1
|
Alvarez-Araos P, Jiménez S, Salazar-Ardiles C, Núñez-Espinosa C, Paez V, Rodriguez-Fernandez M, Raberin A, Millet GP, Iturriaga R, Andrade DC. Baroreflex and chemoreflex interaction in high-altitude exposure: possible role on exercise performance. Front Physiol 2024; 15:1422927. [PMID: 38895516 PMCID: PMC11184637 DOI: 10.3389/fphys.2024.1422927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2024] [Accepted: 05/15/2024] [Indexed: 06/21/2024] Open
Abstract
The hypoxic chemoreflex and the arterial baroreflex are implicated in the ventilatory response to exercise. It is well known that long-term exercise training increases parasympathetic and decreases sympathetic tone, both processes influenced by the arterial baroreflex and hypoxic chemoreflex function. Hypobaric hypoxia (i.e., high altitude [HA]) markedly reduces exercise capacity associated with autonomic reflexes. Indeed, a reduced exercise capacity has been found, paralleled by a baroreflex-related parasympathetic withdrawal and a pronounced chemoreflex potentiation. Additionally, it is well known that the baroreflex and chemoreflex interact, and during activation by hypoxia, the chemoreflex is predominant over the baroreflex. Thus, the baroreflex function impairment may likely facilitate the exercise deterioration through the reduction of parasympathetic tone following acute HA exposure, secondary to the chemoreflex activation. Therefore, the main goal of this review is to describe the main physiological mechanisms controlling baro- and chemoreflex function and their role in exercise capacity during HA exposure.
Collapse
Affiliation(s)
- Pablo Alvarez-Araos
- Exercise Applied Physiology Laboratory, Centro de Investigación en Fisiología y Medicina de Altura, Departamento Biomedico, Facultad de Ciencias de la Salud, Universidad de Antofagasta, Antofagasta, Chile
- Departamento de Kinesiología, Facultad de Ciencias de la Salud, Universidad de Atacama, Copiapó, Chile
| | - Sergio Jiménez
- Departamento de Kinesiología, Facultad de Ciencias de la Salud, Universidad de Atacama, Copiapó, Chile
| | - Camila Salazar-Ardiles
- Exercise Applied Physiology Laboratory, Centro de Investigación en Fisiología y Medicina de Altura, Departamento Biomedico, Facultad de Ciencias de la Salud, Universidad de Antofagasta, Antofagasta, Chile
| | - Cristian Núñez-Espinosa
- Escuela de Medicina de la Universidad de Magallanes, Punta Arenas, Chile
- Centro Asistencial de Docencia e Investigación (CADI-UMAG), Santiago, Chile
| | - Valeria Paez
- Exercise Applied Physiology Laboratory, Centro de Investigación en Fisiología y Medicina de Altura, Departamento Biomedico, Facultad de Ciencias de la Salud, Universidad de Antofagasta, Antofagasta, Chile
- Institute for Biological and Medical Engineering, Schools of Engineering, Medicine and Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Maria Rodriguez-Fernandez
- Institute for Biological and Medical Engineering, Schools of Engineering, Medicine and Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Antoine Raberin
- Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland
| | - Gregoire P. Millet
- Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland
| | - Rodrigo Iturriaga
- Exercise Applied Physiology Laboratory, Centro de Investigación en Fisiología y Medicina de Altura, Departamento Biomedico, Facultad de Ciencias de la Salud, Universidad de Antofagasta, Antofagasta, Chile
- Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Santiago, Chile
| | - David C. Andrade
- Exercise Applied Physiology Laboratory, Centro de Investigación en Fisiología y Medicina de Altura, Departamento Biomedico, Facultad de Ciencias de la Salud, Universidad de Antofagasta, Antofagasta, Chile
| |
Collapse
|
2
|
Simpson LL, Stembridge M, Siebenmann C, Moore JP, Lawley JS. Mechanisms underpinning sympathoexcitation in hypoxia. J Physiol 2024. [PMID: 38533641 DOI: 10.1113/jp284579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Accepted: 02/28/2024] [Indexed: 03/28/2024] Open
Abstract
Sympathoexcitation is a hallmark of hypoxic exposure, occurring acutely, as well as persisting in acclimatised lowland populations and with generational exposure in highland native populations of the Andean and Tibetan plateaus. The mechanisms mediating altitude sympathoexcitation are multifactorial, involving alterations in both peripheral autonomic reflexes and central neural pathways, and are dependent on the duration of exposure. Initially, hypoxia-induced sympathoexcitation appears to be an adaptive response, primarily mediated by regulatory reflex mechanisms concerned with preserving systemic and cerebral tissue O2 delivery and maintaining arterial blood pressure. However, as exposure continues, sympathoexcitation is further augmented above that observed with acute exposure, despite acclimatisation processes that restore arterial oxygen content (C a O 2 ${C_{{\mathrm{a}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ). Under these conditions, sympathoexcitation may become maladaptive, giving rise to reduced vascular reactivity and mildly elevated blood pressure. Importantly, current evidence indicates the peripheral chemoreflex does not play a significant role in the augmentation of sympathoexcitation during altitude acclimatisation, although methodological limitations may underestimate its true contribution. Instead, processes that provide no obvious survival benefit in hypoxia appear to contribute, including elevated pulmonary arterial pressure. Nocturnal periodic breathing is also a potential mechanism contributing to altitude sympathoexcitation, although experimental studies are required. Despite recent advancements within the field, several areas remain unexplored, including the mechanisms responsible for the apparent normalisation of muscle sympathetic nerve activity during intermediate hypoxic exposures, the mechanisms accounting for persistent sympathoexcitation following descent from altitude and consideration of whether there are sex-based differences in sympathetic regulation at altitude.
Collapse
Affiliation(s)
- Lydia L Simpson
- Department of Sport Science, Performance Physiology and Prevention, Universität Innsbruck, Innsbruck, Austria
| | - Mike Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | | | - Jonathan P Moore
- School of Psychology and Sport Science, Institute of Applied Human Physiology, Bangor University, Bangor, UK
| | - Justin S Lawley
- Department of Sport Science, Performance Physiology and Prevention, Universität Innsbruck, Innsbruck, Austria
- Institute of Mountain Emergency Medicine, EURAC Research, Bolzano, Italy
| |
Collapse
|
3
|
Souza JR, Lima-Silveira L, Accorsi-Mendonça D, Machado BH. Enhancement of the Evoked Excitatory Transmission in the Nucleus Tractus Solitarius Neurons after Sustained Hypoxia in Mice Depends on A 2A Receptors. Neuroscience 2024; 536:57-71. [PMID: 37979842 DOI: 10.1016/j.neuroscience.2023.11.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Revised: 11/06/2023] [Accepted: 11/11/2023] [Indexed: 11/20/2023]
Abstract
The first synapses of the afferents of peripheral chemoreceptors are located in the Nucleus Tractus Solitarius (NTS) and there is evidence that short-term sustained hypoxia (SH - 24 h, FiO2 0.1) facilitates glutamatergic transmission in NTS neurons of rats. Adenosine is an important neuromodulator of synaptic transmission and hypoxia contributes to increase its extracellular concentration. The A2A receptors mediate the excitatory actions of adenosine and are active players in the modulation of neuronal networks in the NTS. Herein, we used knockout mice for A2A receptors (A2AKO) and electrophysiological recordings of NTS neurons were performed to evaluate the contribution of these receptors in the changes in synaptic transmission in NTS neurons of mice submitted to SH. The membrane passive properties and excitability of NTS neurons were not affected by SH and were similar between A2AKO and wild-type mice. The overall amplitude of spontaneous glutamatergic currents in NTS neurons of A2AKO mice was lower than in Balb/c WT mice. SH increased the amplitude of evoked glutamatergic currents of NTS neurons from WT mice by a non-presynaptic mechanism, but this enhancement was not observed in NTS neurons of A2AKO mice. Under normoxia, the amplitude of evoked glutamatergic currents was similar between WT and A2AKO mice. The data indicate that A2A receptors (a) modulate spontaneous glutamatergic currents, (b) do not modulate the evoked glutamatergic transmission in the NTS neurons under control conditions, and (c) are required for the enhancement of glutamatergic transmission observed in the NTS neurons of mice submitted to SH.
Collapse
Affiliation(s)
- Juliana R Souza
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto 14049-900, SP, Brazil
| | - Ludmila Lima-Silveira
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto 14049-900, SP, Brazil
| | - Daniela Accorsi-Mendonça
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto 14049-900, SP, Brazil
| | - Benedito H Machado
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto 14049-900, SP, Brazil.
| |
Collapse
|
4
|
Matott MP, Hasser EM, Kline DD. Sustained Hypoxia Alters nTS Glutamatergic Signaling and Expression and Function of Excitatory Amino Acid Transporters. Neuroscience 2020; 430:131-140. [PMID: 32032667 PMCID: PMC7560968 DOI: 10.1016/j.neuroscience.2020.01.034] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2019] [Revised: 01/11/2020] [Accepted: 01/23/2020] [Indexed: 01/16/2023]
Abstract
Glutamate is the major excitatory neurotransmitter in the nucleus tractus solitarii (nTS) and mediates chemoreflex function during periods of low oxygen (i.e. hypoxia). We have previously shown that nTS excitatory amino acid transporters (EAATs), specifically EAAT-2, located on glia modulate neuronal activity, cardiorespiratory and chemoreflex function under normal conditions via its tonic uptake of extracellular glutamate. Chronic sustained hypoxia (SH) elevates nTS synaptic transmission and chemoreflex function. The goal of this study was to determine the extent to which glial EAAT-2 contributes to SH-induced nTS synaptic alterations. To do so, male Sprague-Dawley rats (4-7 weeks) were exposed to either 1, 3, or 7 days of SH (10% O2, 24 h/day) and compared to normoxic controls (21% O2, 24 h/day, i.e., 0 days SH). After which, the nTS was harvested for patch clamp electrophysiology, quantitative real-time PCR, immunohistochemistry and immunoblots. SH induced time- and parameter-dependent increases in excitatory postsynaptic currents (EPSCs). TS-evoked EPSC amplitude increased after 1D SH which returned at 3D and 7D SH. Spontaneous EPSC frequency increased only after 3D SH, which returned to normoxic levels at 7D SH. EPSC enhancement occurred primarily by presynaptic mechanisms. Inhibition of EAAT-2 with dihydrokainate (DHK, 300 µM) did not alter EPSCs following 1D SH but induced depolarizing inward currents (Ihold). After 3D SH, DHK decreased TS-EPSC amplitude yet its resulting Ihold was eliminated. EAAT-2 mRNA and protein increased after 3D and 7D SH, respectively. These data suggest that SH alters the expression and function of EAAT-2 which may have a neuroprotective effect.
Collapse
Affiliation(s)
- Michael P Matott
- Dept. of Biomedical Sciences and Dalton Cardiovascular Research Center, University of Missouri, 134 Research Park Drive, Columbia, MO 65211, USA
| | - Eileen M Hasser
- Dept. of Biomedical Sciences and Dalton Cardiovascular Research Center, University of Missouri, 134 Research Park Drive, Columbia, MO 65211, USA
| | - David D Kline
- Dept. of Biomedical Sciences and Dalton Cardiovascular Research Center, University of Missouri, 134 Research Park Drive, Columbia, MO 65211, USA.
| |
Collapse
|
5
|
Getsy PM, Mayer CA, MacFarlane PM, Jacono FJ, Wilson CG. Acute lung injury in neonatal rats causes postsynaptic depression in nucleus tractus solitarii second-order neurons. Respir Physiol Neurobiol 2019; 269:103250. [PMID: 31352011 DOI: 10.1016/j.resp.2019.103250] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Revised: 06/14/2019] [Accepted: 07/02/2019] [Indexed: 12/28/2022]
Abstract
Acute Lung Injury (ALI) alters pulmonary reflex responses, in part due to changes in modulation within the lung and airway neuronal control networks. We hypothesized that synaptic efficacy of nucleus tractus solitarii (nTS) neurons, receiving input from lung, airway, and other viscerosensory afferent fibers, would decrease following ALI. Sprague Dawley neonatal rats (postnatal days 9-11) were given intratracheal installations of saline or bleomycin (a well-characterized model that reproduces the pattern of ALI) and then, one week later, in vitro slices were prepared for whole-cell and perforated whole-cell patch-clamp experiments (postnatal days 16-21). In preparations from ALI rats, 2nd-order nTS neurons had significantly decreased amplitudes of both spontaneous and miniature excitatory postsynaptic currents (sEPSCs and mEPSCs), compared to saline controls. Rise and decay times of sEPSCs were slower in whole-cell recordings from ALI animals. Similarly, the amplitude of tractus solitarii evoked EPSCs (TS-eEPSCs) were significantly lower in 2nd-order nTS neurons from ALI rats. Overall these results suggest the presence of postsynaptic depression at TS-nTS synapses receiving lung, airway, and other viscerosensory afferent tractus solitarii input after bleomycin-induced ALI.
Collapse
Affiliation(s)
- Paulina M Getsy
- Department of Physiology and Biophysics, CWRU School of Medicine, Cleveland, OH, 44106, United States; Department of Pediatrics, Rainbow Babies & Children's Hospital, CWRU School of Medicine, Cleveland, OH, 44106, United States
| | - Catherine A Mayer
- Department of Pediatrics, Rainbow Babies & Children's Hospital, CWRU School of Medicine, Cleveland, OH, 44106, United States
| | - Peter M MacFarlane
- Department of Pediatrics, Rainbow Babies & Children's Hospital, CWRU School of Medicine, Cleveland, OH, 44106, United States
| | - Frank J Jacono
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, CWRU School of Medicine, Cleveland, OH, 44106, United States; Division of Pulmonary, Critical Care and Sleep Medicine, Louis Stokes VA Medical Center, Cleveland, OH, 44106, United States
| | - Christopher G Wilson
- Department of Pediatrics and Lawrence D. Long, MD Center for Perinatal Biology Loma Linda University Loma Linda, CA, United States.
| |
Collapse
|
6
|
Lima-Silveira L, Accorsi-Mendonça D, Bonagamba LGH, Almado CEL, da Silva MP, Nedoboy PE, Pilowsky PM, Machado BH. Enhancement of excitatory transmission in NTS neurons projecting to ventral medulla of rats exposed to sustained hypoxia is blunted by minocycline. J Physiol 2019; 597:2903-2923. [PMID: 30993693 DOI: 10.1113/jp277532] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 04/16/2019] [Indexed: 01/13/2023] Open
Abstract
KEY POINTS Rats subjected to sustained hypoxia (SH) present increases in arterial pressure (AP) and in glutamatergic transmission in the nucleus tractus solitarius (NTS) neurons sending projections to ventrolateral medulla (VLM). Treatment with minocycline, a microglial inhibitor, attenuated the increase in AP in response to SH. The increase in the amplitude of glutamatergic postsynaptic currents in the NTS-VLM neurons, induced by postsynaptic mechanisms, was blunted by minocycline treatment. The number of microglial cells was increased in the NTS of vehicle-treated SH rats but not in the NTS of minocycline-treated rats. The data show that microglial recruitment/proliferation induced by SH is associated with the enhancement of excitatory neurotransmission in NTS-VLM neurons, which may contribute to the observed increase in AP. ABSTRACT Short-term sustained hypoxia (SH) produces significant autonomic and respiratory adjustments and triggers activation of microglia, the resident immune cells in the brain. SH also enhances glutamatergic neurotransmission in the NTS. Here we evaluated the role of microglial activation induced by SH on the cardiovascular changes and mainly on glutamatergic neurotransmission in NTS neurons sending projections to the ventrolateral medulla (NTS-VLM), using a microglia inhibitor (minocycline). Direct measurement of arterial pressure (AP) in freely moving rats showed that SH (24 h, fraction of inspired oxygen ( F I , O 2 ) 0.1) in vehicle and minocycline (30 mg/kg i.p. for 3 days)-treated groups produced a significant increase in AP in relation to control groups under normoxic conditions, but this increase was significantly lower in minocycline-treated rats. Whole-cell patch-clamp recordings revealed that the active properties of the membrane were comparable among the groups. Nevertheless, the amplitudes of glutamatergic postsynaptic currents, evoked by tractus solitarius stimulation, were increased in NTS-VLM neurons of SH rats. Changes in asynchronous glutamatergic currents indicated that the observed increase in amplitude was due to postsynaptic mechanisms. These changes were blunted in the SH group previously treated with minocycline. Using immunofluorescence, we found that the number of microglial cells was increased in the NTS of vehicle-treated SH rats but not in the NTS neurons of minocycline-treated rats. Our data support the concept that microglial activation induced by SH is associated with the enhancement of excitatory neurotransmission in NTS-VLM neurons, which may contribute to the increase in AP observed in this experimental model.
Collapse
Affiliation(s)
- Ludmila Lima-Silveira
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, 14049-900, SP, Brazil
| | - Daniela Accorsi-Mendonça
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, 14049-900, SP, Brazil
| | - Leni G H Bonagamba
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, 14049-900, SP, Brazil
| | - Carlos Eduardo L Almado
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, 14049-900, SP, Brazil
| | - Melina P da Silva
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, 14049-900, SP, Brazil
| | - Polina E Nedoboy
- The Heart Research Institute, Sydney, New South Wales, 2042, Australia
| | - Paul M Pilowsky
- The Heart Research Institute, Sydney, New South Wales, 2042, Australia
| | - Benedito H Machado
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, 14049-900, SP, Brazil
| |
Collapse
|
7
|
Fogarty MJ, Sieck GC. Evolution and Functional Differentiation of the Diaphragm Muscle of Mammals. Compr Physiol 2019; 9:715-766. [PMID: 30873594 PMCID: PMC7082849 DOI: 10.1002/cphy.c180012] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Symmorphosis is a concept of economy of biological design, whereby structural properties are matched to functional demands. According to symmorphosis, biological structures are never over designed to exceed functional demands. Based on this concept, the evolution of the diaphragm muscle (DIAm) in mammals is a tale of two structures, a membrane that separates and partitions the primitive coelomic cavity into separate abdominal and thoracic cavities and a muscle that serves as a pump to generate intra-abdominal (Pab ) and intrathoracic (Pth ) pressures. The DIAm partition evolved in reptiles from folds of the pleural and peritoneal membranes that was driven by the biological advantage of separating organs in the larger coelomic cavity into separate thoracic and abdominal cavities, especially with the evolution of aspiration breathing. The DIAm pump evolved from the advantage afforded by more effective generation of both a negative Pth for ventilation of the lungs and a positive Pab for venous return of blood to the heart and expulsive behaviors such as airway clearance, defecation, micturition, and child birth. © 2019 American Physiological Society. Compr Physiol 9:715-766, 2019.
Collapse
Affiliation(s)
- Matthew J Fogarty
- Mayo Clinic, Department of Physiology & Biomedical Engineering, Rochester, Minnesota, USA
| | - Gary C Sieck
- Mayo Clinic, Department of Physiology & Biomedical Engineering, Rochester, Minnesota, USA
| |
Collapse
|
8
|
da Silva MP, Moraes DJA, Bonagamba LGH, Mecawi ADS, Varanda WA, Machado BH. Hyperexcitability and plasticity induced by sustained hypoxia on rectus abdominis motoneurons. J Physiol 2019; 597:1935-1956. [PMID: 30747446 DOI: 10.1113/jp277030] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2018] [Accepted: 02/06/2019] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Acute hypoxia induces active expiration in rectus abdominis (RA) muscles in conscious freely moving rats, although its overall contribution is smaller than in internal oblique (IO) muscles. Tonically active and silent RA motoneurons were identified in in vitro preparations of rat spinal cords. Sustained hypoxia (SH) increased the synaptic strength and induced morphological changes in tonically active RA motoneurons. Expiratory RA motoneurons were recorded in the in situ preparation and SH enhanced both the excitability and the synaptic transmission in those firing during the stage 2 expiration. The present study contributes to a better understanding of the mechanisms involved in SH recruitment of RA motoneurons to induce active expiration in rats. ABSTRACT Rectus abdominis (RA) motoneurons translate the complex respiratory brainstem inputs into effective muscle contractions. Despite their fundamental role in respiration, their functional and morphological properties are not fully understood. In the present study, we investigated for the first time the contribution of RA muscle to active expiration and characterized RA motoneurons regarding their electrical, molecular and morphological profiles in control rats and in rats submitted to sustained hypoxia (SH), which induces chronic recruitment of abdominal muscles. Electromyographic experiments in conscious freely moving control rats and SH rats showed that RA contributes to active expiration induced by acute hypoxia, although its contribution is smaller than in internal oblique muscles. in vitro whole-cell patch clamp recordings from RA motoneurons revealed two populations of cells: tonically active and silent. SH induced hyperexcitability in the tonically active cells by changing their action potential properties, and EPSCs. Three-dimensional morphological reconstructions of these cells showed that SH increased the dendritic complexity, stimulated the appearance of dendrite spines, and increased the somatic area and volume. Physiologically identified RA motoneurons, firing in two distinct phases of expiration, were recorded in the brainstem-spinal cord in situ preparation of rats. SH increased the firing frequency and EPSCs of neurons firing during stage 2 expiration. Taken together, our results show that RA motoneurons reconfigure their biophysical properties, morphology and synaptic strength to produce an appropriate expiratory drive in response to SH in rats.
Collapse
Affiliation(s)
- Melina P da Silva
- School of Medicine of Ribeirão Preto, Department of Physiology, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Davi José A Moraes
- School of Medicine of Ribeirão Preto, Department of Physiology, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Leni G H Bonagamba
- School of Medicine of Ribeirão Preto, Department of Physiology, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - André de Souza Mecawi
- Paulista School of Medicine, Department of Biophysics, Federal University of São Paulo, São Paulo, Brazil
| | - Wamberto A Varanda
- School of Medicine of Ribeirão Preto, Department of Physiology, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Benedito H Machado
- School of Medicine of Ribeirão Preto, Department of Physiology, University of São Paulo, Ribeirão Preto, SP, Brazil
| |
Collapse
|
9
|
Farrar MJ, Kolkman KE, Fetcho JR. Features of the structure, development, and activity of the zebrafish noradrenergic system explored in new CRISPR transgenic lines. J Comp Neurol 2018; 526:2493-2508. [PMID: 30070695 DOI: 10.1002/cne.24508] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Revised: 07/24/2018] [Accepted: 07/29/2018] [Indexed: 11/11/2022]
Abstract
The noradrenergic (NA) system of vertebrates is implicated in learning, memory, arousal, and neuroinflammatory responses, but is difficult to access experimentally. Small and optically transparent, larval zebrafish offer the prospect of exploration of NA structure and function in an intact animal. We made multiple transgenic zebrafish lines using the CRISPR/Cas9 system to insert fluorescent reporters upstream of slc6a2, the norepinephrine transporter gene. These lines faithfully express reporters in NA cell populations, including the locus coeruleus (LC), which contains only about 14 total neurons. We used the lines in combination with two-photon microscopy to explore the structure and projections of the NA system in the context of the columnar organization of cell types in the zebrafish hindbrain. We found robust alignment of NA projections with glutamatergic neurotransmitter stripes in some hindbrain segments, suggesting orderly relations to neuronal cell types early in life. We also quantified neurite density in the rostral spinal cord in individual larvae with as much as 100% difference in the number of LC neurons, and found no correlation between neuronal number in the LC and projection density in the rostral spinal cord. Finally, using light sheet microscopy, we performed bilateral calcium imaging of the entire LC. We found that large-amplitude calcium responses were evident in all LC neurons and showed bilateral synchrony, whereas small-amplitude events were more likely to show interhemispheric asynchrony, supporting the potential for targeted LC neuromodulation. Our observations and new transgenic lines set the stage for a deeper understanding of the NA system.
Collapse
Affiliation(s)
- Matthew J Farrar
- Department of Neurobiology and Behavior, Cornell University, Ithaca, New York.,Department of Math, Physics and Statistics, Messiah College, Mechanicsburg, Pennsylvania
| | - Kristine E Kolkman
- Department of Neurobiology and Behavior, Cornell University, Ithaca, New York
| | - Joseph R Fetcho
- Department of Neurobiology and Behavior, Cornell University, Ithaca, New York
| |
Collapse
|
10
|
Litvin DG, Dick TE, Smith CB, Jacono FJ. Lung-injury depresses glutamatergic synaptic transmission in the nucleus tractus solitarii via discrete age-dependent mechanisms in neonatal rats. Brain Behav Immun 2018; 70:398-422. [PMID: 29601943 PMCID: PMC6075724 DOI: 10.1016/j.bbi.2018.03.031] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Revised: 03/20/2018] [Accepted: 03/26/2018] [Indexed: 12/26/2022] Open
Abstract
Transition periods (TPs) are brief stages in CNS development where neural circuits can exhibit heightened vulnerability to pathologic conditions such as injury or infection. This susceptibility is due in part to specialized mechanisms of synaptic plasticity, which may become activated by inflammatory mediators released under pathologic conditions. Thus, we hypothesized that the immune response to lung injury (LI) mediated synaptic changes through plasticity-like mechanisms that depended on whether LI occurred just before or after a TP. We studied the impact of LI on brainstem 2nd-order viscerosensory neurons located in the nucleus tractus solitarii (nTS) during a TP for respiratory control spanning (postnatal day (P) 11-15). We injured the lungs of Sprague-Dawley rats by intratracheal instillation of Bleomycin (or saline) just before (P9-11) or after (P17-19) the TP. A week later, we prepared horizontal slices of the medulla and recorded spontaneous and evoked excitatory postsynaptic currents (sEPSCs/eEPSCs) in vitro from neurons in the nTS that received monosynaptic glutamatergic input from the tractus solitarii (TS). In rats injured before the TP (pre-TP), neurons exhibited blunted sEPSCs and TS-eEPSCs compared to controls. The decreased TS-eEPSCs were mediated by differences in postsynaptic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic-acid receptors (AMPAR). Specifically, compared to controls, LI rats had more Ca2+-impermeable AMPARs (CI-AMPARs) as indicated by: 1) the absence of current-rectification, 2) decreased sensitivity to polyamine, 1-Naphthyl-acetyl-spermine-trihydrochloride (NASPM) and 3) augmented immunoreactive staining for the CI-AMPAR GluA2. Thus, pre-TP-LI acts postsynaptically to blunt glutamatergic transmission. The neuroimmune response to pre-TP-LI included microglia hyper-ramification throughout the nTS. Daily intraperitoneal administration of minocycline, an inhibitor of microglial/macrophage function prevented hyper-ramification and abolished the pre-TP-LI evoked synaptic changes. In contrast, rat-pups injured after the TP (post-TP) exhibited microglia hypo-ramification in the nTS and had increased sEPSC amplitudes/frequencies, and decreased TS-eEPSC amplitudes compared to controls. These synaptic changes were not associated with changes in CI-AMPARs, and instead involved greater TS-evoked use-dependent depression (reduced paired pulse ratio), which is a hallmark of presynaptic plasticity. Thus we conclude that LI regulates the efficacy of TS → nTS synapses through discrete plasticity-like mechanisms that are immune-mediated and depend on whether the injury occurs before or after the TP for respiratory control.
Collapse
Affiliation(s)
- David G Litvin
- Department of Physiology & Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44106, United States; Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106, United States; Division of Pulmonary, Critical Care and Sleep Medicine, Louis Stokes VA Medical Center, Cleveland, OH 44106, United States
| | - Thomas E Dick
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106, United States; Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, United States
| | - Corey B Smith
- Department of Physiology & Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44106, United States
| | - Frank J Jacono
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106, United States; Division of Pulmonary, Critical Care and Sleep Medicine, Louis Stokes VA Medical Center, Cleveland, OH 44106, United States.
| |
Collapse
|
11
|
Fogarty MJ, Mantilla CB, Sieck GC. Breathing: Motor Control of Diaphragm Muscle. Physiology (Bethesda) 2018; 33:113-126. [PMID: 29412056 PMCID: PMC5899234 DOI: 10.1152/physiol.00002.2018] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 01/05/2018] [Indexed: 12/12/2022] Open
Abstract
Breathing occurs without thought but is controlled by a complex neural network with a final output of phrenic motor neurons activating diaphragm muscle fibers (i.e., motor units). This review considers diaphragm motor unit organization and how they are controlled during breathing as well as during expulsive behaviors.
Collapse
Affiliation(s)
- Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic , Rochester, Minnesota
- School of Biomedical Sciences, The University of Queensland , Brisbane , Australia
| | - Carlos B Mantilla
- Department of Physiology and Biomedical Engineering, Mayo Clinic , Rochester, Minnesota
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic , Rochester, Minnesota
| | - Gary C Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic , Rochester, Minnesota
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic , Rochester, Minnesota
| |
Collapse
|
12
|
De La Zerda DJ, Stokes JA, Do J, Go A, Fu Z, Powell FL. Ibuprofen does not reverse ventilatory acclimatization to chronic hypoxia. Respir Physiol Neurobiol 2017; 256:29-35. [PMID: 28757366 DOI: 10.1016/j.resp.2017.07.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 07/18/2017] [Accepted: 07/20/2017] [Indexed: 01/13/2023]
Abstract
Ventilatory acclimatization to hypoxia involves an increase in the acute hypoxic ventilatory response that is blocked by non-steroidal anti-inflammatory drugs administered during sustained hypoxia. We tested the hypothesis that inflammatory signals are necessary to sustain ventilatory acclimatization to hypoxia once it is established. Adult, rats were acclimatized to normoxia or chronic hypoxia (CH, [Formula: see text] =70Torr) for 11-12days and treated with ibuprofen or saline for the last 2days of hypoxia. Ventilation, metabolic rate, and arterial blood gas responses to O2 and CO2 were not affected by ibuprofen after acclimatization had been established. Immunohistochemistry and image analysis showed acute (1h) hypoxia activated microglia in a medullary respiratory center (nucleus tractus solitarius, NTS) and this was blocked by ibuprofen administered from the beginning of hypoxic exposure. Microglia returned to the control state after 7days of CH and were not affected by ibuprofen administered for 2 more days of CH. In contrast, NTS astrocytes were activated by CH but not acute hypoxia and activation was not reversed by administering ibuprofen for the last 2days of CH. Hence, ibuprofen cannot reverse ventilatory acclimatization or astrocyte activation after they have been established by sustained hypoxia. The results are consistent with a model for microglia activation or other ibuprofen-sensitive processes being necessary for the induction but not maintenance of ventilatory acclimatization to hypoxia.
Collapse
Affiliation(s)
- D J De La Zerda
- Division of Pulmonary and Critical Care Medicinea, Department of Medicine, University of California, 9500 Gilman Drive La Jolla, Medicine San Diego, CA 92093, United States; Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Miami, 1600 NW 10th Ave RMSB, Suite 7063, Miami, FL 33136, United States.
| | - J A Stokes
- Division of Physiology, Department of Medicine, University of California, 9500 Gilman Drive La Jolla, San Diego, CA 92093, United States.
| | - J Do
- Division of Physiology, Department of Medicine, University of California, 9500 Gilman Drive La Jolla, San Diego, CA 92093, United States
| | - A Go
- Division of Physiology, Department of Medicine, University of California, 9500 Gilman Drive La Jolla, San Diego, CA 92093, United States.
| | - Z Fu
- Division of Physiology, Department of Medicine, University of California, 9500 Gilman Drive La Jolla, San Diego, CA 92093, United States.
| | - F L Powell
- Division of Physiology, Department of Medicine, University of California, 9500 Gilman Drive La Jolla, San Diego, CA 92093, United States.
| |
Collapse
|
13
|
Cuéllar R, Montero S, Luquín S, García-Estrada J, Melnikov V, Virgen-Ortiz A, Lemus M, Pineda-Lemus M, de Álvarez-Buylla E. BDNF and AMPA receptors in the cNTS modulate the hyperglycemic reflex after local carotid body NaCN stimulation. Auton Neurosci 2017; 205:12-20. [PMID: 28254195 DOI: 10.1016/j.autneu.2017.02.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 11/29/2016] [Accepted: 02/01/2017] [Indexed: 11/30/2022]
Abstract
The application of sodium cyanide (NaCN) to the carotid body receptors (CBR) (CBR stimulation) induces rapid blood hyperglycemia and an increase in brain glucose retention. The commissural nucleus tractus solitarius (cNTS) is an essential relay nucleus in this hyperglycemic reflex; it receives glutamatergic afferents (that also release brain derived neurotrophic factor, BDNF) from the nodose-petrosal ganglia that relays CBR information. Previous work showed that AMPA in NTS blocks hyperglycemia and brain glucose retention after CBR stimulation. In contrast, BDNF, which attenuates glutamatergic AMPA currents in NTS, enhances these glycemic responses. Here we investigated the combined effects of BDNF and AMPA (and their antagonists) in NTS on the glycemic responses to CBR stimulation. Microinjections of BDNF plus AMPA into the cNTS before CBR stimulation in anesthetized rats, induced blood hyperglycemia and an increase in brain arteriovenous (a-v) of blood glucose concentration difference, which we infer is due to increased brain glucose retention. By contrast, the microinjection of the TrkB antagonist K252a plus AMPA abolished the glycemic responses to CBR stimulation similar to what is observed after AMPA pretreatments. In BDNF plus AMPA microinjections preceding CBR stimulation, the number of c-fos immunoreactive cNTS neurons increased. In contrast, in the rats microinjected with K252a plus AMPA in NTS, before CBR stimulation, c-fos expression in cNTS decreased. The expression of AMPA receptors GluR2/3 did not change in any of the studied groups. These results indicate that BDNF in cNTS plays a key role in the modulation of the hyperglycemic reflex initiated by CBR stimulation.
Collapse
Affiliation(s)
- R Cuéllar
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Ave. 25 de Julio 965, Colima 28045, Mexico; Departamento de Neurociencias, Centro Universitario de Ciencias de la Salud, Universidad de Guadalajara, Sierra Mojada 950, Guadalajara 44340, Mexico
| | - S Montero
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Ave. 25 de Julio 965, Colima 28045, Mexico; Facultad de Medicina, Universidad de Colima, Ave. Universidad 333, Colima 28040, Mexico
| | - S Luquín
- Departamento de Neurociencias, Centro Universitario de Ciencias de la Salud, Universidad de Guadalajara, Sierra Mojada 950, Guadalajara 44340, Mexico
| | - J García-Estrada
- Departamento de Neurociencias, Centro Universitario de Ciencias de la Salud, Universidad de Guadalajara, Sierra Mojada 950, Guadalajara 44340, Mexico; División de Investigación Quirúrgica, Centro de Investigación Biomédica de Occidente, IMSS, Guadalajara, Mexico
| | - V Melnikov
- Facultad de Medicina, Universidad de Colima, Ave. Universidad 333, Colima 28040, Mexico
| | - A Virgen-Ortiz
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Ave. 25 de Julio 965, Colima 28045, Mexico
| | - M Lemus
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Ave. 25 de Julio 965, Colima 28045, Mexico
| | - M Pineda-Lemus
- Facultad de Medicina, Universidad de Colima, Ave. Universidad 333, Colima 28040, Mexico
| | - E de Álvarez-Buylla
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Ave. 25 de Julio 965, Colima 28045, Mexico.
| |
Collapse
|
14
|
Stokes JA, Arbogast TE, Moya EA, Fu Z, Powell FL. Minocycline blocks glial cell activation and ventilatory acclimatization to hypoxia. J Neurophysiol 2017; 117:1625-1635. [PMID: 28100653 DOI: 10.1152/jn.00525.2016] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 01/11/2017] [Accepted: 01/11/2017] [Indexed: 01/14/2023] Open
Abstract
Ventilatory acclimatization to hypoxia (VAH) is the time-dependent increase in ventilation, which persists upon return to normoxia and involves plasticity in both central nervous system respiratory centers and peripheral chemoreceptors. We investigated the role of glial cells in VAH in male Sprague-Dawley rats using minocycline, an antibiotic that inhibits microglia activation and has anti-inflammatory properties, and barometric pressure plethysmography to measure ventilation. Rats received either minocycline (45mg/kg ip daily) or saline beginning 1 day before and during 7 days of chronic hypoxia (CH, PiO2 = 70 Torr). Minocycline had no effect on normoxic control rats or the hypercapnic ventilatory response in CH rats, but minocycline significantly (P < 0.001) decreased ventilation during acute hypoxia in CH rats. However, minocycline administration during only the last 3 days of CH did not reverse VAH. Microglia and astrocyte activation in the nucleus tractus solitarius was quantified from 30 min to 7 days of CH. Microglia showed an active morphology (shorter and fewer branches) after 1 h of hypoxia and returned to the control state (longer filaments and extensive branching) after 4 h of CH. Astrocytes increased glial fibrillary acidic protein antibody immunofluorescent intensity, indicating activation, at both 4 and 24 h of CH. Minocycline had no effect on glia in normoxia but significantly decreased microglia activation at 1 h of CH and astrocyte activation at 24 h of CH. These results support a role for glial cells, providing an early signal for the induction but not maintenance of neural plasticity underlying ventilatory acclimatization to hypoxia.NEW & NOTEWORTHY The signals for neural plasticity in medullary respiratory centers underlying ventilatory acclimatization to chronic hypoxia are unknown. We show that chronic hypoxia activates microglia and subsequently astrocytes. Minocycline, an antibiotic that blocks microglial activation and has anti-inflammatory properties, also blocks astrocyte activation in respiratory centers during chronic hypoxia and ventilatory acclimatization. However, minocycline cannot reverse ventilatory acclimatization after it is established. Hence, glial cells may provide signals that initiate but do not sustain ventilatory acclimatization.
Collapse
Affiliation(s)
- Jennifer A Stokes
- Division of Physiology, Department of Medicine; University of California, San Diego, La Jolla, California
| | - Tara E Arbogast
- Division of Physiology, Department of Medicine; University of California, San Diego, La Jolla, California
| | - Esteban A Moya
- Division of Physiology, Department of Medicine; University of California, San Diego, La Jolla, California
| | - Zhenxing Fu
- Division of Physiology, Department of Medicine; University of California, San Diego, La Jolla, California
| | - Frank L Powell
- Division of Physiology, Department of Medicine; University of California, San Diego, La Jolla, California
| |
Collapse
|
15
|
Developmental plasticity in the neural control of breathing. Exp Neurol 2017; 287:176-191. [DOI: 10.1016/j.expneurol.2016.05.032] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Revised: 05/13/2016] [Accepted: 05/26/2016] [Indexed: 12/14/2022]
|
16
|
Pamenter ME, Powell FL. Time Domains of the Hypoxic Ventilatory Response and Their Molecular Basis. Compr Physiol 2016; 6:1345-85. [PMID: 27347896 DOI: 10.1002/cphy.c150026] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Ventilatory responses to hypoxia vary widely depending on the pattern and length of hypoxic exposure. Acute, prolonged, or intermittent hypoxic episodes can increase or decrease breathing for seconds to years, both during the hypoxic stimulus, and also after its removal. These myriad effects are the result of a complicated web of molecular interactions that underlie plasticity in the respiratory control reflex circuits and ultimately control the physiology of breathing in hypoxia. Since the time domains of the physiological hypoxic ventilatory response (HVR) were identified, considerable research effort has gone toward elucidating the underlying molecular mechanisms that mediate these varied responses. This research has begun to describe complicated and plastic interactions in the relay circuits between the peripheral chemoreceptors and the ventilatory control circuits within the central nervous system. Intriguingly, many of these molecular pathways seem to share key components between the different time domains, suggesting that varied physiological HVRs are the result of specific modifications to overlapping pathways. This review highlights what has been discovered regarding the cell and molecular level control of the time domains of the HVR, and highlights key areas where further research is required. Understanding the molecular control of ventilation in hypoxia has important implications for basic physiology and is emerging as an important component of several clinical fields. © 2016 American Physiological Society. Compr Physiol 6:1345-1385, 2016.
Collapse
Affiliation(s)
| | - Frank L Powell
- Physiology Division, Department of Medicine, University of California San Diego, La Jolla, California, USA
| |
Collapse
|
17
|
Basaran KE, Villongco M, Ho B, Ellis E, Zarndt R, Antonova J, Hopkins SR, Powell FL. Ibuprofen Blunts Ventilatory Acclimatization to Sustained Hypoxia in Humans. PLoS One 2016; 11:e0146087. [PMID: 26726885 PMCID: PMC4699648 DOI: 10.1371/journal.pone.0146087] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 11/27/2015] [Indexed: 12/21/2022] Open
Abstract
Ventilatory acclimatization to hypoxia is a time-dependent increase in ventilation and the hypoxic ventilatory response (HVR) that involves neural plasticity in both carotid body chemoreceptors and brainstem respiratory centers. The mechanisms of such plasticity are not completely understood but recent animal studies show it can be blocked by administering ibuprofen, a nonsteroidal anti-inflammatory drug, during chronic hypoxia. We tested the hypothesis that ibuprofen would also block the increase in HVR with chronic hypoxia in humans in 15 healthy men and women using a double-blind, placebo controlled, cross-over trial. The isocapnic HVR was measured with standard methods in subjects treated with ibuprofen (400mg every 8 hrs) or placebo for 48 hours at sea level and 48 hours at high altitude (3,800 m). Subjects returned to sea level for at least 30 days prior to repeating the protocol with the opposite treatment. Ibuprofen significantly decreased the HVR after acclimatization to high altitude compared to placebo but it did not affect ventilation or arterial O2 saturation breathing ambient air at high altitude. Hence, compensatory responses prevent hypoventilation with decreased isocapnic ventilatory O2-sensitivity from ibuprofen at this altitude. The effect of ibuprofen to decrease the HVR in humans provides the first experimental evidence that a signaling mechanism described for ventilatory acclimatization to hypoxia in animal models also occurs in people. This establishes a foundation for the future experiments to test the potential role of different mechanisms for neural plasticity and ventilatory acclimatization in humans with chronic hypoxemia from lung disease.
Collapse
Affiliation(s)
- Kemal Erdem Basaran
- Division of Physiology, Department of Medicine, University of California San Diego, San Diego, California, United States of America
- Department of Medical Physiology, Faculty of Medicine, Erciyes University, Melikgazi, Kayseri, Turkey
| | - Michael Villongco
- Division of Physiology, Department of Medicine, University of California San Diego, San Diego, California, United States of America
| | - Baran Ho
- Division of Physiology, Department of Medicine, University of California San Diego, San Diego, California, United States of America
| | - Erika Ellis
- Division of Physiology, Department of Medicine, University of California San Diego, San Diego, California, United States of America
| | - Rachel Zarndt
- Division of Physiology, Department of Medicine, University of California San Diego, San Diego, California, United States of America
| | - Julie Antonova
- Division of Physiology, Department of Medicine, University of California San Diego, San Diego, California, United States of America
| | - Susan R. Hopkins
- Division of Physiology, Department of Medicine, University of California San Diego, San Diego, California, United States of America
- Department of Radiology, University of California San Diego, San Diego, California, United States of America
| | - Frank L. Powell
- Division of Physiology, Department of Medicine, University of California San Diego, San Diego, California, United States of America
- * E-mail:
| |
Collapse
|
18
|
Boxwell AJ, Chen Z, Mathes CM, Spector AC, Le Roux CW, Travers SP, Travers JB. Effects of high-fat diet and gastric bypass on neurons in the caudal solitary nucleus. Physiol Behav 2015. [PMID: 26216080 DOI: 10.1016/j.physbeh.2015.07.025] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Bariatric surgery is an effective treatment for obesity that involves both peripheral and central mechanisms. To elucidate central pathways by which oral and visceral signals are influenced by high-fat diet (HFD) and Roux-en-Y gastric bypass (RYGB) surgery, we recorded from neurons in the caudal visceral nucleus of the solitary tract (cNST, N=287) and rostral gustatory NST (rNST,N=106) in rats maintained on a HFD and lab chow (CHOW) or CHOW alone, and subjected to either RYGB or sham surgery. Animals on the HFD weighed significantly more than CHOW rats and RYGB reversed and then blunted weight gain regardless of diet. Using whole-cell patch clamp recording in a brainstem slice, we determined the membrane properties of cNST and rNST neurons associated with diet and surgery. We could not detect differences in rNST neurons associated with these manipulations. In cNST neurons, neither the threshold for solitary tract stimulation nor the amplitude of evoked EPSCs at threshold varied by condition; however suprathreshold EPSCs were larger in HFD compared to chow-fed animals. In addition, a transient outward current, most likely an IA current, was increased with HFD and RYGB reduced this current as well as a sustained outward current. Interestingly, hypothalamic projecting cNST neurons preferentially express IA and modulate transmission of afferent signals (Bailey, '07). Thus, diet and RYGB have multiple effects on the cellular properties of neurons in the visceral regions of NST, with potential to influence inputs to forebrain feeding circuits.
Collapse
Affiliation(s)
- A J Boxwell
- Ohio State Univ., Columbus, OH, United States
| | - Z Chen
- Ohio State Univ., Columbus, OH, United States
| | - C M Mathes
- Florida State Univ., Tallahassee, FL, United States
| | - A C Spector
- Florida State Univ., Tallahassee, FL, United States
| | | | - S P Travers
- Ohio State Univ., Columbus, OH, United States
| | - J B Travers
- Ohio State Univ., Columbus, OH, United States.
| |
Collapse
|
19
|
Enhanced Firing in NTS Induced by Short-Term Sustained Hypoxia Is Modulated by Glia-Neuron Interaction. J Neurosci 2015; 35:6903-17. [PMID: 25926465 DOI: 10.1523/jneurosci.4598-14.2015] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Humans ascending to high altitudes are submitted to sustained hypoxia (SH), activating peripheral chemoreflex with several autonomic and respiratory responses. Here we analyzed the effect of short-term SH (24 h, FIO210%) on the processing of cardiovascular and respiratory reflexes using an in situ preparation of rats. SH increased both the sympatho-inhibitory and bradycardiac components of baroreflex and the sympathetic and respiratory responses of peripheral chemoreflex. Electrophysiological properties and synaptic transmission in the nucleus tractus solitarius (NTS) neurons, the first synaptic station of afferents of baroreflexes and chemoreflexes, were evaluated using brainstem slices and whole-cell patch-clamp. The second-order NTS neurons were identified by previous application of fluorescent tracer onto carotid body for chemoreceptor afferents or onto aortic depressor nerve for baroreceptor afferents. SH increased the intrinsic excitability of NTS neurons. Delayed excitation, caused by A-type potassium current (IKA), was observed in most of NTS neurons from control rats. The IKA amplitude was higher in identified second-order NTS neurons from control than in SH rats. SH also blunted the astrocytic inhibition of IKA in NTS neurons and increased the synaptic transmission in response to afferent fibers stimulation. The frequency of spontaneous excitatory currents was also increased in neurons from SH rats, indicating that SH increased the neurotransmission by presynaptic mechanisms. Therefore, short-term SH changed the glia-neuron interaction, increasing the excitability and excitatory transmission of NTS neurons, which may contribute to the observed increase in the reflex sensitivity of baroreflex and chemoreflex in in situ preparation.
Collapse
|
20
|
Mayer CA, Wilson CG, MacFarlane PM. Changes in carotid body and nTS neuronal excitability following neonatal sustained and chronic intermittent hypoxia exposure. Respir Physiol Neurobiol 2014; 205:28-36. [PMID: 25266393 DOI: 10.1016/j.resp.2014.09.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Revised: 09/21/2014] [Accepted: 09/22/2014] [Indexed: 02/07/2023]
Abstract
We investigated whether pre-treatment with neonatal sustained hypoxia (SH) prior to chronic intermittent hypoxia (SH+CIH) would modify in vitro carotid body (CB) chemoreceptor activity and the excitability of neurons in the caudal nucleus of the solitary tract (nTS). Sustained hypoxia followed by CIH exposure simulates an oxygen paradigm experienced by extremely premature infants who developed persistent apnea. Rat pups were treated with 5 days of SH (11% O2) from postnatal age 1 (P1) followed by 10 days of subsequent chronic intermittent hypoxia (CIH, 5% O2/5 min, 8 h/day, between P6 and P15) as described previously (Mayer et al., Respir. Physiol. Neurobiol. 187(2): 167-75, 2013). At the end of SH+CIH exposure (P16), basal firing frequency was enhanced, and the hypoxic sensory response of single unit CB chemoafferents was attenuated. Further, basal firing frequency and the amplitude of evoked excitatory post-synaptic currents (ESPC's) of nTS neurons was augmented compared to age-matched rats raised in normoxia. These effects were unique to SH+CIH exposure as neither SH or CIH alone elicited any comparable effect on chemoafferent activity or nTS function. These data indicated that pre-treatment with neonatal SH prior to CIH exposure uniquely modified mechanisms of peripheral (CB) and central (nTS) neural function in a way that would be expected to disturb the ventilatory response to acute hypoxia.
Collapse
Affiliation(s)
- C A Mayer
- Department of Pediatrics, Case Western Reserve University, Rainbow Babies & Children's Hospital, Cleveland, OH 44106, USA
| | - C G Wilson
- Center for Perinatal Biology, Loma Linda University, Loma Linda, CA 92350, USA
| | - P M MacFarlane
- Department of Pediatrics, Case Western Reserve University, Rainbow Babies & Children's Hospital, Cleveland, OH 44106, USA.
| |
Collapse
|
21
|
Moraes DJA, Bonagamba LGH, Costa KM, Costa-Silva JH, Zoccal DB, Machado BH. Short-term sustained hypoxia induces changes in the coupling of sympathetic and respiratory activities in rats. J Physiol 2014; 592:2013-33. [PMID: 24614747 DOI: 10.1113/jphysiol.2013.262212] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Individuals experiencing sustained hypoxia (SH) exhibit adjustments in the respiratory and autonomic functions by neural mechanisms not yet elucidated. In the present study we evaluated the central mechanisms underpinning the SH-induced changes in the respiratory pattern and their impact on the sympathetic outflow. Using a decerebrated arterially perfused in situ preparation, we verified that juvenile rats exposed to SH (10% O2) for 24 h presented an active expiratory pattern, with increased abdominal, hypoglossal and vagal activities during late-expiration (late-E). SH also enhanced the activity of augmenting-expiratory neurones and depressed the activity of post-inspiratory neurones of the Bötzinger complex (BötC) by mechanisms not related to changes in their intrinsic electrophysiological properties. SH rats exhibited high thoracic sympathetic activity and arterial pressure levels associated with an augmented firing frequency of pre-sympathetic neurones of the rostral ventrolateral medulla (RVLM) during the late-E phase. The antagonism of ionotropic glutamatergic receptors in the BötC/RVLM abolished the late-E bursts in expiratory and sympathetic outputs of SH rats, indicating that glutamatergic inputs to the BötC/RVLM are essential for the changes in the expiratory and sympathetic coupling observed in SH rats. We also observed that the usually silent late-E neurones of the retrotrapezoid nucleus/parafacial respiratory group became active in SH rats, suggesting that this neuronal population may provide the excitatory drive essential to the emergence of active expiration and sympathetic overactivity. We conclude that short-term SH induces the activation of medullary expiratory neurones, which affects the pattern of expiratory motor activity and its coupling with sympathetic activity.
Collapse
Affiliation(s)
- Davi J A Moraes
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, 14049-900, Ribeirão Preto, SP, Brazil.
| | | | | | | | | | | |
Collapse
|
22
|
Pamenter ME, Carr JA, Go A, Fu Z, Reid SG, Powell FL. Glutamate receptors in the nucleus tractus solitarius contribute to ventilatory acclimatization to hypoxia in rat. J Physiol 2014; 592:1839-56. [PMID: 24492841 DOI: 10.1113/jphysiol.2013.268706] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
When exposed to a hypoxic environment the body's first response is a reflex increase in ventilation, termed the hypoxic ventilatory response (HVR). With chronic sustained hypoxia (CSH), such as during acclimatization to high altitude, an additional time-dependent increase in ventilation occurs, which increases the HVR. This secondary increase persists after exposure to CSH and involves plasticity within the circuits in the central nervous system that control breathing. Currently these mechanisms of HVR plasticity are unknown and we hypothesized that they involve glutamatergic synapses in the nucleus tractus solitarius (NTS), where afferent endings from arterial chemoreceptors terminate. To test this, we treated rats held in normoxia (CON) or 10% O2 (CSH) for 7 days and measured ventilation in conscious, unrestrained animals before and after microinjecting glutamate receptor agonists and antagonists into the NTS. In normoxia, AMPA increased ventilation 25% and 50% in CON and CSH, respectively, while NMDA doubled ventilation in both groups (P < 0.05). Specific AMPA and NMDA receptor antagonists (NBQX and MK801, respectively) abolished these effects. MK801 significantly decreased the HVR in CON rats, and completely blocked the acute HVR in CSH rats but had no effect on ventilation in normoxia. NBQX decreased ventilation whenever it was increased relative to normoxic controls; i.e. acute hypoxia in CON and CSH, and normoxia in CSH. These results support our hypothesis that glutamate receptors in the NTS contribute to plasticity in the HVR with CSH. The mechanism underlying this synaptic plasticity is probably glutamate receptor modification, as in CSH rats the expression of phosphorylated NR1 and GluR1 proteins in the NTS increased 35% and 70%, respectively, relative to that in CON rats.
Collapse
Affiliation(s)
- Matthew E Pamenter
- Division of Physiology, Department of Medicine, University of California San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0623, USA.
| | | | | | | | | | | |
Collapse
|
23
|
McGinnis WR, Audhya T, Edelson SM. Proposed toxic and hypoxic impairment of a brainstem locus in autism. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2013; 10:6955-7000. [PMID: 24336025 PMCID: PMC3881151 DOI: 10.3390/ijerph10126955] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Revised: 11/07/2013] [Accepted: 11/11/2013] [Indexed: 01/15/2023]
Abstract
Electrophysiological findings implicate site-specific impairment of the nucleus tractus solitarius (NTS) in autism. This invites hypothetical consideration of a large role for this small brainstem structure as the basis for seemingly disjointed behavioral and somatic features of autism. The NTS is the brain's point of entry for visceral afference, its relay for vagal reflexes, and its integration center for autonomic control of circulatory, immunological, gastrointestinal, and laryngeal function. The NTS facilitates normal cerebrovascular perfusion, and is the seminal point for an ascending noradrenergic system that modulates many complex behaviors. Microvascular configuration predisposes the NTS to focal hypoxia. A subregion--the "pNTS"--permits exposure to all blood-borne neurotoxins, including those that do not readily transit the blood-brain barrier. Impairment of acetylcholinesterase (mercury and cadmium cations, nitrates/nitrites, organophosphates, monosodium glutamate), competition for hemoglobin (carbon monoxide, nitrates/nitrites), and higher blood viscosity (net systemic oxidative stress) are suggested to potentiate microcirculatory insufficiency of the NTS, and thus autism.
Collapse
Affiliation(s)
- Woody R. McGinnis
- Autism Research Institute, 4182 Adams Avenue, San Diego, CA 92116, USA; E-Mail:
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-541-326-8822; Fax: +1-619-563-6840
| | - Tapan Audhya
- Division of Endocrinology, Department of Medicine, New York University Medical School, New York, NY 10016, USA; E-Mail:
| | - Stephen M. Edelson
- Autism Research Institute, 4182 Adams Avenue, San Diego, CA 92116, USA; E-Mail:
| |
Collapse
|
24
|
Accorsi-Mendonça D, Zoccal DB, Bonagamba LGH, Machado BH. Glial cells modulate the synaptic transmission of NTS neurons sending projections to ventral medulla of Wistar rats. Physiol Rep 2013; 1:e00080. [PMID: 24303152 PMCID: PMC3831896 DOI: 10.1002/phy2.80] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Revised: 07/08/2013] [Accepted: 07/14/2013] [Indexed: 12/15/2022] Open
Abstract
There is evidence that sympathoexcitatory and respiratory responses to chemoreflex activation involve ventrolateral medulla-projecting nucleus tractus solitarius (NTS) neurons (NTS-VLM neurons) and also that ATP modulates this neurotransmission. Here, we evaluated whether or not astrocytes is the source of endogenous ATP modulating the synaptic transmission in NTS-VLM neurons. Synaptic activities of putative astrocytes or NTS-VLM neurons were recorded using whole cell patch clamp. Tractus solitarius (TS) stimulation induced TS-evoked excitatory postsynaptic currents (TS-eEPSCs) in NTS-VLM neurons as well in NTS putative astrocytes, which were also identified by previous labeling. Fluoracetate (FAC), an inhibitor of glial metabolism, reduced TS-eEPSCs amplitude (-85.6 ± 16 vs. -39 ± 7.1 pA, n = 12) and sEPSCs frequency (2.8 ± 0.5 vs. 1.8 ± 0.46 Hz, n = 10) in recorded NTS-VLM neurons, indicating a gliomodulation of glutamatergic currents. To verify the involvement of endogenous ATP a purinergic antagonist was used, which reduced the TS-eEPSCs amplitude (-207 ± 50 vs. -149 ± 50 pA, n = 6), the sEPSCs frequency (1.19 ± 0.2 vs. 0.62 ± 0.11 Hz, n = 6), and increased the paired-pulse ratio (PPR) values (∼20%) in NTS-VLM neurons. Simultaneous perfusion of Pyridoxalphosphate-6-azophenyl-2',5'-disulfonic acid (iso-PPADS) and FAC produced reduction in TS-eEPSCs similar to that observed with iso-PPADS or FAC alone, indicating that glial cells are the source of ATP released after TS stimulation. Extracellular ATP measurement showed that FAC reduced evoked and spontaneous ATP release. All together these data show that putative astrocytes are the source of endogenous ATP, which via activation of presynaptic P2X receptors, facilitates the evoked glutamate release and increases the synaptic transmission efficacy in the NTS-VLM neurons probably involved with the peripheral chemoreflex pathways.
Collapse
Affiliation(s)
- Daniela Accorsi-Mendonça
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo Ribeirão Preto, São Paulo, Brazil
| | | | | | | |
Collapse
|
25
|
Ciriello J, Moreau JM. Systemic administration of leptin potentiates the response of neurons in the nucleus of the solitary tract to chemoreceptor activation in the rat. Neuroscience 2012; 229:88-99. [PMID: 23159310 DOI: 10.1016/j.neuroscience.2012.10.065] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2012] [Revised: 10/19/2012] [Accepted: 10/19/2012] [Indexed: 11/30/2022]
Abstract
Leptin microinjections into the nucleus of the solitary tract (NTS) have been shown to elicit sympathoexcitatory responses, and potentiate the cardiovascular responses to activation of the chemoreflex. In this study, experiments were done in Sprague-Dawley rats initially to provide a detailed mapping within the NTS complex of cells containing immunoreactivity to the long form of the leptin receptor (Ob-Rb). In a second series, this NTS region containing Ob-Rb immunoreactive cells was explored for single units antidromically activated by stimulation of pressor sites in the rostral ventrolateral medulla (RVLM). These antidromically identified neurons were then tested for their response to intra-carotid injections of leptin (50-100 ng/0.1 ml), and to activation of peripheral chemoreceptors following an injection of potassium cyanide (KCN) (80 μg/0.1 ml) into the carotid artery. Cells containing Ob-Rb-like immunoreactivity were found predominantly in the caudal NTS: within the medial, commissural and gelatinous (sub-postremal area) subnuclei of the NTS complex. Of 73 single units tested in these NTS regions, 48 were antidromically activated by stimulation of RVLM pressor sites and 25 of these single units responded with an increase in discharge rate after intra-carotid injections of leptin. In addition, 17 of these leptin responsive neurons were excited by the intra-carotid injections of KCN (80 μg/0.1 ml). Furthermore, the excitatory response of these single units to KCN was potentiated (59-83%) immediately following the leptin injection. These data indicate that leptin responsive neurons in NTS mediate chemoreceptor afferent information to pressor sites in the RVLM, and suggest that leptin may act as a facilitator on neuronal circuits within the NTS that potentiates the sympathoexcitatory responses elicited during the reflex activation of arterial chemoreceptors.
Collapse
Affiliation(s)
- J Ciriello
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, Canada N6A 5C1.
| | | |
Collapse
|
26
|
Sekizawa SI, Horowitz JM, Horwitz BA, Chen CY. Realignment of signal processing within a sensory brainstem nucleus as brain temperature declines in the Syrian hamster, a hibernating species. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2012; 198:267-82. [PMID: 22262373 DOI: 10.1007/s00359-011-0706-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2011] [Revised: 11/28/2011] [Accepted: 12/13/2011] [Indexed: 01/24/2023]
Abstract
Crucial for survival, the central nervous system must reliably process sensory information over all stages of a hibernation bout to ensure homeostatic regulation is maintained and well-matched to dramatically altered behavioral states. Comparing neural responses in the nucleus tractus solitarius of rats and euthermic Syrian hamsters, we tested the hypothesis that hamster neurons have adaptations sustaining signal processing while conserving energy. Using patch-clamp techniques, we classified second-order neurons in the nucleus as rapid-onset or delayed-onset spiking phenotypes based on their spiking onset to a depolarizing pulse (following a -80 mV prepulse). As temperature decreased from 33 to 15°C, the excitability of all neurons decreased. However, hamster rapid-onset spiking neurons had the highest spiking response and shortest action potential width at every temperature, while hamster delayed-onset spiking neurons had the most negative resting membrane potential. The frequency of spontaneous excitatory postsynaptic currents in both phenotypes decreased as temperature decreased, yet the amplitudes of tractus solitarius stimulation-evoked currents were greater in hamsters than in rats regardless of phenotype and temperature. Changes were significant (P < 0.05), supporting our hypothesis by showing that, as temperature falls, rapid-onset neurons contribute more to signal processing but less to energy conservation than do delayed-onset neurons.
Collapse
Affiliation(s)
- Shin-Ichi Sekizawa
- Department of Pharmacology, University of California Davis, GBSF 3617, 451 Health Sciences Drive, Davis, CA 95616, USA
| | | | | | | |
Collapse
|
27
|
Accorsi-Mendonça D, Castania J, Bonagamba L, Machado B, Leão R. Synaptic profile of nucleus tractus solitarius neurons involved with the peripheral chemoreflex pathways. Neuroscience 2011; 197:107-20. [DOI: 10.1016/j.neuroscience.2011.08.054] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Revised: 08/22/2011] [Accepted: 08/24/2011] [Indexed: 10/17/2022]
|
28
|
Browning KN, Wan S, Baptista V, Travagli RA. Vanilloid, purinergic, and CCK receptors activate glutamate release on single neurons of the nucleus tractus solitarius centralis. Am J Physiol Regul Integr Comp Physiol 2011; 301:R394-401. [PMID: 21543639 DOI: 10.1152/ajpregu.00054.2011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Baroreceptor inputs to nucleus of the tractus solitarius medialis (mNTS) neurons can be differentiated, among other features, by their response to vanilloid or purinergic agonists, active only on C- or A-fibers, respectively. A major aim of this study was to examine whether neurons of NTS centralis (cNTS), a subnucleus dominated by esophageal inputs, exhibit a similar dichotomy. Since it has been suggested that cholecystokinin (CCK), exerts its gastrointestinal (GI)-related effects via paracrine activation of vagal afferent C-fibers, we tested whether CCK-sensitive fibers impinging upon cNTS neurons are responsive to vanilloid but not purinergic agonists. Using whole cell patch-clamp recordings from cNTS, we recorded miniature excitatory postsynaptic currents (mEPSCs) to test the effects of the vanilloid agonist capsaicin, the purinergic agonist α,β-methylene-ATP (α,β-Met-ATP), and/or CCK-octapeptide (CCK-8s). α,β-Met-ATP, capsaicin; and CCK-8s increased EPSC frequency in 37, 71, and 46% of cNTS neurons, respectively. Approximately 30% of cNTS neurons were responsive to both CCK-8s and α,β-Met-ATP, to CCK-8s and capsaicin, or to α,β-Met-ATP and capsaicin, while 32% of neurons were responsive to all three agonists. All neurons responding to either α,β-Met-ATP or CCK-8s were also responsive to capsaicin. Perivagal capsaicin, which is supposed to induce a selective degeneration of C-fibers, decreased the number of cNTS neurons responding to capsaicin or CCK-8s but not those responding to α,β-Met-ATP. In summary, GI inputs to cNTS neurons cannot be distinguished on the basis of their selective responses to α,β-Met-ATP or capsaicin. Our data also indicate that CCK-8s increases glutamate release from purinergic and vanilloid responsive fibers impinging on cNTS neurons.
Collapse
Affiliation(s)
- Kirsteen N Browning
- Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, Pennsylvania 17033-0850, USA
| | | | | | | |
Collapse
|
29
|
Zakhary SM, Ayubcha D, Ansari F, Kamran K, Karim M, Leheste JR, Horowitz JM, Torres G. A behavioral and molecular analysis of ketamine in zebrafish. Synapse 2011; 65:160-7. [PMID: 20623473 DOI: 10.1002/syn.20830] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Ketamine exerts powerful anesthetic, psychotic, and antidepressant effects in both healthy volunteers and clinically depressed patients. Although ketamine targets particular glutamate receptors, there is a dearth of evidence for additional, alternative molecular substrates for the behavioral actions of this N-methyl-D-aspartate (NMDA) receptor antagonist drug. Here, we provide behavioral and molecular evidence for the actions of ketamine using a new vertebrate model for psychiatric disorders: the zebrafish. Subanesthetic doses of ketamine produced a variety of abnormal behaviors in zebrafish that were qualitatively analogous to those previously measured in humans and rodents treated with drugs that produce transient psychosis. In addition, we revealed that the transcription factor Phox2b is a molecular substrate for the actions of ketamine, particularly during periods of hypoxic stress. Finally, we also show that SIRT1, a histone deacetylase widely recognized for its link to cell survival is also affected by hypoxia crises. These results establish a relevant assay system in which the effects of psychotomimetic drugs can rapidly be assessed, and provide a plausible and novel neuronal mechanism through which ketamine affects critical sensory circuits that monitor breathing behavior.
Collapse
Affiliation(s)
- Sherry M Zakhary
- Department of Neuroscience and Histology, New York College of Osteopathic Medicine of New York Institute of Technology, Old Westbury, New York 11568, USA
| | | | | | | | | | | | | | | |
Collapse
|
30
|
Haploinsufficiency in peptidylglycine alpha-amidating monooxygenase leads to altered synaptic transmission in the amygdala and impaired emotional responses. J Neurosci 2010; 30:13656-69. [PMID: 20943906 DOI: 10.1523/jneurosci.2200-10.2010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The mammalian amygdala expresses various neuropeptides whose signaling has been implicated in emotionality. Many neuropeptides require amidation for full activation by peptidylglycine α-amidating monooxygenase (PAM), a transmembrane vesicular cuproenzyme and regulator of the secretory pathway. Mice heterozygous for the Pam gene (PAM(+/-)) exhibit physiological and behavioral abnormalities related to specific peptidergic pathways. In the present study, we evaluated emotionality and examined molecular and cellular responses that characterize neurophysiological differences in the PAM(+/-) amygdala. PAM(+/-) mice presented with anxiety-like behaviors in the zero maze that were alleviated by diazepam. PAM(+/-) animals were deficient in short- and long-term contextual and cued fear conditioning and required higher shock intensities to establish fear-potentiated startle than their wild-type littermates. Immunohistochemical analysis of the amygdala revealed PAM expression in pyramidal neurons and local interneurons that synthesize GABA. We performed whole-cell recordings of pyramidal neurons in the PAM(+/-) amygdala to elucidate neurophysiological correlates of the fear behavioral phenotypes. Consistent with these observations, thalamic afferent synapses in the PAM(+/-) lateral nucleus were deficient in long-term potentiation. This deficit was apparent in the absence and presence of the GABA(A) receptor antagonist picrotoxin and was abolished when both GABA(A) and GABA(B) receptors were blocked. Both evoked and spontaneous excitatory signals were enhanced in the PAM(+/-) lateral nucleus. Phasic GABAergic signaling was also augmented in the PAM(+/-) amygdala, and this difference comprised activity-independent and -dependent components. These physiological findings represent perturbations in the PAM(+/-) amygdala that may underlie the aberrant emotional responses in the intact animal.
Collapse
|
31
|
Blain GM, Smith CA, Henderson KS, Dempsey JA. Peripheral chemoreceptors determine the respiratory sensitivity of central chemoreceptors to CO(2). J Physiol 2010; 588:2455-71. [PMID: 20421288 DOI: 10.1113/jphysiol.2010.187211] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
We assessed the contribution of carotid body chemoreceptors to the ventilatory response to specific CNS hypercapnia in eight unanaesthetized, awake dogs. We denervated one carotid body (CB) and used extracorporeal blood perfusion of the reversibly isolated remaining CB to maintain normal CB blood gases (normoxic, normocapnic perfusate), to inhibit (hyperoxic, hypocapnic perfusate) or to stimulate (hypoxic, normocapnic perfusate) the CB chemoreflex, while the systemic circulation, and therefore the CNS and central chemoreceptors, were exposed consecutively to four progressive levels of systemic arterial hypercapnia via increased fractional inspired CO(2) for 7 min at each level. Neither unilateral CB denervation nor CB perfusion, per se, affected breathing. Relative to CB control conditions (normoxic, normocapnic perfusion), we found that CB chemoreflex inhibition decreased the slope of the ventilatory response to CNS hypercapnia in all dogs to an average of 19% of control values (range 0-38%; n = 6), whereas CB chemoreflex stimulation increased the slope of the ventilatory response to CNS hypercapnia in all dogs to an average of 223% of control values (range 204-235%; n = 4). We conclude that the gain of the CNS CO(2)/H(+) chemoreceptors in dogs is critically dependent on CB afferent activity and that CNS-CB interaction results in hyperadditive ventilatory responses to central hypercapnia.
Collapse
Affiliation(s)
- Gregory M Blain
- The John Rankin Laboratory of Pulmonary Medicine, Department of Population Health Sciences, School of Medicine and Public Health, University of Wisconsin, Madison, WI, USA.
| | | | | | | |
Collapse
|
32
|
Teppema LJ, Dahan A. The Ventilatory Response to Hypoxia in Mammals: Mechanisms, Measurement, and Analysis. Physiol Rev 2010; 90:675-754. [DOI: 10.1152/physrev.00012.2009] [Citation(s) in RCA: 257] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The respiratory response to hypoxia in mammals develops from an inhibition of breathing movements in utero into a sustained increase in ventilation in the adult. This ventilatory response to hypoxia (HVR) in mammals is the subject of this review. The period immediately after birth contains a critical time window in which environmental factors can cause long-term changes in the structural and functional properties of the respiratory system, resulting in an altered HVR phenotype. Both neonatal chronic and chronic intermittent hypoxia, but also chronic hyperoxia, can induce such plastic changes, the nature of which depends on the time pattern and duration of the exposure (acute or chronic, episodic or not, etc.). At adult age, exposure to chronic hypoxic paradigms induces adjustments in the HVR that seem reversible when the respiratory system is fully matured. These changes are orchestrated by transcription factors of which hypoxia-inducible factor 1 has been identified as the master regulator. We discuss the mechanisms underlying the HVR and its adaptations to chronic changes in ambient oxygen concentration, with emphasis on the carotid bodies that contain oxygen sensors and initiate the response, and on the contribution of central neurotransmitters and brain stem regions. We also briefly summarize the techniques used in small animals and in humans to measure the HVR and discuss the specific difficulties encountered in its measurement and analysis.
Collapse
Affiliation(s)
- Luc J. Teppema
- Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Albert Dahan
- Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands
| |
Collapse
|
33
|
An interdependent model of central/peripheral chemoreception: evidence and implications for ventilatory control. Respir Physiol Neurobiol 2010; 173:288-97. [PMID: 20206717 DOI: 10.1016/j.resp.2010.02.015] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2010] [Revised: 02/23/2010] [Accepted: 02/24/2010] [Indexed: 11/22/2022]
Abstract
In this review we discuss the implications for ventilatory control of newer evidence suggesting that central and peripheral chemoreceptors are not functionally separate but rather that they are dependent upon one another such that the sensitivity of the medullary chemoreceptors is critically determined by input from the carotid body chemoreceptors and vice versa i.e., they are interdependent. We examine potential interactions of the interdependent central and carotid body (CB) chemoreceptors with other ventilatory-related inputs such as central hypoxia, lung stretch, and exercise. The limitations of current approaches addressing this question are discussed and future studies are suggested.
Collapse
|
34
|
Convergence of cranial visceral afferents within the solitary tract nucleus. J Neurosci 2009; 29:12886-95. [PMID: 19828803 DOI: 10.1523/jneurosci.3491-09.2009] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Primary afferent axons within the solitary tract (ST) relay homeostatic information via glutamatergic synapses directly to second-order neurons within the nucleus of the solitary tract (NTS). These primary afferents arise from multiple organ systems and relay multiple sensory modalities. How this compact network organizes the flow of primary afferent information will shape central homeostatic control. To assess afferent convergence and divergence, we recorded ST-evoked synaptic responses in pairs of medial NTS neurons in horizontal brainstem slices. ST shocks activated EPSCs along monosynaptic or polysynaptic pathways. Gradations in shock intensity discriminated multiple inputs and stimulus recruitment profiles indicated that each EPSC was unitary. In 24 pairs, 75% were second-order neurons with 64% receiving one direct ST input with the remainder receiving additional convergent ST afferent inputs (22% two; 14% three monosynaptic ST-EPSCs). Some (34%) second-order neurons received polysynaptic EPSCs. Neurons receiving only higher-order inputs were uncommon (13%). Most ST-EPSCs were completely independent, but 4 EPSCs of a total of 81 had equal thresholds, highly correlated latencies, and synchronized synaptic failures consistent with divergence from a single source ST axon or from a common interneuron producing a pair of polysynaptic EPSCs. We conclude that ST afferent inputs are remarkably independent with little evidence of substantial shared information. Individual cells receive highly focused information from the viscera. Thus, afferent excitation of second-order NTS neurons is generally dominated by single visceral afferents and therefore focused on a single afferent modality and/or organ region.
Collapse
|