151
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Mavanji V, Perez-Leighton CE, Kotz CM, Billington CJ, Parthasarathy S, Sinton CM, Teske JA. Promotion of Wakefulness and Energy Expenditure by Orexin-A in the Ventrolateral Preoptic Area. Sleep 2015; 38:1361-70. [PMID: 25845696 DOI: 10.5665/sleep.4970] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 03/07/2015] [Indexed: 12/25/2022] Open
Abstract
STUDY OBJECTIVES The ventrolateral preoptic area (VLPO) and the orexin/hypocretin neuronal system are key regulators of sleep onset, transitions between vigilance states, and energy homeostasis. Reciprocal projections exist between the VLPO and orexin/hypocretin neurons. Although the importance of the VLPO to sleep regulation is clear, it is unknown whether VLPO neurons are involved in energy balance. The purpose of these studies was to determine if the VLPO is a site of action for orexin-A, and which orexin receptor subtype(s) would mediate these effects of orexin-A. We hypothesized that orexin-A in the VLPO modulates behaviors (sleep and wakefulness, feeding, spontaneous physical activity [SPA]) to increase energy expenditure. DESIGN AND MEASUREMENTS Sleep, wakefulness, SPA, feeding, and energy expenditure were determined after orexin-A microinjection in the VLPO of male Sprague-Dawley rats with unilateral cannulae targeting the VLPO. We also tested whether pretreatment with a dual orexin receptor antagonist (DORA, TCS-1102) or an OX2R antagonist (JNJ-10397049) blocked the effects of orexin-A on the sleep/wake cycle or SPA, respectively. RESULTS Orexin-A injected into the VLPO significantly increased wakefulness, SPA, and energy expenditure (SPA-induced and total) and reduced NREM sleep and REM sleep with no effect on food intake. Pretreatment with DORA blocked the increase in wakefulness and the reduction in NREM sleep elicited by orexin-A, and the OX2R antagonist reduced SPA stimulated by orexin-A. CONCLUSIONS These data show the ventrolateral preoptic area is a site of action for orexin-A, which may promote negative energy balance by modulating sleep/wakefulness and stimulating spontaneous physical activity and energy expenditure.
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Affiliation(s)
| | - Claudio E Perez-Leighton
- Center for Integrative Medicine and Innovative Science, Universidad Andres Bello, Santiago, Chile.,Escuela de Nutricion, Facultad de Medicina, Universidad Andres Bello, Santiago, Chile
| | - Catherine M Kotz
- Minneapolis VA Health Care System, Minneapolis, MN.,Geriatric Research Education and Clinical Center, Minneapolis, MN.,Minnesota Obesity Center, University of Minnesota, Saint Paul, MN.,Department of Food Science and Nutrition, University of Minnesota, Saint Paul, MN
| | - Charles J Billington
- Minneapolis VA Health Care System, Minneapolis, MN.,Minnesota Obesity Center, University of Minnesota, Saint Paul, MN.,Department of Medicine, University of Minnesota, Saint Paul, MN.,Department of Food Science and Nutrition, University of Minnesota, Saint Paul, MN
| | - Sairam Parthasarathy
- Arizona Respiratory Center University of Arizona, Tucson, AZ.,Department of Medicine University of Arizona, Tucson, AZ
| | - Christopher M Sinton
- Arizona Respiratory Center University of Arizona, Tucson, AZ.,Department of Medicine University of Arizona, Tucson, AZ
| | - Jennifer A Teske
- Department of Nutritional Sciences, University of Arizona, Tucson, AZ.,Minneapolis VA Health Care System, Minneapolis, MN.,Minnesota Obesity Center, University of Minnesota, Saint Paul, MN.,Department of Food Science and Nutrition, University of Minnesota, Saint Paul, MN
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152
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Blasiak A, Siwiec M, Grabowiecka A, Blasiak T, Czerw A, Blasiak E, Kania A, Rajfur Z, Lewandowski MH, Gundlach AL. Excitatory orexinergic innervation of rat nucleus incertus--Implications for ascending arousal, motivation and feeding control. Neuropharmacology 2015; 99:432-47. [PMID: 26265304 DOI: 10.1016/j.neuropharm.2015.08.014] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Revised: 07/17/2015] [Accepted: 08/07/2015] [Indexed: 10/23/2022]
Abstract
Orexin/hypocretin peptides play a central role in the integrated control of feeding/reward and behavioural activation, principally via interactions with other neural systems. A brainstem area involved in behavioural activation is the nucleus incertus (NI), located in the posterior ventromedial central grey. Several studies have implicated NI in control of arousal/stress and reward/feeding responses. Orexin receptor mRNA expression identifies NI as a putative target of orexin modulation. Therefore, in this study we performed neural tract-tracing and immunofluorescence staining to characterise the orexinergic innervation of NI. Our results indicate a convergent innervation of the NI area by different orexin neuron populations, with an abundance of orexin-A-containing axons making putative synaptic contacts with relaxin-3-positive NI neurons. The influence of orexin-A on NI neuron activity was investigated using patch-clamp recordings. Orexin-A depolarised the majority (64%) of recorded neurons and this effect was maintained in the presence of tetrodotoxin and glutamate and GABA receptor antagonists, indicating a likely postsynaptic action. Voltage-clamp experiments revealed that in 'type I' NI neurons comprising relaxin-3-positive cells, orexin-A acted via L-type calcium channels, whereas in 'type II' relaxin-3-negative neurons, activation of a sodium/calcium exchanger was involved. A majority of the orexin-A sensitive neurons tested for the presence of orexin receptor mRNA, were OX2 mRNA-positive. Immunohistochemical staining for putative orexin receptors on NI neurons, confirmed stronger expression of OX2 than OX1 receptors. Our data demonstrate a strong influence of orexin-A on NI neurons, consistent with an important role for this hypothalamic/tegmental circuit in the regulation of arousal/vigilance and motivated behaviours.
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Affiliation(s)
- Anna Blasiak
- Department of Neurophysiology and Chronobiology, Institute of Zoology, Jagiellonian University, 30-387 Krakow, Poland.
| | - Marcin Siwiec
- Department of Neurophysiology and Chronobiology, Institute of Zoology, Jagiellonian University, 30-387 Krakow, Poland
| | - Agnieszka Grabowiecka
- Department of Neurophysiology and Chronobiology, Institute of Zoology, Jagiellonian University, 30-387 Krakow, Poland
| | - Tomasz Blasiak
- Department of Neurophysiology and Chronobiology, Institute of Zoology, Jagiellonian University, 30-387 Krakow, Poland
| | - Anna Czerw
- Department of Neurophysiology and Chronobiology, Institute of Zoology, Jagiellonian University, 30-387 Krakow, Poland
| | - Ewa Blasiak
- Department of Physical Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Krakow, Poland
| | - Alan Kania
- Department of Neurophysiology and Chronobiology, Institute of Zoology, Jagiellonian University, 30-387 Krakow, Poland
| | - Zenon Rajfur
- Faculty of Physics, Astronomy and Applied Computer Science, Institute of Physics, Jagiellonian University, 30-348 Krakow, Poland
| | - Marian H Lewandowski
- Department of Neurophysiology and Chronobiology, Institute of Zoology, Jagiellonian University, 30-387 Krakow, Poland
| | - Andrew L Gundlach
- The Florey Institute of Neuroscience and Mental Health, Parkville, Victoria 3052, Australia; Florey Department of Neuroscience and Mental Health, The University of Melbourne, Victoria 3010, Australia; Department of Anatomy and Neuroscience, The University of Melbourne, Victoria 3010, Australia.
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153
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Palus K, Chrobok L, Lewandowski M. Orexins/hypocretins modulate the activity of NPY-positive and -negative neurons in the rat intergeniculate leaflet via OX1 and OX2 receptors. Neuroscience 2015; 300:370-80. [DOI: 10.1016/j.neuroscience.2015.05.039] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Revised: 05/15/2015] [Accepted: 05/16/2015] [Indexed: 01/11/2023]
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154
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Murgatroyd CA, Peña CJ, Podda G, Nestler EJ, Nephew BC. Early life social stress induced changes in depression and anxiety associated neural pathways which are correlated with impaired maternal care. Neuropeptides 2015; 52:103-11. [PMID: 26049556 PMCID: PMC4537387 DOI: 10.1016/j.npep.2015.05.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Revised: 05/06/2015] [Accepted: 05/18/2015] [Indexed: 11/26/2022]
Abstract
Exposures to various types of early life stress can be robust predictors of the development of psychiatric disorders, including depression and anxiety. The objective of the current study was to investigate the roles of the translationally relevant targets of central vasopressin, oxytocin, ghrelin, orexin, glucocorticoid, and the brain-derived neurotrophic factor (BDNF) pathway in an early chronic social stress (ECSS) based rodent model of postpartum depression and anxiety. The present study reports novel changes in gene expression and extracellular signal related kinase (ERK) protein levels in the brains of ECSS exposed rat dams that display previously reported depressed maternal care and increased maternal anxiety. Decreases in oxytocin, orexin, and ERK proteins, increases in ghrelin receptor, glucocorticoid and mineralocorticoid receptor mRNA levels, and bidirectional changes in vasopressin underscore related work on the adverse long-term effects of early life stress on neural activity and plasticity, maternal behavior, responses to stress, and depression and anxiety-related behavior. The differences in gene and protein expression and robust correlations between expression and maternal care and anxiety support increased focus on these targets in animal and clinical studies of the adverse effects of early life stress, especially those focusing on depression and anxiety in mothers and the transgenerational effects of these disorders on offspring.
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Affiliation(s)
- Christopher A Murgatroyd
- Manchester Metropolitan University School of Healthcare Science, All Saints Building, Manchester M15 6BH, UK
| | - Catherine J Peña
- Icahn School of Medicine at Mount Sinai, 1425 Madison Avenue, New York, NY 10029, United States
| | - Giovanni Podda
- Manchester Metropolitan University School of Healthcare Science, All Saints Building, Manchester M15 6BH, UK
| | - Eric J Nestler
- Icahn School of Medicine at Mount Sinai, 1425 Madison Avenue, New York, NY 10029, United States
| | - Benjamin C Nephew
- Tufts University Cummings School of Veterinary Medicine, 200 Westboro Road, North Grafton, MA 01536, United States.
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155
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Valiante S, Liguori G, Tafuri S, Pavone LM, Campese R, Monaco R, Iachetta G, Assisi L, Mirabella N, Forte M, Costagliola A, Vittoria A. Expression and potential role of the peptide orexin-A in prostate cancer. Biochem Biophys Res Commun 2015. [PMID: 26220343 DOI: 10.1016/j.bbrc.2015.07.124] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The peptides orexin-A and orexin-B and their G protein-coupled OX1 and OX2 receptors are involved in multiple physiological processes in the central nervous system and peripheral organs. Altered expression or signaling dysregulation of orexins and their receptors have been associated with a wide range of human diseases including narcolepsy, obesity, drug addiction, and cancer. Although orexin-A, its precursor molecule prepro-orexin and OX1 receptor have been detected in the human normal and hyperplastic prostate tissues, their expression and function in the prostate cancer (PCa) remains to be addressed. Here, we demonstrate for the first time the immunohistochemical localization of orexin-A in human PCa specimens, and the expression of prepro-orexin and OX1 receptor at both protein and mRNA levels in these tissues. Orexin-A administration to the human androgen-dependent prostate carcinoma cells LNCaP up-regulates OX1 receptor expression resulting in a decrease of cell survival. Noteworthy, nanomolar concentrations of the peptide counteract the testosterone-induced nuclear translocation of the androgen receptor in the cells: the orexin-A action is prevented by the addition of the OX1 receptor antagonist SB-408124 to the test system. These findings indicate that orexin-A/OX1 receptor interaction interferes with the activity of the androgen receptor which regulates PCa onset and progression, thus suggesting that orexin-A and its receptor might represent novel therapeutic targets to challenge this aggressive cancer.
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Affiliation(s)
| | - Giovanna Liguori
- Department of Veterinary Medicine and Animal Productions, University of Naples Federico II, Italy
| | - Simona Tafuri
- Department of Veterinary Medicine and Animal Productions, University of Naples Federico II, Italy
| | - Luigi Michele Pavone
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Italy
| | - Roberto Campese
- Department of Urology, "A. Cardarelli" Hospital, Naples, Italy
| | - Roberto Monaco
- Department of Pathology, "A. Cardarelli" Hospital, Naples, Italy
| | | | - Loredana Assisi
- Department of Biology, University of Naples Federico II, Italy
| | - Nicola Mirabella
- Department of Veterinary Medicine and Animal Productions, University of Naples Federico II, Italy
| | - Maurizio Forte
- Institute of Genetics and Biophysics "A. Buzzati-Traverso", CNR, Naples, Italy
| | - Anna Costagliola
- Department of Veterinary Medicine and Animal Productions, University of Naples Federico II, Italy
| | - Alfredo Vittoria
- Department of Veterinary Medicine and Animal Productions, University of Naples Federico II, Italy.
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156
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Perrey DA, Decker AM, Li JX, Gilmour BP, Thomas BF, Harris DL, Runyon SP, Zhang Y. The importance of the 6- and 7-positions of tetrahydroisoquinolines as selective antagonists for the orexin 1 receptor. Bioorg Med Chem 2015. [PMID: 26216017 DOI: 10.1016/j.bmc.2015.07.013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Selective antagonism of the orexin 1 (OX1) receptor has been proposed as a potential mechanism for treatment of drug addiction. We have previously reported studies on the structure-activity relationships of tetrahydroisoquinoline-based antagonists. In this report, we elucidated the respective role of the 6- and 7-substitutions by preparation of a series of either 6-substituted tetrahydroisoquinolines (with no 7-substituents) or vice versa. We found that 7-substituted tetrahydroisoquinolines showed potent antagonism of OX1, indicating that the 7-position is important for OX1 antagonism (10 c, Ke = 23.7 nM). While the 6-substituted analogs were generally inactive, several 6-amino compounds bearing ester groups showed reasonable potency (26 a, Ke = 427 nM). Further, we show evidence that suggests several compounds initially displaying insurmountable antagonism at the OX1 receptor are competitive antagonists with slow dissociation rates.
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Affiliation(s)
- David A Perrey
- Research Triangle Institute, Research Triangle Park, NC 27709, United States
| | - Ann M Decker
- Research Triangle Institute, Research Triangle Park, NC 27709, United States
| | - Jun-Xu Li
- Department of Pharmacology and Toxicology, University at Buffalo, The State University of New York, Buffalo, NY 14214, United States
| | - Brian P Gilmour
- Research Triangle Institute, Research Triangle Park, NC 27709, United States
| | - Brian F Thomas
- Research Triangle Institute, Research Triangle Park, NC 27709, United States
| | - Danni L Harris
- Research Triangle Institute, Research Triangle Park, NC 27709, United States
| | - Scott P Runyon
- Research Triangle Institute, Research Triangle Park, NC 27709, United States
| | - Yanan Zhang
- Research Triangle Institute, Research Triangle Park, NC 27709, United States.
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157
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Do Orexins contribute to impulsivity-driven binge consumption of rewarding stimulus and transition to drug/food dependence? Pharmacol Biochem Behav 2015; 134:31-4. [DOI: 10.1016/j.pbb.2015.04.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Revised: 03/10/2015] [Accepted: 04/13/2015] [Indexed: 01/20/2023]
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158
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Affiliation(s)
- Jolanta Zawilska
- Department of Pharmacodynamics, Medical University of Lodz, Poland
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159
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Perrey DA, German NA, Decker AM, Thorn D, Li JX, Gilmour BP, Thomas BF, Harris DL, Runyon SP, Zhang Y. Effect of 1-substitution on tetrahydroisoquinolines as selective antagonists for the orexin-1 receptor. ACS Chem Neurosci 2015; 6:599-614. [PMID: 25643283 DOI: 10.1021/cn500330v] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Selective blockade of the orexin-1 receptor (OX1) has been suggested as a potential approach to drug addiction therapy because of its role in modulating the brain's reward system. We have recently reported a series of tetrahydroisoquinoline-based OX1 selective antagonists. Aimed at elucidating structure-activity relationship requirements in other regions of the molecule and further enhancing OX1 potency and selectivity, we have designed and synthesized a series of analogues bearing a variety of substituents at the 1-position of the tetrahydroisoquinoline. The results show that an optimally substituted benzyl group is required for activity at the OX1 receptor. Several compounds with improved potency and/or selectivity have been identified. When combined with structural modifications that were previously found to improve selectivity, we have identified compound 73 (RTIOX-251) with an apparent dissociation constant (Ke) of 16.1 nM at the OX1 receptor and >620-fold selectivity over the OX2 receptor. In vivo, compound 73 was shown to block the development of locomotor sensitization to cocaine in rats.
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Affiliation(s)
- David A. Perrey
- Research Triangle Institute, Research Triangle
Park, North Carolina 27709, United States
| | - Nadezhda A. German
- Research Triangle Institute, Research Triangle
Park, North Carolina 27709, United States
| | - Ann M. Decker
- Research Triangle Institute, Research Triangle
Park, North Carolina 27709, United States
| | - David Thorn
- Department
of Pharmacology and Toxicology, University at Buffalo, the State University of New York, Buffalo, New York 14214, United States
| | - Jun-Xu Li
- Department
of Pharmacology and Toxicology, University at Buffalo, the State University of New York, Buffalo, New York 14214, United States
| | - Brian P. Gilmour
- Research Triangle Institute, Research Triangle
Park, North Carolina 27709, United States
| | - Brian F. Thomas
- Research Triangle Institute, Research Triangle
Park, North Carolina 27709, United States
| | - Danni L. Harris
- Research Triangle Institute, Research Triangle
Park, North Carolina 27709, United States
| | - Scott P. Runyon
- Research Triangle Institute, Research Triangle
Park, North Carolina 27709, United States
| | - Yanan Zhang
- Research Triangle Institute, Research Triangle
Park, North Carolina 27709, United States
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160
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Baiula M, Bedini A, Spampinato SM. Role of nociceptin/orphanin FQ in thermoregulation. Neuropeptides 2015; 50:51-6. [PMID: 25812480 DOI: 10.1016/j.npep.2015.03.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2014] [Revised: 02/25/2015] [Accepted: 03/11/2015] [Indexed: 01/30/2023]
Abstract
Nociceptin/Orphanin FQ (N/OFQ) is a 17-amino acid peptide that binds to the nociceptin receptor (NOP). N/OFQ and NOP receptors are expressed in numerous brain areas. The generation of specific agonists, antagonists and receptor-deficient mice or rats has enabled progress in elucidating the biological functions of N/OFQ. These tools have been employed to identify the biological significance of the N/OFQ system and how it interacts with other endogenous systems to regulate several body functions. The present review focuses on the role of N/OFQ in the regulation of body temperature and its relationship with energy balance. Critical evaluation of the literature data suggests that N/OFQ, acting through the NOP receptor, may cause hypothermia by influencing the complex thermoregulatory system that operates as a federation of independent thermoeffector loops to control body temperature at the hypothalamic level. Furthermore, N/OFQ counteracts hyperthermia elicited by cannabinoids or µ-opioid agonists. N/OFQ-induced hypothermia is prevented by ω-conotoxin GVIA, an N-type calcium channel blocker. Hypothermia induced by N/OFQ is considered within the framework of the complex action that this neuropeptide exerts on energy balance. Energy stores are regulated through the complex neural controls exerted on both food intake and energy expenditure. In laboratory rodents, N/OFQ stimulates consummatory behavior and decreases energy expenditure. Taken together, these studies support the idea that N/OFQ contributes to the regulation of energy balance by acting as an "anabolic" neuropeptide as it elicits effects similar to those produced in the hypothalamus by other neuropeptides such as orexins and neuropeptide Y.
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Affiliation(s)
- Monica Baiula
- Department of Pharmacy and Biotechnology, University of Bologna, Italy
| | - Andrea Bedini
- Department of Pharmacy and Biotechnology, University of Bologna, Italy
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161
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Abstract
Sleep is expressed as a circadian rhythm and the two phenomena exist in a poorly understood relationship. Light affects each, simultaneously influencing rhythm phase and rapidly inducing sleep. Light has long been known to modulate sleep, but recent discoveries support its use as an effective nocturnal stimulus for eliciting sleep in certain rodents. “Photosomnolence” is mediated by classical and ganglion cell photoreceptors and occurs despite the ongoing high levels of locomotion at the time of stimulus onset. Brief photic stimuli trigger rapid locomotor suppression, sleep, and a large drop in core body temperature (Tc; Phase 1), followed by a relatively fixed duration interval of sleep (Phase 2) and recovery (Phase 3) to pre-sleep activity levels. Additional light can lengthen Phase 2. Potential retinal pathways through which the sleep system might be light-activated are described and the potential roles of orexin (hypocretin) and melanin-concentrating hormone are discussed. The visual input route is a practical avenue to follow in pursuit of the neural circuitry and mechanisms governing sleep and arousal in small nocturnal mammals and the organizational principles may be similar in diurnal humans. Photosomnolence studies are likely to be particularly advantageous because the timing of sleep is largely under experimenter control. Sleep can now be effectively studied using uncomplicated, nonintrusive methods with behavior evaluation software tools; surgery for EEG electrode placement is avoidable. The research protocol for light-induced sleep is easily implemented and useful for assessing the effects of experimental manipulations on the sleep induction pathway. Moreover, the experimental designs and associated results benefit from a substantial amount of existing neuroanatomical and pharmacological literature that provides a solid framework guiding the conduct and interpretation of future investigations.
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162
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Sorooshyari S, Huerta R, de Lecea L. A Framework for Quantitative Modeling of Neural Circuits Involved in Sleep-to-Wake Transition. Front Neurol 2015; 6:32. [PMID: 25767461 PMCID: PMC4341569 DOI: 10.3389/fneur.2015.00032] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Accepted: 02/08/2015] [Indexed: 12/14/2022] Open
Abstract
Identifying the neuronal circuits and dynamics of sleep-to-wake transition is essential to understanding brain regulation of behavioral states, including sleep–wake cycles, arousal, and hyperarousal. Recent work by different laboratories has used optogenetics to determine the role of individual neuromodulators in state transitions. The optogenetically driven data do not yet provide a multi-dimensional schematic of the mechanisms underlying changes in vigilance states. This work presents a modeling framework to interpret, assist, and drive research on the sleep-regulatory network. We identify feedback, redundancy, and gating hierarchy as three fundamental aspects of this model. The presented model is expected to expand as additional data on the contribution of each transmitter to a vigilance state becomes available. Incorporation of conductance-based models of neuronal ensembles into this model and existing models of cortical excitability will provide more comprehensive insight into sleep dynamics as well as sleep and arousal-related disorders.
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Affiliation(s)
| | - Ramón Huerta
- BioCircuits Institute, University of California San Diego , La Jolla, CA , USA
| | - Luis de Lecea
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine , Stanford, CA , USA
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163
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Abstract
The discovery of hypocretins (orexins) and their causal implication in narcolepsy is the most important advance in sleep research and sleep medicine since the discovery of rapid eye movement sleep. Narcolepsy with cataplexy is caused by hypocretin deficiency owing to destruction of most of the hypocretin-producing neurons in the hypothalamus. Ablation of hypocretin or hypocretin receptors also leads to narcolepsy phenotypes in animal models. Although the exact mechanism of hypocretin deficiency is unknown, evidence from the past 20 years strongly favours an immune-mediated or autoimmune attack, targeting specifically hypocretin neurons in genetically predisposed individuals. These neurons form an extensive network of projections throughout the brain and show activity linked to motivational behaviours. The hypothesis that a targeted immune-mediated or autoimmune attack causes the specific degeneration of hypocretin neurons arose mainly through the discovery of genetic associations, first with the HLA-DQB1*06:02 allele and then with the T-cell receptor α locus. Guided by these genetic findings and now awaiting experimental testing are models of the possible immune mechanisms by which a specific and localised brain cell population could become targeted by T-cell subsets. Great hopes for the identification of new targets for therapeutic intervention in narcolepsy also reside in the development of patient-derived induced pluripotent stem cell systems.
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164
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Xie XS. The neuronal circuit between nociceptin/orphanin FQ and hypocretins/orexins coordinately modulates stress-induced analgesia and anxiety-related behavior. VITAMINS AND HORMONES 2015; 97:295-321. [PMID: 25677777 DOI: 10.1016/bs.vh.2014.11.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2023]
Abstract
The neuropeptide nociceptin/orphanin FQ (N/OFQ), acting on its receptors (NOP), modulates a variety of biological functions and neurobehavior including nociception, stress responses, water and food-intake, locomotor activity, and spatial attention. N/OFQ is conventionally regarded as an "antiopiate" peptide in the brain because central administration of N/OFQ attenuates stress-induced analgesia (SIA) and produces anxiolytic effects. However, naloxone-irreversible SIA and anxiolytic action are unlikely to be mediated by the opiate system. Both N/OFQ and NOP receptors are expressed most abundantly in the hypothalamus, where two other neuropeptides, the hypocretins/orexins (Hcrts), are exclusively synthesized in the lateral hypothalamic area. N/OFQ and Hcrt regulate most cellular physiological responses in opposite directions (e.g., ion channel modulation and second messenger coupling), and produce differential modulations for almost all neurobehavior assessed, including sleep/wake, locomotion, and rewarding behaviors. This chapter focuses on recent studies that provide evidence at a neuroanatomical level showing that a local neuronal circuit linking N/OFQ to Hcrt neurons exists. Functionally, N/OFQ depresses Hcrt neuronal activity at the cellular level, and modulates stress responses, especially SIA and anxiety-related behavior in the whole organism. N/OFQ exerts its attenuation of SIA and anxiolytic action on fear-induced anxiety through direct modulation of Hcrt neuronal activity. The information obtained from these studies has provided insights into how interaction between the Hcrt and N/OFQ systems positively and negatively modulates the complex and integrated stress responses.
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Affiliation(s)
- Xinmin Simon Xie
- AfaSci Research Laboratories, Redwood City, California, USA; Department of Anesthesia, Stanford University School of Medicine, Stanford, California, USA.
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165
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Bonaventure P, Yun S, Johnson PL, Shekhar A, Fitz SD, Shireman BT, Lebold TP, Nepomuceno D, Lord B, Wennerholm M, Shelton J, Carruthers N, Lovenberg T, Dugovic C. A selective orexin-1 receptor antagonist attenuates stress-induced hyperarousal without hypnotic effects. J Pharmacol Exp Ther 2015; 352:590-601. [PMID: 25583879 DOI: 10.1124/jpet.114.220392] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Orexins (OXs) are peptides produced by perifornical (PeF) and lateral hypothalamic neurons that exert a prominent role in arousal-related processes, including stress. A critical role for the orexin-1 receptor (OX1R) in complex emotional behavior is emerging, such as overactivation of the OX1R pathway being associated with panic or anxiety states. Here we characterize a brain-penetrant, selective, and high-affinity OX1R antagonist, compound 56 [N-({3-[(3-ethoxy-6-methylpyridin-2-yl)carbonyl]-3-azabicyclo[4.1.0]hept-4-yl}methyl)-5-(trifluoromethyl)pyrimidin-2-amine]. Ex vivo receptor binding studies demonstrated that, after subcutaneous administration, compound 56 crossed the blood-brain barrier and occupied OX1Rs in the rat brain at lower doses than standard OX1R antagonists GSK-1059865 [5-bromo-N-({1-[(3-fluoro-2-methoxyphenyl)carbonyl]-5-methylpiperidin-2-yl}methyl)pyridin-2-amine], SB-334867 [1-(2-methyl-1,3-benzoxazol-6-yl)-3-(1,5-naphthyridin-4-yl)urea], and SB-408124 [1-(6,8-difluoro-2-methylquinolin-4-yl)-3-[4-(dimethylamino)phenyl]urea]. Although compound 56 did not alter spontaneous sleep in rats and in wild-type mice, its administration in orexin-2 receptor knockout mice selectively promoted rapid eye movement sleep, demonstrating target engagement and specific OX1R blockade. In a rat model of psychological stress induced by cage exchange, the OX1R antagonist prevented the prolongation of sleep onset without affecting sleep duration. In a rat model of panic vulnerability (involving disinhibition of the PeF OX region) to threatening internal state changes (i.e., intravenous sodium lactate infusion), compound 56 attenuated sodium lactate-induced panic-like behaviors and cardiovascular responses without altering baseline locomotor or autonomic activity. In conclusion, OX1R antagonism represents a novel therapeutic strategy for the treatment of various psychiatric disorders associated with stress or hyperarousal states.
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Affiliation(s)
- Pascal Bonaventure
- Janssen Research & Development, LLC, San Diego, California (P.B., S.Y., B.T.S., T.P.L., D.N., B.L., M.W., J.S., N.C., T.L., C.D.); and Indiana University School of Medicine, Indianapolis, Indiana (P.L.J., A.S., S.D.F.)
| | - Sujin Yun
- Janssen Research & Development, LLC, San Diego, California (P.B., S.Y., B.T.S., T.P.L., D.N., B.L., M.W., J.S., N.C., T.L., C.D.); and Indiana University School of Medicine, Indianapolis, Indiana (P.L.J., A.S., S.D.F.)
| | - Philip L Johnson
- Janssen Research & Development, LLC, San Diego, California (P.B., S.Y., B.T.S., T.P.L., D.N., B.L., M.W., J.S., N.C., T.L., C.D.); and Indiana University School of Medicine, Indianapolis, Indiana (P.L.J., A.S., S.D.F.)
| | - Anantha Shekhar
- Janssen Research & Development, LLC, San Diego, California (P.B., S.Y., B.T.S., T.P.L., D.N., B.L., M.W., J.S., N.C., T.L., C.D.); and Indiana University School of Medicine, Indianapolis, Indiana (P.L.J., A.S., S.D.F.)
| | - Stephanie D Fitz
- Janssen Research & Development, LLC, San Diego, California (P.B., S.Y., B.T.S., T.P.L., D.N., B.L., M.W., J.S., N.C., T.L., C.D.); and Indiana University School of Medicine, Indianapolis, Indiana (P.L.J., A.S., S.D.F.)
| | - Brock T Shireman
- Janssen Research & Development, LLC, San Diego, California (P.B., S.Y., B.T.S., T.P.L., D.N., B.L., M.W., J.S., N.C., T.L., C.D.); and Indiana University School of Medicine, Indianapolis, Indiana (P.L.J., A.S., S.D.F.)
| | - Terry P Lebold
- Janssen Research & Development, LLC, San Diego, California (P.B., S.Y., B.T.S., T.P.L., D.N., B.L., M.W., J.S., N.C., T.L., C.D.); and Indiana University School of Medicine, Indianapolis, Indiana (P.L.J., A.S., S.D.F.)
| | - Diane Nepomuceno
- Janssen Research & Development, LLC, San Diego, California (P.B., S.Y., B.T.S., T.P.L., D.N., B.L., M.W., J.S., N.C., T.L., C.D.); and Indiana University School of Medicine, Indianapolis, Indiana (P.L.J., A.S., S.D.F.)
| | - Brian Lord
- Janssen Research & Development, LLC, San Diego, California (P.B., S.Y., B.T.S., T.P.L., D.N., B.L., M.W., J.S., N.C., T.L., C.D.); and Indiana University School of Medicine, Indianapolis, Indiana (P.L.J., A.S., S.D.F.)
| | - Michelle Wennerholm
- Janssen Research & Development, LLC, San Diego, California (P.B., S.Y., B.T.S., T.P.L., D.N., B.L., M.W., J.S., N.C., T.L., C.D.); and Indiana University School of Medicine, Indianapolis, Indiana (P.L.J., A.S., S.D.F.)
| | - Jonathan Shelton
- Janssen Research & Development, LLC, San Diego, California (P.B., S.Y., B.T.S., T.P.L., D.N., B.L., M.W., J.S., N.C., T.L., C.D.); and Indiana University School of Medicine, Indianapolis, Indiana (P.L.J., A.S., S.D.F.)
| | - Nicholas Carruthers
- Janssen Research & Development, LLC, San Diego, California (P.B., S.Y., B.T.S., T.P.L., D.N., B.L., M.W., J.S., N.C., T.L., C.D.); and Indiana University School of Medicine, Indianapolis, Indiana (P.L.J., A.S., S.D.F.)
| | - Timothy Lovenberg
- Janssen Research & Development, LLC, San Diego, California (P.B., S.Y., B.T.S., T.P.L., D.N., B.L., M.W., J.S., N.C., T.L., C.D.); and Indiana University School of Medicine, Indianapolis, Indiana (P.L.J., A.S., S.D.F.)
| | - Christine Dugovic
- Janssen Research & Development, LLC, San Diego, California (P.B., S.Y., B.T.S., T.P.L., D.N., B.L., M.W., J.S., N.C., T.L., C.D.); and Indiana University School of Medicine, Indianapolis, Indiana (P.L.J., A.S., S.D.F.)
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166
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Crystal structure of the human OX2 orexin receptor bound to the insomnia drug suvorexant. Nature 2014; 519:247-50. [DOI: 10.1038/nature14035] [Citation(s) in RCA: 162] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Accepted: 11/04/2014] [Indexed: 12/18/2022]
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167
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Hu B, Yang N, Qiao QC, Hu ZA, Zhang J. Roles of the orexin system in central motor control. Neurosci Biobehav Rev 2014; 49:43-54. [PMID: 25511388 DOI: 10.1016/j.neubiorev.2014.12.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Revised: 11/10/2014] [Accepted: 12/03/2014] [Indexed: 12/15/2022]
Abstract
The neuropeptides orexin-A and orexin-B are produced by one group of neurons located in the lateral hypothalamic/perifornical area. However, the orexins are widely released in entire brain including various central motor control structures. Especially, the loss of orexins has been demonstrated to associate with several motor deficits. Here, we first summarize the present knowledge that describes the anatomical and morphological connections between the orexin system and various central motor control structures. In the next section, the direct influence of orexins on related central motor control structures is reviewed at molecular, cellular, circuitry, and motor activity levels. After the summarization, the characteristic and functional relevance of the orexin system's direct influence on central motor control function are demonstrated and discussed. We also propose a hypothesis as to how the orexin system orchestrates central motor control in a homeostatic regulation manner. Besides, the importance of the orexin system's phasic modulation on related central motor control structures is highlighted in this regulation manner. Finally, a scheme combining the homeostatic regulation of orexin system on central motor control and its effects on other brain functions is presented to discuss the role of orexin system beyond the pure motor activity level, but at the complex behavioral level.
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Affiliation(s)
- Bo Hu
- Department of Physiology, College of Basic Medical Sciences, Third Military Medical University, 30 Gaotanyan Street, Shapingba District, Chongqing 400038, PR China
| | - Nian Yang
- Department of Physiology, College of Basic Medical Sciences, Third Military Medical University, 30 Gaotanyan Street, Shapingba District, Chongqing 400038, PR China
| | - Qi-Cheng Qiao
- Department of Physiology, College of Basic Medical Sciences, Third Military Medical University, 30 Gaotanyan Street, Shapingba District, Chongqing 400038, PR China
| | - Zhi-An Hu
- Department of Physiology, College of Basic Medical Sciences, Third Military Medical University, 30 Gaotanyan Street, Shapingba District, Chongqing 400038, PR China.
| | - Jun Zhang
- Department of Physiology, College of Basic Medical Sciences, Third Military Medical University, 30 Gaotanyan Street, Shapingba District, Chongqing 400038, PR China.
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168
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The hypocretin/orexin system mediates the extinction of fear memories. Neuropsychopharmacology 2014; 39:2732-41. [PMID: 24930888 PMCID: PMC4200503 DOI: 10.1038/npp.2014.146] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Revised: 05/15/2014] [Accepted: 06/09/2014] [Indexed: 01/01/2023]
Abstract
Anxiety disorders are often associated with an inability to extinguish learned fear responses. The hypocretin/orexin system is involved in the regulation of emotional states and could also participate in the consolidation and extinction of aversive memories. Using hypocretin receptor-1 and hypocretin receptor-2 antagonists, hypocretin-1 and hypocretin-2 peptides, and hypocretin receptor-1 knockout mice, we investigated the role of the hypocretin system in cue- and context-dependent fear conditioning and extinction. Hypocretins were crucial for the consolidation of fear conditioning, and this effect was mainly observed in memories with a high emotional component. Notably, after the acquisition of fear memory, hypocretin receptor-1 blockade facilitated fear extinction, whereas hypocretin-1 administration impaired this extinction process. The extinction-facilitating effects of the hypocretin receptor-1 antagonist SB334867 were associated with increased expression of cFos in the basolateral amygdala and the infralimbic cortex. Intra-amygdala, but neither intra-infralimbic prefrontal cortex nor intra-dorsohippocampal infusion of SB334867 enhanced fear extinction. These results reveal a key role for hypocretins in the extinction of aversive memories and suggest that hypocretin receptor-1 blockade could represent a novel therapeutic target for the treatment of diseases associated with inappropriate retention of fear, such as post-traumatic stress disorder and phobias.
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169
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Mahler SV, Moorman DE, Smith RJ, James MH, Aston-Jones G. Motivational activation: a unifying hypothesis of orexin/hypocretin function. Nat Neurosci 2014; 17:1298-303. [PMID: 25254979 PMCID: PMC4335648 DOI: 10.1038/nn.3810] [Citation(s) in RCA: 264] [Impact Index Per Article: 26.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Accepted: 08/19/2014] [Indexed: 12/15/2022]
Abstract
Orexins (hypocretins) are two peptides (orexin A and B) produced from the pre-pro-orexin precursor and expressed in a limited region of dorsolateral hypothalamus. Orexins were originally thought to specifically mediate feeding and promote wakefulness, but it is now clear that they participate in a wide range of behavioral and physiological processes under select circumstances. Orexins primarily mediate behavior under situations of high motivational relevance, such as during physiological need states, exposure to threats or reward opportunities. We hypothesize that many behavioral functions of orexins (including regulation of sleep/wake cycling) reflect a fundamentally integrated function for orexins in translating motivational activation into organized suites of psychological and physiological processes supporting adaptive behaviors. We also discuss how numerous forms of neural heterogeneity modulate this function, allowing orexin neurons to organize diverse, adaptive responses in a variety of motivationally relevant situations. Thus, the involvement of orexins in diverse behaviors may reflect a common underlying function for this peptide system.
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Affiliation(s)
- Stephen V Mahler
- Department of Neuroscience, Medical University of South Carolina, Charleston, South Carolina, USA
| | - David E Moorman
- 1] Department of Neuroscience, Medical University of South Carolina, Charleston, South Carolina, USA. [2] Department of Psychological and Brain Sciences, University of Massachusetts Amherst, Amherst, Massachusetts, USA
| | - Rachel J Smith
- Department of Neuroscience, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Morgan H James
- Department of Neuroscience, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Gary Aston-Jones
- Department of Neuroscience, Medical University of South Carolina, Charleston, South Carolina, USA
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170
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Paul ED, Johnson PL, Shekhar A, Lowry CA. The Deakin/Graeff hypothesis: focus on serotonergic inhibition of panic. Neurosci Biobehav Rev 2014; 46 Pt 3:379-96. [PMID: 24661986 PMCID: PMC4170046 DOI: 10.1016/j.neubiorev.2014.03.010] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Revised: 02/15/2014] [Accepted: 03/01/2014] [Indexed: 12/20/2022]
Abstract
The Deakin/Graeff hypothesis proposes that different subpopulations of serotonergic neurons through topographically organized projections to forebrain and brainstem structures modulate the response to acute and chronic stressors, and that dysfunction of these neurons increases vulnerability to affective and anxiety disorders, including panic disorder. We outline evidence supporting the existence of a serotonergic system originally discussed by Deakin/Graeff that is implicated in the inhibition of panic-like behavioral and physiological responses. Evidence supporting this panic inhibition system comes from the following observations: (1) serotonergic neurons located in the 'ventrolateral dorsal raphe nucleus' (DRVL) as well as the ventrolateral periaqueductal gray (VLPAG) inhibit dorsal periaqueductal gray-elicited panic-like responses; (2) chronic, but not acute, antidepressant treatment potentiates serotonin's panicolytic effect; (3) contextual fear activates a central nucleus of the amygdala-DRVL/VLPAG circuit implicated in mediating freezing and inhibiting panic-like escape behaviors; (4) DRVL/VLPAG serotonergic neurons are central chemoreceptors and modulate the behavioral and cardiorespiratory response to panicogenic agents such as sodium lactate and CO2. Implications of the panic inhibition system are discussed.
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Affiliation(s)
- Evan D Paul
- Department of Integrative Physiology and Center for Neuroscience, University of Colorado Boulder, Boulder, CO 80309-0354, USA.
| | - Philip L Johnson
- Department of Integrative Physiology and Center for Neuroscience, University of Colorado Boulder, Boulder, CO 80309-0354, USA.
| | - Anantha Shekhar
- Department of Integrative Physiology and Center for Neuroscience, University of Colorado Boulder, Boulder, CO 80309-0354, USA.
| | - Christopher A Lowry
- Department of Integrative Physiology and Center for Neuroscience, University of Colorado Boulder, Boulder, CO 80309-0354, USA.
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171
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172
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Godden KE, Landry JP, Slepneva N, Migues PV, Pompeiano M. Early expression of hypocretin/orexin in the chick embryo brain. PLoS One 2014; 9:e106977. [PMID: 25188307 PMCID: PMC4154820 DOI: 10.1371/journal.pone.0106977] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Accepted: 08/11/2014] [Indexed: 01/20/2023] Open
Abstract
Hypocretin/Orexin (H/O) neuropeptides are released by a discrete group of neurons in the vertebrate hypothalamus which play a pivotal role in the maintenance of waking behavior and brain state control. Previous studies have indicated that the H/O neuronal development differs between mammals and fish; H/O peptide-expressing cells are detectable during the earliest stages of brain morphogenesis in fish, but only towards the end of brain morphogenesis (by ∼85% of embryonic development) in rats. The developmental emergence of H/O neurons has never been previously described in birds. With the goal of determining whether the chick developmental pattern was more similar to that of mammals or of fish, we investigated the emergence of H/O-expressing cells in the brain of chick embryos of different ages using immunohistochemistry. Post-natal chick brains were included in order to compare the spatial distribution of H/O cells with that of other vertebrates. We found that H/O-expressing cells appear to originate from two separate places in the region of the diencephalic proliferative zone. These developing cells express the H/O neuropeptide at a comparatively early age relative to rodents (already visible at 14% of the way through fetal development), thus bearing a closer resemblance to fish. The H/O-expressing cell population proliferates to a large number of cells by a relatively early embryonic age. As previously suggested, the distribution of H/O neurons is intermediate between that of mammalian and non-mammalian vertebrates. This work suggests that, in addition to its roles in developed brains, the H/O peptide may play an important role in the early embryonic development of non-mammalian vertebrates.
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Affiliation(s)
- Kyle E. Godden
- Department of Psychology, McGill University, Montreal, Quebec, Canada
| | - Jeremy P. Landry
- Department of Psychology, McGill University, Montreal, Quebec, Canada
| | - Natalya Slepneva
- Department of Psychology, McGill University, Montreal, Quebec, Canada
| | - Paola V. Migues
- Department of Psychology, McGill University, Montreal, Quebec, Canada
| | - Maria Pompeiano
- Department of Psychology, McGill University, Montreal, Quebec, Canada
- * E-mail:
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173
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Shimizu S, Nakamachi T, Konno N, Matsuda K. Orexin A enhances food intake in bullfrog larvae. Peptides 2014; 59:79-82. [PMID: 25064815 DOI: 10.1016/j.peptides.2014.07.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Revised: 07/15/2014] [Accepted: 07/15/2014] [Indexed: 10/25/2022]
Abstract
Orexin is a potent orexigenic peptide implicated in appetite regulation in rodents. However, except for teleost fish, the involvement of orexin in the regulation of feeding in non-mammalian vertebrates has not been well studied. Anuran amphibian larvae feed and grow during the pre- and prometamorphic stages. Therefore, orexigenic factors seem to play important roles in growing larvae. Indeed, our recent studies have demonstrated that neuropeptide Y and ghrelin exert orexigenic actions in bullfrog larvae during the prometamorphic stages. In this study, we examined the effect of intracerebroventricular (ICV) administration of synthetic orexin A on food intake in bullfrog larvae at the prometamorphic stages. Food intake was significantly increased by ICV administration of orexin A (at 6 pmol/g BW) during a 15-min observation period. The orexigenic action of orexin A at 6 pmol/g BW was blocked by treatment with an orexin receptor antagonist, SB334867, at 60 pmol/g BW. These results indicate that orexin A acts as an orexigenic factor in bullfrog larvae.
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Affiliation(s)
- Shunsuke Shimizu
- Laboratory of Regulatory Biology, Graduate School of Science and Engineering, University of Toyama, 3190-Gofuku, Toyama, Toyama 930-8555, Japan
| | - Tomoya Nakamachi
- Laboratory of Regulatory Biology, Graduate School of Science and Engineering, University of Toyama, 3190-Gofuku, Toyama, Toyama 930-8555, Japan
| | - Norifumi Konno
- Laboratory of Regulatory Biology, Graduate School of Science and Engineering, University of Toyama, 3190-Gofuku, Toyama, Toyama 930-8555, Japan
| | - Kouhei Matsuda
- Laboratory of Regulatory Biology, Graduate School of Science and Engineering, University of Toyama, 3190-Gofuku, Toyama, Toyama 930-8555, Japan; Laboratory of Regulatory Biology, Graduate School of Innovative Life Science, University of Toyama, 3190-Gofuku, Toyama, Toyama 930-8555, Japan.
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174
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Kukkonen JP, Leonard CS. Orexin/hypocretin receptor signalling cascades. Br J Pharmacol 2014; 171:314-31. [PMID: 23902572 DOI: 10.1111/bph.12324] [Citation(s) in RCA: 141] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Revised: 07/18/2013] [Accepted: 07/28/2013] [Indexed: 12/16/2022] Open
Abstract
Orexin (hypocretin) peptides and their two known G-protein-coupled receptors play essential roles in sleep-wake control and powerfully influence other systems regulating appetite/metabolism, stress and reward. Consequently, drugs that influence signalling by these receptors may provide novel therapeutic opportunities for treating sleep disorders, obesity and addiction. It is therefore critical to understand how these receptors operate, the nature of the signalling cascades they engage and their physiological targets. In this review, we evaluate what is currently known about orexin receptor signalling cascades, while a sister review (Leonard & Kukkonen, this issue) focuses on tissue-specific responses. The evidence suggests that orexin receptor signalling is multifaceted and is substantially more diverse than originally thought. Indeed, orexin receptors are able to couple to members of at least three G-protein families and possibly other proteins, through which they regulate non-selective cation channels, phospholipases, adenylyl cyclase, and protein and lipid kinases. In the central nervous system, orexin receptors produce neuroexcitation by postsynaptic depolarization via activation of non-selective cation channels, inhibition of K⁺ channels and activation of Na⁺/Ca²⁺ exchange, but they also can stimulate the release of neurotransmitters by presynaptic actions and modulate synaptic plasticity. Ca²⁺ signalling is also prominently influenced by these receptors, both via the classical phospholipase C-Ca²⁺ release pathway and via Ca²⁺ influx, mediated by several pathways. Upon longer-lasting stimulation, plastic effects are observed in some cell types, while others, especially cancer cells, are stimulated to die. Thus, orexin receptor signals appear highly tunable, depending on the milieu in which they are operating.
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Affiliation(s)
- J P Kukkonen
- Biochemistry and Cell Biology, Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland
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175
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Perin M, Longordo F, Massonnet C, Welker E, Lüthi A. Diurnal inhibition of NMDA-EPSCs at rat hippocampal mossy fibre synapses through orexin-2 receptors. J Physiol 2014; 592:4277-95. [PMID: 25085886 DOI: 10.1113/jphysiol.2014.272757] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Diurnal release of the orexin neuropeptides orexin-A (Ox-A, hypocretin-1) and orexin-B (Ox-B, hypocretin-2) stabilises arousal, regulates energy homeostasis and contributes to cognition and learning. However, whether cellular correlates of brain plasticity are regulated through orexins, and whether they do so in a time-of-day-dependent manner, has never been assessed. Immunohistochemically we found sparse but widespread innervation of hippocampal subfields through Ox-A- and Ox-B-containing fibres in young adult rats. The actions of Ox-A were studied on NMDA receptor (NMDAR)-mediated excitatory synaptic transmission in acute hippocampal slices prepared around the trough (Zeitgeber time (ZT) 4-8, corresponding to 4-8 h into the resting phase) and peak (ZT 23) of intracerebroventricular orexin levels. At ZT 4-8, exogenous Ox-A (100 nm in bath) inhibited NMDA receptor-mediated excitatory postsynaptic currents (NMDA-EPSCs) at mossy fibre (MF)-CA3 (to 55.6 ± 6.8% of control, P = 0.0003) and at Schaffer collateral-CA1 synapses (70.8 ± 6.3%, P = 0.013), whereas it remained ineffective at non-MF excitatory synapses in CA3. Ox-A actions were mediated postsynaptically and blocked by the orexin-2 receptor (OX2R) antagonist JNJ10397049 (1 μm), but not by orexin-1 receptor inhibition (SB334867, 1 μm) or by adrenergic and cholinergic antagonists. At ZT 23, inhibitory effects of exogenous Ox-A were absent (97.6 ± 2.9%, P = 0.42), but reinstated (87.2 ± 3.3%, P = 0.002) when endogenous orexin signalling was attenuated for 5 h through i.p. injections of almorexant (100 mg kg(-1)), a dual orexin receptor antagonist. In conclusion, endogenous orexins modulate hippocampal NMDAR function in a time-of-day-dependent manner, suggesting that they may influence cellular plasticity and consequent variations in memory performance across the sleep-wake cycle.
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Affiliation(s)
- Martina Perin
- Department of Fundamental Neurosciences, University of Lausanne, Rue du Bugnon 9, CH-1005, Lausanne, Switzerland
| | - Fabio Longordo
- Department of Fundamental Neurosciences, University of Lausanne, Rue du Bugnon 9, CH-1005, Lausanne, Switzerland
| | - Christine Massonnet
- Department of Fundamental Neurosciences, University of Lausanne, Rue du Bugnon 9, CH-1005, Lausanne, Switzerland
| | - Egbert Welker
- Department of Fundamental Neurosciences, University of Lausanne, Rue du Bugnon 9, CH-1005, Lausanne, Switzerland
| | - Anita Lüthi
- Department of Fundamental Neurosciences, University of Lausanne, Rue du Bugnon 9, CH-1005, Lausanne, Switzerland
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176
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What optogenetic stimulation is telling us (and failing to tell us) about fast neurotransmitters and neuromodulators in brain circuits for wake-sleep regulation. Curr Opin Neurobiol 2014; 29:165-71. [PMID: 25064179 DOI: 10.1016/j.conb.2014.07.016] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Revised: 07/07/2014] [Accepted: 07/07/2014] [Indexed: 12/19/2022]
Abstract
In the last eight years optogenetic tools have been widely used to identify functional synaptic connectivity between specific neuronal populations. Most of our knowledge comes from the photo-activation of channelrhodopsin-2 (ChR2) expressing inputs that release glutamate and GABA. More recent studies have been reporting releases of acetylcholine and biogenic amines but direct evidence for photo-evoked released of neuropeptides is still limited particularly in brain slice studies. The high fidelity in the responses with photo-evoked amino-acid transmission is ideal for ChR2-assisted circuit mapping and this approach has been successfully used in different fields of neuroscience. Conversely, neuropeptides employ a slow mode of communication and might require higher frequency and prolonged stimulations to be released. These factors may have contributed to the apparent lack of success for optogenetic release of neuropeptides. In addition, once released, neuropeptides often act on multiple sites and at various distances from the site of release resulting in a greater complexity of postsynaptic responses. Here, we focus on what optogenetics is telling us-and failing to tell us-about fast neurotransmitters and neuropeptides.
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177
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Chen Q, de Lecea L, Hu Z, Gao D. The hypocretin/orexin system: an increasingly important role in neuropsychiatry. Med Res Rev 2014; 35:152-97. [PMID: 25044006 DOI: 10.1002/med.21326] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Hypocretins, also named as orexins, are excitatory neuropeptides secreted by neurons specifically located in lateral hypothalamus and perifornical areas. Orexinergic fibers are extensively distributed in various brain regions and involved in a number of physiological functions, such as arousal, cognition, stress, appetite, and metabolism. Arousal is the most important function of orexin system as dysfunction of orexin signaling leads to narcolepsy. In addition to narcolepsy, orexin dysfunction is associated with serious neural disorders, including addiction, depression, and anxiety. However, some results linking orexin with these disorders are still contradictory, which may result from differences of detection methods or the precision of tools used in measurements; strategies targeted to orexin system (e.g., antagonists to orexin receptors, gene delivery, and cell transplantation) are promising new tools for treatment of neuropsychiatric disorders, though studies are still in a stage of preclinical or clinical research.
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Affiliation(s)
- Quanhui Chen
- Department of Physiology, Third Military Medical University, Chongqing 400038, China; Department of Sleep and Psychology, Institute of Surgery Research, Daping Hospital, Third Military Medical University, Chongqing 400038, China
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178
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Nakamachi T, Shibata H, Sakashita A, Iinuma N, Wada K, Konno N, Matsuda K. Orexin A enhances locomotor activity and induces anxiogenic-like action in the goldfish, Carassius auratus. Horm Behav 2014; 66:317-23. [PMID: 24937437 DOI: 10.1016/j.yhbeh.2014.06.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Revised: 06/05/2014] [Accepted: 06/06/2014] [Indexed: 12/11/2022]
Abstract
Orexin acts as an orexigenic factor for the regulation of appetite and rhythmicity in rodents. In goldfish, intracerebroventricular (ICV) administration of orexin A has been shown to affect not only food intake, but also locomotor activity. However, as there is still no information regarding the effect of orexin A on emotional behavior in goldfish, we investigated the effect of orexin A on psychomotor activity in this species. Intracerebroventricular administration of synthetic orexin A at 2 and 4pmol/g body weight (BW) enhanced locomotor activity, and this enhancement by orexin A at 4pmol/g BW was attenuated by treatment with the orexin receptor 1 antagonist, SB334867, at 10pmol/g BW. Since intact goldfish prefer a black to a white background area, or the lower to the upper area of a tank, we used two types of preference tests (black/white and upper/lower tests) for measuring anxiety-like behavior in goldfish. Intracerebroventricular administration of orexin A at 4pmol/g BW shortened the time spent in the white background area, and increased the time taken to move from the lower to the upper area. This action of orexin A mimicked that of the central-type benzodiazepine receptor inverse agonist, FG-7142 (an anxiogenic agent), at 4pmol/g BW. The anxiogenic-like effect of orexin A was abolished by treatment with SB334867 at 10pmol/g BW. These results indicate that orexin A potently affects psychomotor activity in goldfish.
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Affiliation(s)
- Tomoya Nakamachi
- Laboratory of Regulatory Biology, Graduate School of Science and Engineering, University of Toyama, 3190-Gofuku, Toyama 930-8555, Japan
| | - Haruki Shibata
- Laboratory of Regulatory Biology, Graduate School of Science and Engineering, University of Toyama, 3190-Gofuku, Toyama 930-8555, Japan
| | - Atsushi Sakashita
- Laboratory of Regulatory Biology, Graduate School of Science and Engineering, University of Toyama, 3190-Gofuku, Toyama 930-8555, Japan
| | - Naoto Iinuma
- Laboratory of Regulatory Biology, Graduate School of Science and Engineering, University of Toyama, 3190-Gofuku, Toyama 930-8555, Japan
| | - Kohei Wada
- Laboratory of Regulatory Biology, Graduate School of Science and Engineering, University of Toyama, 3190-Gofuku, Toyama 930-8555, Japan
| | - Norifumi Konno
- Laboratory of Regulatory Biology, Graduate School of Science and Engineering, University of Toyama, 3190-Gofuku, Toyama 930-8555, Japan
| | - Kouhei Matsuda
- Laboratory of Regulatory Biology, Graduate School of Science and Engineering, University of Toyama, 3190-Gofuku, Toyama 930-8555, Japan; Laboratory of Regulatory Biology, Graduate School of Innovative Life Science, University of Toyama, 3190-Gofuku, Toyama 930-8555, Japan.
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179
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Aluisio L, Fraser I, Berdyyeva T, Tryputsen V, Shireman BT, Shoblock J, Lovenberg T, Dugovic C, Bonaventure P. Pharmacological or genetic orexin1 receptor inhibition attenuates MK-801 induced glutamate release in mouse cortex. Front Neurosci 2014; 8:107. [PMID: 24904253 PMCID: PMC4033200 DOI: 10.3389/fnins.2014.00107] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 04/24/2014] [Indexed: 12/13/2022] Open
Abstract
The orexin/hypocretin neuropeptides are produced by a cluster of neurons within the lateral posterior hypothalamus and participate in neuronal regulation by activating their receptors (OX1 and OX2 receptors). The orexin system projects widely through the brain and functions as an interface between multiple regulatory systems including wakefulness, energy balance, stress, reward, and emotion. Recent studies have demonstrated that orexins and glutamate interact at the synaptic level and that orexins facilitate glutamate actions. We tested the hypothesis that orexins modulate glutamate signaling via OX1 receptors by monitoring levels of glutamate in frontal cortex of freely moving mice using enzyme coated biosensors under inhibited OX1 receptor conditions. MK-801, an NMDA receptor antagonist, was administered subcutaneously (0.178 mg/kg) to indirectly disinhibit pyramidal neurons and therefore increase cortical glutamate release. In wild-type mice, pretreatment with the OX1 receptor antagonist GSK-1059865 (10 mg/kg S.C.) which had no effect by itself, significantly attenuated the cortical glutamate release elicited by MK-801. OX1 receptor knockout mice had a blunted glutamate release response to MK-801 and exhibited about half of the glutamate release observed in wild-type mice in agreement with the data obtained with transient blockade of OX1 receptors. These results indicate that pharmacological (transient) or genetic (permanent) inhibition of the OX1 receptor similarly interfere with glutamatergic function in the cortex. Selectively targeting the OX1 receptor with an antagonist may normalize hyperglutamatergic states and thus may represent a novel therapeutic strategy for the treatment of various psychiatric disorders associated with hyperactive states.
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Affiliation(s)
- Leah Aluisio
- Janssen Pharmaceutical Research and Development, LLC San Diego, USA
| | - Ian Fraser
- Janssen Pharmaceutical Research and Development, LLC San Diego, USA
| | - Tamara Berdyyeva
- Janssen Pharmaceutical Research and Development, LLC San Diego, USA
| | - Volha Tryputsen
- Janssen Pharmaceutical Research and Development, LLC San Diego, USA
| | - Brock T Shireman
- Janssen Pharmaceutical Research and Development, LLC San Diego, USA
| | - James Shoblock
- Janssen Pharmaceutical Research and Development, LLC San Diego, USA
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180
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Smith LB, Leo MC, Anderson C, Wright TJ, Weymann KB, Wood LJ. The role of IL-1β and TNF-α signaling in the genesis of cancer treatment related symptoms (CTRS): a study using cytokine receptor-deficient mice. Brain Behav Immun 2014; 38:66-76. [PMID: 24412646 PMCID: PMC3989411 DOI: 10.1016/j.bbi.2013.12.022] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 12/19/2013] [Accepted: 12/28/2013] [Indexed: 02/01/2023] Open
Abstract
Cytotoxic chemotherapeutic agents often induce a cluster of cancer treatment related symptoms (CTRS). The purpose of this study was to develop a mouse model of CTRS to examine the role of IL-1β and TNF-α signaling in the genesis of these symptoms. CTRS (change in wheel running activity, food intake, and body weight from baseline) were examined in wild type (WT) mice or mice lacking the TNF-α p55 (type 1) receptor (TNFR1-/-) and/or IL-1β type 1 receptor (IL-1R1-/-) injected with four doses of cyclophosphamide/Adriamycin/5-fluorouracil (CAF) at 20-day intervals. Inflammatory cytokines in blood and tissues were measured using multiplex immunoassays and quantitative RT-PCR. ANOVA was used to examine differences between genotype and/or treatment group. Kaplan-Meier analysis was used to estimate survival rate. CAF rapidly increased IL-1β and TNF-α signaling in WT mice. CAF induced acute CTRS immediately following drug injection which returned to baseline prior to the next CAF dose. Persistent CTRS were evident 3weeks after the 4th CAF dose. Acute but not persistent CTRS were associated with increased levels of IL-7, IL-9, KC, MCP-1, GCSF, and IP-10. This CAF induced inflammatory response was blunted in IL-1R1 deficient mice and absent in IL-1R1/TNFR1-deficient mice. IL-1R1-/- mice showed an identical pattern of CTRS to their WT counterparts. The assessment of CTRS in IL-1R1/TNF-R1-deficient mice was precluded by severe toxicity. Our data suggest that an important function of the IL-1β and TNF-α driven inflammatory cascade is to promote recovery following exposure to cytotoxic agents.
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Affiliation(s)
- Logan B. Smith
- School of Nursing, Oregon Health Science University, Portland, OR, 97239
| | - Michael C. Leo
- Center for Health Research, Kaiser Permanente Northwest, Portland, OR 97227
| | - Caroline Anderson
- School of Nursing, Oregon Health Science University, Portland, OR 97239, United States.
| | - Teresa J. Wright
- School of Nursing, Oregon Health Science University, Portland, OR, 97239
| | | | - Lisa J. Wood
- School of Nursing, Oregon Health Science University, Portland, OR, 97239
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181
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Clark IA, Vissel B. Inflammation-sleep interface in brain disease: TNF, insulin, orexin. J Neuroinflammation 2014; 11:51. [PMID: 24655719 PMCID: PMC3994460 DOI: 10.1186/1742-2094-11-51] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Accepted: 03/11/2014] [Indexed: 12/28/2022] Open
Abstract
The depth, pattern, timing and duration of unconsciousness, including sleep, vary greatly in inflammatory disease, and are regarded as reliable indicators of disease severity. Similarly, these indicators are applicable to the encephalopathies of sepsis, malaria, and trypanosomiasis, and to viral diseases such as influenza and AIDS. They are also applicable to sterile neuroinflammatory states, including Alzheimer’s disease, Parkinson’s disease, traumatic brain injury, stroke and type-2 diabetes, as well as in iatrogenic brain states following brain irradiation and chemotherapy. Here we make the case that the cycles of unconsciousness that constitute normal sleep, as well as its aberrations, which range from sickness behavior through daytime sleepiness to the coma of inflammatory disease states, have common origins that involve increased inflammatory cytokines and consequent insulin resistance and loss of appetite due to reduction in orexigenic activity. Orexin reduction has broad implications, which are as yet little appreciated in the chronic inflammatory conditions listed, whether they be infectious or sterile in origin. Not only is reduction in orexin levels characterized by loss of appetite, it is associated with inappropriate and excessive sleep and, when dramatic and chronic, leads to coma. Moreover, such reduction is associated with impaired cognition and a reduction in motor control. We propose that advanced understanding and appreciation of the importance of orexin as a key regulator of pathways involved in the maintenance of normal appetite, sleep patterns, cognition, and motor control may afford novel treatment opportunities.
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Affiliation(s)
- Ian A Clark
- Biomedical Sciences and Biochemistry, Research School of Biology, Australian National University, Acton, Canberra, Australian Capital Territory 0200, Australia.
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Torterolo P, Chase MH. The hypocretins (orexins) mediate the "phasic" components of REM sleep: A new hypothesis. Sleep Sci 2014; 7:19-29. [PMID: 26483897 PMCID: PMC4521687 DOI: 10.1016/j.slsci.2014.07.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 01/27/2014] [Indexed: 12/17/2022] Open
Abstract
In 1998, a group of phenotypically distinct neurons were discovered in the postero-lateral hypothalamus which contained the neuropeptides hypocretin 1 and hypocretin 2 (also called orexin A and orexin B), which are excitatory neuromodulators. Hypocretinergic neurons project throughout the central nervous system and have been involved in the generation and maintenance of wakefulness. The sleep disorder narcolepsy, characterized by hypersomnia and cataplexy, is produced by degeneration of these neurons. The hypocretinergic neurons are active during wakefulness in conjunction with the presence of motor activity that occurs during survival-related behaviors. These neurons decrease their firing rate during non-REM sleep; however there is still controversy upon the activity and role of these neurons during REM sleep. Hence, in the present report we conducted a critical review of the literature of the hypocretinergic system during REM sleep, and hypothesize a possible role of this system in the generation of REM sleep.
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Affiliation(s)
- Pablo Torterolo
- Laboratorio de Neurobiología del Sueño, Departamento de Fisiología, Facultad de Medicina, Universidad de la República, General Flores 2125, 11800 Montevideo, Uruguay
| | - Michael H. Chase
- WebSciences International, Los Angeles, USA
- UCLA School of Medicine, Los Angeles, USA
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183
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Jäntti MH, Mandrika I, Kukkonen JP. Human orexin/hypocretin receptors form constitutive homo- and heteromeric complexes with each other and with human CB1 cannabinoid receptors. Biochem Biophys Res Commun 2014; 445:486-90. [PMID: 24530395 DOI: 10.1016/j.bbrc.2014.02.026] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Accepted: 02/06/2014] [Indexed: 12/17/2022]
Abstract
Human OX1 orexin receptors have been shown to homodimerize and they have also been suggested to heterodimerize with CB1 cannabinoid receptors. The latter has been suggested to be important for orexin receptor responses and trafficking. In this study, we wanted to assess the ability of the other combinations of receptors to also form similar complexes. Vectors for expression of human OX1, OX2 and CB1 receptors, C-terminally fused with either Renilla luciferase or GFP(2) green fluorescent protein variant, were generated. The constructs were transiently expressed in Chinese hamster ovary cells, and constitutive dimerization between the receptors was assessed by bioluminescence energy transfer (BRET). Orexin receptor subtypes readily formed homo- and hetero(di)mers, as suggested by significant BRET signals. CB1 receptors formed homodimers, and they also heterodimerized with both orexin receptors. Interestingly, BRET efficiency was higher for homodimers than for almost all heterodimers. This is likely to be due to the geometry of the interaction; the putatively symmetric dimers may place the C-termini in a more suitable orientation in homomers. Fusion of luciferase to an orexin receptor and GFP(2) to CB1 produced more effective BRET than the opposite fusions, also suggesting differences in geometry. Similar was seen for the OX1-OX2 interaction. In conclusion, orexin receptors have a significant propensity to make homo- and heterodi-/oligomeric complexes. However, it is unclear whether this affects their signaling. As orexin receptors efficiently signal via endocannabinoid production to CB1 receptors, dimerization could be an effective way of forming signal complexes with optimal cannabinoid concentrations available for cannabinoid receptors.
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Affiliation(s)
- Maria H Jäntti
- Department of Veterinary Biosciences, POB 66, FIN-00014 University of Helsinki, Finland.
| | - Ilona Mandrika
- Latvian Biomedical Research and Study Centre, Ratsupites Str. 1, Riga LV 1067, Latvia.
| | - Jyrki P Kukkonen
- Department of Veterinary Biosciences, POB 66, FIN-00014 University of Helsinki, Finland.
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Abstract
Sleep problems are common in attention-deficit/hyperactivity disorder (ADHD) to the extent that they mimic or exacerbate daytime symptoms expression. In this review, we advocate the need for a better understanding of sleep alterations in youths with ADHD and their impact on neurobehavioral functions including learning, memory and emotional regulation. An in-depth exploration of existing data showed that although extensively studied, the actual nature of sleep problems in ADHD and their effects on daytime behavior are still less well understood. Important issues, among which developmental changes in sleep architecture and role of subtle sleep electroencephalogram signatures, are generally neglected. Future research of sleep effects on behavior in ADHD would benefit from considering developmental aspects and links between brain activation patterns during sleep and wake.
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Affiliation(s)
- Roumen Kirov
- Institute of Neurobiology, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. 23, 1113 Sofua, Bulgaria
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185
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Abstract
In 1998, our group discovered a cDNA that encoded the precursor of two putative neuropeptides that we called hypocretins for their hypothalamic expression and their similarity to the secretin family of neuropeptides. In the last 16 years, numerous studies have placed the hypocretin system as an integrator of homeostatic functions with a crucial, non-redundant function as arousal stabilizer. We recently applied optogenetic methods to interrogate the role of individual neuronal circuits in sleep-to-wake transitions. The neuronal connections between the hypocretin system and the locus coeruleus (LC) seem to be crucial in establishing the appropriate dynamic of spontaneous awakenings.
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