh MAR. Beneficial Effects of Selective Orexin-A Receptor Antagonist in 4-aminopyridine-induced Seizures in Male Rats. Adv Biomed Res 2017; 6:162. [PMID: 29387673 PMCID: PMC5767796 DOI: 10.4103/abr.abr_262_16] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Background Orexins are excitatory neuropeptides which stimulate the central regulatory pathways. Orexins increase the penicillin-induced epileptic activity in rats. Orexin-A increases in different types of seizures and its elevated level is the characteristic feature in the epileptic children during polysomnography. Recently, the orexin receptor blockage has been reported to increase seizure threshold in mice; however, effect of the selective orexin-A receptor antagonist (SB-334867) on 4-aminopyridine (4-AP)-induced seizures has not been investigated. Materials and Methods We used the intraperitoneal injection of 4-AP to induce seizure in male rats. Under urethane anesthesia, SB-334867 (50 and 100 nmol) was injected stereotaxically into the ventral hippocampal commissure. Using video recording, the effects of SB-334867 on electroencephalogram and tonic-clonic convulsions were compared to those that received diazepam or dimethyl sulfoxide (DMSO). Results SB-334867 significantly decreased the duration of spike trains compared to DMSO-treated rats (P < 0.001) and reduced the duration of convulsive seizures (P < 0.05). Seizure onset was increased significantly by SB-334867, 50 nmol, compared to DMSO (P < 0.05) and diazepam (P < 0.01) treated rats. Conclusion Antagonism of orexin-A receptor by a low-dose SB-334867 showed protective effects in 4-AP-induced seizure-like activities in anesthetized rats.
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Affiliation(s)
- Parichehr Hayatdavoudi
- Department of Physiology, Neurocognitive Research Center, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Hamid-Reza Sadeghnia
- Department of Pharmacology, Pharmacological Research Center of Medicinal Plants, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Nema Mohamadian-Roshan
- Department of Pathology, Ghaem Hospital, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Mousa Al-Reza Hadjzadeh
- Department of Physiology, Neurocognitive Research Center, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
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Mavanji V, Butterick TA, Duffy CM, Nixon JP, Billington CJ, Kotz CM. Orexin/hypocretin treatment restores hippocampal-dependent memory in orexin-deficient mice. Neurobiol Learn Mem 2017; 146:21-30. [PMID: 29107703 DOI: 10.1016/j.nlm.2017.10.014] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 10/02/2017] [Accepted: 10/27/2017] [Indexed: 12/31/2022]
Abstract
Orexin A is produced in neurons of the lateral, perifornical and dorsomedial regions of the lateral hypothalamic area, which then project widely throughout the central nervous system to regulate arousal state, sleep-wake architecture, energy homeostasis and cognitive processes. Disruption of orexin signaling leads to sleep disturbances and increased body mass index, but recent studies also indicate that orexin neuron activation improves learning and memory. We hypothesized that hippocampal orexin receptor activation improves memory. To test this idea, we obtained orexin/ataxin-3 (O/A3) mice, which become deficient in orexin neurons by about 12 weeks of age. We first measured hippocampal orexin receptor 1 (OX1R) gene expression and protein levels, then tested acquisition and consolidation of two-way active avoidance (TWAA) memory, a hippocampal-dependent learning and memory task. Finally, we determined if exogenous intra-hippocampal OXA treatment could reverse cognitive impairment (as determined by TWAA) in OA/3 mice. We showed that OX1R mRNA expression and protein levels were significantly elevated in O/A3 mice, indicating the potential for preserved orexin responsiveness. The O/A3 mice were significantly impaired in TWAA memory vs. control mice, but OXA treatment (both acute and chronic) reversed these memory deficits. These results demonstrate that orexin plays an important role in hippocampal-dependent consolidation of two-way active avoidance memory, and orexin replacement can rescue the cognitive impairment.
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Affiliation(s)
- Vijayakumar Mavanji
- Research Service, Veterans Affairs Health Care System, Minneapolis, MN 55417 USA
| | - Tammy A Butterick
- Research Service, Veterans Affairs Health Care System, Minneapolis, MN 55417 USA; Department of Food Science and Nutrition, University of Minnesota, St Paul, MN 55108 USA; Minnesota Obesity Center, St Paul, MN 55108 USA
| | - Cayla M Duffy
- Research Service, Veterans Affairs Health Care System, Minneapolis, MN 55417 USA; Department of Food Science and Nutrition, University of Minnesota, St Paul, MN 55108 USA; Minnesota's Discovery, Research and Innovation Economy, Brain Conditions, University of Minnesota, Minneapolis, MN 55455
| | - Joshua P Nixon
- Research Service, Veterans Affairs Health Care System, Minneapolis, MN 55417 USA; Department of Food Science and Nutrition, University of Minnesota, St Paul, MN 55108 USA
| | - Charles J Billington
- Research Service, Veterans Affairs Health Care System, Minneapolis, MN 55417 USA; Minnesota Obesity Center, St Paul, MN 55108 USA; Department of Medicine, University of Minnesota, Minneapolis, MN 55455 USA
| | - Catherine M Kotz
- Research Service, Veterans Affairs Health Care System, Minneapolis, MN 55417 USA; Minnesota Obesity Center, St Paul, MN 55108 USA; Geriatric Research Education Clinical Center, Veterans Affairs Health Care System, Minneapolis, MN 55417 USA; Department of Integrative Biology and Physiology, University of Minnesota, Minneapolis, MN 55455 USA.
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Gauci S, Hosking W, Bruck D. Narcolepsy, cataplexy, hypocretin and co-existing other health complaints: A review. COGENT MEDICINE 2017. [DOI: 10.1080/2331205x.2017.1312791] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Affiliation(s)
- Samantha Gauci
- Psychology Discipline, College of Arts, College of Health and Biomedicine, Victoria University, P.O. Box 14428, Melbourne 8001, Australia
| | - Warwick Hosking
- Psychology Discipline, College of Arts, College of Health and Biomedicine, Victoria University, P.O. Box 14428, Melbourne 8001, Australia
| | - Dorothy Bruck
- Psychology Discipline, College of Arts, College of Health and Biomedicine, Victoria University, P.O. Box 14428, Melbourne 8001, Australia
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Chieffi S, Messina G, Villano I, Messina A, Esposito M, Monda V, Valenzano A, Moscatelli F, Esposito T, Carotenuto M, Viggiano A, Cibelli G, Monda M. Exercise Influence on Hippocampal Function: Possible Involvement of Orexin-A. Front Physiol 2017; 8:85. [PMID: 28261108 PMCID: PMC5306252 DOI: 10.3389/fphys.2017.00085] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Accepted: 01/30/2017] [Indexed: 01/24/2023] Open
Abstract
In the present article, we provide a brief review of current knowledge regarding the effects induced by physical exercise on hippocampus. Research involving animals and humans supports the view that physical exercise, enhancing hippocampal neurogenesis and function, improves cognition, and regulates mood. These beneficial effects depend on the contribute of more factors including the enhancement of vascularization and upregulation of growth factors. Among these, the BDNF seems to play a significant role. Another putative factor that might contribute to beneficial effects of exercise is the orexin-A. In support of this hypothesis there are the following observations: (1) orexin-A enhances hippocampal neurogenesis and function and (2) the levels of orexin-A increase with physical exercise. The beneficial effects of exercise may represent an important resource to hinder the cognitive decline associated with the aging-related hippocampal deterioration and ameliorate depressive symptoms.
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Affiliation(s)
- Sergio Chieffi
- Section of Human Physiology and Unit of Dietetic and Sport Medicine, Department of Experimental Medicine, Second University of Naples Naples, Italy
| | - Giovanni Messina
- Section of Human Physiology and Unit of Dietetic and Sport Medicine, Department of Experimental Medicine, Second University of NaplesNaples, Italy; Department of Clinical and Experimental Medicine, University of FoggiaFoggia, Italy
| | - Ines Villano
- Section of Human Physiology and Unit of Dietetic and Sport Medicine, Department of Experimental Medicine, Second University of Naples Naples, Italy
| | - Antonietta Messina
- Section of Human Physiology and Unit of Dietetic and Sport Medicine, Department of Experimental Medicine, Second University of Naples Naples, Italy
| | - Maria Esposito
- Department of Mental Health, Physical and Preventive Medicine, Clinic of Child and Adolescent Neuropsychiatry, Center for Childhood Headache, Second University of Naples Naples, Italy
| | - Vincenzo Monda
- Section of Human Physiology and Unit of Dietetic and Sport Medicine, Department of Experimental Medicine, Second University of Naples Naples, Italy
| | - Anna Valenzano
- Department of Clinical and Experimental Medicine, University of Foggia Foggia, Italy
| | - Fiorenzo Moscatelli
- Department of Clinical and Experimental Medicine, University of Foggia Foggia, Italy
| | - Teresa Esposito
- Section of Human Physiology and Unit of Dietetic and Sport Medicine, Department of Experimental Medicine, Second University of Naples Naples, Italy
| | - Marco Carotenuto
- Department of Mental Health, Physical and Preventive Medicine, Clinic of Child and Adolescent Neuropsychiatry, Center for Childhood Headache, Second University of Naples Naples, Italy
| | - Andrea Viggiano
- Department of Medicine and Surgery, University of Salerno Salerno, Italy
| | - Giuseppe Cibelli
- Section of Human Physiology and Unit of Dietetic and Sport Medicine, Department of Experimental Medicine, Second University of Naples Naples, Italy
| | - Marcellino Monda
- Department of Clinical and Experimental Medicine, University of Foggia Foggia, Italy
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14
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Kordi Jaz E, Moghimi A, Fereidoni M, Asadi S, Shamsizadeh A, Roohbakhsh A. SB-334867, an orexin receptor 1 antagonist, decreased seizure and anxiety in pentylenetetrazol-kindled rats. Fundam Clin Pharmacol 2016; 31:201-207. [DOI: 10.1111/fcp.12249] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2016] [Revised: 09/30/2016] [Accepted: 10/11/2016] [Indexed: 01/18/2023]
Affiliation(s)
- Elham Kordi Jaz
- Department of Biology; Faculty of Sciences; Ferdowsi University of Mashhad; Azadi Sq. Mashhad Iran
| | - Ali Moghimi
- Department of Biology; Faculty of Sciences; Ferdowsi University of Mashhad; Azadi Sq. Mashhad Iran
| | - Masoud Fereidoni
- Department of Biology; Faculty of Sciences; Ferdowsi University of Mashhad; Azadi Sq. Mashhad Iran
| | - Saeedeh Asadi
- Department of Biology; Faculty of Sciences; Ferdowsi University of Mashhad; Azadi Sq. Mashhad Iran
| | - Ali Shamsizadeh
- Physiology-Pharmacology Research Center and Department of Physiology and Pharmacology; School of Medicine; Rafsanjan University of Medical Sciences; Pistachio Co Street Rafsanjan Iran
| | - Ali Roohbakhsh
- Pharmaceutical Research Center; Mashhad University of Medical Sciences; Azadi Square Mashhad Iran
- School of Pharmacy; Mashhad University of Medical Sciences; Azadi Square Mashhad Iran
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15
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SB 334867, a selective orexin receptor type 1 antagonist, elevates seizure threshold in mice. Life Sci 2016; 150:81-8. [DOI: 10.1016/j.lfs.2016.02.075] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 02/16/2016] [Accepted: 02/20/2016] [Indexed: 11/17/2022]
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16
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Portelli J, Coppens J, Demuyser T, Smolders I. Des-acyl ghrelin attenuates pilocarpine-induced limbic seizures via the ghrelin receptor and not the orexin pathway. Neuropeptides 2015; 51:1-7. [PMID: 26002375 DOI: 10.1016/j.npep.2015.04.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Revised: 03/02/2015] [Accepted: 04/16/2015] [Indexed: 01/27/2023]
Abstract
Des-acyl ghrelin, widely accepted to work independently of the ghrelin receptor, is increasingly being implicated in a number of biological functions. The involvement of des-acyl ghrelin in epilepsy has only been recently reported. In this study, apart from unravelling the effect of des-acyl ghrelin on seizure thresholds and seizure severity in two models of pilocarpine-induced seizures, we mainly attempted to unravel its anticonvulsant mechanism of action. Since it was found that des-acyl ghrelin administration affected food intake via the orexin pathway, we first determined whether this pathway was responsible for des-acyl ghrelin's seizure-attenuating properties using the dual orexin receptor antagonist almorexant. We noted that, while des-acyl ghrelin showed dose-dependent anticonvulsant effects against focal pilocarpine-evoked seizures in rats, almorexant did not affect seizure severity and did not reverse des-acyl ghrelin's anticonvulsant effect. Subsequently, to investigate whether the ghrelin receptor was implicated in des-acyl ghrelin's anticonvulsant properties, we tested this peptide in ghrelin receptor deficient mice and wild type mice, all infused with pilocarpine intravenously. Unexpectedly, we found that des-acyl ghrelin significantly elevated seizure thresholds in C57Bl/6 and wild type mice but not in ghrelin receptor knock-out mice. Taken together, our results indicate the involvement of the ghrelin receptor in the anticonvulsant effects of des-acyl ghrelin on pilocarpine-induced seizures. We also show for the first time that dual antagonism of hippocampal orexin receptors does not affect seizure severity.
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Affiliation(s)
- Jeanelle Portelli
- Center for Neurosciences, Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information, Vrije Universiteit Brussel, Laarbeeklaan 103, Brussels 1090, Belgium; Department of Neurology, UZ Gent, De Pintelaan 185, Ghent 9000, Belgium
| | - Jessica Coppens
- Center for Neurosciences, Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information, Vrije Universiteit Brussel, Laarbeeklaan 103, Brussels 1090, Belgium
| | - Thomas Demuyser
- Center for Neurosciences, Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information, Vrije Universiteit Brussel, Laarbeeklaan 103, Brussels 1090, Belgium
| | - Ilse Smolders
- Center for Neurosciences, Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information, Vrije Universiteit Brussel, Laarbeeklaan 103, Brussels 1090, Belgium.
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17
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Song J, Kim E, Kim CH, Song HT, Lee JE. The role of orexin in post-stroke inflammation, cognitive decline, and depression. Mol Brain 2015; 8:16. [PMID: 25884812 PMCID: PMC4357085 DOI: 10.1186/s13041-015-0106-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 02/23/2015] [Indexed: 01/02/2023] Open
Abstract
Ischemic stroke results in diverse pathophysiologies, including cerebral inflammation, neuronal loss, cognitive dysfunction, and depression. Studies aimed at identifying therapeutic solutions to alleviate these outcomes are important due to the increase in the number of stroke patients annually. Recently, many studies have reported that orexin, commonly known as a neuropeptide regulator of sleep/wakefulness and appetite, is associated with neuronal cell apoptosis, memory function, and depressive symptoms. Here, we briefly summarize recent studies regarding the role and future perspectives of orexin in post-ischemic stroke. This review advances our understanding of the role of orexin in post-stroke pathologies, focusing on its possible function as a therapeutic regulator in the post-ischemic brain. Ultimately, we suggest the clinical potential of orexin to regulate post-stroke pathologies.
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Affiliation(s)
- Juhyun Song
- Department of Anatomy, Yonsei University College of Medicine, Seoul, 120-752, South Korea.
| | - Eosu Kim
- Department of Pharmacology, Yonsei University College of Medicine, 120-752, Seoul, South Korea.
| | - Chul-Hoon Kim
- Department of Psychiatry, Yonsei University College of Medicine, 120-752, Seoul, South Korea.
| | - Ho-Taek Song
- Department of Diagnostic Radiology, Yonsei University College of Medicine, 120-752, Seoul, South Korea.
| | - Jong Eun Lee
- Department of Anatomy, Yonsei University College of Medicine, Seoul, 120-752, South Korea. .,BK21 Plus Project for Medical Sciences, and Brain Research Institute, Yonsei University, College of Medicine, Seoul, 120-752, South Korea.
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18
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Hippocampal orexin receptors inactivation reduces PTZ induced seizures of male rats. Pharmacol Biochem Behav 2015; 130:77-83. [DOI: 10.1016/j.pbb.2015.01.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Revised: 01/06/2015] [Accepted: 01/09/2015] [Indexed: 11/23/2022]
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19
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Zhao X, Zhang RX, Tang S, Ren YY, Yang WX, Liu XM, Tang JY. Orexin-A-induced ERK1/2 activation reverses impaired spatial learning and memory in pentylenetetrazol-kindled rats via OX1R-mediated hippocampal neurogenesis. Peptides 2014; 54:140-7. [PMID: 24321199 DOI: 10.1016/j.peptides.2013.11.019] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2013] [Revised: 11/15/2013] [Accepted: 11/15/2013] [Indexed: 01/07/2023]
Abstract
Epilepsy is characterized by the occurrence of repetitive seizures and can greatly affect a patient's cognition, particularly in terms of learning and memory. Orexin-A is an excitatory neuropeptide produced by the lateral hypothalamus that has been shown to be involved in learning and memory. A reduction in the levels of orexin-A after seizures may underlie the learning and memory impairments induced by epilepsy. Thus, we used pentylenetetrazol (PTZ)-kindled rats to investigate the effects of orexin-A on learning and memory and the involvement of neurogenesis in the dentate gyrus in OX1R-mediated ERK1/2 activation. A Morris water maze test revealed reduced escape latencies, prolonged times in the target quadrant and an increased number of platform crossings in PTZ-kindled rats exposed to orexin-A. These ameliorating effects of orexin-A on spatial learning and memory were attenuated by the intracerebroventricular injection of the OX1R antagonist SB334867 or the ERK1/2 inhibitor U0126. Further studies using bromodeoxyuridine (BrdU) revealed that orexin-A increased the number of BrdU-positive cells, doublecortin (DCX)/BrdU levels and the number of NeuN/BrdU double-positive nuclei in the dentate gyrus of PTZ-kindled rats. However, these effects were inhibited by treatment with SB334867 or U0126. Taken together, these data suggest that orexin-A attenuated the impairment of spatial learning and memory in PTZ-kindled rats and that this attenuation involved neurogenesis in the dentate gyrus via OX1R-mediated ERK1/2 activation.
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Affiliation(s)
- Xuan Zhao
- Department of Neurology, Qianfoshan Hospital, Shandong University, 16766 Jingshi Road, Jinan, Shandong 250014, PR China
| | - Rui xue Zhang
- Department of Neurology, Qianfoshan Hospital, Shandong University, 16766 Jingshi Road, Jinan, Shandong 250014, PR China
| | - Shi Tang
- Department of Neurology, Qianfoshan Hospital, Shandong University, 16766 Jingshi Road, Jinan, Shandong 250014, PR China
| | - Yan yan Ren
- Department of Neurology, Qianfoshan Hospital, Shandong University, 16766 Jingshi Road, Jinan, Shandong 250014, PR China
| | - Wei xia Yang
- Department of Neurology, Qianfoshan Hospital, Shandong University, 16766 Jingshi Road, Jinan, Shandong 250014, PR China
| | - Xiao min Liu
- Department of Neurology, Qianfoshan Hospital, Shandong University, 16766 Jingshi Road, Jinan, Shandong 250014, PR China
| | - Ji you Tang
- Department of Neurology, Qianfoshan Hospital, Shandong University, 16766 Jingshi Road, Jinan, Shandong 250014, PR China.
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20
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Ni LY, Zhu MJ, Song Y, Liu XM, Tang JY. Pentylenetetrazol-induced seizures are exacerbated by sleep deprivation through orexin receptor-mediated hippocampal cell proliferation. Neurol Sci 2013; 35:245-52. [DOI: 10.1007/s10072-013-1495-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Accepted: 06/24/2013] [Indexed: 01/29/2023]
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21
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Poli F, Overeem S, Lammers GJ, Plazzi G, Lecendreux M, Bassetti CL, Dauvilliers Y, Keene D, Khatami R, Li Y, Mayer G, Nohynek H, Pahud B, Paiva T, Partinen M, Scammell TE, Shimabukuro T, Sturkenboom M, van Dinther K, Wiznitzer M, Bonhoeffer J. Narcolepsy as an adverse event following immunization: Case definition and guidelines for data collection, analysis and presentation. Vaccine 2013; 31:994-1007. [PMID: 23246545 DOI: 10.1016/j.vaccine.2012.12.014] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Accepted: 12/05/2012] [Indexed: 01/11/2023]
Affiliation(s)
- Francesca Poli
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Bologna, Italy
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22
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Kaciński M, Budziszewska B, Lasoń W, Zając A, Skowronek-Bała B, Leśkiewicz M, Kubik A, Basta-Kaim A. Level of S100B protein, neuron specific enolase, orexin A, adiponectin and insulin-like growth factor in serum of pediatric patients suffering from sleep disorders with or without epilepsy. Pharmacol Rep 2012; 64:1427-33. [DOI: 10.1016/s1734-1140(12)70940-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Revised: 11/09/2012] [Indexed: 11/29/2022]
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23
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Erken HA, Erken G, Genç O, Kortunay S, Sahiner M, Turgut G, Turgut S. Orexins cause epileptic activity. Peptides 2012; 37:161-4. [PMID: 22771311 DOI: 10.1016/j.peptides.2012.06.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Revised: 06/05/2012] [Accepted: 06/05/2012] [Indexed: 11/21/2022]
Abstract
Orexins have been implicated in the regulation of sleep-wake cycle, energy homeostasis, drinking behavior, analgesia, attention, learning and memory but their effects on epileptic activity are controversial. We investigated whether intracortical injections of orexin A (100 pmol) and B (100 pmol) cause epileptic activity in rats. We observed epileptic seizure findings on these two groups rats. Orexin A and B also significantly increased total EEG power spectrum. Our findings indicate that orexins cause epileptic activity.
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Kortunay S, Erken HA, Erken G, Genç O, Sahiner M, Turgut S, Turgut G. Orexins increase penicillin-induced epileptic activity. Peptides 2012; 34:419-22. [PMID: 22394654 DOI: 10.1016/j.peptides.2012.02.013] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Revised: 02/18/2012] [Accepted: 02/18/2012] [Indexed: 11/17/2022]
Abstract
Orexins have been implicated with physiological function including sleep-wake cycle, energy homeostasis, drinking behavior, analgesia, attention, learning and memory but their effects on excitability are controversial. We investigated the effects of intracortical injections of orexin A (100 pmol) and B (100 pmol) on the electrophysiological manifestation of epileptic seizures induced by cortical penicillin application in adult male rats. In comparison to saline, orexin A and B enhanced significantly the spike number, spike amplitude and spectral power values induced by cortical penicillin. Our findings indicates that orexins enhances the hyperexcitable and hypersyncronic cortical epileptic activity induced by focal application of penicillin-G.
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Affiliation(s)
- Selim Kortunay
- Pamukkale University, Faculty of Medicine, Department of Pharmacology, Denizli, Turkey
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25
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Kothare SV, Kaleyias J. Sleep and epilepsy in children and adolescents. Sleep Med 2010; 11:674-85. [PMID: 20620102 DOI: 10.1016/j.sleep.2010.01.012] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2009] [Revised: 01/04/2010] [Accepted: 01/07/2010] [Indexed: 01/04/2023]
Abstract
Epilepsy and sleep disorders are considered by many to be common bedfellows. Several sleep phenomena may occur during nighttime taking a wide variety of forms and which can mimic seizures. Although most seizure sub-types have the potential to occur during sleep or wakefulness, sleep has a well-documented and strong association with specific epilepsy syndromes. Seizures in sleep also tend to occur during lighter stages of non-REM (NREM) sleep. The neurophysiologic process involved in the deepening of NREM sleep may also facilitate both seizures and IEDs. Epilepsy per se and/or seizures themselves promote sleep disruption and significantly affect the quality, quantity, and architecture of sleep. There are many causes of sleep disruption in patients with epilepsy, including inadequate sleep hygiene, coexisting sleep disorders, and circadian rhythm disturbances. Seizures themselves can disrupt sleep, even when they occur during wakefulness. Anti-epileptic drugs (AEDs) can also alter sleep in positive and negative ways, and these effects are independent of anticonvulsant actions. The end result of sleep disruption is excessive daytime sleepiness, worsening seizures, and poor quality of life. Screening for sleep disorders in the epilepsy population and appropriate intervention strategies will lead to overall improved quality of life and seizure control.
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Affiliation(s)
- Sanjeev V Kothare
- Division of Epilepsy & Clinical Neurophysiology, Department of Neurology, Children's Hospital, Boston, Harvard Medical School, Fegan 9, 300 Longwood Avenue, Boston, MA 02115, USA.
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26
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Abstract
Orexin-A (hypocretin-1) and orexin-B (hypocretin-2) are hypothalamic neuropeptides that play key roles in the regulation of wakefulness, feeding, reward, autonomic functions and energy homeostasis. To control these functions indispensable for survival, orexin-expressing neurones integrate peripheral metabolic signals, interact with many types of neurones in the brain and modulate their activities via the activation of orexin-1 receptor or orexin-2 receptor. In addition, a new functional role of orexin is emerging in the regulation of insulin and leptin sensitivities responsible for whole-body glucose metabolism. Recent evidence indicates that orexin efficiently protects against the development of peripheral insulin resistance induced by ageing or high-fat feeding in mice. In particular, the orexin receptor-2 signalling appears to confer resistance to diet-induced obesity and insulin insensitivity by improving leptin sensitivity. In fact, the expression of orexin gene is known to be down-regulated by hyperglycaemia in the rodent model of diabetes, such as ob/ob and db/db mice. Moreover, the levels of orexin receptor-2 mRNA have been shown to decline in the brain of mice along with ageing. These suggest that hyperglycaemia due to insulin insensitivity during ageing or by habitual consumption of a high-fat diet leads to the reduction in orexin expression in the hypothalamus, thereby further exacerbating peripheral insulin resistance. Therefore, orexin receptor controlling hypothalamic insulin/leptin actions may be a new target for possible future treatment of hyperglycaemia in patients with type 2 diabetes.
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Affiliation(s)
- H Tsuneki
- Department of Clinical Pharmacology, University of Toyama, Toyama, Japan
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