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Turk AZ, Millwater M, SheikhBahaei S. Whole-brain analysis of CO 2 chemosensitive regions and identification of the retrotrapezoid and medullary raphé nuclei in the common marmoset ( Callithrix jacchus). BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.26.558361. [PMID: 37986845 PMCID: PMC10659419 DOI: 10.1101/2023.09.26.558361] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Respiratory chemosensitivity is an important mechanism by which the brain senses changes in blood partial pressure of CO2 (PCO2). It is proposed that special neurons (and astrocytes) in various brainstem regions play key roles as CO2 central respiratory chemosensors in rodents. Although common marmosets (Callithrix jacchus), New-World non-human primates, show similar respiratory responses to elevated inspired CO2 as rodents, the chemosensitive regions in marmoset brain have not been defined yet. Here, we used c-fos immunostainings to identify brain-wide CO2-activated brain regions in common marmosets. In addition, we mapped the location of the retrotrapezoid nucleus (RTN) and raphé nuclei in the marmoset brainstem based on colocalization of CO2-induced c-fos immunoreactivity with Phox2b, and TPH immunostaining, respectively. Our data also indicated that, similar to rodents, marmoset RTN astrocytes express Phox2b and have complex processes that create a meshwork structure at the ventral surface of medulla. Our data highlight some cellular and structural regional similarities in brainstem of the common marmosets and rodents.
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Affiliation(s)
- Ariana Z. Turk
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, 20892 MD, USA
| | - Marissa Millwater
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, 20892 MD, USA
| | - Shahriar SheikhBahaei
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, 20892 MD, USA
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2
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Kurogochi K, Uechi M, Orito K. Involvement of neurokinin-1 receptors in the autonomic nervous system in colorectal distension-induced cardiovascular suppression in rats. Front Pharmacol 2022; 13:1020685. [DOI: 10.3389/fphar.2022.1020685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Accepted: 10/07/2022] [Indexed: 11/13/2022] Open
Abstract
Situational syncope, which includes rectally mediated reflexes, is defined as syncope induced by a specific situation. Its pathogenesis generally involves disorders of the autonomic nervous system. However, the mechanisms and preventive strategies are not yet well understood. Therefore, we hypothesized that a tachykinin neurokinin-1 receptor might be involved in the autonomic nervous system, and that a neurokinin-1 receptor antagonist could mitigate reflex syncope. This study used a rat model in which the reflex was induced by afferent vagal stimulation with colorectal distension (CRD). In the study, the rats were divided into three groups: non-CRD, CRD, and CRD with a neurokinin-1 receptor antagonist. First, we examined the effect of fosaprepitant, a neurokinin-1 receptor antagonist, on the circulatory response in this model. We then determined the brain regions that showed increased numbers of c-Fos immunoreactive cells in the respective groups. Our results suggest that the colorectal distension procedure reduced blood pressure and that fosaprepitant lowered this response. In addition, the number of c-Fos immunoreactive cells was increased in the caudal ventrolateral medullary region with colorectal distension, and this number was decreased by the administration of fosaprepitant. In conclusion, fosaprepitant might be involved in the vagal reflex pathway and potentially suppress the circulatory response to colorectal distension.
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Sakai N, Ohno H, Yoshida M, Iwamoto E, Kurogi A, Jiang D, Sato T, Miyazato M, Kojima M, Kato J, Ida T. Characterization of putative tachykinin peptides in Caenorhabditis elegans. Biochem Biophys Res Commun 2021; 559:197-202. [PMID: 33945998 DOI: 10.1016/j.bbrc.2021.04.063] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2021] [Revised: 04/07/2021] [Accepted: 04/10/2021] [Indexed: 12/19/2022]
Abstract
Tachykinin-like peptides, such as substance P, neurokinin A, and neurokinin B, are among the earliest discovered and best-studied neuropeptide families, and research on them has contributed greatly to our understanding of the endocrine control of many physiological processes. However, there are still many orphan tachykinin receptor homologs for which cognate ligands have not yet been identified, especially in small invertebrates, such as the nematode Caenorhabditis elegans (C. elegans). We here show that the C. elegans nlp-58 gene encodes putative ligands for the orphan G protein-coupled receptor (GPCR) TKR-1, which is a worm ortholog of tachykinin receptors. We first determine, through an unbiased biochemical screen, that a peptide derived from the NLP-58 preprotein stimulates TKR-1. Three mature peptides that are predicted to be generated from NLP-58 show potent agonist activity against TKR-1. We designate these peptides as C. elegans tachykinin (CeTK)-1, -2, and -3. The CeTK peptides contain the C-terminal sequence GLR-amide, which is shared by tachykinin-like peptides in other invertebrate species. nlp-58 exhibits a strongly restricted expression pattern in several neurons, implying that CeTKs behave as neuropeptides. The discovery of CeTKs provides important information to aid our understanding of tachykinin-like peptides and their functional interaction with GPCRs.
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Affiliation(s)
- Naoko Sakai
- Department of Genetics, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
| | - Hayao Ohno
- Developmental Biology Program, Sloan Kettering Institute, New York, NY, 10065, USA
| | - Morikatsu Yoshida
- Department of Biochemistry, National Cerebral and Cardiovascular Center Research Institute, Osaka, 564-8565, Japan
| | - Eri Iwamoto
- Clinical Research Center, Kurume University Hospital, Fukuoka, 830-0011, Japan
| | - Akito Kurogi
- Division for Identification and Analysis of Bioactive Peptides, Department of Bioactive Peptides, Frontier Science Research, University of Miyazaki, Miyazaki, 889-1692, Japan
| | - Danfeng Jiang
- Division for Identification and Analysis of Bioactive Peptides, Department of Bioactive Peptides, Frontier Science Research, University of Miyazaki, Miyazaki, 889-1692, Japan
| | - Takahiro Sato
- Division of Molecular Genetics, Institute of Life Sciences, Kurume University, Fukuoka, 830-0011, Japan
| | - Mikiya Miyazato
- Department of Biochemistry, National Cerebral and Cardiovascular Center Research Institute, Osaka, 564-8565, Japan
| | - Masayasu Kojima
- Division of Molecular Genetics, Institute of Life Sciences, Kurume University, Fukuoka, 830-0011, Japan
| | - Johji Kato
- Division for Identification and Analysis of Bioactive Peptides, Department of Bioactive Peptides, Frontier Science Research, University of Miyazaki, Miyazaki, 889-1692, Japan
| | - Takanori Ida
- Division for Identification and Analysis of Bioactive Peptides, Department of Bioactive Peptides, Frontier Science Research, University of Miyazaki, Miyazaki, 889-1692, Japan.
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4
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Wang X, Lv Y, Xie J, Li B, Zhou T, Chen Y, Chen Y, Song J. Brain regions of marine medaka activated by acute and short-term ocean acidification. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 720:137279. [PMID: 32145610 DOI: 10.1016/j.scitotenv.2020.137279] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 02/10/2020] [Accepted: 02/11/2020] [Indexed: 05/28/2023]
Abstract
Altered behaviors have been reported in many marine fish following exposure to high CO2 concentrations. However, the mechanistic link between elevated CO2 and activation of brain regions in fish is unknown. Herein, we examined the relative quantification and location of c-Fos expression in marine medaka following acute (360 min) and short-term (7 d) exposure to CO2-enriched water (1000 ppm and 1800 ppm CO2). In the control and two treatment groups, pH was stable at 8.21, 7.92 and 7.64, respectively. After acute exposure to seawater acidified by enrichment with CO2, there was a clear upregulation of c-Fos protein in the medaka brain (P < 0.05). c-Fos protein expression peaked after 120 min exposure in the two treatment groups and thereafter began to decline. There were marked increases in c-Fos-labeling in the ventricular and periventricular zones of the cerebral hemispheres and the medulla oblongata. After 1800 ppm CO2 exposure for 7 d, medaka showed significant preference for dark zones during the initial 2 min period. c-Fos protein expression in the ventricular and periventricular zones of the diencephalon in medaka exposed to 1000 ppm and 1800 ppm CO2 were 0.51 ± 0.10 and 1.34 ± 0.30, respectively, which were significantly higher than controls (P < 0.05). Highest doublecortin protein expression occurred in theventricular zones of the diencephalon and mesencephalon. These findings suggest that the ventricular and periventricular zones of the cerebral hemispheres and the medulla oblongata of marine medaka are involved in rapid acid-base regulation. Prolonged ocean acidification may induce cell mitosis and differentiation in the adult medaka brain.
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Affiliation(s)
- Xiaojie Wang
- Institute for Marine Biosystem and Neurosciences, Shanghai Ocean University, Shanghai 201306, China; International Research Center for Marine Biosciences at Shanghai Ocean University, Ministry of Science and Technology, China; National Demonstration Center for Experimental Fisheries Science Education (Shanghai Ocean University), China; Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources (Shanghai Ocean University), Ministry of Education, China.
| | - Yutao Lv
- National Demonstration Center for Experimental Fisheries Science Education (Shanghai Ocean University), China
| | - Jinling Xie
- National Demonstration Center for Experimental Fisheries Science Education (Shanghai Ocean University), China
| | - Baolin Li
- National Demonstration Center for Experimental Fisheries Science Education (Shanghai Ocean University), China
| | - Tangjian Zhou
- National Demonstration Center for Experimental Fisheries Science Education (Shanghai Ocean University), China
| | - Yaqi Chen
- National Demonstration Center for Experimental Fisheries Science Education (Shanghai Ocean University), China
| | - Yi Chen
- National Demonstration Center for Experimental Fisheries Science Education (Shanghai Ocean University), China
| | - Jiakun Song
- Institute for Marine Biosystem and Neurosciences, Shanghai Ocean University, Shanghai 201306, China; International Research Center for Marine Biosciences at Shanghai Ocean University, Ministry of Science and Technology, China
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5
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Venner A, Todd WD, Fraigne J, Bowrey H, Eban-Rothschild A, Kaur S, Anaclet C. Newly identified sleep-wake and circadian circuits as potential therapeutic targets. Sleep 2020; 42:5306564. [PMID: 30722061 DOI: 10.1093/sleep/zsz023] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Accepted: 01/25/2019] [Indexed: 02/06/2023] Open
Abstract
Optogenetics and chemogenetics are powerful tools, allowing the specific activation or inhibition of targeted neuronal subpopulations. Application of these techniques to sleep and circadian research has resulted in the unveiling of several neuronal populations that are involved in sleep-wake control, and allowed a comprehensive interrogation of the circuitry through which these nodes are coordinated to orchestrate the sleep-wake cycle. In this review, we discuss six recently described sleep-wake and circadian circuits that show promise as therapeutic targets for sleep medicine. The parafacial zone (PZ) and the ventral tegmental area (VTA) are potential druggable targets for the treatment of insomnia. The brainstem circuit underlying rapid eye movement sleep behavior disorder (RBD) offers new possibilities for treating RBD and neurodegenerative synucleinopathies, whereas the parabrachial nucleus, as a nexus linking arousal state control and breathing, is a promising target for developing treatments for sleep apnea. Therapies that act upon the hypothalamic circuitry underlying the circadian regulation of aggression or the photic regulation of arousal and mood pathway carry enormous potential for helping to reduce the socioeconomic burden of neuropsychiatric and neurodegenerative disorders on society. Intriguingly, the development of chemogenetics as a therapeutic strategy is now well underway and such an approach has the capacity to lead to more focused and less invasive therapies for treating sleep-wake disorders and related comorbidities.
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Affiliation(s)
- Anne Venner
- Department of Neurology, Beth Israel Deaconess Medical Center, Boston, MA.,Department of Neurology, Harvard Medical School, Boston, MA
| | - William D Todd
- Department of Neurology, Beth Israel Deaconess Medical Center, Boston, MA.,Department of Neurology, Harvard Medical School, Boston, MA
| | - Jimmy Fraigne
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Hannah Bowrey
- Department of Psychiatry, Rutgers Biomedical Health Sciences, Rutgers University, Newark, NJ.,Save Sight Institute, The University of Sydney, Sydney, New South Wales, Australia
| | | | - Satvinder Kaur
- Department of Neurology, Beth Israel Deaconess Medical Center, Boston, MA.,Department of Neurology, Harvard Medical School, Boston, MA
| | - Christelle Anaclet
- Department of Neurobiology, Brudnick Neuropsychiatric Research Institute, NeuroNexus Institute, Graduate Program in Neuroscience - Graduate School of Biomedical Sciences, University of Massachusetts Medical School, Worcester, MA
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6
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5-HT neurons and central CO2 chemoreception. ACTA ACUST UNITED AC 2020. [DOI: 10.1016/b978-0-444-64125-0.00021-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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7
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Kaur S, Saper CB. Neural Circuitry Underlying Waking Up to Hypercapnia. Front Neurosci 2019; 13:401. [PMID: 31080401 PMCID: PMC6497806 DOI: 10.3389/fnins.2019.00401] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Accepted: 04/08/2019] [Indexed: 12/13/2022] Open
Abstract
Obstructive sleep apnea is a sleep and breathing disorder, in which, patients suffer from cycles of atonia of airway dilator muscles during sleep, resulting in airway collapse, followed by brief arousals that help re-establish the airway patency. These repetitive arousals which can occur hundreds of times during the course of a night are the cause of the sleep-disruption, which in turn causes cognitive impairment as well as cardiovascular and metabolic morbidities. To prevent this potential outcome, it is important to target preventing the arousal from sleep while preserving or augmenting the increase in respiratory drive that reinitiates breathing, but will require understanding of the neural circuits that regulate the cortical and respiratory responses to apnea. The parabrachial nucleus (PB) is located in rostral pons. It receives chemosensory information from medullary nuclei that sense increase in CO2 (hypercapnia), decrease in O2 (hypoxia) and mechanosensory inputs from airway negative pressure during apneas. The PB area also exerts powerful control over cortical arousal and respiration, and therefore, is an excellent candidate for mediating the EEG arousal and restoration of the airway during sleep apneas. Using various genetic tools, we dissected the neuronal sub-types responsible for relaying the stimulus for cortical arousal to forebrain arousal circuits. The present review will focus on the circuitries that regulate waking-up from sleep in response to hypercapnia.
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Affiliation(s)
- Satvinder Kaur
- Department of Neurology, Program in Neuroscience, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, United States
| | - Clifford B Saper
- Department of Neurology, Program in Neuroscience, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, United States
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8
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The brain acid–base homeostasis and serotonin: A perspective on the use of carbon dioxide as human and rodent experimental model of panic. Prog Neurobiol 2015; 129:58-78. [DOI: 10.1016/j.pneurobio.2015.04.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Revised: 04/16/2015] [Accepted: 04/20/2015] [Indexed: 12/14/2022]
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9
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Montero D, Terova G, Rimoldi S, Tort L, Negrin D, Zamorano MJ, Izquierdo M. Modulation of adrenocorticotrophin hormone (ACTH)-induced expression of stress-related genes by PUFA in inter-renal cells from European sea bass (Dicentrarchus labrax). J Nutr Sci 2015; 4:e16. [PMID: 26090096 PMCID: PMC4463938 DOI: 10.1017/jns.2015.6] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Revised: 09/11/2014] [Accepted: 01/05/2015] [Indexed: 01/29/2023] Open
Abstract
Dietary fatty acids have been shown to exert a clear effect on the stress response, modulating the release of cortisol. The role of fatty acids on the expression of steroidogenic genes has been described in mammals, but little is known in fish. The effect of different fatty acids on the release of cortisol and expression of stress-related genes of European sea bass (Dicentrarchus labrax) head kidney, induced by a pulse of adenocorticotrophin hormone (ACTH), was studied. Tissue was maintained in superfusion with 60 min of incubation with EPA, DHA, arachidonic acid (ARA), linoleic acid or α-linolenic acid (ALA) during 490 min. Cortisol was measured by RIA. The quantification of stress-related genes transcripts was conducted by One-Step TaqMan real-time RT-PCR. There was an effect of the type of fatty acid on the ACTH-induced release of cortisol, values from ALA treatment being elevated within all of the experimental period. The expression of some steroidogenic genes, such as the steroidogenic acute regulatory protein (StAR) and c-fos, were affected by fatty acids, ALA increasing the expression of StAR after 1 h of ACTH stimulation whereas DHA, ARA and ALA increased the expression of c-fos after 20 min. ARA increased expression of the 11β-hydroxylase gene. Expression of heat shock protein 70 (HSP70) was increased in all the experimental treatments except for ARA. Results corroborate previous studies of the effect of different fatty acids on the release of cortisol in marine fish and demonstrate that those effects are mediated by alteration of the expression of steroidogenic genes.
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Key Words
- ACTH, adrenocorticotrophin hormone
- ALA, α-linolenic acid
- ARA, arachidonic acid
- Adrenocorticotrophin hormone-induced stress response
- COX, cyclo-oxygenase
- CYP11b, cytochrome P450 11β
- Dicentrarchus labrax
- Fatty acids
- GR, glucocorticoid receptor
- HSP, heat shock protein
- LA, linoleic acid
- LOX, lipo-oxygenase
- Nutritional modulation of steroidogenesis
- PKA, protein kinase A
- PLA2, phospholipase A2
- StAR, steroidogenic acute regulatory protein
- Stress-related gene expression
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Affiliation(s)
- Daniel Montero
- Universidad de Las Palmas de Gran Canaria
(ULPGC), Grupo de Investigación en acuicultura (GIA),
Instituto Universitario de Sanidad Animal y Seguridad Alimentaria
(IUSA), c/ Transmontaña, s/n,
35413, Arucas, Las
Palmas, Canary Islands, Spain
| | - Genciana Terova
- University of Insubria,
Department of Biotechnology and Life Sciences, Via
Dunant, 3-21100 Varese, Italy
| | - Simona Rimoldi
- University of Insubria,
Department of Biotechnology and Life Sciences, Via
Dunant, 3-21100 Varese, Italy
| | - Lluis Tort
- Universitat Autonoma de Barcelona,
Department de Biologia Cel.lular, Fisiologia i
immunologia, Edifici M. 08193,
Bellaterra, Cerdanyola del Vallès,
Barcelona, Spain
| | - Davinia Negrin
- Universidad de Las Palmas de Gran Canaria
(ULPGC), Grupo de Investigación en acuicultura (GIA),
Instituto Universitario de Sanidad Animal y Seguridad Alimentaria
(IUSA), c/ Transmontaña, s/n,
35413, Arucas, Las
Palmas, Canary Islands, Spain
| | - María Jesús Zamorano
- Universidad de Las Palmas de Gran Canaria
(ULPGC), Grupo de Investigación en acuicultura (GIA),
Instituto Universitario de Sanidad Animal y Seguridad Alimentaria
(IUSA), c/ Transmontaña, s/n,
35413, Arucas, Las
Palmas, Canary Islands, Spain
| | - Marisol Izquierdo
- Universidad de Las Palmas de Gran Canaria
(ULPGC), Grupo de Investigación en acuicultura (GIA),
Instituto Universitario de Sanidad Animal y Seguridad Alimentaria
(IUSA), c/ Transmontaña, s/n,
35413, Arucas, Las
Palmas, Canary Islands, Spain
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10
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Buchanan GF. Timing, sleep, and respiration in health and disease. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 119:191-219. [PMID: 23899599 DOI: 10.1016/b978-0-12-396971-2.00008-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Breathing is perhaps the physiological function that is most vital to human survival. Without breathing and adequate oxygenation of tissues, life ceases. As would be expected for such a vital function, breathing occurs automatically, without the requirement of conscious input. Breathing is subject to regulation by a variety of factors including circadian rhythms and vigilance state. Given the need for breathing to occur continuously with little tolerance for interruption, it is not surprising that breathing is subject to both circadian phase-dependent and vigilance-state-dependent regulation. Similarly, the information regarding respiratory state, including blood-gas concentrations, can affect circadian timing and sleep-wake state. The exact nature of the interactions between breathing, circadian phase, and vigilance state can vary depending upon the species studied and the methodologies employed. These interactions between breathing, circadian phase, and vigilance state may have important implications for a variety of human diseases, including sleep apnea, asthma, sudden unexpected death in epilepsy, and sudden infant death syndrome.
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Affiliation(s)
- Gordon F Buchanan
- Department of Neurology, Yale University School of Medicine, New Haven, and Veteran's Affairs Medical Center, West Haven, Connecticut, USA
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11
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Teran FA, Massey CA, Richerson GB. Serotonin neurons and central respiratory chemoreception: where are we now? PROGRESS IN BRAIN RESEARCH 2014; 209:207-33. [PMID: 24746050 DOI: 10.1016/b978-0-444-63274-6.00011-4] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Serotonin (5-hydroxytryptamine, 5-HT) neurons are widely considered to play an important role in central respiratory chemoreception. Although many studies in the past decades have supported this hypothesis, there had been concerns about its validity until recently. One recurring claim had been that 5-HT neurons are not consistently sensitive to hypercapnia in vivo. Another belief was that 5-HT neurons do not stimulate breathing; instead, they inhibit or modulate respiratory output. It was also believed by some that 5-HT neuron chemosensitivity is dependent on TASK channels, but mice with genetic deletion of TASK-1 and TASK-3 have a normal hypercapnic ventilatory response. This review explains why these principal arguments against the hypothesis are not supported by existing data. Despite repeated challenges, a large body of evidence now supports the conclusion that at least a subset of 5-HT neurons are central chemoreceptors.
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Affiliation(s)
- Frida A Teran
- St. Mary's University, One Camino Santa Maria, San Antonio, TX, USA
| | - Cory A Massey
- Interdisciplinary Graduate Program in Neuroscience, University of Iowa Carver College of Medicine, Iowa City, IA, USA; Department of Neurology, University of Iowa Carver College of Medicine, Iowa City, IA, USA
| | - George B Richerson
- Interdisciplinary Graduate Program in Neuroscience, University of Iowa Carver College of Medicine, Iowa City, IA, USA; Department of Neurology, University of Iowa Carver College of Medicine, Iowa City, IA, USA; Department of Molecular Physiology and Biophysics, University of Iowa Carver College of Medicine, Iowa City, IA, USA; VAMC, Iowa City, IA, USA.
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12
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Iceman KE, Harris MB. A group of non-serotonergic cells is CO2-stimulated in the medullary raphé. Neuroscience 2013; 259:203-13. [PMID: 24333211 DOI: 10.1016/j.neuroscience.2013.11.060] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Revised: 11/13/2013] [Accepted: 11/30/2013] [Indexed: 01/22/2023]
Abstract
Serotonin/substance P synthesizing cells in the raphé nuclei of the brain are candidates for designation as central chemoreceptors that are stimulated by CO2/pH. We have previously demonstrated that these neurons are CO2-stimulated in situ. Evidence also suggests that CO2-inhibited raphé neurons recorded in vitro and in situ synthesize GABA. Unknown is whether there are other types of chemosensitive cells in the raphé. Here, we showed that a previously unrecognized pool of raphé neurons also exhibit chemosensitivity, and that they are not serotonergic. We used extracellular recording of individual raphé neurons in the unanesthetized juvenile rat in situ perfused decerebrate brainstem preparation to assess chemosensitivity of raphé neurons. Subsequent juxtacellular labeling of individually recorded cells, and immunohistochemistry for the serotonin synthesizing enzyme tryptophan hydroxylase and for neurokinin-1 receptor (NK1R; the receptor for substance P) indicated a group of CO2-stimulated cells that are not serotonergic, but express NK1R and are closely apposed to surrounding serotonergic cells. CO2-stimulated 5-HT and non-5-HT cells constitute distinct groups that have different firing characteristics and hypercapnic sensitivities. Non-5-HT cells fire faster and are more robustly stimulated by CO2 than are 5-HT cells. Thus, we have characterized a previously unrecognized type of CO2-stimulated medullary raphé neuron that is not serotonergic, but may receive input from neighboring serotonin/substance P synthesizing chemosensitive neurons. The potential network properties of the three types of chemosensitive raphé neurons (the present non-5-HT cells, serotonergic cells, and CO2-inhibited cells) remain to be elucidated.
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Affiliation(s)
- K E Iceman
- Institute of Arctic Biology, University of Alaska, Fairbanks, AK 99775, USA; Department of Biology and Wildlife, University of Alaska, Fairbanks, AK 99775, USA.
| | - M B Harris
- Institute of Arctic Biology, University of Alaska, Fairbanks, AK 99775, USA; Department of Biology and Wildlife, University of Alaska, Fairbanks, AK 99775, USA
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13
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Iceman KE, Richerson GB, Harris MB. Medullary serotonin neurons are CO2 sensitive in situ. J Neurophysiol 2013; 110:2536-44. [PMID: 24047906 DOI: 10.1152/jn.00288.2013] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Brainstem central chemoreceptors are critical to the hypercapnic ventilatory response, but their location and identity are poorly understood. When studied in vitro, serotonin-synthesizing (5-HT) neurons within the rat medullary raphé are intrinsically stimulated by CO2/acidosis. The contributions of these neurons to central chemosensitivity in vivo, however, are controversial. Lacking is documentation of CO2-sensitive 5-HT neurons in intact experimental preparations and understanding of their spatial and proportional distribution. Here we test the hypothesis that 5-HT neurons in the rat medullary raphé are sensitive to arterial hypercapnia. We use extracellular recording and hypercapnic challenge of spontaneously active medullary raphé neurons in the unanesthetized in situ perfused decerebrate brainstem preparation to assess chemosensitivity of individual cells. Juxtacellular labeling of a subset of recorded neurons and subsequent immunohistochemistry for the 5-HT-synthesizing enzyme tryptophan hydroxylase (TPH) identify or exclude this neurotransmitter phenotype in electrophysiologically characterized chemosensitive and insensitive cells. We show that the medullary raphé houses a heterogeneous population, including chemosensitive and insensitive 5-HT neurons. Of 124 recorded cells, 16 cells were juxtacellularly filled, visualized, and immunohistochemically identified as 5-HT synthesizing, based on TPH-immunoreactivity. Forty-four percent of 5-HT cells were CO2 stimulated (increased firing rate with hypercapnia), while 56% were unstimulated. Our results demonstrate that medullary raphé neurons are heterogeneous and clearly include a subset of 5-HT neurons that are excited by arterial hypercapnia. Together with data identifying intrinsically CO2-sensitive 5-HT neurons in vitro, these results support a role for such cells as central chemoreceptors in the intact system.
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Affiliation(s)
- Kimberly E Iceman
- Department of Biology and Wildlife, University of Alaska, Fairbanks, Alaska
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14
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Spirovski D, Li Q, Pilowsky PM. Brainstem galanin-synthesizing neurons are differentially activated by chemoreceptor stimuli and represent a subpopulation of respiratory neurons. J Comp Neurol 2011; 520:154-73. [DOI: 10.1002/cne.22723] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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15
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Hodges MR, Richerson GB. Medullary serotonin neurons and their roles in central respiratory chemoreception. Respir Physiol Neurobiol 2010; 173:256-63. [PMID: 20226279 PMCID: PMC4554718 DOI: 10.1016/j.resp.2010.03.006] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2010] [Revised: 03/03/2010] [Accepted: 03/04/2010] [Indexed: 11/13/2022]
Abstract
Much progress has been made in our understanding of central chemoreception since the seminal experiments of Fencl, Loeschcke, Mitchell and others, including identification of new brainstem regions and specific neuron types that may serve as central "sensors" of CO(2)/pH. In this review, we discuss key attributes, or minimal requirements a neuron/cell must possess to be defined as a central respiratory chemoreceptor, and summarize how well each of the various candidates fulfill these minimal criteria-especially the presence of intrinsic chemosensitivity. We then discuss some of the in vitro and in vivo evidence in support of the conclusion that medullary serotonin (5-HT) neurons are central chemoreceptors. We also provide an additional hypothesis that chemosensitive medullary 5-HT neurons are poised to integrate multiple synaptic inputs from various other sources thought to influence ventilation. Finally, we discuss open questions and future studies that may aid in continuing our advances in understanding central chemoreception.
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Affiliation(s)
- Matthew R Hodges
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
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16
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Dean JB, Putnam RW. The caudal solitary complex is a site of central CO(2) chemoreception and integration of multiple systems that regulate expired CO(2). Respir Physiol Neurobiol 2010; 173:274-87. [PMID: 20670695 DOI: 10.1016/j.resp.2010.07.002] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2010] [Revised: 06/30/2010] [Accepted: 07/01/2010] [Indexed: 12/16/2022]
Abstract
The solitary complex is comprised of the nucleus tractus solitarius (NTS, sensory) and dorsal motor nucleus of the vagus (DMV, motor), which functions as an integrative center for neural control of multiple systems including the respiratory, cardiovascular and gastroesophageal systems. The caudal NTS-DMV is one of the several sites of central CO(2) chemoreception in the brain stem. CO(2) chemosensitive neurons are fully responsive to CO(2) at birth and their responsiveness seems to depend on pH-sensitive K(+) channels. In addition, chemosensitive neurons are highly sensitive to conditions such as hypoxia (e.g., neural plasticity) and hyperoxia (e.g., stimulation), suggesting they employ redox and nitrosative signaling mechanisms. Here we review the cellular and systems physiological evidence supporting our hypothesis that the caudal NTS-DMV is a site for integration of respiratory, cardiovascular and gastroesophageal systems that work together to eliminate CO(2) during acute and chronic respiratory acidosis to restore pH homeostasis.
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Affiliation(s)
- Jay B Dean
- Dept. of Molecular Pharmacology & Physiology, Hyperbaric Biomedical Research Laboratory, University of South Florida, Tampa, FL 33612, USA.
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17
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Hodges MR, Richerson GB. The role of medullary serotonin (5-HT) neurons in respiratory control: contributions to eupneic ventilation, CO2 chemoreception, and thermoregulation. J Appl Physiol (1985) 2010; 108:1425-32. [PMID: 20133432 DOI: 10.1152/japplphysiol.01270.2009] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The functional roles of the medullary raphé, and specifically 5-HT neurons, are not well understood. It has previously been stated that the role of 5-HT has been so difficult to understand, because "it is implicated in virtually everything, but responsible for nothing"(Cowen PJ. Foreword. In: Serotonin and Sleep: Molecular, Functional and Clinical Aspects, edited by Monti JM, Prandi-Perumal SR, Jacobs BL, Nutt DJ. Switzerland: Birkhauser, 2008). Are 5-HT neurons important, and can we assign a general, or even specific, function to them given their diffuse projections? Recent data obtained from transgenic animals and other model systems indicate that the 5-HT system is not expendable, particularly during postnatal development, and likely plays specific roles in vital functions such as respiratory and thermoregulatory control. We recently provided a detailed and updated review of one specific function of 5-HT neurons, as central respiratory chemoreceptors contributing to the brain's ability to detect changes in pH/CO2 and stimulate adjustments to ventilation accordingly (9). Here, we turn our focus to recent data demonstrating that 5-HT neurons provide an essential excitatory drive to the respiratory network. We then further discuss their role in the CO2 chemoreflex, as well as other homeostatic functions that are closely related to ventilatory control. Last, we provide additional hypotheses/concepts that are worthy of further study, and how 5-HT neurons may be involved in human disease.
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Affiliation(s)
- Matthew R Hodges
- BSB-504, Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226, USA.
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18
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Transgenic mice lacking serotonin neurons have severe apnea and high mortality during development. J Neurosci 2009; 29:10341-9. [PMID: 19692608 DOI: 10.1523/jneurosci.1963-09.2009] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Central serotonin (5-HT) neurons modulate many vital brain functions, including respiratory control. Whether breathing depends critically on 5-HT neurons, or whether their influence is excitatory or inhibitory, remains controversial. Here we show that neonatal Lmx1b(flox/flox;ePet-Cre/+) mice (also called Lmx1b(f/f/p) mice), which selectively lack serotonin neurons, display frequent and severe apnea lasting as long as 55 s. This was associated with a marked decrease in ventilation to less than one-half of normal. These respiratory abnormalities were most severe during the postnatal period, markedly improving by the time the pups were 2-4 weeks old. Despite the severe breathing dysfunction, many of these mice survived, but there was a high perinatal mortality, and those that survived had a decrease in growth rate until the age at which the respiratory defects resolved. Consistent with these in vivo observations, respiratory output was markedly reduced in isolated brainstem-spinal cord preparations from neonatal Lmx1b(f/f/p) mice and completely blocked in perfused brain preparations from neonatal rats treated with selective antagonists of 5-HT(2A) and neurokinin 1 (NK-1) receptors. The ventilatory deficits in neonatal Lmx1b(f/f/p) mice were reversed in vitro and in vivo with agonists of 5-HT(2A) and/or NK-1 receptors. These results demonstrate that ventilatory output in the neonatal period is critically dependent on serotonin neurons, which provide excitatory drive to the respiratory network via 5-HT(2A) and NK-1 receptor activation. These findings provide insight into the mechanisms of sudden infant death syndrome, which has been associated with abnormalities of 5-HT neurons and of cardiorespiratory control.
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19
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Corcoran AE, Hodges MR, Wu Y, Wang W, Wylie CJ, Deneris ES, Richerson GB. Medullary serotonin neurons and central CO2 chemoreception. Respir Physiol Neurobiol 2009; 168:49-58. [PMID: 19394450 PMCID: PMC2787387 DOI: 10.1016/j.resp.2009.04.014] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2009] [Revised: 04/15/2009] [Accepted: 04/18/2009] [Indexed: 11/18/2022]
Abstract
Serotonergic (5-HT) neurons are putative central respiratory chemoreceptors, aiding in the brain's ability to detect arterial changes in PCO2 and implement appropriate ventilatory responses to maintain blood homeostasis. These neurons are in close proximity to large medullary arteries and are intrinsically chemosensitive in vitro, characteristics expected for chemoreceptors. 5-HT neurons of the medullary raphé are stimulated by hypercapnia in vivo, and their disruption results in a blunted hypercapnic ventilatory response. More recently, data collected from transgenic and knockout mice have provided further insight into the role of 5-HT in chemosensitivity. This review summarizes current evidence in support of the hypothesis that 5-HT neurons are central chemoreceptors, and addresses arguments made against this role. We also briefly explore the relationship between the medullary raphé and another chemoreceptive site, the retrotrapezoid nucleus, and discuss how they may interact during hypercapnia to produce a robust ventilatory response.
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Affiliation(s)
- Andrea E Corcoran
- Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK 99775, USA.
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20
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Role of chemoreceptors in mediating dyspnea. Respir Physiol Neurobiol 2008; 167:9-19. [PMID: 19118647 DOI: 10.1016/j.resp.2008.12.002] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2008] [Revised: 11/26/2008] [Accepted: 12/04/2008] [Indexed: 11/22/2022]
Abstract
Dyspnea, or the uncomfortable awareness of respiratory distress, is a common symptom experienced by most people at some point during their lifetime. It is commonly encountered in individuals with pulmonary disease, such as chronic obstructive pulmonary disease (COPD), but can also be seen in healthy individuals after strenuous exercise, at altitude or in response to psychological stress. Dyspnea is a multifactorial sensation involving the brainstem, cortex, and limbic system, as well as mechanoreceptors, irritant receptors and chemoreceptors. Chemoreceptors appear to contribute to the sensation of dyspnea in two ways. They stimulate the respiratory control system in response to hypoxia and/or hypercapnia, and the resultant increase respiratory motor output can be consciously perceived as unpleasant. They also can induce the sensation of dyspnea through an as yet undetermined mechanism-potentially via direct ascending connections to the limbic system and cortex. The goal of this article is to briefly review how changes in blood gases reach conscious awareness and how chemoreceptors are involved in dyspnea.
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21
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Rojas A, Su J, Yang L, Lee M, Cui N, Zhang X, Fountain D, Jiang C. Modulation of the heteromeric Kir4.1-Kir5.1 channel by multiple neurotransmitters via Galphaq-coupled receptors. J Cell Physiol 2007; 214:84-95. [PMID: 17559083 PMCID: PMC4132838 DOI: 10.1002/jcp.21169] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The heteromeric Kir4.1-Kir5.1 channel is a candidate sensing molecule for central CO(2) chemoreception. Since central CO(2) chemoreception is subject to neural modulations, we performed studies to test the hypothesis that the Kir4.1-Kir5.1 channel is modulated by the neurotransmitters critical for respiratory control, including serotonin (5-HT), substance-P (SP), and thyrotropin releasing hormone (TRH). The heteromeric Kir4.1-Kir5.1 channel was strongly inhibited by SP, TRH, and 5-HT when expressed in Xenopus oocytes, whereas these neurotransmitters had no effect on the homomeric Kir4.1 channel. Such an inhibition was dose-dependent and relied on specific G(alphaq)-protein-coupled receptors and protein kinase C (PKC). No direct interaction of the channel with G-proteins was found. Channel sensitivity to CO(2)/pH was not compromised with the inhibition by these neurotransmitters, as the channel remained to be inhibited by acidic pH following an exposure to the neurotransmitters. The firing rate of CO(2)-sensitive brainstem neurons cultured in microelectrode arrays was augmented by SP or a 5-HT2A receptor agonist, which was blocked by PKC inhibitors suggesting that PKC underscores the inhibitory effect of SP and 5-HT in cultured brainstem neurons as well. Immunostaining showed that both Kir4.1 and Kir5.1 proteins were co-localized in the cultured brainstem neurons. These results therefore indicate that the heteromeric Kir4.1-Kir5.1 channel is modulated by the neurotransmitters critical for respiratory control, suggesting a novel neuromodulatory mechanism for the chemosensitivity of brainstem neurons to elevated PCO(2) and acidic pH.
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Affiliation(s)
| | | | | | | | | | | | | | - Chun Jiang
- Correspondence to: Dr. Chun Jiang, Department of Biology, Georgia State University, 24 Peachtree Center Avenue, Atlanta, GA 30302-4010, Phone: 404-651-0913, Fax: 404-651-2509,
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22
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Nattie E, Li A. Neurokinin-1 receptor-expressing neurons in the ventral medulla are essential for normal central and peripheral chemoreception in the conscious rat. J Appl Physiol (1985) 2006; 101:1596-606. [PMID: 16902062 DOI: 10.1152/japplphysiol.00347.2006] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Neurokinin-1 receptor immunoreactive (NK1R-ir) neurons and processes are widely distributed within the medulla, prominently at central chemoreceptor sites. Focal lesions of NK1R-ir neurons in the medullary raphe or the retrotrapezoid nucleus partially reduced the CO(2) response in conscious rats. We ask if NK1R-ir cells and processes over a wide region of the ventral medulla are essential for central and peripheral chemoreception by cisterna magna injection of SSP-SAP, a high-affinity version of substance P-saporin. After 22 days, NK1R-ir cell loss was -79% in the retrotrapezoid nucleus and -65% in the A5 region, which lie close to the ventral surface, and -38% in the medullary raphe and -49% in the pre-Bötzinger complex/rostral ventral respiratory group, which lie deeper. Dorsal chemoreceptor sites, the caudal nucleus tractus solitarius and the A6 region, were unaffected. At 8 and 22 days, these lesions produced 1) hypoventilation during air breathing in wakefulness ( approximately 8%) and in non-rapid eye movement (NREM) ( approximately 9%) and rapid eye movement ( approximately 14%) sleep, as measured over a 4-h period; 2) a substantially reduced ventilatory response to 7% CO(2) by 61% in wakefulness and 46-57% in NREM sleep; and 3) a decreased ventilatory response to 12% O(2) by 40% in wakefulness and 35% in NREM sleep at 8 days, with partial recovery by 22 days. NK1R-ir neurons in the ventral medulla are essential for normal central chemoreception, provide a drive to breathe, and modulate the peripheral chemoreceptor responses. These effects are not state dependent.
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Affiliation(s)
- Eugene Nattie
- Department of Physiology, Dartmouth Medical School, Borwell Bldg., Lebanon, NH 03756-0001, USA.
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23
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Ribas-Salgueiro JL, Gaytán SP, Ribas J, Pásaro R. Characterization of efferent projections of chemosensitive neurons in the caudal parapyramidal area of the rat brain. Brain Res Bull 2005; 66:235-48. [PMID: 16023921 DOI: 10.1016/j.brainresbull.2005.05.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2004] [Revised: 03/31/2005] [Accepted: 05/05/2005] [Indexed: 11/16/2022]
Abstract
The caudal parapyramidal area of the rat brain contains a population of neurons that are highly sensitive to an increase in the extracellular hydrogen ion concentration ([H+]o). Some of them fire synchronously with respiration when [H+]o is increased. These chemosensitive neurons are located in the caudal ventrolateral medulla in a medial region, closest to the pyramidal tract, and a lateral region, beneath the lateral reticular nucleus. To assess the nature of medullary connections, biotinylated dextran amine injections were performed after recordings from the neurons had been completed. The injections were located within the areas containing serotonergic neurons of the caudal parapyramidal area. The injections within the medial and lateral parts of the caudal parapyramidal region revealed bilateral terminal fields of varicosities within the nucleus of the solitary tract and the ventral respiratory column. Efferent bilateral projections to the lateral paragigantocellular, lateral reticular, and inferior olive nuclei, as well as ipsilateral projections to medial and lateral caudal parapyramidal regions were also identified. Efferent projections towards the raphe obscurus from both medial and lateral caudal parapyramidal regions were found. Medial caudal parapyramidal regions also sent efferent projections towards the raphe pallidus, B1-B3 region, and to the dorsal and ventral parts of the medullary reticular nuclei. The detection of H(+)-sensitive neurons in the caudal parapyramidal area and their projections towards the nucleus of the solitary tract and to the ventral respiratory column, associated with respiratory regulation, indicate that this region could be an excellent candidate for central chemoreception.
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24
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Li Q, Goodchild AK, Seyedabadi M, Pilowsky PM. Preprotachykinin A mRNA is colocalized with tyrosine hydroxylase-immunoreactivity in bulbospinal neurons. Neuroscience 2005; 136:205-16. [PMID: 16198496 DOI: 10.1016/j.neuroscience.2005.07.057] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2005] [Revised: 06/06/2005] [Accepted: 07/20/2005] [Indexed: 11/16/2022]
Abstract
Previous studies have generated controversy about the extent of co-localization between substance P- and catecholamine-containing neurons that project to the spinal cord. In earlier studies, estimates using immunofluorescence after colchicine have ranged from almost all, to almost none. We sought to resolve this issue by combining in situ hybridization and immunofluorescence. Catecholamine (A1 to A7, C1 to C3; tyrosine hydroxylase immunoreactive) neurons in the rat brainstem were examined to determine their content of mRNA for the preprotachykinin-A gene. In the A1 to A7 and the C1 to C3 cell groups, preprotachykinin-A mRNA was found only in substantial amounts in the C1-C3 cell groups. On average 20.9+/-0.9% (234/1120, n=3) of rostral C1 neurons contained preprotachykinin-A mRNA. Co-localization was also observed in C2 and C3 neurons to a similar extent. Retrograde tract-tracing with cholera toxin B subunit was used to identify bulbospinal neurons and 17.9+/-2.7% (96/529 cells) of the bulbospinal tyrosine hydroxylase-containing neurons of the rostral C1 cell group were found to contain preprotachykinin-A mRNA. In addition a new population of non-catecholaminergic bulbospinal preprotachykinin-A neurons is described in an area corresponding to the recently described caudal pressor area. To confirm that the preprotachykinin-A mRNA observed in cells in the medulla was converted to protein, dual immunofluorescence for fiber labeling at the confocal level was carried out. This confirmed colocalization of substance P and tyrosine hydroxylase in the intermediolateral cell column, but nowhere else, in a small number of cases. The results provide evidence for a much larger population of substance P/neurokinin A containing neurons in the brainstem than was previously suspected. Furthermore, many of these neurons are catecholaminergic and spinally projecting. The specific sympathetic outflow that these neurons influence remains to be determined.
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Affiliation(s)
- Q Li
- Department of Physiology, University of Sydney, NSW 2000, Australia
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25
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Richerson GB. Serotonergic neurons as carbon dioxide sensors that maintain pH homeostasis. Nat Rev Neurosci 2004; 5:449-61. [PMID: 15152195 DOI: 10.1038/nrn1409] [Citation(s) in RCA: 378] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- George B Richerson
- Department of Neurology, Yale University School of Medicine, New Haven, and the Veteran's Affairs Medical Center, West Haven, Connecticut, USA
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26
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Nattie EE, Li A, Richerson GB, Richerson G, Lappi DA. Medullary serotonergic neurones and adjacent neurones that express neurokinin-1 receptors are both involved in chemoreception in vivo. J Physiol 2004; 556:235-53. [PMID: 14724193 PMCID: PMC1664900 DOI: 10.1113/jphysiol.2003.059766] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Neurokinin-1 receptor (NK1R)-expressing neurones that are involved in chemoreception at the retrotrapezoid nucleus (Nattie & Li, 2002b) are also prominent at locations that contain medullary serotonergic neurones, which are chemosensitive in vitro. In medullary regions containing both types, we evaluated their role in central chemoreception by specific cell killing. We injected (2 x 100 nl) (a) substance P-saporin (SP-SAP; 1 microm) to kill NK1R-expressing neurones, (b) a novel conjugate of a monoclonal antibody to the serotonin transporter (SERT) and saporin (anti-SERT-SAP; 1 microm) to kill serotonergic neurones, or (c) SP-SAP and anti-SERT-SAP together to kill both types. Controls received IgG-SAP injections (1 microm). There was no double-labelling of NK1R-immunoreactive (ir) and tryptophan-hydroxylase (TPOH)-ir neurones. Cell (somatic profile) counts showed that NK1R-ir neurones in the SP-SAP group were reduced by 31%; TPOH-ir neurones in the anti-SERT-SAP group by 28%; and NK1R-ir and TPOH-ir neurones, respectively, in the combined lesion group by 55% and 31% (P < 0.001; two-way ANOVA; P < 0.05, Tukey's post hoc test). The treatments had no significant effect on sleep/wake time, body temperature, or oxygen consumption but all three reduced the ventilatory response to 7% inspired CO(2) in wakefulness and sleep by a similar amount. SP-SAP treatment decreased the averaged CO(2) responses (3, 7 and 14 days after lesions) in wakefulness and sleep by 21% and 16%, anti-SERT-SAP decreased the responses by 15% and 18%, and the combined treatment decreased the responses by 12% and 12% (P < 0.001; two-way ANOVA; P < 0.05, Tukey's post hoc test). We conclude that separate populations of serotonergic and adjacent NK1R-expressing neurones in the medulla are both involved in central chemoreception in vivo.
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Affiliation(s)
- Eugene E Nattie
- Department of Physiology, Dartmouth Medical School, Borwell Bldg, Lebanon, NH 03756-0001, USA.
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27
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Zhang L, Wilson CG, Liu S, Haxhiu MA, Martin RJ. Hypercapnia-induced activation of brainstem GABAergic neurons during early development. Respir Physiol Neurobiol 2003; 136:25-37. [PMID: 12809796 DOI: 10.1016/s1569-9048(03)00041-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
During early development, GABAergic mechanisms contribute to the regulation of respiratory timing in response to CO2. In 5-7 day old piglets, a double labeling technique was used to determine whether GABA-containing neurons are activated by normoxic hypercapnia (10% CO2, 21% O2, and 69% N2). The c-Fos gene encoded protein (c-Fos) was employed to localize CO2 activated cells within the piglet medulla oblongata. Parvalbumin was used as a marker for GABAergic neurons. In animals breathing room air, only scant c-Fos-like immunoreactive neurons were observed. A marked increase in c-Fos positive cells was induced after a 60 min exposure to hypercapnia. Colocalization studies revealed that hypercapnia significantly increased c-Fos expression in GABA-containing neurons in the medulla oblongata, especially in the ventral aspect of the medulla, within the Bötzinger region, the gigantocellular reticular nucleus, and the caudal raphe nuclei. Only a few double-labeled cells were observed within the nucleus tractus solitarius. Therefore, brainstem GABAergic neurons are part of the neural networks that respond to CO2 and may contribute to respiratory frequency responses to hypercapnia during early development.
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Affiliation(s)
- L Zhang
- Department of Pediatrics, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA
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