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Distinct neural networks derived from galanin-containing nociceptors and neurotensin-expressing pruriceptors. Proc Natl Acad Sci U S A 2022; 119:e2118501119. [PMID: 35943985 PMCID: PMC9388111 DOI: 10.1073/pnas.2118501119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Pain and itch are distinct sensations arousing evasion and compulsive desire for scratching, respectively. It's unclear whether they could invoke different neural networks in the brain. Here, we use the type 1 herpes simplex virus H129 strain to trace the neural networks derived from two types of dorsal root ganglia (DRG) neurons: one kind of polymodal nociceptors containing galanin (Gal) and one type of pruriceptors expressing neurotensin (Nts). The DRG microinjection and immunosuppression were performed in transgenic mice to achieve a successful tracing from specific types of DRG neurons to the primary sensory cortex. About one-third of nuclei in the brain were labeled. More than half of them were differentially labeled in two networks. For the ascending pathways, the spinothalamic tract was absent in the network derived from Nts-expressing pruriceptors, and the two networks shared the spinobulbar projections but occupied different subnuclei. As to the motor systems, more neurons in the primary motor cortex and red nucleus of the somatic motor system participated in the Gal-containing nociceptor-derived network, while more neurons in the nucleus of the solitary tract (NST) and the dorsal motor nucleus of vagus nerve (DMX) of the emotional motor system was found in the Nts-expressing pruriceptor-derived network. Functional validation of differentially labeled nuclei by c-Fos test and chemogenetic inhibition suggested the red nucleus in facilitating the response to noxious heat and the NST/DMX in regulating the histamine-induced scratching. Thus, we reveal the organization of neural networks in a DRG neuron type-dependent manner for processing pain and itch.
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Sung YW, Kiyama S, Choi US, Ogawa S. Involvement of the intrinsic functional network of the red nucleus in complex behavioral processing. Cereb Cortex Commun 2022; 3:tgac037. [PMID: 36159204 PMCID: PMC9491841 DOI: 10.1093/texcom/tgac037] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 08/25/2022] [Indexed: 11/15/2022] Open
Abstract
Abstract
Previous studies suggested the possibility that the red nucleus (RN) is involved in other cognitive functions than motion per se, even though such functions have yet to be clarified. We investigated the activation of RN during several tasks and its intrinsic functional network associated with social cognition and musical practice. The tasks included finger tapping, n-back, and memory recall tasks. Region of interest for RN was identified through those tasks, anatomical information of RN, and a brain atlas. The intrinsic functional network was identified for RN by an analysis of connectivity between RN and other regions typically involved in seven known resting state functional networks with RN used as the seed region. Association of the RN network with a psychological trait of the interpersonal reactivity index and musical training years revealed subnetworks that included empathy related regions or music practice related regions. These social or highly coordinated motor activity represent the most complex functions ever known to involve the RN, adding further evidence for the multifunctional roles of RN. These discoveries may lead to a new direction of investigations to clarify probable novel roles for RN in high-level human behavior.
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Affiliation(s)
- Yul-Wan Sung
- Kansei Fukushi Research Institute, Tohoku Fukushi University , Sendai, Miyagi 9893201 , Japan
| | - Sachiko Kiyama
- Department of Linguistics, Tohoku University , Sendai, Miyagi 9800862 , Japan
| | - Uk-Su Choi
- Medical Device Development Center, Daegu-Gyeongbuk Medical Innovation Foundation , Daegu 41061 , Republic of Korea
| | - Seiji Ogawa
- Kansei Fukushi Research Institute, Tohoku Fukushi University , Sendai, Miyagi 9893201 , Japan
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Yang CF, Kim EJ, Callaway EM, Feldman JL. Monosynaptic Projections to Excitatory and Inhibitory preBötzinger Complex Neurons. Front Neuroanat 2020; 14:58. [PMID: 33013329 PMCID: PMC7507425 DOI: 10.3389/fnana.2020.00058] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2020] [Accepted: 08/04/2020] [Indexed: 01/01/2023] Open
Abstract
The key driver of breathing rhythm is the preBötzinger Complex (preBötC) whose activity is modulated by various functional inputs, e.g., volitional, physiological, and emotional. While the preBötC is highly interconnected with other regions of the breathing central pattern generator (bCPG) in the brainstem, there is no data about the direct projections to either excitatory and inhibitory preBötC subpopulations from other elements of the bCPG or from suprapontine regions. Using modified rabies tracing, we identified neurons throughout the brain that send monosynaptic projections to identified excitatory and inhibitory preBötC neurons in mice. Within the brainstem, neurons from sites in the bCPG, including the contralateral preBötC, Bötzinger Complex, the nucleus of the solitary tract (NTS), parafacial region (pF L /pF V ), and parabrachial nuclei (PB), send direct projections to both excitatory and inhibitory preBötC neurons. Suprapontine inputs to the excitatory and inhibitory preBötC neurons include the superior colliculus, red nucleus, amygdala, hypothalamus, and cortex; these projections represent potential direct pathways for volitional, emotional, and physiological control of breathing.
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Affiliation(s)
- Cindy F. Yang
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - Euiseok J. Kim
- Systems Neurobiology Laboratory, Salk Institute for Biological Studies, La Jolla, CA, United States
| | - Edward M. Callaway
- Systems Neurobiology Laboratory, Salk Institute for Biological Studies, La Jolla, CA, United States
| | - Jack L. Feldman
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
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Macey PM, Sarma MK, Prasad JP, Ogren JA, Aysola R, Harper RM, Thomas MA. Obstructive sleep apnea is associated with altered midbrain chemical concentrations. Neuroscience 2017; 363:76-86. [PMID: 28893651 PMCID: PMC5983363 DOI: 10.1016/j.neuroscience.2017.09.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 08/25/2017] [Accepted: 09/03/2017] [Indexed: 12/28/2022]
Abstract
Obstructive sleep apnea (OSA) is accompanied by altered structure and function in cortical, limbic, brainstem, and cerebellar regions. The midbrain is relatively unexamined, but contains many integrative nuclei which mediate physiological functions that are disrupted in OSA. We therefore assessed the chemistry of the midbrain in OSA in this exploratory study. We used a recently developed accelerated 2D magnetic resonance spectroscopy (2D-MRS) technique, compressed sensing-based 4D echo-planar J-resolved spectroscopic imaging (4D-EP-JRESI), to measure metabolites in the midbrain of 14 OSA (mean age±SD:54.6±10.6years; AHI:35.0±19.4; SAO2 min:83±7%) and 26 healthy control (50.7±8.5years) subjects. High-resolution T1-weighted scans allowed voxel localization. MRS data were processed with custom MATLAB-based software, and metabolite ratios calculated with respect to the creatine peak using a prior knowledge fitting (ProFit) algorithm. The midbrain in OSA showed decreased N-acetylaspartate (NAA; OSA:1.24±0.43, Control:1.47±0.41; p=0.03; independent samples t-test), a marker of neuronal viability. Increased levels in OSA over control subjects appeared in glutamate (Glu; OSA:1.23±0.57, Control:0.98±0.33; p=0.03), ascorbate (Asc; OSA:0.56±0.28, Control:0.42±0.20; (50.7±8.5years; p=0.03), and myo-inositol (mI; OSA:0.96±0.48, Control:0.72±0.35; p=0.03). No differences between groups appeared in γ-aminobutyric acid (GABA) or taurine. The midbrain in OSA patients shows decreased NAA, indicating neuronal injury or dysfunction. Higher Glu levels may reflect excitotoxic processes and astrocyte activation, and higher mI is also consistent with glial activation. Higher Asc levels may result from oxidative stress induced by intermittent hypoxia in OSA. Additionally, Asc and Glu are involved with glutamatergic processes, which are likely upregulated in the midbrain nuclei of OSA patients. The altered metabolite levels help explain dysfunction and structural deficits in the midbrain of OSA patients.
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Key Words
- Asc, ascorbate
- Asp, aspartate
- Ch, choline
- GABA, gamma-aminobutyric acid
- GPC, glycerophosphorylcholine
- GSH, glutathione
- Gln, glutamine
- Glu, glutamate
- Gly, glycine
- NAA, N-acetylaspartate
- NAAG, N-acetylaspartate glutamate
- PCh, phosphocholine
- PE, phosphoethanolamine
- Scy, scyllo-inositol
- Tau, taurine
- Thr, threonine
- autonomic
- intermittent hypoxia
- mI, myo-inositol
- magnetic resonance spectroscopy
- periaqueductal gray
- respiration
- sleep-disordered breathing
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Affiliation(s)
- Paul M Macey
- School of Nursing, David Geffen School of Medicine at UCLA, University of California at Los Angeles, Los Angeles, CA 90095, United States; Brain Research Institute, David Geffen School of Medicine at UCLA, University of California at Los Angeles, Los Angeles, CA 90095, United States.
| | - Manoj K Sarma
- Department of Radiological Sciences, David Geffen School of Medicine at UCLA, University of California at Los Angeles, Los Angeles, CA 90095, United States
| | - Janani P Prasad
- School of Nursing, David Geffen School of Medicine at UCLA, University of California at Los Angeles, Los Angeles, CA 90095, United States
| | - Jennifer A Ogren
- Department of Neurobiology, David Geffen School of Medicine at UCLA, University of California at Los Angeles, Los Angeles, CA 90095, United States
| | - Ravi Aysola
- Department of Medicine (Division of Pulmonary and Critical Care), David Geffen School of Medicine at UCLA, University of California at Los Angeles, Los Angeles, CA 90095, United States
| | - Ronald M Harper
- Brain Research Institute, David Geffen School of Medicine at UCLA, University of California at Los Angeles, Los Angeles, CA 90095, United States; Department of Neurobiology, David Geffen School of Medicine at UCLA, University of California at Los Angeles, Los Angeles, CA 90095, United States
| | - M Albert Thomas
- Department of Radiological Sciences, David Geffen School of Medicine at UCLA, University of California at Los Angeles, Los Angeles, CA 90095, United States
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Koos BJ, Rajaee A, Ibe B, Guerra C, Kruger L. Thalamic mediation of hypoxic respiratory depression in lambs. Am J Physiol Regul Integr Comp Physiol 2016; 310:R586-95. [PMID: 26818057 PMCID: PMC4867384 DOI: 10.1152/ajpregu.00412.2015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Accepted: 01/27/2016] [Indexed: 11/22/2022]
Abstract
Immaturity of respiratory controllers in preterm infants dispose to recurrent apnea and oxygen deprivation. Accompanying reductions in brain oxygen tensions evoke respiratory depression, potentially exacerbating hypoxemia. Central respiratory depression during moderate hypoxia is revealed in the ventilatory decline following initial augmentation. This study determined whether the thalamic parafascicular nuclear (Pf) complex involved in adult nociception and sensorimotor regulation (Bentivoglio M, Balerecia G, Kruger L. Prog Brain Res 87: 53-80, 1991) also becomes a postnatal controller of hypoxic ventilatory decline. Respiratory responses to moderate isocapnic hypoxia were studied in conscious lambs. Hypoxic ventilatory decline was compared with peak augmentation. Pf and/or adjacent thalamic structures were destroyed by the neuron-specific toxin ibotenic acid (IB). IB lesions involving the thalamic Pf abolished hypoxic ventilatory decline. Lesions of adjacent thalamic nuclei that spared Pf and control injections of vehicle failed to blunt hypoxic respiratory depression. Our findings reveal that the thalamic Pf region is a critical controller of hypoxic ventilatory depression and thus a key target for exploring molecular concomitants of forebrain pathways regulating hypoxic ventilatory depression in early development.
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Affiliation(s)
- Brian J Koos
- Department of Obstetrics & Gynecology, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California;
| | - Arezoo Rajaee
- Department of Obstetrics & Gynecology, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California
| | - Basil Ibe
- Department of Pediatrics, C. W. Steers Biological Resource Center, Los Angeles Biomedical Research Institute, Harbor-University of California Los Angeles Medical Center, Torrance, California; and
| | - Catalina Guerra
- C. W. Steers Biological Resource Center, Los Angeles Biomedical Research Institute, Harbor-University of California Los Angeles Medical Center, Torrance, California
| | - Lawrence Kruger
- Department of Neurobiology, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California
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Abstract
Breathing movements have been demonstrated in the fetuses of every mammalian species investigated and are a critical component of normal fetal development. The classic sheep preparations instrumented for chronic fetal monitoring determined that fetal breathing movements (FBMs) occur in aggregates interspersed with long periods of quiescence that are strongly associated with neurophysiological state. The fetal sheep model also provided data regarding the neurochemical modulation of behavioral state and FBMs under a variety of in utero conditions. Subsequently, in vitro rodent models have been developed to advance our understanding of cellular, synaptic, network, and more detailed neuropharmacological aspects of perinatal respiratory neural control. This includes the ontogeny of the inspiratory rhythm generating center, the preBötzinger complex (preBötC), and the anatomical and functional development of phrenic motoneurons (PMNs) and diaphragm during the perinatal period. A variety of newborn animal models and studies of human infants have provided insights into age-dependent changes in state-dependent respiratory control, responses to hypoxia/hypercapnia and respiratory pathologies.
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Affiliation(s)
- John J Greer
- Department of Physiology, Centre for Neuroscience, Women and Children Health Research Institute, University of Alberta, Edmonton, Alberta, Canada.
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7
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Koos BJ. Adenosine A₂a receptors and O₂ sensing in development. Am J Physiol Regul Integr Comp Physiol 2011; 301:R601-22. [PMID: 21677265 DOI: 10.1152/ajpregu.00664.2010] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Reduced mitochondrial oxidative phosphorylation, via activation of adenylate kinase and the resulting exponential rise in the cellular AMP/ATP ratio, appears to be a critical factor underlying O₂ sensing in many chemoreceptive tissues in mammals. The elevated AMP/ATP ratio, in turn, activates key enzymes that are involved in physiologic adjustments that tend to balance ATP supply and demand. An example is the conversion of AMP to adenosine via 5'-nucleotidase and the resulting activation of adenosine A(₂A) receptors, which are involved in acute oxygen sensing by both carotid bodies and the brain. In fetal sheep, A(₂A) receptors associated with carotid bodies trigger hypoxic cardiovascular chemoreflexes, while central A(₂A) receptors mediate hypoxic inhibition of breathing and rapid eye movements. A(₂A) receptors are also involved in hypoxic regulation of fetal endocrine systems, metabolism, and vascular tone. In developing lambs, A(₂A) receptors play virtually no role in O₂ sensing by the carotid bodies, but brain A(₂A) receptors remain critically involved in the roll-off ventilatory response to hypoxia. In adult mammals, A(₂A) receptors have been implicated in O₂ sensing by carotid glomus cells, while central A(₂A) receptors likely blunt hypoxic hyperventilation. In conclusion, A(₂A) receptors are crucially involved in the transduction mechanisms of O₂ sensing in fetal carotid bodies and brains. Postnatally, central A(₂A) receptors remain key mediators of hypoxic respiratory depression, but they are less critical for O₂ sensing in carotid chemoreceptors, particularly in developing lambs.
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Affiliation(s)
- Brian J Koos
- Department of Obstetrics and Gynecology; Brain Research Institute, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California, USA.
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8
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Areza-Fegyveres R, Kairalla RA, Carvalho CRR, Nitrini R. Cognition and chronic hypoxia in pulmonary diseases. Dement Neuropsychol 2010; 4:14-22. [PMID: 29213655 PMCID: PMC5619525 DOI: 10.1590/s1980-57642010dn40100003] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Lung disease with chronic hypoxia has been associated with cognitive impairment
of the subcortical type.
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Affiliation(s)
- Renata Areza-Fegyveres
- Neurologist, collaborating researcher of the Cognitive and Behavioral Neurology Unit, Hospital das Clínicas, University of São Paulo Medical School
| | - Ronaldo A Kairalla
- Assistant Professor, Pulmonary Division, Heart Institute (InCor), University of São Paulo Medical School
| | - Carlos R R Carvalho
- Associate Professor, Pulmonary Division, Heart Institute (InCor), University of São Paulo Medical School
| | - Ricardo Nitrini
- Associate Professor of the Department of Neurology and Director of the Cognitive and Behavioral Neurology Unit, Hospital das Clínicas, University of São Paulo Medical School
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9
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McKay LC, Critchley HD, Murphy K, Frackowiak RS, Corfield DR. Sub-cortical and brainstem sites associated with chemo-stimulated increases in ventilation in humans. Neuroimage 2010; 49:2526-35. [DOI: 10.1016/j.neuroimage.2009.11.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2009] [Revised: 11/03/2009] [Accepted: 11/04/2009] [Indexed: 01/29/2023] Open
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10
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Lavezzi AM, Corna M, Matturri L, Santoro F. Neuropathology of the Guillain-Mollaret Triangle (Dentato-Rubro-Olivary Network) in Sudden Unexplained Perinatal Death and SIDS. Open Neurol J 2009; 3:48-53. [PMID: 19597559 PMCID: PMC2708385 DOI: 10.2174/1874205x00903010048] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2009] [Revised: 04/09/2009] [Accepted: 04/15/2009] [Indexed: 11/22/2022] Open
Abstract
The present study was undertaken to evaluate the possible alterations of the triangle of Guillain and Mollaret (G-Mt), a neuronal brainstem/cerebellum network (from the dentate nucleus to red nucleus and inferior olivary nucleus) already known for its involvement in the pathogenesis of the palatal myoclonus, in sudden unexplained perinatal and infant death. In 44 cases of perinatal and infant death victims, aged from 26 gestational weeks to 10 months of life, we investigated, besides the histological morphology of the three nuclei, the c-fos and apoptotic expression, as well as the possible effects elicited by maternal cigarette smoking. A significant increase of lesions (hypoplasia and/or increased c-fos and apoptotic neuronal immunopositivity) of the three nuclei was found in unexplained death victims, compared with age-matched controls. These alterations were related to maternal cigarette smoking habit. We postulated that the G-Mt is an important network involved in the pathogenesis of a wide spectrum of pathological manifestations and that maternal smoking during pregnancy can exert an adverse influence on this complex, even leading to sudden death in vulnerable periods of perinatal or infant development.
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Affiliation(s)
- Anna Maria Lavezzi
- Department of Surgical, Reconstructive and Diagnostic Sciences - "Lino Rossi" Research Center for the study and prevention of unexpected perinatal death and SIDS, University of Milan, Italy
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Ishiguro T, Iwase M, Kanamaru M, Izumizaki M, Ohshima Y, Homma I. Impaired ventilation and metabolism response to hypoxia in histamine H1 receptor-knockout mice. Respir Physiol Neurobiol 2006; 154:331-41. [PMID: 16540381 DOI: 10.1016/j.resp.2006.01.017] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2005] [Revised: 01/26/2006] [Accepted: 01/30/2006] [Indexed: 10/24/2022]
Abstract
The role of central histamine in the hypoxic ventilatory response was examined in conscious wild-type (WT) and histamine type1 receptor-knockout (H1RKO) mice. Hypoxic gas (7% O(2) and 3% CO(2) in N(2)) exposure initially increased and then decreased ventilation, referred to as hypoxic ventilatory decline (HVD). The initial increase in ventilation did not differ between genotypes. However, H1RKO mice showed a blunted HVD, in which mean inspiratory flow was greater than that in WT mice. O(2) consumption (V(O2)) and CO(2) excretion were reduced 10min after hypoxic gas exposure in both genotypes, but (V(O2)) was greater in H1RKO mice than in WT mice. The ratio of minute ventilation to (V(O2)) during HVD did not differ between genotypes, indicating that ventilation is adequately controlled according to metabolic demand in both mice. Peripheral chemoreceptor sensitivity did not differ between genotypes. We conclude that central histamine contributes via the H1 receptor to changes in metabolic rate during hypoxia to increase HVD in conscious mice.
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Affiliation(s)
- Takashi Ishiguro
- Department of Physiology, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan
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Greer JJ, Funk GD, Ballanyi K. Preparing for the first breath: prenatal maturation of respiratory neural control. J Physiol 2005; 570:437-44. [PMID: 16284077 PMCID: PMC1479880 DOI: 10.1113/jphysiol.2005.097238] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
By birth, the regulatory neural network responsible for respiratory control is capable of generating robust rhythm-driving ventilation that can adjust to homeostatic needs. The advent of in vitro models isolated from prenatal rodents has significantly advanced our understanding of these processes. In this topical review, we examine the development of medullary respiratory rhythm-generating centres and phrenic motoneurone-diaphragm properties during the prenatal period.
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Affiliation(s)
- John J Greer
- University of Alberta, Department of Physiology, 513 HMRC, Edmonton, AB, Canada T6G 2S2.
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13
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Abstract
This mini-review summarizes the present knowledge regarding central oxygen-chemosensitive sites with special emphasis on their function in regulating changes in cardiovascular and respiratory responses. These oxygen-chemosensitive sites are distributed throughout the brain stem from the thalamus to the medulla and may form an oxygen-chemosensitive network. The ultimate effect on respiratory or sympathetic activity presumably depends on the specific neural projections from each of these brain stem oxygen-sensitive regions as well as on the developmental age of the animal. Little is known regarding the cellular mechanisms involved in the chemotransduction process of the central oxygen sensors. The limited information available suggests some conservation of mechanisms used by other oxygen-sensing systems, e.g., carotid body glomus cells and pulmonary vascular smooth muscle cells. However, major gaps exist in our understanding of the specific ion channels and oxygen sensors required for transducing central hypoxia by these central oxygen-sensitive neurons. Adaptation of these central oxygen-sensitive neurons during chronic or intermittent hypoxia likely contributes to responses in both physiological conditions (ascent to high altitude, hypoxic conditioning) and clinical conditions (heart failure, chronic obstructive pulmonary disease, obstructive sleep apnea syndrome, hypoventilation syndromes). This review underscores the lack of knowledge about central oxygen chemosensors and highlights real opportunities for future research.
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Affiliation(s)
- Judith A Neubauer
- Division of Pulmonary and Critical Care Medicine, Deparment of Medicine, Uversity of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, New Brunswick, NJ 08903-0019, USA.
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14
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Licata F, Li Volsi G, Di Mauro M, Fretto G, Ciranna L, Santangelo F. Serotonin modifies the neuronal inhibitory responses to gamma-aminobutyric acid in the red nucleus: a microiontophoretic study in the rat. Exp Neurol 2001; 167:95-107. [PMID: 11161597 DOI: 10.1006/exnr.2001.7533] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effects of 5-hydroxytryptamine (5-HT) on the inhibitory responses evoked by gamma-aminobutyric acid (GABA) in neurons of the red nucleus (RN) were studied using a microiontophoretic technique. Extracellular unitary recordings performed in anesthetized rats demonstrated that 5-HT ejection influenced GABA-evoked inhibition in 94% of RN neurons, enhancing them in 52% and depressing them in 46% of cases. Both effects were specific and dose-dependent,although enhancements or depressions of the GABA responses were respectively inversely and directly related to the doses of 5-HT applied. The type of modulation exerted by 5-HT on the GABA responses was independent of the action of the amine on background firing. In fact, 5-HT induced an enhancement of the GABA responses in neurons mostly located in the rostral RN and a depression in those in the caudal RN. The application of 8-hydroxy-2(di-n-propylamino)tetralin, a specific 5-HT(1A) receptor agonist, enhanced GABA responses, whereas alpha-methyl-5-hydroxytryptamine, a 5-HT(2A) receptor agonist, depressed them. Both the 5-HT(2) antagonist methysergide and the 5-HT(2A) selective antagonist ketanserin were able to block partially or totally the depressive action of 5-HT on GABA responses. In contrast, the same 5-HT antagonists mimicked the enhancing action of 5-HT on the GABA responses or were ineffective. Application of bicuculline, a GABA(A) receptor antagonist, enhanced the excitatory action of 5-HT on the background firing and slightly reduced the inhibitory action. It is concluded that 5-HT is able to modulate GABA-evoked responses in RN neurons by acting on both 5-HT(1A) and 5-HT(2A) receptors. The functional significance of a serotonergic control on GABAergic inhibitory effects in RN is discussed.
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Affiliation(s)
- F Licata
- Department of Physiological Sciences, University of Catania, Catania, 95125, Italy
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Bissonnette JM. Mechanisms regulating hypoxic respiratory depression during fetal and postnatal life. Am J Physiol Regul Integr Comp Physiol 2000; 278:R1391-400. [PMID: 10848503 DOI: 10.1152/ajpregu.2000.278.6.r1391] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Selected topics in the respiratory response to acute hypoxia in the fetus and newborn are reviewed. Peripheral chemoreceptors acting through ionotrophic glutamate receptors play an important role in affecting the initial augmentation phase. Whether fall off in peripheral chemoreceptor activity contributes to the secondary depressive phase remains controversial. A number of approaches including permanent electrolytic and reversible cooling lesions, Fos protein activation, and double-labeling immunohistochemistry has converged to show that an area in and around the locus ceruleus in the rostral pons affects the central depression. There is evidence that this is mediated by catecholamines acting at alpha(2)-adrenergic receptors. Tonic activity in early expiratory (postinspiratory) neurons may contribute to hypoxia-induced apneic episodes in the fetus and newborn. Desensitization of alpha-amino-3-hydroxy-5-methylisoxazole-4-proprionic acid receptors has been demonstrated in respiratory-related neurons both in vivo and in vitro. The role that this process might play in the depressive phase of the hypoxic ventilatory response has not been established. In vitro experiments with isolated brain stem-spinal cord preparations or transverse brain stem slices usually involve anoxia, whereas whole animal experiments use 8-15% O(2). Therefore, caution must be exercised in attempting to construct a unifying framework from these two approaches.
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Affiliation(s)
- J M Bissonnette
- Departments of Obstetrics and Gynecology and Cell and Developmental Biology, Oregon Health Sciences University, Portland, Oregon 97201-3098, USA.
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Abstract
In this review, the maturational changes occurring in the mammalian respiratory network from fetal to adult ages are analyzed. Most of the data presented were obtained on rodents using in vitro approaches. In gestational day 18 (E18) fetuses, this network functions but is not yet able to sustain a stable respiratory activity, and most of the neonatal modulatory processes are not yet efficient. Respiratory motoneurons undergo relatively little cell death, and even if not yet fully mature at E18, they are capable of firing sustained bursts of potentials. Endogenous serotonin exerts a potent facilitation on the network and appears to be necessary for the respiratory rhythm to be expressed. In E20 fetuses and neonates, the respiratory activity has become quite stable. Inhibitory processes are not yet necessary for respiratory rhythmogenesis, and the rostral ventrolateral medulla (RVLM) contains inspiratory bursting pacemaker neurons that seem to constitute the kernel of the network. The activity of the network depends on CO2 and pH levels, via cholinergic relays, as well as being modulated at both the RVLM and motoneuronal levels by endogenous serotonin, substance P, and catecholamine mechanisms. In adults, the inhibitory processes become more important, but the RVLM is still a crucial area. The neonatal modulatory processes are likely to continue during adulthood, but they are difficult to investigate in vivo. In conclusion, 1) serotonin, which greatly facilitates the activity of the respiratory network at all developmental ages, may at least partly define its maturation; 2) the RVLM bursting pacemaker neurons may be the kernel of the network from E20 to adulthood, but their existence and their role in vivo need to be further confirmed in both neonatal and adult mammals.
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Affiliation(s)
- G Hilaire
- Unité Propre de Recherche, Centre National de la Recherche Scientifique 9011, Biologie des Rythmes et du Développement, Marseille; and Laboratoire de Neurophysiologie Clinique et Expérimentale, Amiens, France
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17
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Abstract
Effects of chronic hypoxia on chemoreceptors and chemoreflexes in the fetus and neonate are reviewed. The effects are discussed in relation to those in the adult, in which there is an apparent paradox between the increase in chemoreflex gain during acclimatisation to the hypoxia of altitude vs the 'blunting' reported during chronic hypoxia. The possible location and importance of "chemoreceptors" in the brainstem is discussed. In the neonate, chronic hypoxia blunts the ventilatory response to acute hypoxia, an effect largely due to blunting of chemoreceptor sensitivity. Whether this is mediated via a reduction or delay in the normal process of postnatal resetting of hypoxia sensitivity is not known. In addition, there is evidence that the effects on neonatal chemoreceptors are reversible on return to normoxia. Such differences from the adult suggest that special processes, affected by chronic hypoxia, operate in the neonate. In the fetus there is no direct information on the effect of chronic hypoxia on chemoreceptor responses, but it appears that chemoreflexes are augmented, as may occur in the adult during acclimatisation to hypoxia. Recent evidence suggests that arterial chemoreceptors play an important role in fetal cardiovascular and endocrine responses to prolonged hypoxaemia. This will be a productive avenue for future research.
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Affiliation(s)
- M A Hanson
- Department of Obstetrics and Gynaecology, University College London Medical School, U.K.
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