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Lozano-Tovar S, Nuccetelli M, Placidi F, Izzi F, Sancesario G, Bernardini S, Biagio Mercuri N, Liguori C. CSF dynamics of orexin and β-amyloid 42 levels in narcolepsy and Alzheimer's disease patients: a controlled study. Neurosci Lett 2024; 837:137914. [PMID: 39032802 DOI: 10.1016/j.neulet.2024.137914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Revised: 06/12/2024] [Accepted: 07/17/2024] [Indexed: 07/23/2024]
Abstract
β-amyloid42 (Aβ42) in Alzheimer's disease (AD) and orexin in narcolepsy are considered crucial biomarkers for diagnosis and therapeutic targets. Recently, orexin and Aβ cerebral dynamics have been studied in both pathologies, but how they interact with each other remains further to be known. In this study, we investigated the reliability of using the correlation between orexin-A and Aβ42 CSF levels as a candidate marker to explain the chain of events leading to narcolepsy or AD pathology. In order to test the correlation between these biomarkers, patients diagnosed with AD (n = 76), narcolepsy type 1 (NT1, n = 17), narcolepsy type 2 (NT2, n = 23) and healthy subjects (n = 91) were examined. Patients and healthy subjects underwent lumbar puncture between 8:00 and 10:00 am at the Neurology Unit of the University Hospital of Rome "Tor Vergata". CSF levels of Aβ42, total-tau, phosphorylated-tau, and orexin-A were assessed. The results showed that CSF levels of Aβ42 were significantly lower (p < 0.001) in AD (332.28 ± 237.36 pg/mL) compared to NT1 (569.88 ± 187.00 pg/mL), NT2 (691.00 ± 292.63 pg/mL) and healthy subjects (943.68 ± 198.12 pg/mL). CSF orexin-A levels were statistically different (p < 0.001) between AD (148.01 ± 29.49 pg/mL), NT1 (45.94 ± 13.63 pg/mL), NT2 (104.92 ± 25.55 pg/mL) and healthy subjects (145.18 ± 27.01 pg/mL). Moderate-severe AD patients (mini mental state examination < 21) showed the highest CSF orexin-A levels, whereas NT1 patients showed the lowest CSF orexin-A levels. Correlation between CSF levels of Aβ42 and orexin-A was found only in healthy subjects (r = 0.26; p = 0.01), and not in narcolepsy or AD patients. This lack of correlation in both diseases may be explained by the pathology itself since the correlation between these two biomarkers is evident only in the healthy subjects. This study adds to the present literature by further documenting the interplay between orexinergic neurotransmission and cerebral Aβ dynamics, possibly sustained by sleep.
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Affiliation(s)
- Susana Lozano-Tovar
- Facultad de Psicología, Universidad Nacional Autónoma de México (UNAM), Circuito Ciudad Universitaria Avenida, C.U., Mexico City 04510, Mexico
| | - Marzia Nuccetelli
- Department of Clinical Biochemistry and Molecular Biology, University of Rome "Tor Vergata", Rome, Italy
| | - Fabio Placidi
- Department of Systems Medicine, University of Rome "Tor Vergata", 00133 Rome, Italy; Sleep Medicine Centre, Neurology Unit, University Hospital of Rome "Tor Vergata", 00133 Rome, Italy
| | - Francesca Izzi
- Sleep Medicine Centre, Neurology Unit, University Hospital of Rome "Tor Vergata", 00133 Rome, Italy
| | - Giuseppe Sancesario
- Department of Systems Medicine, University of Rome "Tor Vergata", 00133 Rome, Italy
| | - Sergio Bernardini
- Department of Clinical Biochemistry and Molecular Biology, University of Rome "Tor Vergata", Rome, Italy
| | - Nicola Biagio Mercuri
- Department of Systems Medicine, University of Rome "Tor Vergata", 00133 Rome, Italy; Sleep Medicine Centre, Neurology Unit, University Hospital of Rome "Tor Vergata", 00133 Rome, Italy
| | - Claudio Liguori
- Department of Systems Medicine, University of Rome "Tor Vergata", 00133 Rome, Italy; Sleep Medicine Centre, Neurology Unit, University Hospital of Rome "Tor Vergata", 00133 Rome, Italy.
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2
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Stark R. The olfactory bulb: A neuroendocrine spotlight on feeding and metabolism. J Neuroendocrinol 2024; 36:e13382. [PMID: 38468186 DOI: 10.1111/jne.13382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 02/22/2024] [Accepted: 02/25/2024] [Indexed: 03/13/2024]
Abstract
Olfaction is the most ancient sense and is needed for food-seeking, danger protection, mating and survival. It is often the first sensory modality to perceive changes in the external environment, before sight, taste or sound. Odour molecules activate olfactory sensory neurons that reside on the olfactory epithelium in the nasal cavity, which transmits this odour-specific information to the olfactory bulb (OB), where it is relayed to higher brain regions involved in olfactory perception and behaviour. Besides odour processing, recent studies suggest that the OB extends its function into the regulation of food intake and energy balance. Furthermore, numerous hormone receptors associated with appetite and metabolism are expressed within the OB, suggesting a neuroendocrine role outside the hypothalamus. Olfactory cues are important to promote food preparatory behaviours and consumption, such as enhancing appetite and salivation. In addition, altered metabolism or energy state (fasting, satiety and overnutrition) can change olfactory processing and perception. Similarly, various animal models and human pathologies indicate a strong link between olfactory impairment and metabolic dysfunction. Therefore, understanding the nature of this reciprocal relationship is critical to understand how olfactory or metabolic disorders arise. This present review elaborates on the connection between olfaction, feeding behaviour and metabolism and will shed light on the neuroendocrine role of the OB as an interface between the external and internal environments. Elucidating the specific mechanisms by which olfactory signals are integrated and translated into metabolic responses holds promise for the development of targeted therapeutic strategies and interventions aimed at modulating appetite and promoting metabolic health.
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Affiliation(s)
- Romana Stark
- Monash Biomedicine Discovery Institute and Department of Physiology, Monash University, Clayton, Victoria, Australia
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3
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Maness EB, Blumenthal SA, Burk JA. Dual orexin/hypocretin receptor antagonism attenuates NMDA receptor hypofunction-induced attentional impairments in a rat model of schizophrenia. Behav Brain Res 2023; 450:114497. [PMID: 37196827 PMCID: PMC10330488 DOI: 10.1016/j.bbr.2023.114497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 05/12/2023] [Accepted: 05/14/2023] [Indexed: 05/19/2023]
Abstract
Schizophrenia is a neuropsychiatric condition that is associated with impaired attentional processing and performance. Failure to support increasing attentional load may result, in part, from inhibitory failure in attention-relevant cortical regions, and available antipsychotics often fail to address this issue. Orexin/hypocretin receptors are found throughout the brain and are expressed on neurons relevant to both attention and schizophrenia, highlighting them as a potential target to treat schizophrenia-associated attentional dysfunction. In the present experiment, rats (N = 14) trained in a visual sustained attention task that required discrimination of trials which presented a visual signal from trials during which no signal was presented. Once trained, rats were then co-administered the psychotomimetic N-methyl-D-aspartate (NMDA) receptor antagonist dizocilpine (MK-801: 0 or 0.1 mg/kg, intraperitoneal injections) and the dual orexin receptor antagonist filorexant (MK-6096: 0, 0.1, or 1 mM, intracerebroventricular infusions) prior to task performance across six sessions. Dizocilpine impaired overall accuracy during signal trials, slowed reaction times for correctly-responded trials, and increased the number of omitted trials throughout the task. Dizocilpine-induced increases in signal trial deficits, correct response latencies, and errors of omission were reduced following infusions of the 0.1 mM, but not 1 mM, dose of filorexant. As such, orexin receptor blockade may improve attentional deficits in a state of NMDA receptor hypofunction.
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Affiliation(s)
- Eden B Maness
- Department of Psychological Sciences, College of William and Mary, Williamsburg, VA 23187, USA; VA Boston Healthcare System and Department of Psychiatry, Harvard Medical School, West Roxbury, MA 02132, USA.
| | - Sarah A Blumenthal
- Center for Translational Social Neuroscience, Emory National Primate Research Center, Emory University, Atlanta, GA 30329, USA
| | - Joshua A Burk
- Department of Psychological Sciences, College of William and Mary, Williamsburg, VA 23187, USA
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4
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Durairaja A, Pandey S, Kahl E, Fendt M. Nasal administration of orexin A partially rescues dizocilpine-induced cognitive impairments in female C57BL/6J mice. Behav Brain Res 2023; 450:114491. [PMID: 37172740 DOI: 10.1016/j.bbr.2023.114491] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 05/08/2023] [Accepted: 05/09/2023] [Indexed: 05/15/2023]
Abstract
Sex difference has been reported in several behavioural endophenotypes of neuropsychiatric disorder in both rodents and humans. However, sex difference in cognitive symptoms associated with neuropsychiatric disorders has not been studied in detail. In this study, we induced cognitive impairment using the NMDA receptor antagonist, dizocilpine (MK-801), in male and female C57BL/6J mice and performed a visual discrimination task in an automated touchscreen system. We found that discrimination performance decreased with increased doses of MK-801 in both sexes. However, female mice showed stronger deficit in discrimination performance than the male mice especially after administration of low (0.01mg/kg) and high (0.15mg/kg) doses of MK-801. Furthermore, we tested if administration of orexin A, orexin-1 receptor antagonist SB-334867 or orexin-2 receptor antagonist EMPA rescued MK-801 (0.15mg/kg) induced cognitive impairment in visual discrimination. We found that nasal administration of orexin A partially rescued the cognitive impairment induced by MK-801 in females but not in males. Taken together, our data show that female C57BL/6J mice are more sensitive compared to males to some doses of MK-801 in discrimination learning task and that orexin A partially rescues this cognitive impairment in females.
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Affiliation(s)
- Archana Durairaja
- Institute for Pharmacology and Toxicology, Otto-von-Guericke University, Magdeburg, Germany.
| | - Samiksha Pandey
- Institute for Pharmacology and Toxicology, Otto-von-Guericke University, Magdeburg, Germany; Integrative Neuroscience Programme, Otto-von-Guericke University, Magdeburg, Germany
| | - Evelyn Kahl
- Institute for Pharmacology and Toxicology, Otto-von-Guericke University, Magdeburg, Germany
| | - Markus Fendt
- Institute for Pharmacology and Toxicology, Otto-von-Guericke University, Magdeburg, Germany; Center of Behavioral Brain Sciences, Otto-von-Guericke University, Magdeburg, Germany
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5
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Maness EB, Blumenthal SA, Burk JA. Dual orexin/hypocretin receptor antagonism attenuates attentional impairments in an NMDA receptor hypofunction model of schizophrenia. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.05.527043. [PMID: 36778441 PMCID: PMC9915718 DOI: 10.1101/2023.02.05.527043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Schizophrenia is a neuropsychiatric condition that is associated with impaired attentional processing and performance. Failure to support increasing attentional load may result, in part, from abnormally overactive basal forebrain projections to the prefrontal cortex, and available antipsychotics often fail to address this issue. Orexin/hypocretin receptors are expressed on corticopetal cholinergic neurons, and their blockade has been shown to decrease the activity of cortical basal forebrain outputs and prefrontal cortical cholinergic neurotransmission. In the present experiment, rats (N = 14) trained in a visual sustained attention task that required discrimination of trials which presented a visual signal from trials during which no signal was presented. Once trained, rats were then co-administered the psychotomimetic N-methyl-D-aspartate (NMDA) receptor antagonist dizocilpine (MK-801: 0 or 0.1 mg/kg, intraperitoneal injections) and the dual orexin receptor antagonist filorexant (MK-6096: 0, 0.1, or 1 mM, intracerebroventricular infusions) prior to task performance across six sessions. Dizocilpine impaired overall accuracy during signal trials, slowed reaction times for correctly-responded trials, and increased the number of omitted trials throughout the task. Dizocilpine-induced increases in signal trial deficits, correct response latencies, and errors of omission were reduced following infusions of the 0.1 mM, but not 1 mM, dose of filorexant. Orexin receptor blockade, perhaps through anticholinergic mechanisms, may improve attentional deficits in a state of NMDA receptor hypofunction. Highlights Schizophrenia is associated with attentional deficits that may stem from abnormally reactive BF projections to the prefrontal cortexOrexin receptor antagonists decrease acetylcholine release and reduce prefrontal cortical activityThe dual orexin receptor antagonist filorexant alleviated impairments of attention following NMDA receptor blockade.
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Affiliation(s)
- Eden B. Maness
- VA Boston Healthcare System and Department of Psychiatry, Harvard Medical School, West Roxbury, MA, 02132, USA
- Department of Psychological Sciences, College of William and Mary, Williamsburg, VA, 23187, USA
| | - Sarah A. Blumenthal
- Center for Translational Social Neuroscience, Emory National Primate Research Center, Emory University, Atlanta, GA, 30329, USA
| | - Joshua A. Burk
- Department of Psychological Sciences, College of William and Mary, Williamsburg, VA, 23187, USA
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6
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Durairaja A, Steinecke CS, Fendt M. Intracerebroventricular infusion of the selective orexin 1 receptor antagonist SB-334867 impairs cognitive flexibility in a sex-dependent manner. Behav Brain Res 2022; 424:113791. [DOI: 10.1016/j.bbr.2022.113791] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2021] [Revised: 02/08/2022] [Accepted: 02/08/2022] [Indexed: 11/17/2022]
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7
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Erichsen JM, Calva CB, Reagan LP, Fadel JR. Intranasal insulin and orexins to treat age-related cognitive decline. Physiol Behav 2021; 234:113370. [PMID: 33621561 PMCID: PMC8053680 DOI: 10.1016/j.physbeh.2021.113370] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Accepted: 02/19/2021] [Indexed: 02/06/2023]
Abstract
The intranasal (IN) administration of neuropeptides, such as insulin and orexins, has been suggested as a treatment strategy for age-related cognitive decline (ARCD). Because dysfunctional neuropeptide signaling is an observed characteristic of ARCD, it has been suggested that IN delivery of insulin and/or orexins may restore endogenous peptide signaling and thereby preserve cognition. IN administration is particularly alluring as it is a relatively non-invasive method that directly targets peptides to the brain. Several laboratories have examined the behavioral effects of IN insulin in young, aged, and cognitively impaired rodents and humans. These studies demonstrated improved performance on various cognitive tasks following IN insulin administration. Fewer laboratories have assessed the effects of IN orexins; however, this peptide also holds promise as an effective treatment for ARCD through the activation of the cholinergic system and/or the reduction of neuroinflammation. Here, we provide a brief overview of the advantages of IN administration and the delivery pathway, then summarize the current literature on IN insulin and orexins. Additional preclinical studies will be useful to ultimately uncover the mechanisms underlying the pro-cognitive effects of IN insulin and orexins, whereas future clinical studies will aid in the determination of the most efficacious dose and dosing paradigm. Eventually, IN insulin and/or orexin administration may be a widely used treatment strategy in the clinic for ARCD.
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Affiliation(s)
- Jennifer M Erichsen
- University of South Carolina School of Medicine, Department of Pharmacology, Physiology, and Neuroscience, Columbia, SC 29208, United States.
| | - Coleman B Calva
- University of South Carolina School of Medicine, Department of Pharmacology, Physiology, and Neuroscience, Columbia, SC 29208, United States
| | - Lawrence P Reagan
- University of South Carolina School of Medicine, Department of Pharmacology, Physiology, and Neuroscience, Columbia, SC 29208, United States; Columbia VA Health Care System, Columbia, SC, 29208, United States
| | - Jim R Fadel
- University of South Carolina School of Medicine, Department of Pharmacology, Physiology, and Neuroscience, Columbia, SC 29208, United States
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8
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Durairaja A, Fendt M. Orexin deficiency modulates cognitive flexibility in a sex-dependent manner. GENES BRAIN AND BEHAVIOR 2020; 20:e12707. [PMID: 33070452 DOI: 10.1111/gbb.12707] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 10/01/2020] [Accepted: 10/14/2020] [Indexed: 12/18/2022]
Abstract
Cognitive flexibility is an important executive function and refers to the ability to adapt behaviors in response to changes in the environment. Of note, many brain disorders are associated with impairments in cognitive flexibility. Several classical neurotransmitter systems including dopamine, acetylcholine and noradrenaline are shown to be important for cognitive flexibility, however, there is not much known about the role of neuropeptides. The neuropeptide orexin, which is brain-widely released by neurons in the lateral hypothalamus, is a major player in maintaining sleep/wake cycle, feeding behavior, arousal, and motivational behavior. Recent studies showed a role of orexin in attention, cognition and stress-induced attenuation of cognitive flexibility by disrupting orexin signaling locally or systemically. However, it is not known so far whether brain-wide reduction or loss of orexin affects cognitive flexibility. We investigated this question by testing male and female orexin-deficient mice in the attentional set shifting task (ASST), an established paradigm of cognitive flexibility. We found that orexin deficiency impaired the intra-dimensional shift phase of the ASST selectively in female homozygous orexin-deficient mice and improved the first reversal learning phase selectively in male homozygous orexin-deficient mice. We also found that these orexin-mediated sex-based modulations of cognitive flexibility were not correlated with trait anxiety, narcoleptic episodes, and reward consumption. Our findings highlight a sexually dimorphic role of orexin in regulating cognitive flexibility and the need for further investigations of sex-specific functions of the orexin circuitry.
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Affiliation(s)
- Archana Durairaja
- Institute for Pharmacology and Toxicology, Otto-von-Guericke University, Magdeburg, Germany
| | - Markus Fendt
- Institute for Pharmacology and Toxicology, Otto-von-Guericke University, Magdeburg, Germany.,Center of Behavioral Brain Sciences, Otto-von-Guericke University, Magdeburg, Germany
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9
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Um YH, Lim HK. Orexin and Alzheimer's Disease: A New Perspective. Psychiatry Investig 2020; 17:621-626. [PMID: 32517419 PMCID: PMC7385219 DOI: 10.30773/pi.2020.0136] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 05/12/2020] [Indexed: 12/13/2022] Open
Abstract
Orexin's role in human cognition has recently been emphasized and emerging evidences indicate its close relationship with Alzheimer's disease (AD). This review aimed to demonstrate recent research on the relationship between orexin and AD. Orexin's role in stress regulation and memory is discussed, with significant findings related to sexual disparities in stress response, with potential clinical implications pertaining to AD pathology. There are controversies regarding the orexin levels in AD patients, but the role of orexin in the trajectory of AD is still emphasized in recent literatures. Orexin is also accentuated in the context of tau pathology, and orexin as a potential therapeutic target for AD is frequently discussed. Future directions with regard to the relationship between orexin and AD are suggested: 1) consideration for AD trajectory in the measurement of orexin levels, 2) the need for objective measure such as polysomnography and actigraphy, 3) the need for close observation of cognitive profiles of orexin-deficient narcolepsy patients, 4) the need for validation studies by neuroimaging 5) the need for taking account sexual disparities in orexinergic activiation, and 6) consideration for orexin's role as a stress regulator. The aforementioned new perspectives could help unravel the relationship between orexin and AD.
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Affiliation(s)
- Yoo Hyun Um
- Department of Psychiatry, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea
| | - Hyun Kook Lim
- Department of Psychiatry, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea
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10
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Al-Kuraishy HM, Abdulhadi MH, Hussien NR, Al-Niemi MS, Rasheed HA, Al-Gareeb AI. Involvement of orexinergic system in psychiatric and neurodegenerative disorders: A scoping review. Brain Circ 2020; 6:70-80. [PMID: 33033776 PMCID: PMC7511915 DOI: 10.4103/bc.bc_42_19] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Revised: 02/20/2020] [Accepted: 03/20/2020] [Indexed: 12/12/2022] Open
Abstract
Orexin is a neuropeptide secreted from lateral hypothalamus and pre-frontal cortex concerned in the wakefulness and excitement. This study aimed to review the possible neurobiological effect of orexin. A diversity of search strategies was adopted and assumed which included electronic database searches of Medline and PubMed using MeSH terms, keywords, and title words during the search. Orexin plays a vital role in activation of learning, memory acquisition, and consolidation through activation of monoaminergic system, which affect cognitive flexibility and cognitive function. Orexin stimulates adrenocorticotropin and corticosteroid secretions via activation of central corticotropin-releasing hormone. Cerebrospinal fluid (CSF) and serum orexin serum levels are reduced in depression, schizophrenia, and narcolepsy. However, high orexin serum levels are revealed in drug addictions. Regarding neurodegenerative brain diseases, CSF and serum orexin serum levels are reduced Parkinson disease, Alzheimer dementia, Huntington's disease, amyotrphic lateral sclerosis, and multiple sclerosis. Orexin antagonist leads to significant reduction of sympathetic over-activity during withdrawal syndrome. As well, orexin antagonist improves sleep pattern. Orexinergic system is involved in the different psychiatric and neurological disorders; therefore, targeting of this system could be possible novel pathway in the management of these disorders. In addition, measurement of CSF and serum orexin levels might predict the relapse and withdrawal of addict patients.
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Affiliation(s)
- Hayder M Al-Kuraishy
- Department of Pharmacology, Toxicology and Medicine, College of Medicine Almustansiriya University, Baghdad, Iraq
| | - May H Abdulhadi
- Department of Pharmacology, Toxicology and Medicine, College of Medicine Almustansiriya University, Baghdad, Iraq
| | - Nawar R Hussien
- Department of Pharmacology, Toxicology and Medicine, College of Medicine Almustansiriya University, Baghdad, Iraq
| | - Marwa S Al-Niemi
- Department of Pharmacology, Toxicology and Medicine, College of Medicine Almustansiriya University, Baghdad, Iraq
| | - Huda A Rasheed
- Department of Pharmacology, Toxicology and Medicine, College of Medicine Almustansiriya University, Baghdad, Iraq
| | - Ali I Al-Gareeb
- Department of Pharmacology, Toxicology and Medicine, College of Medicine Almustansiriya University, Baghdad, Iraq
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11
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Orexin-1 receptor blockade differentially affects spatial and visual discrimination memory facilitation by intracranial self-stimulation. Neurobiol Learn Mem 2020; 169:107188. [PMID: 32061874 DOI: 10.1016/j.nlm.2020.107188] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Revised: 02/06/2020] [Accepted: 02/11/2020] [Indexed: 01/07/2023]
Abstract
Intracranial self-stimulation (ICSS) of the medial forebrain bundle is an effective treatment to facilitate memory. Performance in both explicit and implicit memory tasks has been improved by ICSS, and this treatment has even been capable of recovering loss of memory function due to lesions or old age. Several neurochemical systems have been studied in regard to their role in ICSS effects on memory, however the possible involvement of the orexinergic system in this facilitation has yet to be explored. The present study aims to examine the relationship between the OX1R and the facilitative effects of ICSS on two different types of memory tasks, both carried out in the Morris Water Maze: spatial and visual discrimination. Results show that the OX1R blockade, by intraventricular administration of SB-334867, partially negates the facilitating effect of ICSS on spatial memory, whereas it hinders ICSS facilitation of the discrimination task. However, ICSS treatment was capable of compensating for the severe detrimental effects of OX1R blockade on both memory paradigms. These results suggest different levels of involvement of the orexinergic system in the facilitation of memory by ICSS, depending on the memory task.
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12
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Li SB, de Lecea L. The hypocretin (orexin) system: from a neural circuitry perspective. Neuropharmacology 2020; 167:107993. [PMID: 32135427 DOI: 10.1016/j.neuropharm.2020.107993] [Citation(s) in RCA: 65] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 01/23/2020] [Accepted: 02/05/2020] [Indexed: 12/11/2022]
Abstract
Hypocretin/orexin neurons are distributed restrictively in the hypothalamus, a brain region known to orchestrate diverse functions including sleep, reward processing, food intake, thermogenesis, and mood. Since the hypocretins/orexins were discovered more than two decades ago, extensive studies have accumulated concrete evidence showing the pivotal role of hypocretin/orexin in diverse neural modulation. New method of viral-mediated tracing system offers the possibility to map the monosynaptic inputs and detailed anatomical connectivity of Hcrt neurons. With the development of powerful research techniques including optogenetics, fiber-photometry, cell-type/pathway specific manipulation and neuronal activity monitoring, as well as single-cell RNA sequencing, the details of how hypocretinergic system execute functional modulation of various behaviors are coming to light. In this review, we focus on the function of neural pathways from hypocretin neurons to target brain regions. Anatomical and functional inputs to hypocretin neurons are also discussed. We further briefly summarize the development of pharmaceutical compounds targeting hypocretin signaling. This article is part of the special issue on Neuropeptides.
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Affiliation(s)
- Shi-Bin Li
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, 1201 Welch Road, Stanford, CA, 94305, USA.
| | - Luis de Lecea
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, 1201 Welch Road, Stanford, CA, 94305, USA.
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13
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Steward T, Mestre-Bach G, Granero R, Sánchez I, Riesco N, Vintró-Alcaraz C, Sauchelli S, Jiménez-Murcia S, Agüera Z, Fernández-García JC, Garrido-Sánchez L, Tinahones FJ, Casanueva FF, Baños RM, Botella C, Crujeiras AB, Torre RDL, Fernández-Real JM, Frühbeck G, Ortega FJ, Rodríguez A, Menchón JM, Fernández-Aranda F. Reduced Plasma Orexin-A Concentrations are Associated with Cognitive Deficits in Anorexia Nervosa. Sci Rep 2019; 9:7910. [PMID: 31133733 PMCID: PMC6536521 DOI: 10.1038/s41598-019-44450-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 05/07/2019] [Indexed: 01/06/2023] Open
Abstract
Orexins/hypocretins are neuropeptides implicated in numerous processes, including food intake and cognition. The role of these peptides in the psychopathology of anorexia nervosa (AN) remains poorly understood. The aim of the current study was to evaluate the associations between plasma orexin-A (OXA) concentrations and neuropsychological functioning in adult women with AN, and a matched control group. Fasting plasma OXA concentrations were taken in 51 females with AN and in 51 matched healthy controls. Set-shifting was assessed using the Wisconsin Card Sorting Test (WCST), whereas decision making was measured using the Iowa Gambling Task (IGT). The AN group exhibited lower plasma OXA levels than the HC group. Lower mean scores were obtained on the IGT in AN patients. WCST perseverative errors were significantly higher in the AN group compared to HC. In both the AN and HC group, OXA levels were negatively correlated with WCST non-perseverative errors. Reduced plasma OXA concentrations were found to be associated with set-shifting impairments in AN. Taking into consideration the function of orexins in promoting arousal and cognitive flexibility, future studies should explore whether orexin partly underpins the cognitive impairments found in AN.
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Affiliation(s)
- Trevor Steward
- Department of Psychiatry, Bellvitge University Hospital-IDIBELL, Barcelona, Spain.,Ciber Fisiopatologia Obesidad y Nutrición, Instituto Salud Carlos III (Spain), Madrid, Spain
| | - Gemma Mestre-Bach
- Department of Psychiatry, Bellvitge University Hospital-IDIBELL, Barcelona, Spain.,Ciber Fisiopatologia Obesidad y Nutrición, Instituto Salud Carlos III (Spain), Madrid, Spain
| | - Roser Granero
- Ciber Fisiopatologia Obesidad y Nutrición, Instituto Salud Carlos III (Spain), Madrid, Spain.,Departament de Psicobiologia i Metodologia, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Isabel Sánchez
- Department of Psychiatry, Bellvitge University Hospital-IDIBELL, Barcelona, Spain.,Ciber Fisiopatologia Obesidad y Nutrición, Instituto Salud Carlos III (Spain), Madrid, Spain
| | - Nadine Riesco
- Department of Psychiatry, Bellvitge University Hospital-IDIBELL, Barcelona, Spain.,Ciber Fisiopatologia Obesidad y Nutrición, Instituto Salud Carlos III (Spain), Madrid, Spain
| | - Cristina Vintró-Alcaraz
- Department of Psychiatry, Bellvitge University Hospital-IDIBELL, Barcelona, Spain.,Ciber Fisiopatologia Obesidad y Nutrición, Instituto Salud Carlos III (Spain), Madrid, Spain
| | - Sarah Sauchelli
- Department of Psychiatry, Bellvitge University Hospital-IDIBELL, Barcelona, Spain
| | - Susana Jiménez-Murcia
- Department of Psychiatry, Bellvitge University Hospital-IDIBELL, Barcelona, Spain.,Ciber Fisiopatologia Obesidad y Nutrición, Instituto Salud Carlos III (Spain), Madrid, Spain.,Department of Clinical Sciences, School of Medicine, University of Barcelona, Barcelona, Spain
| | - Zaida Agüera
- Department of Psychiatry, Bellvitge University Hospital-IDIBELL, Barcelona, Spain.,Ciber Fisiopatologia Obesidad y Nutrición, Instituto Salud Carlos III (Spain), Madrid, Spain
| | - Jose C Fernández-García
- Ciber Fisiopatologia Obesidad y Nutrición, Instituto Salud Carlos III (Spain), Madrid, Spain.,Unidad de Gestión Clínica de Endocrinología y Nutrición, Instituto de Investigación Biomédica de Málaga (IBIMA), Universidad de Málaga, Hospital Clínico Virgen de la Victoria, Málaga, Spain
| | - Lourdes Garrido-Sánchez
- Ciber Fisiopatologia Obesidad y Nutrición, Instituto Salud Carlos III (Spain), Madrid, Spain.,Unidad de Gestión Clínica de Endocrinología y Nutrición, Instituto de Investigación Biomédica de Málaga (IBIMA), Universidad de Málaga, Hospital Clínico Virgen de la Victoria, Málaga, Spain
| | - Francisco J Tinahones
- Ciber Fisiopatologia Obesidad y Nutrición, Instituto Salud Carlos III (Spain), Madrid, Spain.,Unidad de Gestión Clínica de Endocrinología y Nutrición, Instituto de Investigación Biomédica de Málaga (IBIMA), Universidad de Málaga, Hospital Clínico Virgen de la Victoria, Málaga, Spain
| | - Felipe F Casanueva
- Ciber Fisiopatologia Obesidad y Nutrición, Instituto Salud Carlos III (Spain), Madrid, Spain.,Molecular and Celular Endocrinology, Instituto de Investigacion Sanitaria (IDIS), Complejo Hospitalario Universitario de Santiago (CHUS) and Santiago de Compostela University (USC), Santiago de Compostela, Spain
| | - Rosa M Baños
- Ciber Fisiopatologia Obesidad y Nutrición, Instituto Salud Carlos III (Spain), Madrid, Spain.,Department of Psychological, Personality, Evaluation and Treatment of the University of Valencia, Valencia, Spain
| | - Cristina Botella
- Ciber Fisiopatologia Obesidad y Nutrición, Instituto Salud Carlos III (Spain), Madrid, Spain
| | - Ana B Crujeiras
- Ciber Fisiopatologia Obesidad y Nutrición, Instituto Salud Carlos III (Spain), Madrid, Spain.,Molecular and Celular Endocrinology, Instituto de Investigacion Sanitaria (IDIS), Complejo Hospitalario Universitario de Santiago (CHUS) and Santiago de Compostela University (USC), Santiago de Compostela, Spain
| | - Rafael de la Torre
- Ciber Fisiopatologia Obesidad y Nutrición, Instituto Salud Carlos III (Spain), Madrid, Spain.,Integrated Pharmacology and Systems Neurosciences Research Group, Neuroscience Research Program Organization IMIM (Hospital del Mar Medical Research Institute), Barcelona, Spain.,Department of Health and Experimental Sciences, Universitat Pompeu Fabra Barcelona, Barcelona, Spain
| | - Jose M Fernández-Real
- Ciber Fisiopatologia Obesidad y Nutrición, Instituto Salud Carlos III (Spain), Madrid, Spain.,Department of Diabetes, Endocrinology and Nutrition, Institut d'Investigació, Biomèdica de Girona (IdIBGi), Hospital Dr Josep Trueta, Girona, Spain
| | - Gema Frühbeck
- Ciber Fisiopatologia Obesidad y Nutrición, Instituto Salud Carlos III (Spain), Madrid, Spain.,Metabolic Research Laboratory, Clínica Universidad de Navarra, University of Navarra-IdiSNA, Pamplona, Spain
| | - Francisco J Ortega
- Ciber Fisiopatologia Obesidad y Nutrición, Instituto Salud Carlos III (Spain), Madrid, Spain.,Department of Diabetes, Endocrinology and Nutrition, Institut d'Investigació, Biomèdica de Girona (IdIBGi), Hospital Dr Josep Trueta, Girona, Spain
| | - Amaia Rodríguez
- Ciber Fisiopatologia Obesidad y Nutrición, Instituto Salud Carlos III (Spain), Madrid, Spain.,Metabolic Research Laboratory, Clínica Universidad de Navarra, University of Navarra-IdiSNA, Pamplona, Spain
| | - José M Menchón
- Department of Psychiatry, Bellvitge University Hospital-IDIBELL, Barcelona, Spain.,Department of Clinical Sciences, School of Medicine, University of Barcelona, Barcelona, Spain.,CIBER Salud Mental, Instituto Salud Carlos III (Spain), Madrid, Spain
| | - Fernando Fernández-Aranda
- Department of Psychiatry, Bellvitge University Hospital-IDIBELL, Barcelona, Spain. .,Ciber Fisiopatologia Obesidad y Nutrición, Instituto Salud Carlos III (Spain), Madrid, Spain. .,Department of Clinical Sciences, School of Medicine, University of Barcelona, Barcelona, Spain.
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14
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García-Brito S, Aldavert-Vera L, Huguet G, Álvarez A, Kádár E, Segura-Torres P. Increased training compensates for OX1R blockage-impairment of spatial memory and c-Fos expression in different cortical and subcortical areas. Behav Brain Res 2018; 353:21-31. [PMID: 29953904 DOI: 10.1016/j.bbr.2018.05.028] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Revised: 05/21/2018] [Accepted: 05/26/2018] [Indexed: 11/29/2022]
Abstract
It has been suggested that the orexin system modulates learning and memory-related processes. However, the possible influence that training could have on the effect of the blockade of orexin-A selective receptor (OX1R) on a spatial memory task has not been explored. Therefore, the present study attempts to compare the effects of OX1R antagonist SB-334867 infusion on spatial memory in two different conditions in the Morris Water Maze (MWM). This experiment evaluated the animals' performance in weak training (2 trials per session) vs strong training (6 trials per session) protocols in a spatial version of the MWM. We found that in the 2-trial condition the post-training SB-334867 infusion had a negative effect on consolidation as well as on the retention and reversal learning of the task 72 h later. This effect was not apparent in the 6-trial condition. In addition, while the strong training groups showed a general increase in c-Fos expression in several brain areas of the hippocampal-thalamic-cortical circuit, SB-334867 administration had the opposite effect in areas that have been previously reported to have a high density of OX1R. Specifically, the SB-infused group in the 2-trial condition showed a decrease in c-Fos immunoreactivity in the dentate gyrus, granular retrosplenial and prelimbic cortices, and centrolateral thalamic nucleus. This was not observed for subjects in the 6-trial condition. The activation of these areas could constitute a neuroanatomical substrate involved in the compensatory mechanisms of training upon SB-334867 impairing effects on a MWM spatial task.
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Affiliation(s)
- Soleil García-Brito
- Universitat Autónoma de Barcelona, Departament de Psicobiologia i de Metodologia de les Ciències de la Salut, Institut de Neurociències, 08193 Bellaterra, Barcelona, Spain.
| | - Laura Aldavert-Vera
- Universitat Autónoma de Barcelona, Departament de Psicobiologia i de Metodologia de les Ciències de la Salut, Institut de Neurociències, 08193 Bellaterra, Barcelona, Spain
| | - Gemma Huguet
- Universitat de Girona, Departament de Biologia, 17071 Girona, Spain
| | - Adam Álvarez
- Universitat Autónoma de Barcelona, Departament de Psicobiologia i de Metodologia de les Ciències de la Salut, Institut de Neurociències, 08193 Bellaterra, Barcelona, Spain
| | - Elisabet Kádár
- Universitat de Girona, Departament de Biologia, 17071 Girona, Spain
| | - Pilar Segura-Torres
- Universitat Autónoma de Barcelona, Departament de Psicobiologia i de Metodologia de les Ciències de la Salut, Institut de Neurociències, 08193 Bellaterra, Barcelona, Spain
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15
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Sargin D. The role of the orexin system in stress response. Neuropharmacology 2018; 154:68-78. [PMID: 30266600 DOI: 10.1016/j.neuropharm.2018.09.034] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Revised: 09/18/2018] [Accepted: 09/21/2018] [Indexed: 11/30/2022]
Abstract
Orexins are neuropeptides that are exclusively produced by hypothalamic neurons, which project throughout the entire brain. Orexin, also known as hypocretins, were initially identified to play a fundamental role in food intake, arousal and the regulation of sleep and wakefulness. Recent studies identified orexins to be critical for diverse physiological processes including motivation, reward, attention, emotional regulation, stress and anxiety. Here, I review recent findings that indicate orexin has an important role in acute and chronic stress. I also summarize the recent optogenetic and chemogenetic studies that have advanced our understanding of the orexin system. I will conclude by discussing clinical studies that implicate orexins in mental health disorders. This article is part of the Special Issue entitled 'Hypothalamic Control of Homeostasis'.
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Affiliation(s)
- Derya Sargin
- Hotchkiss Brain Institute and the Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1, Canada.
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16
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Barson JR. Orexin/hypocretin and dysregulated eating: Promotion of foraging behavior. Brain Res 2018; 1731:145915. [PMID: 30125533 DOI: 10.1016/j.brainres.2018.08.018] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Revised: 07/31/2018] [Accepted: 08/15/2018] [Indexed: 12/14/2022]
Abstract
At its discovery, orexin/hypocretin (OX) was hypothesized to promote food intake. Subsequently, with the identification of the participation of OX in numerous other phenomena, including arousal and drug seeking, this neuropeptide was proposed to be involved in highly motivated behaviors. The present review develops the hypothesis that the primary evolutionary function of OX is to promote foraging behavior, seeking for food under conditions of limited availability. Thus, it will first describe published literature on OX and homeostatic food intake, which shows that OX neurons are activated by conditions of food deprivation and in turn stimulate food intake. Next, it will present literature on excessive and binge-like food intake, which demonstrates that OX stimulates both intake and willingness to work for palatable food. Importantly, studies show that binge-like eating can be inhibited by OX antagonists at doses far lower than those required to suppress homeostatic intake (3 mg/kg vs. 30 mg/kg), suggesting that an OX-based pharmacotherapy, at the right dose, could specifically control dysregulated eating. Finally, the review will discuss the role of OX in foraging behavior, citing literature which shows that OX neurons, which are activated during the anticipation of food reward, can promote a number of phenomena involved in successful foraging, including food-anticipatory locomotor behavior, olfactory sensitivity, visual attention, spatial memory, and mastication. Thus, OX may promote homeostatic eating, as well as binge eating of palatable food, due to its ability to stimulate and coordinate the activities involved in foraging behavior.
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Affiliation(s)
- Jessica R Barson
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, USA.
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17
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Abstract
Purpose of Review The aim of this review was to summarize collected data on the role of orexin and orexin neurons in the control of sleep and blood pressure. Recent Findings Although orexins (hypocretins) have been known for only 20 years, an impressive amount of data is now available regarding their physiological role. Hypothalamic orexin neurons are responsible for the control of food intake and energy expenditure, motivation, circadian rhythm of sleep and wake, memory, cognitive functions, and the cardiovascular system. Multiple studies show that orexinergic stimulation results in increased blood pressure and heart rate and that this effect may be efficiently attenuated by orexinergic antagonism. Increased activity of orexinergic neurons is also observed in animal models of hypertension. Summary Pharmacological intervention in the orexinergic system is now one of the therapeutic possibilities in insomnia. Although the role of orexin in the control of blood pressure is well described, we are still lacking clinical evidence that this is a possibility for a new approach in the treatment of cardiovascular diseases.
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Affiliation(s)
- Mariusz Sieminski
- Department of Emergency Medicine, Medical University of Gdansk, Smoluchowskiego 17, 80-235, Gdansk, Poland.
| | - Jacek Szypenbejl
- Department of Emergency Medicine, Medical University of Gdansk, Smoluchowskiego 17, 80-235, Gdansk, Poland
| | - Eemil Partinen
- Department of Neurology, University of Helsinki, Helsinki, Finland
- Vitalmed Helsinki Sleep Clinic, Helsinki, Finland
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18
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Moorman DE. The hypocretin/orexin system as a target for excessive motivation in alcohol use disorders. Psychopharmacology (Berl) 2018; 235:1663-1680. [PMID: 29508004 PMCID: PMC5949267 DOI: 10.1007/s00213-018-4871-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 02/20/2018] [Indexed: 12/17/2022]
Abstract
The hypocretin/orexin (ORX) system has been repeatedly demonstrated to regulate motivation for drugs of abuse, including alcohol. In particular, ORX seems to be critically involved in highly motivated behaviors, as is observed in high-seeking individuals in a population, in the seeking of highly palatable substances, and in models of dependence. It seems logical that this system could be considered as a potential target for treatment for addiction, particularly alcohol addiction, as ORX pharmacological manipulations significantly reduce drinking. However, the ORX system also plays a role in a wide range of other behaviors, emotions, and physiological functions and is disrupted in a number of non-dependence-associated disorders. It is therefore important to consider how the ORX system might be optimally targeted for potential treatment for alcohol use disorders either in combination with or separate from its role in other functions or diseases. This review will focus on the role of ORX in alcohol-associated behaviors and whether and how this system could be targeted to treat alcohol use disorders while avoiding impacts on other ORX-relevant functions. A brief overview of the ORX system will be followed by a discussion of some of the factors that makes it particularly intriguing as a target for alcohol addiction treatment, a consideration of some potential challenges associated with targeting this system and, finally, some future directions to optimize new treatments.
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Affiliation(s)
- David E Moorman
- Department of Psychological and Brain Sciences, Neuroscience and Behavior Graduate Program, University of Massachusetts Amherst, 528 Tobin Hall, 135 Hicks Way, Amherst, MA, 01003, USA.
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19
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Zajo KN, Fadel JR, Burk JA. Orexin A-induced enhancement of attentional processing in rats: role of basal forebrain neurons. Psychopharmacology (Berl) 2016; 233:639-47. [PMID: 26534765 PMCID: PMC4729649 DOI: 10.1007/s00213-015-4139-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 10/26/2015] [Indexed: 12/28/2022]
Abstract
RATIONALE Orexins are neuropeptides released in multiple brain regions from neurons that originate within the lateral hypothalamus and contiguous perfornical area. The basal forebrain, a structure implicated in attentional processing, receives orexinergic inputs. Our previous work demonstrated that administration of an orexin-1 receptor antagonist, SB-334867, systemically or via infusion directly into the basal forebrain, can disrupt performance in a task that places explicit demands on attentional processing. OBJECTIVES Given that the orexin-1 receptor binds orexin A with high affinity, we tested whether orexin A could enhance attention in rats. METHODS Attentional performance was assessed using a task that required discrimination of variable duration visual signals from trials when no signal was presented. We also tested whether infusions of orexin A into the lateral ventricle could attenuate deficits following lesions of medial prefrontal cortical cholinergic projections that arise from the basal forebrain. RESULTS Infusions of orexin A into the basal forebrain attenuated distracter-induced decreases in attentional performance. Orexin A attenuated deficits in lesioned animals when a visual distracter was presented. CONCLUSION The present results support the view that orexin A can enhance attentional performance via actions in the basal forebrain and may be beneficial for some conditions characterized by attentional dysfunction due to disruption of cortical cholinergic inputs.
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Affiliation(s)
- Kristin N. Zajo
- Department of Psychology, College of William & Mary, Williamsburg, Virginia 23187, USA
| | - Jim R. Fadel
- Department of Pharmacology, Physiology and Neuroscience, University of South Carolina School of Medicine, Columbia, South Carolina 29208, USA
| | - Joshua A. Burk
- Department of Psychology, College of William & Mary, Williamsburg, Virginia 23187, USA
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20
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Abstract
The hypocretins (Hcrts), also known as orexins, have been among the most intensely studied neuropeptide systems since their discovery about two decades ago. Anatomical evidence shows that the hypothalamic neurons that produce hypocretins/orexins project widely throughout the entire brain, innervating the noradrenergic locus coeruleus, the cholinergic basal forebrain, the dopaminergic ventral tegmental area, the serotonergic raphe nuclei, the histaminergic tuberomammillary nucleus, and many other brain regions. By interacting with other neural systems, the Hcrt system profoundly modulates versatile physiological processes including arousal, food intake, emotion, attention, and reward. Importantly, interruption of the interactions between these systems has the potential to cause neurological and psychiatric diseases. Here, we review the modulation of diverse neural systems by Hcrts and summarize potential therapeutic strategies based on our understanding of the Hcrt system's role in physiology and pathophysiological processes.
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