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Tramonti Fantozzi MP, De Cicco V, d’Ascanio P, Cataldo E, De Cicco D, Bruschini L, Barresi M, Faraguna U, Manzoni D. Trigeminal Stimulation and Visuospatial Performance: The Struggle between Chewing and Trigeminal Asymmetries. Biomedicines 2023; 11:2307. [PMID: 37626803 PMCID: PMC10452603 DOI: 10.3390/biomedicines11082307] [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: 07/08/2023] [Revised: 07/31/2023] [Accepted: 08/13/2023] [Indexed: 08/27/2023] Open
Abstract
Chewing improves visuospatial performance through locus coeruleus (LC) activation. The effects of bilateral and unilateral mastication were investigated in subjects showing different degrees of asymmetry in masseter electromyographic (EMG) activity during clenching and in pupil size at rest (anisocoria), which is a proxy of LC imbalance. Correlations between performance changes and asymmetry values were found in males, but not in females. Among males, subjects with low asymmetry values (balanced-BAL) were more sensitive than those with high asymmetry values (imbalanced-IMB) to bilateral and unilateral chewing on the side with higher EMG activity (hypertonic). The opposite was true for hypotonic side chewing. BAL subjects were sensitive to unilateral chewing on both sides, while in IMB subjects, hypertonic side chewing did not influence performance in either males or females. Bilateral chewing elicited larger effects in BAL subjects than in IMB subjects, exceeding the values predicted from unilateral chewing in both groups. Finally, pupil size and anisocoria changes elicited by chewing were correlated with asymmetry values, independent of sex. Data confirmed the facilitation of visuospatial performance exerted by chewing. Trigeminal asymmetries modulate the chewing effects, making occlusal rebalancing an appropriate strategy to improve performance.
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Affiliation(s)
- Maria Paola Tramonti Fantozzi
- Department of Translational Research and of New Surgical and Medical Technologies, University of Pisa, 56123 Pisa, Italy
| | - Vincenzo De Cicco
- Department of Translational Research and of New Surgical and Medical Technologies, University of Pisa, 56123 Pisa, Italy
| | - Paola d’Ascanio
- Department of Translational Research and of New Surgical and Medical Technologies, University of Pisa, 56123 Pisa, Italy
| | - Enrico Cataldo
- Department of Physics, University of Pisa, 56127 Pisa, Italy
| | - Davide De Cicco
- Department of Translational Research and of New Surgical and Medical Technologies, University of Pisa, 56123 Pisa, Italy
| | - Luca Bruschini
- Department of Surgical, Medical and Molecular Pathology and Critical Care Medicine, University of Pisa, 56124 Pisa, Italy
| | - Massimo Barresi
- Department of Translational Research and of New Surgical and Medical Technologies, University of Pisa, 56123 Pisa, Italy
| | - Ugo Faraguna
- Department of Translational Research and of New Surgical and Medical Technologies, University of Pisa, 56123 Pisa, Italy
- Department of Developmental Neuroscience, IRCCS Fondazione Stella Maris, 56128 Pisa, Italy
| | - Diego Manzoni
- Department of Translational Research and of New Surgical and Medical Technologies, University of Pisa, 56123 Pisa, Italy
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2
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Bateman JT, Saunders SE, Levitt ES. Understanding and countering opioid-induced respiratory depression. Br J Pharmacol 2023; 180:813-828. [PMID: 34089181 PMCID: PMC8997313 DOI: 10.1111/bph.15580] [Citation(s) in RCA: 27] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 05/06/2021] [Accepted: 05/23/2021] [Indexed: 02/06/2023] Open
Abstract
Respiratory depression is the proximal cause of death in opioid overdose, yet the mechanisms underlying this potentially fatal outcome are not well understood. The goal of this review is to provide a comprehensive understanding of the pharmacological mechanisms of opioid-induced respiratory depression, which could lead to improved therapeutic options to counter opioid overdose, as well as other detrimental effects of opioids on breathing. The development of tolerance in the respiratory system is also discussed, as are differences in the degree of respiratory depression caused by various opioid agonists. Finally, potential future therapeutic agents aimed at reversing or avoiding opioid-induced respiratory depression through non-opioid receptor targets are in development and could provide certain advantages over naloxone. By providing an overview of mechanisms and effects of opioids in the respiratory network, this review will benefit future research on countering opioid-induced respiratory depression. LINKED ARTICLES: This article is part of a themed issue on Advances in Opioid Pharmacology at the Time of the Opioid Epidemic. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.7/issuetoc.
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Affiliation(s)
- Jordan T Bateman
- Department of Pharmacology & Therapeutics, University of Florida, Gainesville, Florida, USA
| | - Sandy E Saunders
- Department of Pharmacology & Therapeutics, University of Florida, Gainesville, Florida, USA
| | - Erica S Levitt
- Department of Pharmacology & Therapeutics, University of Florida, Gainesville, Florida, USA
- Breathing Research and Therapeutics Center, University of Florida, Gainesville, Florida, USA
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3
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Bigalke JA, Shan Z, Carter JR. Orexin, Sleep, Sympathetic Neural Activity, and Cardiovascular Function. Hypertension 2022; 79:2643-2655. [PMID: 36148653 PMCID: PMC9649879 DOI: 10.1161/hypertensionaha.122.19796] [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] [Indexed: 11/04/2022]
Abstract
Inadequate sleep duration and quality are associated with reduced cardiovascular health and increased mortality. Experimental evidence points to the sympathetic nervous system as a key mediator in the observed relationship between poor sleep and cardiovascular dysfunction. However, brain mechanisms underpinning the impaired sympathetic function associated with poor sleep remain unclear. Recent evidence suggests the central orexin system, particularly orexins A and B and their receptors, have a key regulatory role for sleep in animal and human models. While orexin system activity has been observed to significantly impact sympathetic regulation in animals, the extension of these findings to humans has been difficult due to an inability to directly assess orexin system activity in humans. However, direct measures of sympathetic activity in populations with narcolepsy and chronic insomnia, 2 sleep disorders associated with deficient and excessive orexin neural activity, have allowed indirect assessment of the relationships between orexin, sleep, and sympathetic regulation. Further, the recent pharmaceutical development of dual orexin receptor antagonists for use in clinical insomnia populations offers an unprecedented opportunity to examine the mechanistic role of orexin in sleep and cardiovascular health in humans. The current review assesses the role of orexin in both sleep and sympathetic regulation from a translational perspective, spanning animal and human studies. The review concludes with future research directions necessary to fully elucidate the mechanistic role for orexin in sleep and sympathetic regulation in humans.
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Affiliation(s)
- Jeremy A. Bigalke
- Department of Health and Human Development, Montana State University, Bozeman, Montana
- Department of Psychology, Montana State University, Bozeman, Montana
| | - Zhiying Shan
- Department of Kinesiology and Integrative Physiology, Michigan Technological University, Houghton, Michigan
| | - Jason R. Carter
- Department of Health and Human Development, Montana State University, Bozeman, Montana
- Department of Psychology, Montana State University, Bozeman, Montana
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4
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Deli SB, Bonab SI, Khakpay R, Khakpai F, Feyzi MH. An interaction between basolateral amygdala orexinergic and endocannabinoid systems in inducing anti-nociception in the rat formalin test. Psychopharmacology (Berl) 2022; 239:3171-3184. [PMID: 35918531 DOI: 10.1007/s00213-022-06199-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 07/22/2022] [Indexed: 11/29/2022]
Abstract
The amygdala has emerged as the main brain center for the emotional affective dimension of pain and pain modulation. In the amygdala, orexin and cannabinoid receptors are expressed in relatively high concentrations. To investigate the possible interaction between the amygdala orexin and cannabinoid systems on the modulation of inflammatory pain, we conducted formalin, rotarod, and plethysmometer tests, as well as analyzing mRNA expression of orexin and cannabinoid receptors in male rats. The basolateral amygdala (BLA) was unilaterally implanted by a guide cannula. Our results showed that, compared to saline and DMSO/saline, intra-BLA microinjection of orexin-A (50 and 100 µM) decreased flinch response in the early phase, but not in the late phase of the formalin test. However, these injections had no significant effect on the mRNA expression level of BLA, orexin receptor type-1 (Orx1), and cannabinoid receptor type-1 (Cb1). Moreover, intra-BLA administration of Orx1 receptor antagonist (SB-334867; 50 nM) and Cb1 receptor antagonist (AM251; 250 and 500 nM) decreased flinch response only in the early phase of the formalin test as compared to the DMSO group. Although the intra-BLA infusion of orexin-A alone and along with SB-334867 or AM251 decreased flinch response in the early phase of the formalin test, intra-BLA co-microinjection of SB-334867/AM251/OrxA increased flinch response in both early and late phases of the formalin test when compared to the DMSO/OrxA group. Interestingly, in the SB-334867/AM251/OrxA group, the Cb1 receptor was upregulated in all groups in comparison to Orx1 receptors. Our results revealed an interaction between BLA, orexin-A, and Cb1 receptors in inducing anti-nociception in the formalin test.
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Affiliation(s)
- Soghra Borneh Deli
- Department of Animal Biology, Faculty of Natural Sciences, University of Tabriz, Tabriz, Iran
| | - Samira Iman Bonab
- Department of Animal Biology, Faculty of Natural Sciences, University of Tabriz, Tabriz, Iran
| | - Roghaieh Khakpay
- Department of Animal Biology, Faculty of Natural Sciences, University of Tabriz, Tabriz, Iran.
| | - Fatemeh Khakpai
- Cognitive and Neuroscience Research Center (CNRC), Tehran Medical Sciences, Islamic Azad University, Tehran, Iran
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5
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Coleman P, de Lecea L, Gotter A, Hagan J, Hoyer D, Kilduff T, Kukkonen JP, Porter R, Renger J, Siegel JM, Sutcliffe G, Upton N, Winrow CJ. Orexin receptors in GtoPdb v.2021.3. IUPHAR/BPS GUIDE TO PHARMACOLOGY CITE 2021; 2021. [PMID: 34927075 DOI: 10.2218/gtopdb/f51/2021.3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Orexin receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Orexin receptors [42]) are activated by the endogenous polypeptides orexin-A and orexin-B (also known as hypocretin-1 and -2; 33 and 28 aa) derived from a common precursor, preproorexin or orexin precursor, by proteolytic cleavage and some typical peptide modifications [109]. Currently the only orexin receptor ligands in clinical use are suvorexant and lemborexant, which are used as hypnotics. Orexin receptor crystal structures have been solved [134, 133, 54, 117, 46].
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6
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Intranasal insulin and orexins to treat age-related cognitive decline. Physiol Behav 2021; 234:113370. [PMID: 33621561 DOI: 10.1016/j.physbeh.2021.113370] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [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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7
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Nam MH, Won W, Han KS, Lee CJ. Signaling mechanisms of μ-opioid receptor (MOR) in the hippocampus: disinhibition versus astrocytic glutamate regulation. Cell Mol Life Sci 2021; 78:415-426. [PMID: 32671427 PMCID: PMC11073310 DOI: 10.1007/s00018-020-03595-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 07/02/2020] [Accepted: 07/09/2020] [Indexed: 02/07/2023]
Abstract
μ-opioid receptor (MOR) is a class of opioid receptors that is critical for analgesia, reward, and euphoria. MOR is distributed in various brain regions, including the hippocampus, where traditionally, it is believed to be localized mainly at the presynaptic terminals of the GABAergic inhibitory interneurons to exert a strong disinhibitory effect on excitatory pyramidal neurons. However, recent intensive research has uncovered the existence of MOR in hippocampal astrocytes, shedding light on how astrocytic MOR participates in opioid signaling via glia-neuron interaction in the hippocampus. Activation of astrocytic MOR has shown to cause glutamate release from hippocampal astrocytes and increase the excitability of presynaptic axon fibers to enhance the release of glutamate at the Schaffer Collateral-CA1 synapses, thereby, intensifying the synaptic strength and plasticity. This novel mechanism involving astrocytic MOR has been shown to participate in hippocampus-dependent conditioned place preference. Furthermore, the signaling of hippocampal MOR, whose action is sexually dimorphic, is engaged in adult neurogenesis, seizure, and stress-induced memory impairment. In this review, we focus on the two profoundly different hippocampal opioid signaling pathways through either GABAergic interneuronal or astrocytic MOR. We further compare and contrast their molecular and cellular mechanisms and their possible roles in opioid-associated conditioned place preference and other hippocampus-dependent behaviors.
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Affiliation(s)
- Min-Ho Nam
- Center for Neuroscience, Korea Institute of Science and Technology, Seoul, 02792, Republic of Korea
| | - Woojin Won
- KU-KIST Graduate School of Converging Science and Technology, Korea University, 145 Anam-ro, Seogbuk-gu, Seoul, 02841, Republic of Korea
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon, 34126, Republic of Korea
| | - Kyung-Seok Han
- Department of Medical Biotechnology, Dongguk University-Gyeongju, 123 Dongdae-ro, Gyeongju, Gyeongbuk, Republic of Korea
| | - C Justin Lee
- KU-KIST Graduate School of Converging Science and Technology, Korea University, 145 Anam-ro, Seogbuk-gu, Seoul, 02841, Republic of Korea.
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon, 34126, Republic of Korea.
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8
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Lee J, Raycraft L, Johnson AW. The dynamic regulation of appetitive behavior through lateral hypothalamic orexin and melanin concentrating hormone expressing cells. Physiol Behav 2020; 229:113234. [PMID: 33130035 DOI: 10.1016/j.physbeh.2020.113234] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 10/20/2020] [Accepted: 10/21/2020] [Indexed: 02/07/2023]
Abstract
The lateral hypothalamic area (LHA) is a heterogeneous brain structure extensively studied for its potent role in regulating energy balance. The anatomical and molecular diversity of the LHA permits the orchestration of responses to energy sensing cues from the brain and periphery. Two of the primary cell populations within the LHA associated with integration of this information are Orexin (ORX) and Melanin Concentrating Hormone (MCH). While both of these non-overlapping populations exhibit orexigenic properties, the activities of these two systems support feeding behavior through contrasting mechanisms. We describe the anatomical and functional properties as well as interaction with other neuropeptides and brain reward and hedonic systems. Specific outputs relating to arousal, food seeking, feeding, and metabolism are coordinated through these mechanisms. We then discuss how both the ORX and MCH systems harmonize in a divergent yet overall cooperative manner to orchestrate feeding behavior through transitions between various appetitive states, and thus offer novel insights into LHA allostatic control of appetite.
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Affiliation(s)
| | | | - Alexander W Johnson
- Department of Psychology; Neuroscience Program, Michigan State University, East Lansing.
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9
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Tang H, Zhu Q, Li W, Qin S, Gong Y, Wang H, Shioda S, Li S, Huang J, Liu B, Fang Y, Liu Y, Wang S, Guo Y, Xia Q, Guo Y, Xu Z. Neurophysiology and Treatment of Disorders of Consciousness Induced by Traumatic Brain Injury: Orexin Signaling as a Potential Therapeutic Target. Curr Pharm Des 2020; 25:4208-4220. [PMID: 31663471 DOI: 10.2174/1381612825666191029101830] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Accepted: 10/21/2019] [Indexed: 02/07/2023]
Abstract
BACKGROUND Traumatic brain injury (TBI) can cause disorders of consciousness (DOC) by impairing the neuronal circuits of the ascending reticular activating system (ARAS) structures, including the hypothalamus, which are responsible for the maintenance of the wakefulness and awareness. However, the effectiveness of drugs targeting ARAS activation is still inadequate, and novel therapeutic modalities are urgently needed. METHODS The goal of this work is to describe the neural loops of wakefulness, and explain how these elements participate in DOC, with emphasis on the identification of potential new therapeutic options for DOC induced by TBI. RESULTS Hypothalamus has been identified as a sleep/wake center, and its anterior and posterior regions have diverse roles in the regulation of the sleep/wake function. In particular, the posterior hypothalamus (PH) possesses several types of neurons, including the orexin neurons in the lateral hypothalamus (LH) with widespread projections to other wakefulness-related regions of the brain. Orexins have been known to affect feeding and appetite, and recently their profound effect on sleep disorders and DOC has been identified. Orexin antagonists are used for the treatment of insomnia, and orexin agonists can be used for narcolepsy. Additionally, several studies demonstrated that the agonists of orexin might be effective in the treatment of DOC, providing novel therapeutic opportunities in this field. CONCLUSION The hypothalamic-centered orexin has been adopted as the point of entry into the system of consciousness control, and modulators of orexin signaling opened several therapeutic opportunities for the treatment of DOC.
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Affiliation(s)
- Huiling Tang
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Qiumei Zhu
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Wei Li
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Siru Qin
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Yinan Gong
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Hong Wang
- Acu-moxibustion and Tuina Department, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Seiji Shioda
- Peptide Drug Innovation, Global Research Center for Innovative Life Science, Hoshi University School of Pharmacy and Pharmaceutical Sciences, 2-4-41 Ebara, Shinagawa, Tokyo 142-8501, Japan
| | - Shanshan Li
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Jin Huang
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Baohu Liu
- Department of Rehabilitation, Wangjing Hospital, China Academy of Chinese Medical Sciences, Beijing, China
| | - Yuxin Fang
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China.,Acu-moxibustion and Tuina Department, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Yangyang Liu
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China.,Acu-moxibustion and Tuina Department, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Shenjun Wang
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China.,Acu-moxibustion and Tuina Department, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Yongming Guo
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China.,Acu-moxibustion and Tuina Department, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Qing Xia
- Acu-moxibustion and Tuina Department, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Yi Guo
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China.,College of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Zhifang Xu
- Acupuncture Research Center, Tianjin University of Traditional Chinese Medicine, Tianjin, China.,Acu-moxibustion and Tuina Department, Tianjin University of Traditional Chinese Medicine, Tianjin, China
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10
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The role of co-neurotransmitters in sleep and wake regulation. Mol Psychiatry 2019; 24:1284-1295. [PMID: 30377299 PMCID: PMC6491268 DOI: 10.1038/s41380-018-0291-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2017] [Revised: 09/17/2018] [Accepted: 10/08/2018] [Indexed: 12/11/2022]
Abstract
Sleep and wakefulness control in the mammalian brain requires the coordination of various discrete interconnected neurons. According to the most conventional sleep model, wake-promoting neurons (WPNs) and sleep-promoting neurons (SPNs) compete for network dominance, creating a systematic "switch" that results in either the sleep or awake state. WPNs and SPNs are ubiquitous in the brainstem and diencephalon, areas that together contain <1% of the neurons in the human brain. Interestingly, many of these WPNs and SPNs co-express and co-release various types of the neurotransmitters that often have opposing modulatory effects on the network. Co-transmission is often beneficial to structures with limited numbers of neurons because it provides increasing computational capability and flexibility. Moreover, co-transmission allows subcortical structures to bi-directionally control postsynaptic neurons, thus helping to orchestrate several complex physiological functions such as sleep. Here, we present an in-depth review of co-transmission in hypothalamic WPNs and SPNs and discuss its functional significance in the sleep-wake network.
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11
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Palus-Chramiec K, Chrobok L, Kepczynski M, Lewandowski MH. Orexin A depolarises rat intergeniculate leaflet neurons through non-selective cation channels. Eur J Neurosci 2019; 50:2683-2693. [PMID: 30803080 DOI: 10.1111/ejn.14394] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 02/12/2019] [Accepted: 02/15/2019] [Indexed: 12/22/2022]
Abstract
Orexins/hypocretins are hypothalamic neuropeptides that have a variety of functions, including maintenance of arousal, control over the sleep/wake cycle, reward and feeding. Accumulating evidence links orexins to the time-keeping system with a documented action in the master clock-the suprachiasmatic nucleus. The intergeniculate leaflet (IGL) is a thalamic structure with the well-known function of collecting photic and non-photic cues to adjust the rhythm of the suprachiasmatic nucleus to changing environmental conditions. The IGL consists of GABAergic neurons that are intrinsically active, even in slice preparations. Our previous studies revealed the excitatory postsynaptic effects of orexins on single IGL neurons, even though the ionic mechanism underlying this effect remained elusive. Therefore, in this study, we used patch clamp electrophysiology to identify the ions and distinct ion channels responsible for the observed depolarisations. The major finding of this article is that the orexin A-evoked depolarisation of IGL neurons depends on non-selective cation channels, implicating the orexinergic tone in establishing the basal firing rate in these cells. The data presented here strengthen the mutual connections between the time-keeping and orexinergic systems.
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Affiliation(s)
- Katarzyna Palus-Chramiec
- Department of Neurophysiology and Chronobiology, Institute of Zoology and Biomedical Research, Faculty of Biology, Jagiellonian University in Krakow, Krakow, Poland
| | - Lukasz Chrobok
- Department of Neurophysiology and Chronobiology, Institute of Zoology and Biomedical Research, Faculty of Biology, Jagiellonian University in Krakow, Krakow, Poland
| | - Mariusz Kepczynski
- Department of Physical Chemistry and Electrochemistry, Faculty of Chemistry, Jagiellonian University in Krakow, Krakow, Poland
| | - Marian Henryk Lewandowski
- Department of Neurophysiology and Chronobiology, Institute of Zoology and Biomedical Research, Faculty of Biology, Jagiellonian University in Krakow, Krakow, Poland
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12
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Orexinergic Modulation of Spinal Motor Activity in the Neonatal Mouse Spinal Cord. eNeuro 2018; 5:eN-NWR-0226-18. [PMID: 30417080 PMCID: PMC6223113 DOI: 10.1523/eneuro.0226-18.2018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 10/15/2018] [Accepted: 10/20/2018] [Indexed: 11/21/2022] Open
Abstract
The role of orexin during development, and especially in terms of spinal cord function, is not well understood. It is for this reason that we focused on the network actions of orexin during the first week of development. We found that orexinergic fibers were present in the lumbar spinal cord of postnatal day 0 (P0) to P3 mice. The fibers were expressed mainly in the dorsal horn, but occasional fibers were observed in the ventral horn. Both orexin (OX) A and OXB increased the motoneurons (MNs) tonic neurogram discharge. However, only OXA was found to significantly increase spontaneous bursting activity and the frequency of fictive locomotor bursts. We show that OXA is able to act directly on MNs. To test the contribution of the recurrent MN collaterals, we blocked the nicotinic cholinergic drive and observed that OXA retained its ability to increase fictive locomotor activity. Additionally, we recorded neurograms from ventral lateral funiculi, where OXA had no effect on population discharge. These effects were also confirmed by recording from descending commissural interneurons via patch recordings. The loci of the effects of OXA were further investigated in a dorsal horn-removed preparation where OXA also shows an increase in the discharge from ventral root neurograms but no increase in the frequency of spontaneous or fictive locomotion burst activity. In summary, multiple lines of evidence from our work demonstrate the robust effects of orexins on spinal cord networks and MNs at the time of birth.
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13
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Activation of galanin receptor 1 inhibits locus coeruleus neurons via GIRK channels. Biochem Biophys Res Commun 2018; 503:79-85. [DOI: 10.1016/j.bbrc.2018.05.181] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Accepted: 05/26/2018] [Indexed: 01/15/2023]
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14
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Abstract
Orexin/hypocretin peptide (orexin-A and orexin-B) signaling is believed to take place via the two G-protein-coupled receptors (GPCRs), named OX1 and OX2 orexin receptors, as described in the previous chapters. Signaling of orexin peptides has been investigated in diverse endogenously orexin receptor-expressing cells - mainly neurons but also other types of cells - and in recombinant cells expressing the receptors in a heterologous manner. Findings in the different systems are partially convergent but also indicate cellular background-specific signaling. The general picture suggests an inherently high degree of diversity in orexin receptor signaling.In the current chapter, I present orexin signaling on the cellular and molecular levels. Discussion of the connection to (potential) physiological orexin responses is only brief since these are in focus of other chapters in this book. The same goes for the post-synaptic signaling mechanisms, which are dealt with in Burdakov: Postsynaptic actions of orexin. The current chapter is organized according to the tissue type, starting from the central nervous system. Finally, receptor signaling pathways are discussed across tissues, cell types, and even species.
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Affiliation(s)
- Jyrki P Kukkonen
- Biochemistry and Cell Biology, Department of Veterinary Biosciences, University of Helsinki, POB 66, FIN-00014, Helsinki, Finland.
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15
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Chrobok L, Palus-Chramiec K, Chrzanowska A, Kepczynski M, Lewandowski MH. Multiple excitatory actions of orexins upon thalamo-cortical neurons in dorsal lateral geniculate nucleus - implications for vision modulation by arousal. Sci Rep 2017; 7:7713. [PMID: 28794459 PMCID: PMC5550457 DOI: 10.1038/s41598-017-08202-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Accepted: 07/06/2017] [Indexed: 01/08/2023] Open
Abstract
The orexinergic system of the lateral hypothalamus plays a crucial role in maintaining wakefulness and mediating arousal in a circadian time-dependent manner. Due to the extensive connections of orexinergic neurons, both orexins (OXA and OXB) exert mainly excitatory effects upon remote brain areas, including the thalamus. The dorsal lateral geniculate nucleus (DLG) is a relay thalamic centre for the visual system. Its thalamo-cortical (TC) neurons convey photic information from the retina to the primary visual cortex. The present study shows that orexins are powerful modulators of neuronal activity in the DLG. OXA directly depolarised the majority of neurons tested, acting predominately on postsynaptic OX2 receptors. Moreover, OXA was found to increase excitability and enhance neuronal responses to both glutamate and γ-aminobutyric acid (GABA). Mechanistic studies showed the involvement of voltage-gated calcium currents and GIRK channels in the observed depolarisations. Immunohistochemical staining showed sparse orexinergic innervation of the DLG during the light phase, with increased density at night. We hypothesise that the depolarising effects of orexins upon DLG neurons may facilitate signal transmission through the visual thalamo-cortical pathway during behavioural arousal. Thus, the action of orexin on DLG TC neurons may underlie the circadian/behavioural modulation of vision.
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Affiliation(s)
- Lukasz Chrobok
- Department of Neurophysiology and Chronobiology, Institute of Zoology and Biomedical Research, Jagiellonian University in Krakow, Gronostajowa 9 Street, 30-387, Krakow, Poland
| | - Katarzyna Palus-Chramiec
- Department of Neurophysiology and Chronobiology, Institute of Zoology and Biomedical Research, Jagiellonian University in Krakow, Gronostajowa 9 Street, 30-387, Krakow, Poland
| | - Anna Chrzanowska
- Department of Neurophysiology and Chronobiology, Institute of Zoology and Biomedical Research, Jagiellonian University in Krakow, Gronostajowa 9 Street, 30-387, Krakow, Poland
| | - Mariusz Kepczynski
- Faculty of Chemistry, Jagiellonian University in Krakow, Ingardena 3 Street, 30-060, Krakow, Poland
| | - Marian Henryk Lewandowski
- Department of Neurophysiology and Chronobiology, Institute of Zoology and Biomedical Research, Jagiellonian University in Krakow, Gronostajowa 9 Street, 30-387, Krakow, Poland.
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16
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Schöne C, Burdakov D. Orexin/Hypocretin and Organizing Principles for a Diversity of Wake-Promoting Neurons in the Brain. Curr Top Behav Neurosci 2017; 33:51-74. [PMID: 27830577 PMCID: PMC5767105 DOI: 10.1007/7854_2016_45] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
An enigmatic feature of behavioural state control is the rich diversity of wake-promoting neural systems. This diversity has been rationalized as 'robustness via redundancy', wherein wakefulness control is not critically dependent on one type of neuron or molecule. Studies of the brain orexin/hypocretin system challenge this view by demonstrating that wakefulness control fails upon loss of this neurotransmitter system. Since orexin neurons signal arousal need, and excite other wake-promoting neurons, their actions illuminate nonredundant principles of arousal control. Here, we suggest such principles by reviewing the orexin system from a collective viewpoint of biology, physics and engineering. Orexin peptides excite other arousal-promoting neurons (noradrenaline, histamine, serotonin, acetylcholine neurons), either by activating mixed-cation conductances or by inhibiting potassium conductances. Ohm's law predicts that these opposite conductance changes will produce opposite effects on sensitivity of neuronal excitability to current inputs, thus enabling orexin to differentially control input-output gain of its target networks. Orexin neurons also produce other transmitters, including glutamate. When orexin cells fire, glutamate-mediated downstream excitation displays temporal decay, but orexin-mediated excitation escalates, as if orexin transmission enabled arousal controllers to compute a time integral of arousal need. Since the anatomical and functional architecture of the orexin system contains negative feedback loops (e.g. orexin ➔ histamine ➔ noradrenaline/serotonin-orexin), such computations may stabilize wakefulness via integral feedback, a basic engineering strategy for set point control in uncertain environments. Such dynamic behavioural control requires several distinct wake-promoting modules, which perform nonredundant transformations of arousal signals and are connected in feedback loops.
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Affiliation(s)
- Cornelia Schöne
- Department of Neurology, University of Bern, Bern University Hospital, 3010, Bern, Switzerland
| | - Denis Burdakov
- The Francis Crick Institute, Mill Hill Laboratory, London, NW7 1AA, UK.
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17
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Abstract
Cortical electroencephalographic activity arises from corticothalamocortical interactions, modulated by wake-promoting monoaminergic and cholinergic input. These wake-promoting systems are regulated by hypothalamic hypocretin/orexins, while GABAergic sleep-promoting nuclei are found in the preoptic area, brainstem and lateral hypothalamus. Although pontine acetylcholine is critical for REM sleep, hypothalamic melanin-concentrating hormone/GABAergic cells may "gate" REM sleep. Daily sleep-wake rhythms arise from interactions between a hypothalamic circadian pacemaker and a sleep homeostat whose anatomical locus has yet to be conclusively defined. Control of sleep and wakefulness involves multiple systems, each of which presents vulnerability to sleep/wake dysfunction that may predispose to physical and/or neuropsychiatric disorders.
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Affiliation(s)
- Michael D Schwartz
- Biosciences Division, Center for Neuroscience, SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025, USA
| | - Thomas S Kilduff
- Biosciences Division, Center for Neuroscience, SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025, USA.
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18
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Riahi E, Arezoomandan R, Fatahi Z, Haghparast A. The electrical activity of hippocampal pyramidal neuron is subjected to descending control by the brain orexin/hypocretin system. Neurobiol Learn Mem 2015; 119:93-101. [DOI: 10.1016/j.nlm.2015.02.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Revised: 12/23/2014] [Accepted: 02/03/2015] [Indexed: 11/16/2022]
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19
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Hippocampal orexin receptors inactivation reduces PTZ induced seizures of male rats. Pharmacol Biochem Behav 2015; 130:77-83. [DOI: 10.1016/j.pbb.2015.01.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Revised: 01/06/2015] [Accepted: 01/09/2015] [Indexed: 11/23/2022]
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20
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Brown JA, Woodworth HL, Leinninger GM. To ingest or rest? Specialized roles of lateral hypothalamic area neurons in coordinating energy balance. Front Syst Neurosci 2015; 9:9. [PMID: 25741247 PMCID: PMC4332303 DOI: 10.3389/fnsys.2015.00009] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Accepted: 01/15/2015] [Indexed: 12/26/2022] Open
Abstract
Survival depends on an organism’s ability to sense nutrient status and accordingly regulate intake and energy expenditure behaviors. Uncoupling of energy sensing and behavior, however, underlies energy balance disorders such as anorexia or obesity. The hypothalamus regulates energy balance, and in particular the lateral hypothalamic area (LHA) is poised to coordinate peripheral cues of energy status and behaviors that impact weight, such as drinking, locomotor behavior, arousal/sleep and autonomic output. There are several populations of LHA neurons that are defined by their neuropeptide content and contribute to energy balance. LHA neurons that express the neuropeptides melanin-concentrating hormone (MCH) or orexins/hypocretins (OX) are best characterized and these neurons play important roles in regulating ingestion, arousal, locomotor behavior and autonomic function via distinct neuronal circuits. Recently, another population of LHA neurons containing the neuropeptide Neurotensin (Nts) has been implicated in coordinating anorectic stimuli and behavior to regulate hydration and energy balance. Understanding the specific roles of MCH, OX and Nts neurons in harmonizing energy sensing and behavior thus has the potential to inform pharmacological strategies to modify behaviors and treat energy balance disorders.
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Affiliation(s)
- Juliette A Brown
- Department of Pharmacology and Toxicology, Michigan State University East Lansing, MI, USA ; Center for Integrative Toxicology East Lansing, MI, USA
| | | | - Gina M Leinninger
- Center for Integrative Toxicology East Lansing, MI, USA ; Department of Physiology, Michigan State University East Lansing, MI, USA
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21
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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: 2] [Impact Index Per Article: 0.2] [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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22
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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: 140] [Impact Index Per Article: 14.0] [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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23
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Abstract
Addiction is a chronic relapsing disorder which presents a significant global health burden and unmet medical need. The orexin/hypocretin system is an attractive potential therapeutic target as demonstrated by the successful clinical trials of antagonist medications like Suvorexant for insomnia. It is composed of two neuropeptides, orexin-A and orexin-B and two excitatory and promiscuous G-protein coupled receptors, OX1 and OX2. Orexins are known to have a variety of functions, most notably in regulating arousal, appetite and reward. The orexins have been shown to have a role in mediating the effects of several drugs of abuse, such as cocaine, morphine and alcohol via projections to key brain regions such as the ventral tegmental area, nucleus accumbens and prefrontal cortex. However, it has not yet been demonstrated whether the dual orexin receptor antagonists (DORAs) under development for insomnia are ideal drugs for the treatment of addiction. The question of whether to use a DORA or single orexin receptor antagonist (SORA) for the treatment of addiction is a key question that will need to be answered in order to maximize the clinical utility of orexin receptor antagonists. This review will examine the role of the orexin/hypocretin system in addiction, orexin-based pharmacotherapies under development and factors affecting the selection of one or both orexin receptors as drug targets for the treatment of addiction.
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24
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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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25
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Anxiolytic function of the orexin 2/hypocretin A receptor in the basolateral amygdala. Psychoneuroendocrinology 2014; 40:17-26. [PMID: 24485472 PMCID: PMC4361941 DOI: 10.1016/j.psyneuen.2013.10.010] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Revised: 10/01/2013] [Accepted: 10/23/2013] [Indexed: 12/15/2022]
Abstract
The orexin/hypocretin system interacts with many of the same circuitries contributing to stress-associated disorders like depression and anxiety. These include potentially reciprocal connections with corticotropin releasing factor (CRF) neurons which drive the hypothalamic-pituitary-adrenal (HPA) endocrine response in addition to having an anxiogenic effect in the central amygdala (CeA). Antagonism of the orexin type 1 receptor (Orx1) in the hypothalamus has also been shown to block panic attacks. However, few studies have investigated the effect of orexinergic signaling in the basolateral amygdala (BLA) which is responsible for contextual fear, and modulates the activity of the CeA. To this end, we chronically stressed c57bl/6 mice with social defeat and examined the gene expression of the orexin receptors in the BLA. We found that the transcripts for the Orx1 and Orx2 receptors diverged in the BLA with Orx1 increasing and Orx2 decreasing in animals that were susceptible to the chronic defeat. These changes were not seen in the prelimbic cortex (PrL) which sends efferents to the BLA. We then tried to recapitulate these expression patterns in the BLA using short hairpin interfering sequences delivered by adeno-associated viruses to knock down the orexin receptors. While the Orx1 knockdown did reduce locomotor activity, it did not decrease depressive or anxious behaviors. Knocking down the Orx2 receptors in the BLA increased anxious behavior as measured by reduced social preference and reduced time spent in the center of an open field. Due to the divergent expression patterns of the two receptors in response to chronic stress, orexinergic activity in the BLA may be responsible for bidirectional modulation of anxious behavior. Furthermore, these data raise the possibility that an Orx2 agonist may serve as an effective means to treat anxiety disorders.
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26
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Leonard CS, Kukkonen JP. Orexin/hypocretin receptor signalling: a functional perspective. Br J Pharmacol 2014; 171:294-313. [PMID: 23848055 PMCID: PMC3904253 DOI: 10.1111/bph.12296] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Revised: 06/17/2013] [Accepted: 07/03/2013] [Indexed: 10/26/2022] Open
Abstract
Multiple homeostatic systems are regulated by orexin (hypocretin) peptides and their two known GPCRs. Activation of orexin receptors promotes waking and is essential for expression of normal sleep and waking behaviour, with the sleep disorder narcolepsy resulting from the absence of orexin signalling. Orexin receptors also influence systems regulating appetite/metabolism, stress and reward, and are found in several peripheral tissues. Nevertheless, much remains unknown about the signalling pathways and targets engaged by native receptors. In this review, we integrate knowledge about the orexin receptor signalling capabilities obtained from studies in expression systems and various native cell types (as presented in Kukkonen and Leonard, this issue of British Journal of Pharmacology) with knowledge of orexin signalling in different tissues. The tissues reviewed include the CNS, the gastrointestinal tract, the pituitary gland, pancreas, adrenal gland, adipose tissue and the male reproductive system. We also summarize the findings in different native and recombinant cell lines, especially focusing on the different cascades in CHO cells, which is the most investigated cell line. This reveals that while a substantial gap exists between what is known about orexin receptor signalling and effectors in recombinant systems and native systems, mounting evidence suggests that orexin receptor signalling is more diverse than originally thought. Moreover, rather than being restricted to orexin receptor 'overexpressing' cells, this signalling diversity may be utilized by native receptors in a site-specific manner.
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Affiliation(s)
- C S Leonard
- Department of Physiology, New York Medical College, Valhalla, NY, USA
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27
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Kohlmeier KA, Tyler CJ, Kalogiannis M, Ishibashi M, Kristensen MP, Gumenchuk I, Chemelli RM, Kisanuki YY, Yanagisawa M, Leonard CS. Differential actions of orexin receptors in brainstem cholinergic and monoaminergic neurons revealed by receptor knockouts: implications for orexinergic signaling in arousal and narcolepsy. Front Neurosci 2013; 7:246. [PMID: 24391530 PMCID: PMC3869224 DOI: 10.3389/fnins.2013.00246] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Accepted: 11/29/2013] [Indexed: 12/14/2022] Open
Abstract
Orexin neuropeptides influence multiple homeostatic functions and play an essential role in the expression of normal sleep-wake behavior. While their two known receptors (OX1 and OX2) are targets for novel pharmacotherapeutics, the actions mediated by each receptor remain largely unexplored. Using brain slices from mice constitutively lacking either receptor, we used whole-cell and Ca2+ imaging methods to delineate the cellular actions of each receptor within cholinergic [laterodorsal tegmental nucleus (LDT)] and monoaminergic [dorsal raphe (DR) and locus coeruleus (LC)] brainstem nuclei—where orexins promote arousal and suppress REM sleep. In slices from OX−/−2 mice, orexin-A (300 nM) elicited wild-type responses in LDT, DR, and LC neurons consisting of a depolarizing current and augmented voltage-dependent Ca2+ transients. In slices from OX−/−1 mice, the depolarizing current was absent in LDT and LC neurons and was attenuated in DR neurons, although Ca2+-transients were still augmented. Since orexin-A produced neither of these actions in slices lacking both receptors, our findings suggest that orexin-mediated depolarization is mediated by both receptors in DR, but is exclusively mediated by OX1 in LDT and LC neurons, even though OX2 is present and OX2 mRNA appears elevated in brainstems from OX−/−1 mice. Considering published behavioral data, these findings support a model in which orexin-mediated excitation of mesopontine cholinergic and monoaminergic neurons contributes little to stabilizing spontaneous waking and sleep bouts, but functions in context-dependent arousal and helps restrict muscle atonia to REM sleep. The augmented Ca2+ transients produced by both receptors appeared mediated by influx via L-type Ca2+ channels, which is often linked to transcriptional signaling. This could provide an adaptive signal to compensate for receptor loss or prolonged antagonism and may contribute to the reduced severity of narcolepsy in single receptor knockout mice.
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Affiliation(s)
- Kristi A Kohlmeier
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen Copenhagen, Denmark
| | | | - Mike Kalogiannis
- Department of Physiology, New York Medical College Valhalla, NY, USA
| | - Masaru Ishibashi
- Department of Physiology, New York Medical College Valhalla, NY, USA
| | - Morten P Kristensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen Copenhagen, Denmark
| | - Iryna Gumenchuk
- Department of Physiology, New York Medical College Valhalla, NY, USA
| | - Richard M Chemelli
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center Dallas, TX, USA
| | - Yaz Y Kisanuki
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center Dallas, TX, USA
| | - Masashi Yanagisawa
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center Dallas, TX, USA
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28
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Kukkonen JP. Lipid signaling cascades of orexin/hypocretin receptors. Biochimie 2013; 96:158-65. [PMID: 23810911 DOI: 10.1016/j.biochi.2013.06.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Accepted: 06/18/2013] [Indexed: 11/18/2022]
Abstract
Orexins - orexin-A and orexin-B - are neuropeptides with significant role in regulation of fundamental physiological processes such as sleep-wakefulness cycle. Orexins act via G-protein-coupled OX1 and OX2 receptors, which are found, in addition to the central nervous system, also in a number of peripheral organs. Orexin receptors show high degree of signaling promiscuity. One particularly prominent way of signaling for these receptors is via phospholipase cascades, including the phospholipase C, phospholipase D and phospholipase A2 cascades, and also diacylglycerol lipase and phosphoinositide-3-kinase pathways. Most analyses have been performed in recombinant cells; there are indications of some of these cascades in native cells while the significance of other cascades remains to be shown. In this review, I present these pathways, their activation mechanisms and their physiological significance.
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Key Words
- 2-AG
- 2-arachidonoylglycerol
- AA
- CNS
- DAG
- DAG lipase
- DAGL
- DOG
- ERK
- Endocannabinoid
- G-protein-coupled receptor
- GPCR
- GPL
- Hypocretin
- IP(3)
- Ion fluxes
- KB-R7943
- MAFP
- N-acyl-phosphatidylethanolamine
- N-arachidonoylethanolamine
- NAPE
- NSCC
- OX(1)
- OX(2)
- Orexin
- PA
- PC
- PC-PLC
- PC-specific PLC
- PDK1
- PI
- PI3K
- PIP
- PIP(2)
- PIP(3)
- PIs
- PKB, PKC and PKD
- PLA(1), PLA(2), PLB, PLC and PLD
- Phospholipase
- TRP (channel)
- U73122
- a NCX inhibitor
- a PLC inhibitor
- a cPLA(2)α/ζ inhibitor
- anandamide
- arachidonic acid
- cPLA(2) and iPLA(2)
- central nervous system
- cytosolic (Ca(2+)-dependent) and intracellular (Ca(2+)-independent) PLA(2), respectively
- diacylglycerol
- dioctanoylglycerol
- extracellular signal-regulated kinase
- glycerophospholipid
- inositol-1,4,5-trisphosphate
- lyso(glycero)phospholipid
- lysoGPL
- lysoPA
- lysophosphatidic acid
- methyl arachidonyl fluorophosphonate
- non-selective cation channel
- orexin 1 receptor
- orexin 2 receptor
- phosphatidic acid
- phosphatidylcholine
- phosphatidylinositol
- phosphatidylinositol-3,4,5-trisphosphate
- phosphatidylinositol-4,5-bisphosphate
- phosphatidylinositolmonophosphate
- phosphatidylinositols (including differentially phosphorylated species PI, PIP, PIP(2) and PIP(3))
- phosphoinositide-3-kinase
- phosphoinositide-dependent kinase 1
- phospholipase A(1), A(2), B, C and D, respectively
- protein kinase B, C and D, respectively
- pyrrophenone
- transient receptor potential (channel)
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Affiliation(s)
- Jyrki P Kukkonen
- Biochemistry and Cell Biology, Department of Veterinary Biosciences, POB 66, FIN-00014, University of Helsinki, Finland.
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29
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Mieda M, Tsujino N, Sakurai T. Differential roles of orexin receptors in the regulation of sleep/wakefulness. Front Endocrinol (Lausanne) 2013; 4:57. [PMID: 23730297 PMCID: PMC3656340 DOI: 10.3389/fendo.2013.00057] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Accepted: 04/25/2013] [Indexed: 01/15/2023] Open
Abstract
Orexin A and orexin B are hypothalamic neuropeptides that play critical roles in the regulation of sleep/wakefulness, as well as in a variety of physiological functions such as emotion, reward, and energy homeostasis. The actions of orexins are mediated by two receptors, orexin 1 (OX1R) and orexin 2 (OX2R) receptors. OX1R and OX2R show partly overlapping but distinct distributions throughout the central nervous system, suggesting their differential roles. This review presents and discusses the current knowledge concerning the physiological roles of each orexin receptor subtype, focusing on the regulation of sleep/wakefulness.
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Affiliation(s)
- Michihiro Mieda
- Department of Molecular Neuroscience and Integrative Physiology, Graduate School of Medical Science, Kanazawa UniversityKanazawa, Ishikawa, Japan
- *Correspondence: Michihiro Mieda and Takeshi Sakurai, Department of Molecular Neuroscience and Integrative Physiology, Graduate School of Medical Science, Kanazawa University, 13-1 Takara-machi, Kanazawa, Ishikawa 920-8640, Japan. e-mail: ;
| | - Natsuko Tsujino
- Department of Molecular Neuroscience and Integrative Physiology, Graduate School of Medical Science, Kanazawa UniversityKanazawa, Ishikawa, Japan
| | - Takeshi Sakurai
- Department of Molecular Neuroscience and Integrative Physiology, Graduate School of Medical Science, Kanazawa UniversityKanazawa, Ishikawa, Japan
- *Correspondence: Michihiro Mieda and Takeshi Sakurai, Department of Molecular Neuroscience and Integrative Physiology, Graduate School of Medical Science, Kanazawa University, 13-1 Takara-machi, Kanazawa, Ishikawa 920-8640, Japan. e-mail: ;
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30
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Abstract
Neuropeptides are found in many mammalian CNS neurons where they play key roles in modulating neuronal activity. In contrast to amino acid transmitter release at the synapse, neuropeptide release is not restricted to the synaptic specialization, and after release, a neuropeptide may diffuse some distance to exert its action through a G protein-coupled receptor. Some neuropeptides such as hypocretin/orexin are synthesized only in single regions of the brain, and the neurons releasing these peptides probably have similar functional roles. Other peptides such as neuropeptide Y (NPY) are synthesized throughout the brain, and neurons that synthesize the peptide in one region have no anatomical or functional connection with NPY neurons in other brain regions. Here, I review converging data revealing a complex interaction between slow-acting neuromodulator peptides and fast-acting amino acid transmitters in the control of energy homeostasis, drug addiction, mood and motivation, sleep-wake states, and neuroendocrine regulation.
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31
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Kukkonen JP. Physiology of the orexinergic/hypocretinergic system: a revisit in 2012. Am J Physiol Cell Physiol 2012; 304:C2-32. [PMID: 23034387 DOI: 10.1152/ajpcell.00227.2012] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The neuropeptides orexins and their G protein-coupled receptors, OX(1) and OX(2), were discovered in 1998, and since then, their role has been investigated in many functions mediated by the central nervous system, including sleep and wakefulness, appetite/metabolism, stress response, reward/addiction, and analgesia. Orexins also have peripheral actions of less clear physiological significance still. Cellular responses to the orexin receptor activity are highly diverse. The receptors couple to at least three families of heterotrimeric G proteins and other proteins that ultimately regulate entities such as phospholipases and kinases, which impact on neuronal excitation, synaptic plasticity, and cell death. This article is a 10-year update of my previous review on the physiology of the orexinergic/hypocretinergic system. I seek to provide a comprehensive update of orexin physiology that spans from the molecular players in orexin receptor signaling to the systemic responses yet emphasizing the cellular physiological aspects of this system.
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Affiliation(s)
- Jyrki P Kukkonen
- Dept. of Veterinary Biosciences, University of Helsinki, Finland.
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Kotz C, Nixon J, Butterick T, Perez-Leighton C, Teske J, Billington C. Brain orexin promotes obesity resistance. Ann N Y Acad Sci 2012; 1264:72-86. [PMID: 22803681 PMCID: PMC3464355 DOI: 10.1111/j.1749-6632.2012.06585.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Resistance to obesity is becoming an exception rather than the norm, and understanding mechanisms that lead some to remain lean in spite of an obesigenic environment is critical if we are to find new ways to reverse this trend. Levels of energy intake and physical activity both contribute to body weight management, but it is challenging for most to adopt major long-term changes in either factor. Physical activity outside of formal exercise, also referred to as activity of daily living, and in stricter form, spontaneous physical activity (SPA), may be an attractive modifiable variable for obesity prevention. In this review, we discuss individual variability in SPA and NEAT (nonexercise thermogenesis, or the energy expended by SPA) and its relationship to obesity resistance. The hypothalamic neuropeptide orexin (hypocretin) may play a key role in regulating SPA and NEAT. We discuss how elevated orexin signaling capacity, in the context of a brain network modulating SPA, may play a major role in defining individual variability in SPA and NEAT. Greater activation of this SPA network leads to a lower propensity for fat mass gain and therefore may be an attractive target for obesity prevention and therapy.
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Affiliation(s)
- Catherine Kotz
- Department of Veterans Affairs, GRECC and Research Service, Minneapolis, Minnesota 55417, USA.
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33
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Kloukina V, Herzer S, Karlsson N, Perez M, Daraio T, Meister B. G-protein-gated inwardly rectifying K+ channel 4 (GIRK4) immunoreactivity in chemically defined neurons of the hypothalamic arcuate nucleus that control body weight. J Chem Neuroanat 2012; 44:14-23. [PMID: 22465809 DOI: 10.1016/j.jchemneu.2012.03.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Revised: 02/10/2012] [Accepted: 03/15/2012] [Indexed: 01/10/2023]
Abstract
G-protein-gated inwardly rectifying K(+) channels (GIRKs; also called Kir3) are a family of K(+) channels, which are activated (opened) via a signal transduction cascade starting with ligand-stimulated G-protein-coupled receptors (GPCRs). Four GIRK genes have been identified (GIRK1-4). GIRK4 (Kir3.4) has a role in regulating energy homeostasis, since mice with a targeted mutation in the GIRK4 gene exhibit a predisposition to late-onset obesity. GIRK4 mRNA is expressed in hypothalamic regions that harbor neurons involved in the regulation of food intake and body weight. Using goat and rabbit antisera to the GIRK4 protein, the cellular localization and transmitter content of GIRK4-immunoreactive neurons was determined in the hypothalamic arcuate nucleus, a region that contains neurons which are accessible to circulating hormones and is intimately associated with the control of body weight. GIRK4-immunoreactive large cell bodies were demonstrated in the ventrolateral part of the arcuate nucleus, with smaller neuronal cell bodies in the ventromedial part of the nucleus. Double-labeling showed presence of GIRK4 immunoreactivity in large neurons of the ventrolateral arcuate nucleus containing the peptides α-melanocyte-stimulating hormone (α-MSH), a marker for pro-opiomelanocortin (POMC) neurons, and cocaine- and amphetamine-regulated transcript (CART). GIRK4 immunoreactivity was also seen in neurons of the ventromedial part of the arcuate nucleus containing agouti-regulated peptide (AgRP) and neuropeptide Y (NPY). The results suggest that the GIRK4 channel protein plays a role in regulating membrane excitability in chemically defined neurons of the arcuate nucleus that control body weight.
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Affiliation(s)
- Vaia Kloukina
- Department of Neuroscience, Karolinska Institutet, SE-171 77 Stockholm, Sweden
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34
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Abstract
The orexin peptides and their two receptors are involved in multiple physiological processes, including energy homeostasis, arousal, stress and reward. Higher signaling of the orexin peptides at the orexin receptors (OXR) protects against obesity, but it is less clear how their activation in different brain regions contributes to this behavioral output. This review summarizes the evidence available for a role of central OXR in energy homeostasis and their contribution to obesity. A detailed analysis of anatomical, cellular and behavioral evidence shows that modulation of energy homeostasis by the OXR is largely dependent upon anatomical and cellular context. It also shows that obesity resistance provided by activation of the OXR is distributed across multiple brain sites with site-specific actions. We suggest that understanding the role of the OXR in the development of obesity requires considering both specific mechanisms within brain regions and interactions of orexinergic input between multiple sites.
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35
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Abstract
The orexins/hypocretins are endogenous, modulatory and multifunctional neuropeptides with prominent influence on several physiological processes. The influence of orexins on energy expenditure is highlighted with focus on orexin action on individual components of energy expenditure. As orexin stabilizes and maintains normal states of arousal and the sleep/wake cycle, we also highlight orexin mediation of sleep and how sleep interacts with energy expenditure.
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Affiliation(s)
- Jennifer A Teske
- Department of Nutritional Sciences, University of Arizona and Southern Arizona VA Health Care System, Tucson, Arizona, USA
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36
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Urbańska A, Sokołowska P, Woldan-Tambor A, Biegańska K, Brix B, Jöhren O, Namiecińska M, Zawilska JB. Orexins/hypocretins acting at Gi protein-coupled OX 2 receptors inhibit cyclic AMP synthesis in the primary neuronal cultures. J Mol Neurosci 2011; 46:10-7. [PMID: 21547533 PMCID: PMC3260434 DOI: 10.1007/s12031-011-9526-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2011] [Accepted: 04/19/2011] [Indexed: 11/24/2022]
Abstract
Orexins A and B are newly discovered neuropeptides with pleiotropic activity. They signal through two G protein-coupled receptors: OX1 and OX2. In this study, we examined the expression of orexin receptors and effects of the receptors’ activation on cyclic AMP formation in the primary neuronal cell cultures from rat cerebral cortex. Both types of orexin receptors were expressed in rat cortical neurons; the level of OX2R was markedly higher compared to OX1R. Orexin A (an agonist of OX1R and OX2R) and [Ala11-D-Leu15]orexin B (a selective agonist of OX2R) did not affect basal cyclic AMP formation in the primary neuronal cell cultures. Both peptides (0.001–1 μM) inhibited, in a concentration-dependent manner and IC50 values in low nanomolar range, the increase in the nucleotide production evoked by forskolin (1 μM; a direct activator of adenylyl cyclase), pituitary adenylate cyclase-activating polypeptide (PACAP27; 0.1 μM), and vasoactive intestinal peptide (VIP; 3 μM). Effects of orexin A on forskolin-, PACAP27-, and VIP-stimulated cyclic AMP synthesis were blocked by TCS OX2 29 (a selective antagonist of OX2R), and unaffected by SB 408124 (a selective antagonist of OX1R). Pretreatment of neuronal cell cultures with pertussis toxin (PTX) abolished the inhibitory action of orexin A on forskolin- and PACAP-stimulated cyclic AMP accumulation. It is suggested that in cultured rat cortical neurons orexins, acting at OX2 receptors coupled to PTX-sensitive Gi protein, inhibit cyclic AMP synthesis.
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Affiliation(s)
- Anna Urbańska
- Institute for Medical Biology, Polish Academy of Sciences, Lodowa 106, PL 93-232, Łódź, Poland
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37
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Abstract
Orexin-A and -B (also known as hypocretin-1 and -2) are neuropeptides produced in the lateral hypothalamus that promote many aspects of arousal through the OX1 and OX2 receptors. In fact, they are necessary for normal wakefulness, as loss of the orexin-producing neurons causes narcolepsy in humans and rodents. This has generated considerable interest in developing small-molecule orexin receptor antagonists as a novel therapy for the treatment of insomnia. Orexin antagonists, especially those that block OX2 or both OX1 and OX2 receptors, clearly promote sleep in animals, and clinical results are encouraging: Several compounds are in Phase III trials. As the orexin system mainly promotes arousal, these new compounds will likely improve insomnia without incurring many of the side effects encountered with current medications.
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Affiliation(s)
- Thomas E Scammell
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA.
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38
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Sinton CM. Orexin/hypocretin plays a role in the response to physiological disequilibrium. Sleep Med Rev 2011; 15:197-207. [PMID: 21269851 DOI: 10.1016/j.smrv.2010.12.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2010] [Revised: 12/14/2010] [Accepted: 12/15/2010] [Indexed: 11/28/2022]
Abstract
In the decade since the discovery that pathology of the orexin/hypocretin system is causative for the sleep disorder narcolepsy, considerable progress has been made in understanding the functional role of the neuropeptide. Two, apparently separate functions of orexin have emerged as a consensus from studies to date. The first is the effect on vigilance state boundaries, as exemplified by narcolepsy. Thus the absence of orexin severely limits the ability to maintain prolonged periods of wakefulness or sleep and also allows the unregulated appearance of cataplexy as sudden muscle weakness during wakefulness. The second function is that orexin acts as a signaling molecule in transferring information about physiological disequilibrium to the central nervous system. Orexin activates the central arousal and motor systems during such disequilibrium and so may facilitate the necessary response and adaptation to restore equilibrium. A feasible relationship between these two functions is therefore that the maintenance of prolonged and active wakefulness is an integral part of this adaptive process. Furthermore, the limit placed on the onset of sleep by orexin suggests that these adaptive processes then continue during sleep to become integrated into the development of a coping strategy for the longer term.
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Affiliation(s)
- Christopher M Sinton
- Department of Internal Medicine, UT Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75390-8874, USA.
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39
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Achike FI, To NHP, Wang H, Kwan CY. Obesity, metabolic syndrome, adipocytes and vascular function: A holistic viewpoint. Clin Exp Pharmacol Physiol 2010; 38:1-10. [DOI: 10.1111/j.1440-1681.2010.05460.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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40
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Arrigoni E, Mochizuki T, Scammell TE. Activation of the basal forebrain by the orexin/hypocretin neurones. Acta Physiol (Oxf) 2010; 198:223-35. [PMID: 19723027 DOI: 10.1111/j.1748-1716.2009.02036.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The orexin neurones play an essential role in driving arousal and in maintaining normal wakefulness. Lack of orexin neurotransmission produces a chronic state of hypoarousal characterized by excessive sleepiness, frequent transitions between wake and sleep, and episodes of cataplexy. A growing body of research now suggests that the basal forebrain (BF) may be a key site through which the orexin-producing neurones promote arousal. Here we review anatomical, pharmacological and electrophysiological studies on how the orexin neurones may promote arousal by exciting cortically projecting neurones of the BF. Orexin fibres synapse on BF cholinergic neurones and orexin-A is released in the BF during waking. Local application of orexins excites BF cholinergic neurones, induces cortical release of acetylcholine and promotes wakefulness. The orexin neurones also contain and probably co-release the inhibitory neuropeptide dynorphin. We found that orexin-A and dynorphin have specific effects on different classes of BF neurones that project to the cortex. Cholinergic neurones were directly excited by orexin-A, but did not respond to dynorphin. Non-cholinergic BF neurones that project to the cortex seem to comprise at least two populations with some directly excited by orexin-A that may represent wake-active, GABAergic neurones, whereas others did not respond to orexin-A but were inhibited by dynorphin and may be sleep-active, GABAergic neurones. This evidence suggests that the BF is a key site through which orexins activate the cortex and promote behavioural arousal. In addition, orexins and dynorphin may act synergistically in the BF to promote arousal and improve cognitive performance.
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Affiliation(s)
- E Arrigoni
- Department of Neurology, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA.
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41
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Abstract
The hypocretins or orexins are endogenous neuropeptides synthesized in discrete lateral, perifornical and dorsal hypothalamic neurones. These multi-functional neuropeptides modulate energy homeostasis, arousal, stress, reward, reproduction and cardiovascular function. This review summarizes the role of hypocretins in modulating non-sleep-related energy expenditure with specific focus on the augmentation of whole body energy expenditure as well as hypocretin-induced physical activity and sympathetic outflow. We compare the efficacy of hypocretin-1 and 2 on energy expenditure and evaluate whether the literature implicates hypocretin signalling though the hypocretin-1 and -2 receptor as having shared and or functionally specific physiological effects. Thus far data suggest that hypocretin-1 has a more robust stimulatory effect relative to hypocretin-2. Furthermore, hypocretin-1 receptor predominantly mediates behaviours known to influence energy expenditure. Further studies on the hypocretin-2 receptor are needed.
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Affiliation(s)
- J A Teske
- Veterans Affairs Medical Center, Minneapolis, MN 55417, USA.
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42
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Jeong Y, Holden JE. The role of spinal orexin-1 receptors in posterior hypothalamic modulation of neuropathic pain. Neuroscience 2009; 159:1414-21. [PMID: 19409203 PMCID: PMC3463132 DOI: 10.1016/j.neuroscience.2009.02.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2009] [Accepted: 02/04/2009] [Indexed: 12/24/2022]
Abstract
The posterior hypothalamus (PH) is known to reduce nociceptive pain, but the effect of PH stimulation on neuropathic pain is not known. Because neurons containing the neurotransmitter orexin-A are located in the PH in some strains of rat and intrathecal injection of orexin-A produces antinociception in a neuropathic pain model, we hypothesized that orexin-A from neurons in the PH modifies nociception in the spinal cord dorsal horn. To test this hypothesis, the cholinergic agonist carbachol or normal saline was microinjected into the PH of lightly anesthetized female Sprague-Dawley rats with chronic constriction injury (CCI) and foot withdrawal latencies (FWL) were measured. Carbachol-induced PH stimulation produced dose dependent antinociception as shown by significantly increased FWL compared to saline controls. To investigate the role of orexin-A in PH-induced antinociception, the orexin-1 receptor antagonist SB-334867 or dimethyl sulfoxide (DMSO) for control, was given intrathecally following carbachol-induced PH stimulation. SB-334867 decreased FWL compared to DMSO controls. These data are suggestive that stimulating the PH produces antinociception in a neuropathic pain model and that the antinociceptive effect is mediated in part by orexin-1 receptors in the spinal cord dorsal horn.
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Affiliation(s)
- Younhee Jeong
- Kyunghee University, 1 Hoegi-dong, Dongdaemun-gu, Seoul, 130-701, Korea (ROK), Phone : 82-2-961-2210, Fax : 82-2-961-9398, Email :
| | - Janean E. Holden
- The University of Michigan, 400 N. Ingalls, Room 2340, Ann Arbor, MI 48109-5482, Phone: 734-763-0011, Fax: 734 936-5525,
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43
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Kohlmeier KA, Watanabe S, Tyler CJ, Burlet S, Leonard CS. Dual orexin actions on dorsal raphe and laterodorsal tegmentum neurons: noisy cation current activation and selective enhancement of Ca2+ transients mediated by L-type calcium channels. J Neurophysiol 2008; 100:2265-81. [PMID: 18667550 DOI: 10.1152/jn.01388.2007] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The hypocretin/orexins (Hcrt/Orxs) are hypothalamic neuropeptides that regulate stress, addiction, feeding, and arousal behaviors. They depolarize many types of central neurons and can increase [Ca2+]i in some, including those of the dorsal raphe (DR) and laterodorsal tegmental (LDT) nuclei-two structures likely to contribute to the behavioral actions of Hcrt/Orx. In this study, we used simultaneous whole cell and Ca2+-imaging methods in mouse brain slices to compare the Hcrt/Orx-activated current in DR and LDT neurons and to determine whether it contributes to the Ca2+ influx evoked by Hcrt/Orx. We found Hcrt/Orx activates a similar noisy cation current that reversed near 0 mV in both cell types. Contrary to our expectation, this current did not contribute to the somatic Ca2+ influx evoked by Hcrt/Orx. In contrast, Hcrt/Orx enhanced the Ca2+ transients produced by voltage steps (-60 to -30 mV) by approximately 30% even in neurons lacking an inward current. This effect was abolished by nifedipine, augmented by Bay-K and abolished by bisindolylmaleimide I. Thus Hcrt/Orx has two independent actions: activation of noisy cation channels that generate depolarization and activation of a protein kinase C (PKC)-dependent enhancement of Ca2+ transients mediated by L-type Ca2+ channels. Immunocytochemistry verified that both these actions occurred in serotonergic and cholinergic neurons, indicating that Hcrt/Orx can function as a neuromodulator in these key neurons of the reticular activating system. Because regulation of Ca2+ transients mediated by L-channels is often linked to the control of transcriptional signaling, our findings imply that Hcrt/Orxs may also function in the regulation of long-term homeostatic or trophic processes.
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Affiliation(s)
- K A Kohlmeier
- Department of Physiology, New York Medical College, Valhalla, NY 10595, USA
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44
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Xie X, Wisor JP, Hara J, Crowder TL, LeWinter R, Khroyan TV, Yamanaka A, Diano S, Horvath TL, Sakurai T, Toll L, Kilduff TS. Hypocretin/orexin and nociceptin/orphanin FQ coordinately regulate analgesia in a mouse model of stress-induced analgesia. J Clin Invest 2008; 118:2471-81. [PMID: 18551194 PMCID: PMC2423866 DOI: 10.1172/jci35115] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Accepted: 05/07/2008] [Indexed: 11/17/2022] Open
Abstract
Stress-induced analgesia (SIA) is a key component of the defensive behavioral "fight-or-flight" response. Although the neural substrates of SIA are incompletely understood, previous studies have implicated the hypocretin/orexin (Hcrt) and nociceptin/orphanin FQ (N/OFQ) peptidergic systems in the regulation of SIA. Using immunohistochemistry in brain tissue from wild-type mice, we identified N/OFQ-containing fibers forming synaptic contacts with Hcrt neurons at both the light and electron microscopic levels. Patch clamp recordings in GFP-tagged mouse Hcrt neurons revealed that N/OFQ hyperpolarized, decreased input resistance, and blocked the firing of action potentials in Hcrt neurons. N/OFQ postsynaptic effects were consistent with opening of a G protein-regulated inwardly rectifying K+ (GIRK) channel. N/OFQ also modulated presynaptic release of GABA and glutamate onto Hcrt neurons in mouse hypothalamic slices. Orexin/ataxin-3 mice, in which the Hcrt neurons degenerate, did not exhibit SIA, although analgesia was induced by i.c.v. administration of Hcrt-1. N/OFQ blocked SIA in wild-type mice, while coadministration of Hcrt-1 overcame N/OFQ inhibition of SIA. These results establish what is, to our knowledge, a novel interaction between the N/OFQ and Hcrt systems in which the corticotropin-releasing factor and N/OFQ systems coordinately modulate the Hcrt neurons to regulate SIA.
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Affiliation(s)
- Xinmin Xie
- Biosciences Division, SRI International, Menlo Park, California 94025, USA.
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45
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Gompf HS, Aston-Jones G. Role of orexin input in the diurnal rhythm of locus coeruleus impulse activity. Brain Res 2008; 1224:43-52. [PMID: 18614159 DOI: 10.1016/j.brainres.2008.05.060] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2008] [Revised: 04/28/2008] [Accepted: 05/16/2008] [Indexed: 10/22/2022]
Abstract
Activation of noradrenergic locus coeruleus (LC) neurons promotes wakefulness and behavioral arousal. In rats, LC neurons receive circadian inputs via a circuit that originates in the suprachiasmatic nucleus (SCN) and relays through the dorsomedial hypothalamus (DMH) to LC; this circuit input increases LC activity during the active period. DMH neurons expressing the peptide neurotransmitter orexin/hypocretin are ideally situated to act as a relay between SCN and LC due to their synaptic inputs from SCN and innervation of LC. Here, we examined the hypothesis that orexin is involved in transmitting circadian signals to LC using single-unit recordings of LC neurons in anesthetized rats maintained in 12:12 light-dark housing. We replicated earlier findings from this lab that LC neurons fire significantly faster on average during the active compared to rest periods. Local microinjection of an orexin antagonist, SB-334867-A attenuated the impulse activities of the fastest firing population of LC neurons during the active period. We also found that DMH orexin neurons project preferentially to LC and express a diurnal rhythm of activation that correlates with LC neuronal firing frequency. Therefore, we propose that DMH orexin neurons play a role in modulating the day-night differences of LC impulse activity.
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Affiliation(s)
- Heinrich S Gompf
- Department of Psychiatry, University of Pennsylvania, Philadelphia, PA, USA
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46
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Yasufuku-Takano J, Nakajima S, Nakajima Y. Morphological and physiological properties of serotonergic neurons in dissociated cultures from the postnatal rat dorsal raphe nucleus. J Neurosci Methods 2007; 167:258-67. [PMID: 17920133 DOI: 10.1016/j.jneumeth.2007.08.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2007] [Revised: 08/23/2007] [Accepted: 08/23/2007] [Indexed: 11/30/2022]
Abstract
We have developed dissociated primary cultures of the dorsal raphe nucleus from postnatal 9-12-day-old rats. The nucleus was dissected out from brain slices, dissociated, and cultured over a glial feeder layer. Serotonin immunocytochemistry revealed that 62% of cultured neurons were serotonergic. There was no significant difference in diameters between serotonergic and non-serotonergic neurons. With the whole-cell patch-clamp method, cultured neurons were tested for responses to 8-hydroxydipropylaminotetraline (8-OH-DPAT, a selective agonist for 5-HT(1A)), and then treated with serotonin immunocytochemistry. Ninety-two percent of neurons responding to 8-OH-DPAT were serotonergic. These results were used to identify serotonergic neurons. In most cases, serotonergic neurons did not show spontaneous firings of action potentials. Constant current depolarizations elicited trains of action potentials that usually did not show marked adaptation. Application of 8-OH-DPAT inhibited action potential firing. The current-voltage relation of the 8-OH-DPAT-induced current indicated an inward rectification with its reversal potential near E(K). Serotonergic neurons were depolarized by phenylephrine, bombesin, and gastrin-releasing peptide. This culture system will serve as a useful tool for elucidating the cellular, physiological, and molecular properties of brain serotonergic neurons.
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Affiliation(s)
- Junko Yasufuku-Takano
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, College of Medicine (M/C 512), 808 South Wood Street, Chicago, IL 60612, USA
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47
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Kawano T, Zhao P, Floreani CV, Nakajima Y, Kozasa T, Nakajima S. Interaction of Galphaq and Kir3, G protein-coupled inwardly rectifying potassium channels. Mol Pharmacol 2007; 71:1179-84. [PMID: 17296805 DOI: 10.1124/mol.106.032508] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Activation of substance P receptors, which are coupled to Galpha(q), inhibits the Kir3.1/3.2 channels, resulting in neuronal excitation. We have shown previously that this channel inactivation is not caused by reduction of the phosphatidylinositol 4,5-bisphosphate level in membrane. Moreover, Galpha(q) immunoprecipitates with Kir3.2 (J Physiol 564:489-500, 2005), suggesting that Galpha(q) interacts with Kir3.2. Positive immunoprecipitation, however, does not necessarily indicate direct interaction between the two proteins. Here, the glutathione transferase pull-down assay was used to investigate interaction between Galpha(q) and the K(+) channels. We found that Galpha(q) interacted with N termini of Kir3.1, Kir3.2, and Kir3.4. However, Galpha(q) did not interact with the C terminus of any Kir3 or with the C or N terminus of Kir2.1. TRPC6 is regulated by the signal initiated by Galpha(q). Immunoprecipitation, however, showed that Galpha(q) did not interact with TRPC6. Thus, the interaction between Galpha(q) and the Kir3 N terminus is quite specific. This interaction occurred in the presence of GDP or GDP-AlF(-)(4). The Galpha(q) binding could take place somewhere between residues 51 to 90 of Kir3.2; perhaps the segment between 81 to 90 residues is crucial. Gbetagamma, which is known to bind to N terminus of Kir3, did not compete with Galpha(q) for the binding, suggesting that these two binding regions are different. These findings agree with the hypothesis (J Physiol 564:489-500, 2005) that the signal to inactivate the Kir3 channel could be mainly transmitted directly from Galpha(q) to Kir3.
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Affiliation(s)
- Takeharu Kawano
- Departments of Anatomy & Cell Biology, College of Medicine, University of Illinois at Chicago, Illinois 60612, USA
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Gorojankina T, Grébert D, Salesse R, Tanfin Z, Caillol M. Study of orexins signal transduction pathways in rat olfactory mucosa and in olfactory sensory neurons-derived cell line Odora: multiple orexin signalling pathways. ACTA ACUST UNITED AC 2007; 141:73-85. [PMID: 17292491 DOI: 10.1016/j.regpep.2006.12.012] [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: 04/27/2006] [Revised: 12/04/2006] [Accepted: 12/21/2006] [Indexed: 10/23/2022]
Abstract
Orexins A and B (OxA and OxB) are multifunctional neuropeptides implicated in the regulation of energy metabolism, wakefulness but also in a broad range of motivated behaviours. They signal through two G-protein-coupled receptors: orexin receptor 1 and 2 (Ox1R and Ox2R). The orexins and their receptors are present at all levels of the rat olfactory system: epithelium, bulb, piriform cortex but their signalling mechanisms remain unknown. We have studied orexins signal transduction pathways in the rat olfactory mucosa (OM) and in the Odora cell line derived from olfactory sensory neurons and heterologously expressing Ox1R or Ox2R. We have demonstrated by western blot and RT-PCR that multiple components of adenylyl cyclase (AC) and phospholipase C (PLC) signalling pathways were identical in OM and Odora cells. OxA and OxB induced a weak increase in IP3 in OM; they induced a significant rise in cAMP and IP3 in Odora transfected cells, suggesting the activation of AC and PLC pathways. Both OxA and OxB induced intracellular calcium elevation and transient activation of MAP kinases (ERK42/44) in Odora/Ox1R and Odora/Ox2R cells. These results suggest the existence of multiple orexins signalling pathways in Odora cells and probably in OM, corresponding to different possible roles of these peptides.
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Affiliation(s)
- Tatiana Gorojankina
- Unité de Neurobiologie de l'Olfaction et de la Prise Alimentaire, UMR1197 - INRA - Université Paris 11, Equipe Récepteurs et Communication Chimique, CRJ, Domaine de Vilvert, 78352 Jouy-en-Josas Cedex, France
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Best TK, Siarey RJ, Galdzicki Z. Ts65Dn, a Mouse Model of Down Syndrome, Exhibits Increased GABAB-Induced Potassium Current. J Neurophysiol 2007; 97:892-900. [PMID: 17093127 DOI: 10.1152/jn.00626.2006] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Down syndrome (DS) is the most common nonheritable cause of mental retardation. DS is the result of the presence of an extra chromosome 21 and its phenotype may be a consequence of overexpressed genes from that chromosome. One such gene is Kcnj6/Girk2, which encodes the G-protein-coupled inward rectifying potassium channel subunit 2 (GIRK2). We have recently shown that the DS mouse model, Ts65Dn, overexpresses GIRK2 throughout the brain and in particular the hippocampus. Here we report that this overexpression leads to a significant increase (∼2-fold) in GABAB-mediated GIRK current in primary cultured hippocampal neurons. The dose response curves for peak and steady-state GIRK current density is significantly shifted left toward lower concentrations of baclofen in Ts65Dn neurons compared with diploid controls, consistent with increased functional expression of GIRK channels. Stationary fluctuation analysis of baclofen-induced GIRK current from Ts65Dn neurons indicated no significant change in single-channel conductance compared with diploid. However, significant increases in GIRK channel density was found in Ts65Dn neurons. In normalized baclofen-induced GIRK current and GIRK current kinetics no difference was found between diploid and Ts65Dn neurons, which suggests unimpaired mechanisms of interaction between GIRK channel and GABAB receptor. These results indicate that increased expression of GIRK2 containing channels have functional consequences that likely affect the balance between excitatory and inhibitory neuronal transmission.
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Affiliation(s)
- Tyler K Best
- Neuroscience Graduate Program, School of Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Rd., Bethesda, MD 20814, USA
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Magga J, Bart G, Oker-Blom C, Kukkonen JP, Akerman KEO, Näsman J. Agonist potency differentiates G protein activation and Ca2+ signalling by the orexin receptor type 1. Biochem Pharmacol 2006; 71:827-36. [PMID: 16430869 DOI: 10.1016/j.bcp.2005.12.021] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2005] [Revised: 12/09/2005] [Accepted: 12/19/2005] [Indexed: 10/25/2022]
Abstract
The G protein coupling characteristics of a flag epitope-tagged orexin receptor type 1 (OX1R) was investigated in HEK293 cells. Immunoprecipitation of the OX1R and immunoblotting revealed interactions with Gq/G11 proteins as well as with Gs and Gi proteins. Stimulation with orexin-A did not affect the ability of the OX1R to coprecipitate Gq/G11 proteins, but it robustly elevated the intracellular concentration of Ca2+, [Ca2+]i. No changes in cAMP levels could be detected upon receptor stimulation. To get further insight into the functional correlation of G protein activation and Ca2+ signalling, we used baculovirus transduction to express chimeric G proteins, containing the Galphas protein backbone with various Galpha donor sequences (Galphas/x) at the N and C termini, and measured cAMP as functional output. The Galphas/x chimeric proteins with Galpha11(Galphaq) and Galpha16 structure in the C terminus were stimulated by the OX1R. Concentration-response curves with Galphas/16 revealed an agonist potency correlation between G protein activation and the elevation of [Ca2+]i via discharge of intracellular Ca2+ stores, a feature also recognized for the muscarinic M3 receptor. However, in contrast to the M3 receptor, the OX1R elevated [Ca2+]i via influx from extracellular space at about 30-fold lower agonist concentration. The results suggest that the OX1R is linked to influx of Ca2+ through a signal pathway independent of Gq/G11 protein activation.
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Affiliation(s)
- Johanna Magga
- A.I. Virtanen Institute for Molecular Sciences, University of Kuopio, FIN-70211 Kuopio, Finland
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