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Kniazkina M, Dyachuk V. Does EGFR Signaling Mediate Orexin System Activity in Sleep Initiation? Int J Mol Sci 2023; 24:ijms24119505. [PMID: 37298454 DOI: 10.3390/ijms24119505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 05/21/2023] [Accepted: 05/26/2023] [Indexed: 06/12/2023] Open
Abstract
Sleep-wake cycle disorders are an important symptom of many neurological diseases, including Parkinson's disease, Alzheimer's disease, and multiple sclerosis. Circadian rhythms and sleep-wake cycles play a key role in maintaining the health of organisms. To date, these processes are still poorly understood and, therefore, need more detailed elucidation. The sleep process has been extensively studied in vertebrates, such as mammals and, to a lesser extent, in invertebrates. A complex, multi-step interaction of homeostatic processes and neurotransmitters provides the sleep-wake cycle. Many other regulatory molecules are also involved in the cycle regulation, but their functions remain largely unclear. One of these signaling systems is epidermal growth factor receptor (EGFR), which regulates the activity of neurons in the modulation of the sleep-wake cycle in vertebrates. We have evaluated the possible role of the EGFR signaling pathway in the molecular regulation of sleep. Understanding the molecular mechanisms that underlie sleep-wake regulation will provide critical insight into the fundamental regulatory functions of the brain. New findings of sleep-regulatory pathways may provide new drug targets and approaches for the treatment of sleep-related diseases.
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Affiliation(s)
- Marina Kniazkina
- A.V. Zhirmunsky National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok 690041, Russia
| | - Vyacheslav Dyachuk
- A.V. Zhirmunsky National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok 690041, Russia
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2
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Azeez IA, Igado OO, Olopade JO. An overview of the orexinergic system in different animal species. Metab Brain Dis 2021; 36:1419-1444. [PMID: 34224065 DOI: 10.1007/s11011-021-00761-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Accepted: 06/06/2021] [Indexed: 01/13/2023]
Abstract
Orexin (hypocretin), is a neuropeptide produced by a subset of neurons in the lateral hypothalamus. From the lateral hypothalamus, the orexin-containing neurons project their fibres extensively to other brain structures, and the spinal cord constituting the central orexinergic system. Generally, the term ''orexinergic system'' usually refers to the orexin peptides and their receptors, as well as to the orexin neurons and their projections to different parts of the central nervous system. The extensive networks of orexin axonal fibres and their terminals allow these neuropeptidergic neurons to exert great influence on their target regions. The hypothalamic neurons containing the orexin neuropeptides have been implicated in diverse functions, especially related to the control of a variety of homeostatic functions including feeding behaviour, arousal, wakefulness stability and energy expenditure. The broad range of functions regulated by the orexinergic system has led to its description as ''physiological integrator''. In the last two decades, the orexinergic system has been a topic of great interest to the scientific community with many reports in the public domain. From the documentations, variations exist in the neuroanatomical profile of the orexinergic neuron soma, fibres and their receptors from animal to animal. Hence, this review highlights the distinct variabilities in the morphophysiological aspects of the orexinergic system in the vertebrate animals, mammals and non-mammals, its presence in other brain-related structures, including its involvement in ageing and neurodegenerative diseases. The presence of the neuropeptide in the cerebrospinal fluid and peripheral tissues, as well as its alteration in different animal models and conditions are also reviewed.
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Affiliation(s)
- Idris A Azeez
- Department of Veterinary Anatomy, University of Jos, Jos, Nigeria
| | - Olumayowa O Igado
- Department of Veterinary Anatomy, University of Ibadan, Ibadan, Nigeria
| | - James O Olopade
- Department of Veterinary Anatomy, University of Ibadan, Ibadan, Nigeria.
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Suzuki H, Yamamoto T. Orexin-B-like immunoreactivity in pituitary αMSH-producing cells and median eminence GnRH-containing fibres of the flat-tailed house gecko. Anat Histol Embryol 2019; 48:415-420. [PMID: 31241795 DOI: 10.1111/ahe.12461] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Revised: 04/12/2019] [Accepted: 06/02/2019] [Indexed: 11/28/2022]
Abstract
We examined the distribution of the orexin-like peptides in the pituitary and median eminence of the flat-tailed house gecko (Hemidactylus platyurus) using immunohistochemistry. Orexin-B-like, but not orexin-A-like, immunoreactivity was detected in the pituitary, specifically in the pars intermedia, and these cells corresponded to alpha-melanocyte-stimulating hormone (αMSH)-producing cells. Orexin-B and αMSH secreted from pars intermedia may modulate secretion of adenohypophyseal cells in the pars distalis. In the median eminence, orexin-B-immunoreactive puncta and fibres were observed, and these structures corresponded to gonadotropin-releasing hormone (GnRH)-immunoreactive puncta and fibres. Orexin-B secreted from GnRH-containing neurons in the hypothalamus may affect thyrotropin-releasing hormone-containing neurons resulting in modulation of αMSH secretion of melanotrophs in the pars intermedia.
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Affiliation(s)
- Hirohumi Suzuki
- Department of Biology, University of Teacher Education Fukuoka, Munakata, Japan.,Brain Functions and Neuroscience Unit, Department of Oral Science, Graduate School of Dentistry, Kanagawa Dental University, Yokosuka, Japan
| | - Toshiharu Yamamoto
- Brain Functions and Neuroscience Unit, Department of Oral Science, Graduate School of Dentistry, Kanagawa Dental University, Yokosuka, Japan
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Wang P, Wang M, Zhang L, Zhong S, Jiang W, Wang Z, Sun C, Zhang S, Liu Z. Functional characterization of an orexin neuropeptide in amphioxus reveals an ancient origin of orexin/orexin receptor system in chordate. SCIENCE CHINA-LIFE SCIENCES 2019; 62:1655-1669. [PMID: 30945108 DOI: 10.1007/s11427-018-9421-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2018] [Accepted: 10/10/2018] [Indexed: 01/09/2023]
Abstract
Amphioxus belongs to the subphylum cephalochordata, an extant representative of the most basal chordates, whose regulation of endocrine system remains ambiguous. Here we clearly demonstrated the existence of a functional orexin neuropeptide in amphioxus, which is able to interact with orexin receptor, activate both PKC and PKA pathways, decrease leptin expression, and stimulate lipogenesis. We also showed the transcription level of amphioxus orexin was affected by fasting or temperature, indicating a role of this gene in the regulation of energy balance. In addition, the expression of the amphioxus orexin was detected at cerebral vesicle, which has been proposed to be a homolog of the vertebrate brain. These data collectively suggest that a functional orexin neuropeptide has already emerged in amphioxus, which provide insights into the evolutionary origin of orexin in chordate and the functional homology between the cerebral vesicle and vertebrate brain.
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Affiliation(s)
- Peng Wang
- Institute of Evolution & Marine Biodiversity, College of Marine Life Science, Ocean University of China, Qingdao, 266003, China
| | - Meng Wang
- Institute of Evolution & Marine Biodiversity, College of Marine Life Science, Ocean University of China, Qingdao, 266003, China
| | - Liping Zhang
- Institute of Evolution & Marine Biodiversity, College of Marine Life Science, Ocean University of China, Qingdao, 266003, China
| | - Shenjie Zhong
- Institute of Evolution & Marine Biodiversity, College of Marine Life Science, Ocean University of China, Qingdao, 266003, China
| | - Wanyue Jiang
- Institute of Evolution & Marine Biodiversity, College of Marine Life Science, Ocean University of China, Qingdao, 266003, China
| | - Ziyue Wang
- Institute of Evolution & Marine Biodiversity, College of Marine Life Science, Ocean University of China, Qingdao, 266003, China
| | - Chen Sun
- Institute of Evolution & Marine Biodiversity, College of Marine Life Science, Ocean University of China, Qingdao, 266003, China
| | - Shicui Zhang
- Institute of Evolution & Marine Biodiversity, College of Marine Life Science, Ocean University of China, Qingdao, 266003, China.
| | - Zhenhui Liu
- Institute of Evolution & Marine Biodiversity, College of Marine Life Science, Ocean University of China, Qingdao, 266003, China.
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López JM, Sanz-Morello B, González A. Organization of the orexin/hypocretin system in the brain of two basal actinopterygian fishes, the cladistians Polypterus senegalus and Erpetoichthys calabaricus. Peptides 2014; 61:23-37. [PMID: 25169954 DOI: 10.1016/j.peptides.2014.08.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Revised: 08/19/2014] [Accepted: 08/19/2014] [Indexed: 01/12/2023]
Abstract
Cladistians are primitive actinopterygian fishes mostly neglected in neuroanatomical studies. In the present study, the detailed neuroanatomical distribution of orexin (hypocretin)-like immunoreactive (OX-ir) cell bodies and fibers was analyzed in the brain of two species representative of the two extant genera of cladistians. Antibodies against mammalian orexin-A and orexin-B peptides were used. Simultaneous detection of orexins with neuropeptide Y (NPY), tyrosine hydroxylase (TH), and serotonin (5-HT) was used to establish accurately the topography of the orexin system and to evaluate the possible interactions with NPY and monoaminergic systems. A largely common pattern of OX-ir distribution in the two cladistian species was observed. Most OX-ir cells were located in the suprachiasmatic nucleus and tuberal hypothalamus, whereas scarce cells were observed in the posterior tubercle. In addition, a population of OX-ir cells was found in the preoptic area only in Polypterus and some cells also contained TH. The observed widespread distribution of OX-ir fibers was especially abundant in the retrobulbar area, subpallial areas, preoptic area, suprachiasmatic nucleus, tuberal hypothalamic area, prethalamus, thalamus, pretectum, optic tectum, and tegmentum. Low innervation was found in relation to monoaminergic cell groups, whereas a high NPY innervation was observed in all OX-ir cell groups. These relationships would represent the anatomical substrate for the functional interdependence between these systems. The organization of the orexin system in cladistians revealed a pattern largely consistent with those reported for all studied groups of vertebrates, suggesting that the primitive organization of this peptidergic system occurred in the common ancestor of gnathostome vertebrates.
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Affiliation(s)
- Jesús M López
- Department of Cell Biology, Faculty of Biology, University Complutense, 28040 Madrid, Spain
| | - Berta Sanz-Morello
- Department of Cell Biology, Faculty of Biology, University Complutense, 28040 Madrid, Spain
| | - Agustín González
- Department of Cell Biology, Faculty of Biology, University Complutense, 28040 Madrid, Spain.
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Pérez Sirkin DI, Suzuki H, Cánepa MM, Vissio PG. Orexin and neuropeptide Y: tissue specific expression and immunoreactivity in the hypothalamus and preoptic area of the cichlid fish Cichlasoma dimerus. Tissue Cell 2013; 45:452-9. [PMID: 24138942 DOI: 10.1016/j.tice.2013.09.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Revised: 09/09/2013] [Accepted: 09/10/2013] [Indexed: 01/28/2023]
Abstract
Neuropeptide Y (NPY) and orexin are neuropeptides involved in the regulation of feeding in vertebrates. In this study we determined the NPY and orexin mRNA tissue expression and their immunoreactivity distribution in both preoptic area and hypothalamus, regions involved in the regulation of feeding behavior. Both peptides presented a wide expression in all tissues examined. The NPY-immunoreactive (ir) cells were localized in the ventral nucleus posterioris periventricularis (NPPv) and numerous ir-NPY fibers were found in the nucleus lateralis tuberis (NLT), the nucleus recess lateralis (NRL) and the neurohypophysis. Ir-orexin cells were observed in the NPPv, dorsal NLT, ventral NLT, lateral NLT (NLTl) and the lateral NRL. Ir-orexin fibers were widespread distributed along all the hypothalamus, especially in the NLTl. Additionally, we observed the presence of ir-orexin immunostaining in adenohypophyseal cells, especially in somatotroph cells and the presence of a few ir-orexin-A fibers in the neurohypophysis. In conclusion, both peptides have an ubiquitous mRNA tissue expression and are similarly distributed in the hypothalamus and preoptic area of Cichlasoma dimerus. The presence of ir-orexin in adenohypohyseal cells and the presence of ir-orexin and NPY fibers in the neurohypophysis suggest that both peptides may play an important neuroendocrine role in anterior pituitary.
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Affiliation(s)
- D I Pérez Sirkin
- Laboratorio de Neuroendocrinología del Crecimiento y la Reproducción, Dpto. de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, C1428EHA Buenos Aires, Argentina; IBBEA, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina
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Suzuki H, Yamamoto T. Orexin-B-like immunoreactivity localizes in both luteinizing-hormone-containing cells and melanin-concentrating hormone-containing fibers in the red-bellied piranha (Pygocentrus nattereri) pituitary. Cell Tissue Res 2012; 351:175-82. [PMID: 23161098 DOI: 10.1007/s00441-012-1516-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Accepted: 10/08/2012] [Indexed: 11/24/2022]
Abstract
We examined orexin-like immunoreactivity in the pituitary of the red-bellied piranha (Pygocentrus nattereri). Orexin-B-immunoreactive (IR) cells corresponded to luteinizing hormone (LH)-containing cells in the pars distalis, and orexin-B-IR fibers corresponded to melanin-concentrating hormone (MCH)-containing fibers in the pars nervosa. In the pars distalis, orexin-B-IR puncta that were also immunoreactive for MCH were observed around the orexin-B-IR cells. In the ventral hypothalamus, orexin-B-IR and MCH-IR neurons were found in the nucleus lateralis tuberis. Immunoelectron-microscopic analysis revealed that the orexin-B-like substance co-localized with LH in secretory granules and with MCH in MCH-containing neurons. Some of the MCH secreted in the pituitary might participate in the modulation of LH secretion from the gonadotrophs, together with orexin-B, leading to food intake by the stimulation of growth hormone secretion from the somatotrophs.
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Affiliation(s)
- Hirohumi Suzuki
- Department of Biology, Fukuoka University of Education, Akamabunkyo-machi, Munakata, Fukuoka, Japan.
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9
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Nixon JP, Kotz CM, Novak CM, Billington CJ, Teske JA. Neuropeptides controlling energy balance: orexins and neuromedins. Handb Exp Pharmacol 2012:77-109. [PMID: 22249811 DOI: 10.1007/978-3-642-24716-3_4] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
In this chapter, we review the feeding and energy expenditure effects of orexin (also known as hypocretin) and neuromedin. Orexins are multifunctional neuropeptides that affect energy balance by participating in regulation of appetite, arousal, and spontaneous physical activity. Central orexin signaling for all functions originates in the lateral hypothalamus-perifornical area and is likely functionally differentiated based on site of action and on interacting neural influences. The effect of orexin on feeding is likely related to arousal in some ways but is nonetheless a separate neural process that depends on interactions with other feeding-related neuropeptides. In a pattern distinct from other neuropeptides, orexin stimulates both feeding and energy expenditure. Orexin increases in energy expenditure are mainly by increasing spontaneous physical activity, and this energy expenditure effect is more potent than the effect on feeding. Global orexin manipulations, such as in transgenic models, produce energy balance changes consistent with a dominant energy expenditure effect of orexin. Neuromedins are gut-brain peptides that reduce appetite. There are gut sources of neuromedin, but likely the key appetite-related neuromedin-producing neurons are in the hypothalamus and parallel other key anorectic neuropeptide expression in the arcuate to paraventricular hypothalamic projection. As with other hypothalamic feeding-related peptides, hindbrain sites are likely also important sources and targets of neuromedin anorectic action. Neuromedin increases physical activity in addition to reducing appetite, thus producing a consistent negative energy balance effect. Together with the other various neuropeptides, neurotransmitters, neuromodulators, and neurohormones, neuromedin and orexin act in the appetite network to produce changes in food intake and energy expenditure, which ultimately influences the regulation of body weight.
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Affiliation(s)
- Joshua P Nixon
- Veterans Affairs Medical Center, Research Service (151), Minneapolis, MN, USA
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10
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López M, Tena-Sempere M, Diéguez C. Cross-talk between orexins (hypocretins) and the neuroendocrine axes (hypothalamic-pituitary axes). Front Neuroendocrinol 2010; 31:113-27. [PMID: 19654017 DOI: 10.1016/j.yfrne.2009.07.001] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2008] [Revised: 07/28/2009] [Accepted: 07/29/2009] [Indexed: 02/06/2023]
Abstract
Lesioning and electrical stimulation experiments carried out during the first half of the twentieth century showed that the lateral hypothalamic area (LHA) is involved in the neuroendocrine control of hormone secretion. However, the molecular basis of this phenomenon remained unclear until fifty years later when in 1998, two different laboratories discovered a new family of hypothalamic neuropeptides, the orexins or hypocretins (OX-A/Hcrt1 and OX-B/Hcrt2). Since then, remarkable evidence has revealed that orexins/hypocretins play a prominent role in regulating virtually all the neuroendocrine axes, acting as pivotal signals in the coordination of endocrine responses with regards to sleep, arousal and energy homeostasis. The clinical relevance of these actions is supported by human data showing impairment of virtually all the neuroendocrine axes in orexin/hypocretin-deficient narcoleptic patients. Here, we summarize more than ten years of knowledge about the orexins/hypocretins with particular focus on their role as neuroendocrine regulators. Understanding this aspect of orexin/hypocretin physiology could open new therapeutic possibilities in the treatment of sleep, energy homeostasis and endocrine pathologies.
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Affiliation(s)
- Miguel López
- Department of Physiology, School of Medicine, University of Santiago de Compostela - Instituto de Investigación Sanitaria, Santiago de Compostela 15782, Spain.
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Domínguez L, Morona R, Joven A, González A, López JM. Immunohistochemical localization of orexins (hypocretins) in the brain of reptiles and its relation to monoaminergic systems. J Chem Neuroanat 2010; 39:20-34. [DOI: 10.1016/j.jchemneu.2009.07.007] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2009] [Revised: 07/30/2009] [Accepted: 07/30/2009] [Indexed: 12/01/2022]
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López JM, Domínguez L, Moreno N, González A. Comparative immunohistochemical analysis of the distribution of orexins (hypocretins) in the brain of amphibians. Peptides 2009; 30:873-87. [PMID: 19428764 DOI: 10.1016/j.peptides.2009.01.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2008] [Revised: 01/20/2009] [Accepted: 01/21/2009] [Indexed: 10/21/2022]
Abstract
The orexins (hypocretins) are peptides found primarily in neurons of the hypothalamus of all vertebrates. Many differences were reported about the precise location of orexin containing cells and their projections throughout the brain in different species. However, there are few direct cross-species comparisons. Previous studies in anuran amphibians have also reported notable species differences. We examined and directly compared the distribution of orexinergic neurons and fibers within the brains of representatives of the three amphibian orders, anurans, urodeles and gymnophionans. Simultaneous detection of orexins and tyrosine hydroxylase was used to assess the precise location of the orexins in the brain and to evaluate the possible influence of the orexin system on the catecholaminergic cell groups. Although some differences were noted, a common pattern for the distribution of orexins in amphibians was observed. In all species, most immunoreactive neurons were observed in the suprachiasmatic nucleus, whereas the cells in the preoptic area and the tuberal region were more variable. Orexin immunoreactive fibers in the brain of all species included abundant fibers throughout the preoptic area and hypothalamus, whereas moderate amounts of fibers were present in the pallium, striatum, septum, thalamus, optic tectum, torus semicircularis, rhombencephalon and spinal cord. The use of double immunohistochemistry in amphibians revealed orexinergic innervation in dopaminergic and noradrenergic cell groups, such as the midbrain tegmentum, locus coeruleus and nucleus of the solitary tract, as was previously reported in mammals.
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Affiliation(s)
- Jesús M López
- Department of Cell Biology, Faculty of Biology, University Complutense, Madrid, Spain
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Facciolo RM, Crudo M, Giusi G, Alò R, Canonaco M. Light- and dark-dependent orexinergic neuronal signals promote neurodegenerative phenomena accounting for distinct behavioral responses in the teleostThalassoma pavo. J Neurosci Res 2009; 87:748-57. [DOI: 10.1002/jnr.21886] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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14
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Suzuki H, Matsumoto A, Yamamoto T. Orexin-B-like immunoreactivity localized in both luteinizing hormone- and thyroid-stimulating hormone-containing cells in the Nile tilapia (Oreochromis niloticus) pituitary. Tissue Cell 2009; 41:75-8. [DOI: 10.1016/j.tice.2008.06.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2008] [Revised: 06/03/2008] [Accepted: 06/17/2008] [Indexed: 10/21/2022]
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Suzuki H, Kubo Y, Yamamoto T. Orexin-A immunoreactive cells and fibers in the central nervous system of the axolotl brain and their association with tyrosine hydroxylase and serotonin immunoreactive somata. J Chem Neuroanat 2008; 35:295-305. [DOI: 10.1016/j.jchemneu.2008.02.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2007] [Revised: 02/13/2008] [Accepted: 02/13/2008] [Indexed: 11/25/2022]
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Suzuki H, Takemoto Y, Yamamoto T. Differential distribution of orexin-A-like and orexin receptor 1 (OX1R)-like immunoreactivities in the Xenopus pituitary. Tissue Cell 2007; 39:423-30. [PMID: 17897692 DOI: 10.1016/j.tice.2007.08.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2007] [Revised: 07/19/2007] [Accepted: 08/01/2007] [Indexed: 11/17/2022]
Abstract
Immunohistochemical techniques were employed to investigate orexin-A-like and orexin receptor 1 (OX1R)-like immunoreactivities in the Xenopus pituitary gland. Orexin-A-immunoreactive cells were mainly scattered in the posterior half of the pars distalis. They corresponded to thyroid-stimulating hormone (TSH)-containing cells and so far have not corresponded to other types of pituitary adenocytes. On the other hand, OX1R-immunoreactive cells were mainly distributed in the anterior half of the pars distalis and corresponded to prolactin (PRL)-containing cells; however, we found that OX1R-immunoreactive cells did not correspond to other types of adenocytes in the Xenopus pituitary. These results suggest that an orexin-A-like substance secretes with and/or without TSH from TSH-containing cells and that the peptide modulates the functions of PRL-containing cells via OX1R in a paracrine fashion.
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Affiliation(s)
- H Suzuki
- Department of Biology, Fukuoka University of Education, Akamabunkyo-machi 1-1, Munakata, Fukuoka 811-4192, Japan.
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Xu M, Volkoff H. Molecular characterization of prepro-orexin in Atlantic cod (Gadus morhua): cloning, localization, developmental profile and role in food intake regulation. Mol Cell Endocrinol 2007; 271:28-37. [PMID: 17434256 DOI: 10.1016/j.mce.2007.03.003] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2007] [Accepted: 03/13/2007] [Indexed: 11/18/2022]
Abstract
A full-length cDNA encoding for prepro-orexin (prepro-OX) was cloned from Atlantic cod (Gadus morhua) hypothalamus using reverse transcription and rapid amplification of cDNA ends (RACE). The 143 amino acids (aa) prepro-OX contains a 38 aa signal peptide, a 50 aa orexin-A peptide and a 29 aa orexin-B peptide. Semi-quantitative RT-PCR shows that prepro-OX mRNA is present in brain and pituitary and in peripheral tissues, including gill, spleen, stomach and gut. Within the brain, high expression levels are seen in the hypothalamus. During development, prepro-OX is expressed from the cleavage stage up to the hatched larvae. Slot blot analysis shows that prepro-OX expression levels are higher in fish fed low (0.2% BW) and medium (0.8% BW) rations than in fish fed high rations (1.5% BW). Fish fed low and medium rations also display periprandial changes in prepro-OX expression, with higher expression levels at meal time (0 h) compared to 2h before and 2h after feeding. Our results suggest that orexins might be involved in development and feeding regulation in Atlantic cod.
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Affiliation(s)
- Meiyu Xu
- Department of Biology, Memorial University of Newfoundland, St. John's, Nfld A1B 3X9, Canada
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Nixon JP, Smale L. A comparative analysis of the distribution of immunoreactive orexin A and B in the brains of nocturnal and diurnal rodents. Behav Brain Funct 2007; 3:28. [PMID: 17567902 PMCID: PMC1913054 DOI: 10.1186/1744-9081-3-28] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2006] [Accepted: 06/13/2007] [Indexed: 12/02/2022] Open
Abstract
Background The orexins (hypocretins) are a family of peptides found primarily in neurons in the lateral hypothalamus. Although the orexinergic system is generally thought to be the same across species, the orexins are involved in behaviors which show considerable interspecific variability. There are few direct cross-species comparisons of the distributions of cells and fibers containing these peptides. Here, we addressed the possibility that there might be important species differences by systematically examining and directly comparing the distribution of orexinergic neurons and fibers within the forebrains of species with very different patterns of sleep-wake behavior. Methods We compared the distribution of orexin-immunoreactive cell bodies and fibers in two nocturnal species (the lab rat, Rattus norvegicus and the golden hamster, Mesocricetus auratus) and two diurnal species (the Nile grass rat, Arvicanthis niloticus and the degu, Octodon degus). For each species, tissue from the olfactory bulbs through the brainstem was processed for immunoreactivity for orexin A and orexin B (hypocretin-1 and -2). The distribution of orexin-positive cells was noted for each species. Orexin fiber distribution and density was recorded and analyzed using a principal components factor analysis to aid in evaluating potential species differences. Results Orexin-positive cells were observed in the lateral hypothalamic area of each species, though there were differences with respect to distribution within this region. In addition, cells positive for orexin A but not orexin B were observed in the paraventricular nucleus of the lab rat and grass rat, and in the supraoptic nucleus of the lab rat, grass rat and hamster. Although the overall distributions of orexin A and B fibers were similar in the four species, some striking differences were noted, especially in the lateral mammillary nucleus, ventromedial hypothalamic nucleus and flocculus. Conclusion The orexin cell and fiber distributions observed in this study were largely consistent with those described in previous studies. However, the present study shows significant species differences in the distribution of orexin cell bodies and in the density of orexin-IR fibers in some regions. Finally, we note previously undescribed populations of orexin-positive neurons outside the lateral hypothalamus in three of the four species examined.
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Affiliation(s)
- Joshua P Nixon
- Department of Zoology, Michigan State University, 203 Natural Science Building, East Lansing, MI 48824-1115 USA
- Department of Food Science and Nutrition and Minnesota Craniofacial Research Training Program (MinnCResT), 17-164 Moos Tower, 515 Delaware St. SE, Minneapolis, MN 55455-0357 USA
| | - Laura Smale
- Department of Zoology, Michigan State University, 203 Natural Science Building, East Lansing, MI 48824-1115 USA
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