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Guyenet PG, Stornetta RL, Holloway BB, Souza GMPR, Abbott SBG. Rostral Ventrolateral Medulla and Hypertension. Hypertension 2019; 72:559-566. [PMID: 30354763 DOI: 10.1161/hypertensionaha.118.10921] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Patrice G Guyenet
- From the Department of Pharmacology, University of Virginia, Charlottesville
| | - Ruth L Stornetta
- From the Department of Pharmacology, University of Virginia, Charlottesville
| | - Benjamin B Holloway
- From the Department of Pharmacology, University of Virginia, Charlottesville
| | - George M P R Souza
- From the Department of Pharmacology, University of Virginia, Charlottesville
| | - Stephen B G Abbott
- From the Department of Pharmacology, University of Virginia, Charlottesville
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do Carmo JM, da Silva AA, Moak SP, da Silva FS, Spradley FT, Hall JE. Role of melanocortin 4 receptor in hypertension induced by chronic intermittent hypoxia. Acta Physiol (Oxf) 2019; 225:e13222. [PMID: 30466186 DOI: 10.1111/apha.13222] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Revised: 11/13/2018] [Accepted: 11/15/2018] [Indexed: 12/23/2022]
Abstract
AIM We previously demonstrated that central nervous system (CNS) melanocortin 4 receptors (MC4R) play a key role in regulating blood pressure (BP) in some conditions associated with increased SNS activity, including obesity. In this study, we examined whether activation of CNS MC4R contributes to chronic intermittent hypoxia (CIH)-induced hypertension and ventilatory responses to hypercapnia. METHODS Rats were instrumented with an intracerebroventricular (ICV) cannula in the lateral cerebral ventricle for continuous infusion of MC4R antagonist (SHU-9119) and telemetry probes for measuring mean arterial pressure (MAP) and heart rate (HR). Untreated and SHU-9119-treated rats as well as obese and lean MC4R-deficient rats were exposed to CIH for 7-18 consecutive days. RESULTS Chronic intermittent hypoxia reduced cumulative food intake by 18 ± 5 g while MAP and HR increased by 10 ± 3 mm Hg and 9 ± 5 bpm in untreated rats. SHU-9119 increased food intake (from 15 ± 1 to 46 ± 3 g) and prevented CIH-induced reduction in food intake. CIH-induced hypertension was not attenuated by MC4R antagonism (average increase of 10 ± 1 vs 9 ± 1 mm Hg for untreated and SHU-9119 treated rats). In obese MC4R-deficient rats, CIH for 7 days raised BP by 11 ± 4 mm Hg. However, when MC4R-deficient rats were food restricted to prevent obesity, CIH-induced hypertension was attenuated by 32%. We also found that MC4R deficiency was associated with impaired ventilatory responses to hypercapnia independently of obesity. CONCLUSION These results show that obesity and the CNS melanocortin system interact in complex ways to elevate BP during CIH and that MC4R may be important in the ventilatory responses to hypercapnia.
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Affiliation(s)
- Jussara M. do Carmo
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Cardiovascular‐Renal Research Center University of Mississippi Medical Center Jackson Mississippi
| | - Alexandre A. da Silva
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Cardiovascular‐Renal Research Center University of Mississippi Medical Center Jackson Mississippi
- Barão de Mauá University Center Ribeirão Preto Brazil
- Universidade Estadual de Minas Gerais Passos Brazil
| | - Sydney P. Moak
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Cardiovascular‐Renal Research Center University of Mississippi Medical Center Jackson Mississippi
| | - Fernanda S. da Silva
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Cardiovascular‐Renal Research Center University of Mississippi Medical Center Jackson Mississippi
- Barão de Mauá University Center Ribeirão Preto Brazil
| | - Frank T. Spradley
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Cardiovascular‐Renal Research Center University of Mississippi Medical Center Jackson Mississippi
- Department of Surgery University of Mississippi Medical Center Jackson Mississippi
| | - John E. Hall
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, Cardiovascular‐Renal Research Center University of Mississippi Medical Center Jackson Mississippi
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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.
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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
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Lavezzi AM, Poloniato A, Rovelli R, Lorioli L, Iasi GA, Pusiol T, Barera G, Ferrero S. Massive Amniotic Fluid Aspiration in a Case of Sudden Neonatal Death With Severe Hypoplasia of the Retrotrapezoid/Parafacial Respiratory Group. Front Pediatr 2019; 7:116. [PMID: 31019904 PMCID: PMC6458245 DOI: 10.3389/fped.2019.00116] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Accepted: 03/11/2019] [Indexed: 11/24/2022] Open
Abstract
We report a case of a baby, who, after pregnancy complicated by maternal Addison's disease and Hashimoto's thyroiditis and natural delivery, unexpectedly presented a cardiorespiratory collapse and died 1 hour after birth without responding to prolonged neonatal resuscitation maneuvers. The cause of death was reliably established by carrying out a forensic postmortem examination. More specifically, the histological examination of the lungs showed the presence of abundant endoalveolar and endobronchial cornea scales caused by absorption of amniotic fluid. The neuropathological examination of the brainstem highlighted severe hypodevelopment of the retrotrapezoid/parafacial respiratory group, which is a complex of neurons located in the caudal pons that is involved in respiratory rhythm coordination, especially expiration, in conditions of enhanced respiratory drive, as well as in chemoreception. This neuropathological finding shed new light on the mechanisms underlying the massive amniotic fluid aspiration which led to this early death.
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Affiliation(s)
- Anna M Lavezzi
- Department of Biomedical, Surgical and Dental Sciences, Lino Rossi Research Center for the Study and Prevention of Unexpected Perinatal Death and SIDS, University of Milan, Milan, Italy
| | | | | | - Laura Lorioli
- Neonatal Unit, IRCCS Ospedale San Raffaele, Milan, Italy
| | | | - Teresa Pusiol
- Institute of Pathology, Hospital of Rovereto, Rovereto, Italy
| | | | - Stefano Ferrero
- Department of Biomedical, Surgical and Dental Sciences, Lino Rossi Research Center for the Study and Prevention of Unexpected Perinatal Death and SIDS, University of Milan, Milan, Italy.,Division of Pathology, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico, Milan, Italy
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55
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da Silva EF, Bassi M, Menani JV, Colombari DSA, Zoccal DB, Pedrino GR, Colombari E. Carotid bodies contribute to sympathoexcitation induced by acute salt overload. Exp Physiol 2018; 104:15-27. [PMID: 30370945 DOI: 10.1113/ep087110] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 10/12/2018] [Indexed: 01/24/2023]
Abstract
NEW FINDINGS What is the central question of this study? Does carotid body input contribute to the hyperosmotic responses? What is the main finding and its importance? The response to NaCl overload is sympathorespiratory excitation. Eliminating the carotid body input reduced sympathoexcitation but did not affect the increase in phrenic burst frequency, whereas eliminating the hypothalamus prevented the tachypnoea and sympathoexcitation. We conclude that the carotid body inputs are essential for the full expression of the sympathetic activity during acute NaCl overload, whereas the tachypnoea depends on hypothalamic mechanisms. ABSTRACT Acute salt excess activates central osmoreceptors, which trigger an increase in sympathetic and respiratory activity. The carotid bodies also respond to hyperosmolality of the extracellular compartment, but their contribution to the sympathoexcitatory and ventilatory responses to NaCl overload remains unknown. To evaluate their contribution to acute NaCl overload, we recorded thoracic sympathetic (tSNA), phrenic (PNA) and carotid sinus nerve activities in decorticate in situ preparations of male Holtzman rats (60-100 g) while delivering intra-arterial infusions of hyperosmotic NaCl (0.17, 0.3, 0.7, 1.5 and 2.0 mol l-1 ; 200 μl infusion over 25-30 s, with a 10 min time interval between solutions) or mannitol (0.3, 0.5, 1.0, 2.7 and 3.8 mol l-1 ) progressively. The cumulative infusions of hyperosmotic NaCl increased the perfusate osmolality to 341 ± 5 mosmol (kg water)-1 and elicited an immediate increase in PNA and tSNA (n = 6, P < 0.05) in sham-denervated rats. Carotid body removal attenuated sympathoexcitation (n = 5, P < 0.05) but did not affect the tachypnoeic response. A precollicular transection disconnecting the hypothalamus abolished the sympathoexcitatory and tachypnoeic responses to NaCl overload (n = 6, P < 0.05). Equi-osmolar infusions of mannitol did not alter the PNA and tSNA in sham-denervated rats (n = 5). Sodium chloride infusions increased carotid sinus nerve activity (n = 10, P < 0.05), whereas mannitol produced negligible changes (n = 5). The results indicate that carotid bodies are activated by acute NaCl overload, but not by mannitol. We conclude that the carotid bodies contribute to the increased sympathetic activity during acute NaCl overload, whereas the ventilatory response is mainly mediated by hypothalamic mechanisms.
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Affiliation(s)
- Elaine Fernanda da Silva
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University - UNESP, Araraquara, São Paulo, Brazil
| | - Mirian Bassi
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University - UNESP, Araraquara, São Paulo, Brazil
| | - José Vanderlei Menani
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University - UNESP, Araraquara, São Paulo, Brazil
| | - Débora Simões Almeida Colombari
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University - UNESP, Araraquara, São Paulo, Brazil
| | - Daniel Breseghello Zoccal
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University - UNESP, Araraquara, São Paulo, Brazil
| | - Gustavo Rodrigues Pedrino
- Department of Physiological Sciences, Biological Sciences Institute, Federal University of Goias, Goiânia, Goias, Brazil
| | - Eduardo Colombari
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University - UNESP, Araraquara, São Paulo, Brazil
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56
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Sex differences in the respiratory-sympathetic coupling in rats exposed to chronic intermittent hypoxia. Respir Physiol Neurobiol 2018; 256:109-118. [DOI: 10.1016/j.resp.2017.09.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Revised: 09/02/2017] [Accepted: 09/06/2017] [Indexed: 02/06/2023]
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Nogueira V, Brito-Alves J, Fontes D, Oliveira L, Lucca W, Tourneur Y, Wanderley A, da Silva GSF, Leandro C, Costa-Silva JH. Carotid body removal normalizes arterial blood pressure and respiratory frequency in offspring of protein-restricted mothers. Hypertens Res 2018; 41:1000-1012. [PMID: 30242293 DOI: 10.1038/s41440-018-0104-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Revised: 03/12/2018] [Accepted: 03/26/2018] [Indexed: 12/25/2022]
Abstract
The aim of this study is to evaluate the short-term and long-term effects elicited by carotid body removal (CBR) on ventilatory function and the development of hypertension in the offspring of malnourished rats. Wistar rats were fed a normo-protein (NP, 17% casein) or low-protein (LP, 8% casein) diet during pregnancy and lactation. At 29 days of age, the animals were submitted to CBR or a sham surgery, according to the following groups: NP-cbr, LP-cbr, NP-sham, or LP-sham. In the short-term, at 30 days of age, the respiratory frequency (RF) and immunoreactivity for Fos on the retrotrapezoid nucleus (RTN; brainstem site containing CO2 sensitive neurons) after exposure to CO2 were evaluated. In the long term, at 90 days of age, arterial pressure (AP), heart rate (HR), and cardiovascular variability were evaluated. In the short term, an increase in the baseline RF (~6%), response to CO2 (~8%), and Fos in the RTN (~27%) occurred in the LP-sham group compared with the NP-sham group. Interestingly, the CBR in the LP group normalized the RF in response to CO2 as well as RTN cell activation. In the long term, CBR reduced the mean AP by ~20 mmHg in malnourished rats. The normalization of the arterial pressure was associated with a decrease in the low-frequency (LF) oscillatory component of AP (~58%) and in the sympathetic tonus to the cardiovascular system (~29%). In conclusion, carotid body inputs in malnourished offspring may be responsible for the following: (i) enhanced respiratory frequency and CO2 chemosensitivity in early life and (ii) the production of autonomic imbalance and the development of hypertension.
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Affiliation(s)
- Viviane Nogueira
- Department of Physical Education and Sports Sciences, Federal University of Pernambuco, Vitória de Santo Antão, PE, Brazil
| | - Jose Brito-Alves
- Department of Physical Education and Sports Sciences, Federal University of Pernambuco, Vitória de Santo Antão, PE, Brazil
| | - Danilo Fontes
- Department of Physical Education and Sports Sciences, Federal University of Pernambuco, Vitória de Santo Antão, PE, Brazil
| | - Larissa Oliveira
- Department of Morphology, Federal University of Sergipe, Aracajú, SE, Brazil
| | - Waldecy Lucca
- Department of Morphology, Federal University of Sergipe, Aracajú, SE, Brazil
| | - Yves Tourneur
- Department of Physical Education and Sports Sciences, Federal University of Pernambuco, Vitória de Santo Antão, PE, Brazil.,Centre National de la Recherche Scientifique, Université Claude Bernard, Lyon 1, Lyon, France
| | - Almir Wanderley
- Department of Physiology and Pharmacology, Federal University of Pernambuco, Recife, PE, Brazil
| | - Glauber S F da Silva
- Department of Physiology and Biophysics, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil
| | - Carol Leandro
- Department of Physical Education and Sports Sciences, Federal University of Pernambuco, Vitória de Santo Antão, PE, Brazil
| | - João Henrique Costa-Silva
- Department of Physical Education and Sports Sciences, Federal University of Pernambuco, Vitória de Santo Antão, PE, Brazil.
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Zoccal DB, Silva JN, Barnett WH, Lemes EV, Falquetto B, Colombari E, Molkov YI, Moreira TS, Takakura AC. Interaction between the retrotrapezoid nucleus and the parafacial respiratory group to regulate active expiration and sympathetic activity in rats. Am J Physiol Lung Cell Mol Physiol 2018; 315:L891-L909. [PMID: 30188747 DOI: 10.1152/ajplung.00011.2018] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The retrotrapezoid nucleus (RTN) contains chemosensitive cells that distribute CO2-dependent excitatory drive to the respiratory network. This drive facilitates the function of the respiratory central pattern generator (rCPG) and increases sympathetic activity. It is also evidenced that during hypercapnia, the late-expiratory (late-E) oscillator in the parafacial respiratory group (pFRG) is activated and determines the emergence of active expiration. However, it remains unclear the microcircuitry responsible for the distribution of the excitatory signals to the pFRG and the rCPG in conditions of high CO2. Herein, we hypothesized that excitatory inputs from chemosensitive neurons in the RTN are necessary for the activation of late-E neurons in the pFRG. Using the decerebrated in situ rat preparation, we found that lesions of neurokinin-1 receptor-expressing neurons in the RTN region with substance P-saporin conjugate suppressed the late-E activity in abdominal nerves (AbNs) and sympathetic nerves (SNs) and attenuated the increase in phrenic nerve (PN) activity induced by hypercapnia. On the other hand, kynurenic acid (100 mM) injections in the pFRG eliminated the late-E activity in AbN and thoracic SN but did not modify PN response during hypercapnia. Iontophoretic injections of retrograde tracer into the pFRG of adult rats revealed labeled phox2b-expressing neurons within the RTN. Our findings are supported by mathematical modeling of chemosensitive and late-E populations within the RTN and pFRG regions as two separate but interacting populations in a way that the activation of the pFRG late-E neurons during hypercapnia require glutamatergic inputs from the RTN neurons that intrinsically detect changes in CO2/pH.
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Affiliation(s)
- Daniel B Zoccal
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University , São Paulo , Brazil
| | - Josiane N Silva
- Department of Pharmacology, Institute of Biomedical Science, University of São Paulo , São Paulo , Brazil
| | - William H Barnett
- Deptartment of Mathematics and Statistics, Georgia State University , Atlanta, Georgia
| | - Eduardo V Lemes
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University , São Paulo , Brazil
| | - Barbara Falquetto
- Department of Pharmacology, Institute of Biomedical Science, University of São Paulo , São Paulo , Brazil
| | - Eduardo Colombari
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University , São Paulo , Brazil
| | - Yaroslav I Molkov
- Deptartment of Mathematics and Statistics, Georgia State University , Atlanta, Georgia.,Neuroscience Institute, Georgia State University , Atlanta, Georgia
| | - Thiago S Moreira
- Department of Physiology and Biophysics, Institute of Biomedical Science, University of São Paulo , São Paulo , Brazil
| | - Ana C Takakura
- Department of Pharmacology, Institute of Biomedical Science, University of São Paulo , São Paulo , Brazil
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Cabrera-Aguilera I, Rizo-Roca D, Marques EA, Santocildes G, Pagès T, Viscor G, Ascensão AA, Magalhães J, Torrella JR. Additive Effects of Intermittent Hypobaric Hypoxia and Endurance Training on Bodyweight, Food Intake, and Oxygen Consumption in Rats. High Alt Med Biol 2018; 19:278-285. [PMID: 29957064 DOI: 10.1089/ham.2018.0013] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Cabrera-Aguilera, Ignacio, David Rizo-Roca, Elisa A. Marques, Garoa Santocildes, Teresa Pagès, Gines Viscor, António A. Ascensão, José Magalhães, and Joan Ramon Torrella. Additive effects of intermittent hypobaric hypoxia and endurance training on bodyweight, food intake, and oxygen consumption in rats. High Alt Med Biol. 19:278-285, 2018.-We used an animal model to elucidate the effects of an intermittent hypobaric hypoxia (IHH) and endurance exercise training (EET) protocol on bodyweight (BW), food and water intake, and oxygen consumption. Twenty-eight young adult male rats were divided into four groups: normoxic sedentary (NS), normoxic exercised (NE), hypoxic sedentary (HS), and hypoxic exercised (HE). Normoxic groups were maintained at an atmospheric pressure equivalent to sea level, whereas the IHH protocol consisted of 5 hours per day for 33 days at a simulated altitude of 6000 m. Exercised groups ran in normobaric conditions on a treadmill for 1 hour/day for 5 weeks at a speed of 25 m/min. At the end of the protocol, both hypoxic groups showed significant decreases in BW from the ninth day of exposure, reaching final 10% (HS) to 14.5% (HE) differences when compared with NS. NE rats also showed a significant weight reduction after the 19th day, with a decrease of 7.4%. The BW of hypoxic animals was related to significant hypophagia elicited by IHH exposure (from 8% to 12%). In contrast, EET had no effect on food ingestion. Total water intake was not affected by hypoxia but was significantly increased by exercise. An analysis of oxygen consumption at rest (mL O2/[kg·min]) revealed two findings: a significant decrease in both hypoxic groups after the protocol (HS, 21.7 ± 0.70 vs. 19.1 ± 0.78 and HE, 22.8 ± 0.80 vs. 17.1 ± 0.90) and a significant difference at the end of the protocol between NE (21.3 ± 0.77) and HE (17.1 ± 0.90). These results demonstrate that IHH and EET had an additive effect on BW loss, providing evidence that rats underwent a metabolic adaptation through a reduction in oxygen consumption measured under normoxic conditions. These data suggest that the combination of IHH and EET could serve as an alternative treatment for the management of overweight and obesity.
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Affiliation(s)
- Ignacio Cabrera-Aguilera
- 1 Departament de Biologia Cel·lular, Fisiologia i Immunologia, Facultat de Biologia, Universitat de Barcelona , Barcelona, Spain
| | - David Rizo-Roca
- 1 Departament de Biologia Cel·lular, Fisiologia i Immunologia, Facultat de Biologia, Universitat de Barcelona , Barcelona, Spain .,2 LaMetEx-Laboratory of Metabolism and Exercise, Faculdade de Desporto, Centro de Investigação em Atividade Física e Lazer (CIAFEL), Universidade do Porto , Porto, Portugal
| | - Elisa A Marques
- 3 Centro de Investigação em Desporto, Saúde e Desenvolvimento Humano (CIDESD), Instituto Universitário da Maia (ISMAI) , Maia, Portugal
| | - Garoa Santocildes
- 1 Departament de Biologia Cel·lular, Fisiologia i Immunologia, Facultat de Biologia, Universitat de Barcelona , Barcelona, Spain
| | - Teresa Pagès
- 1 Departament de Biologia Cel·lular, Fisiologia i Immunologia, Facultat de Biologia, Universitat de Barcelona , Barcelona, Spain
| | - Gines Viscor
- 1 Departament de Biologia Cel·lular, Fisiologia i Immunologia, Facultat de Biologia, Universitat de Barcelona , Barcelona, Spain
| | - António A Ascensão
- 2 LaMetEx-Laboratory of Metabolism and Exercise, Faculdade de Desporto, Centro de Investigação em Atividade Física e Lazer (CIAFEL), Universidade do Porto , Porto, Portugal
| | - José Magalhães
- 2 LaMetEx-Laboratory of Metabolism and Exercise, Faculdade de Desporto, Centro de Investigação em Atividade Física e Lazer (CIAFEL), Universidade do Porto , Porto, Portugal
| | - Joan Ramon Torrella
- 1 Departament de Biologia Cel·lular, Fisiologia i Immunologia, Facultat de Biologia, Universitat de Barcelona , Barcelona, Spain
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60
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Bober SL, Ciriello J, Jones DL. Atrial arrhythmias and autonomic dysfunction in rats exposed to chronic intermittent hypoxia. Am J Physiol Heart Circ Physiol 2018; 314:H1160-H1168. [DOI: 10.1152/ajpheart.00173.2017] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Obstructive sleep apnea, which involves chronic intermittent hypoxia (CIH), is a major risk factor for developing atrial fibrillation (AF). Whether or not CIH alone alters cardiac mechanisms to support AF is unknown. This study investigated the effects of CIH on atrial electrophysiology and arrhythmia vulnerability and evaluated the role of autonomics in CIH promotion of AF. Adult male Sprague-Dawley rats were exposed to 8 h/day of CIH or normoxia for 7 days. After exposure, rats were anesthetized for intracardiac electrophysiological experiments. Atrial effective refractory periods (AERPs) and AF inducibility were determined using programmed electrical stimulation and burst pacing in the absence and presence of autonomic receptor agonists and antagonists. Western blot analysis measured atrial protein expression of muscarinic M2, M3, and β1-adrenergic receptors. Compared with normoxia-exposed control rats, CIH-exposed rats had enhanced AF vulnerability using both programmed electrical stimulation and burst pacing, accompanied by greater AERP responses to carbachol and propranolol, lesser responses to isoproterenol, and higher atrial M2 receptor protein levels. Enhanced atrial vulnerability was accentuated by carbachol and abolished by atropine, indicating that the AF-promoting effects of CIH depended principally on parasympathetic activation. Enhancement of atrial vulnerability and AERP shortening with cholinergic agonists in CIH-exposed rats is consistent with sensitivity to parasympathetic activation. Higher responses to adrenergic receptor blockade in CIH-exposed rats is consistent with sympathetic potentiation. These findings implicate CIH as an important mediator of enhanced AF susceptibility in obstructive sleep apnea and provide novel insights into the underlying mechanisms. NEW & NOTEWORTHY Our study demonstrates, for the first time, that chronic intermittent hypoxia alone enhances vulnerability to atrial arrhythmia induction, which depends principally on parasympathetic activation. Enhanced atrial vulnerability was accompanied by heightened electrophysiological responses of the atrial myocardium to carbachol and isoproterenol, dampened responses to propranolol, and increased atrial M2 receptor protein levels.
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Affiliation(s)
- Sara L. Bober
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - John Ciriello
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Douglas L. Jones
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
- Department of Medicine, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
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Abstract
PURPOSE OF REVIEW An abnormal heightened carotid body (CB) chemoreflex, which produces autonomic dysfunction and sympathetic overactivation, is the common hallmark of obstructive sleep apnea (OSA), resistant hypertension, systolic heart failure (HF), and cardiometabolic diseases. Accordingly, it has been proposed that the elimination of the CB chemosensory input to the brainstem may reduce the autonomic and cardiorespiratory alterations in sympathetic-associated diseases in humans. RECENT FINDINGS A growing body of evidence obtained in preclinical animal models support that an enhanced CB discharge produces sympathetic hyperactivity, baroreflex sensitivity and heart rate variability impairment, breathing instability, hypertension, and insulin resistance. The elimination CB chemosensory input reduces the sympathetic hyperactivity, the elevated arterial blood pressure in OSA and hypertensive models, abolishes breathing instability and improves animal survival in HF models, and restores insulin tolerance in metabolic models. These results highlight the role played by the enhanced CB drive in the progression of sympathetic-related diseases and support the proposal that the surgical ablation of the CB is useful to restore the autonomic balance and normal cardiorespiratory function in humans. Accordingly, the CB ablation has been used in pilot human studies as a therapeutic treatment for resistant hypertension and HF-induced sympathetic hyperactivity. In this review, I will discuss the supporting evidence for a crucial contribution of the CB in the central autonomic dysfunction and the pros and cons of the CB ablation as a therapy to revert autonomic overactivation. The CB ablation could be a useful method to reverse the enhanced chemoreflex in HF and severe hypertension, but caution is required before extensive use of bilateral CB ablation, which abolished ventilatory responses to hypoxia and may impair baroreceptor function.
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Flor KC, Silva EF, Menezes MF, Pedrino GR, Colombari E, Zoccal DB. Short-Term Sustained Hypoxia Elevates Basal and Hypoxia-Induced Ventilation but Not the Carotid Body Chemoreceptor Activity in Rats. Front Physiol 2018. [PMID: 29535636 PMCID: PMC5835044 DOI: 10.3389/fphys.2018.00134] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Exposure to chronic sustained hypoxia (SH), as experienced in high altitudes, elicits an increase in ventilation, named ventilatory acclimatization to hypoxia (VAH). We previously showed that rats exposed to short-term (24 h) SH exhibit enhanced abdominal expiratory motor activity at rest, accompanied by augmented baseline sympathetic vasoconstrictor activity. In the present study, we investigated whether the respiratory and sympathetic changes elicited by short-term SH are accompanied by carotid body chemoreceptor sensitization. Juvenile male Holtzman rats (60-80 g) were exposed to SH (10% O2 for 24 h) or normoxia (control) to examine basal and hypoxic-induced ventilatory parameters in unanesthetized conditions, as well as the sensory response of carotid body chemoreceptors in artificially perfused in situ preparations. Under resting conditions (normoxia/normocapnia), SH rats (n = 12) exhibited higher baseline respiratory frequency, tidal volume, and minute ventilation compared to controls (n = 11, P < 0.05). SH group also showed greater hypoxia ventilatory response than control group (P < 0.05). The in situ preparations of SH rats (n = 8) exhibited augmented baseline expiratory and sympathetic activities under normocapnia, with additional bursts in abdominal and thoracic sympathetic nerves during late expiratory phase that were not seen in controls (n = 8, P < 0.05). Interestingly, basal and potassium cyanide-induced afferent activity of carotid sinus nerve (CSN) was similar between SH and control rats. Our findings indicate that the maintenance of elevated resting ventilation, baseline sympathetic overactivity, and enhanced ventilatory responses to hypoxia in rats exposed to 24 h of SH are not dependent on increased basal and sensorial activity of carotid body chemoreceptors.
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Affiliation(s)
- Karine C Flor
- Department of Physiology and Pathology, São Paulo State University, Araraquara, Brazil
| | - Elaine F Silva
- Department of Physiological Sciences, Federal University of Goiás, Goiânia, Brazil
| | - Miguel F Menezes
- Department of Physiology and Pathology, São Paulo State University, Araraquara, Brazil
| | - Gustavo R Pedrino
- Department of Physiological Sciences, Federal University of Goiás, Goiânia, Brazil
| | - Eduardo Colombari
- Department of Physiology and Pathology, São Paulo State University, Araraquara, Brazil
| | - Daniel B Zoccal
- Department of Physiology and Pathology, São Paulo State University, Araraquara, Brazil
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63
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Perim RR, Amorim MR, Bonagamba TLLGH, Machado BH. Previous exposure to chronic intermittent hypoxia blunts the development of one-kidney, one-clip hypertension in rats. Exp Physiol 2018; 103:473-482. [DOI: 10.1113/ep086734] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Accepted: 01/10/2018] [Indexed: 12/13/2022]
Affiliation(s)
- Raphael R. Perim
- Department of Physiology, School of Medicine of Ribeirão Preto; University of São Paulo; Ribeirão Preto SP 14049-900 Brazil
| | - Mateus R. Amorim
- Department of Physiology, School of Medicine of Ribeirão Preto; University of São Paulo; Ribeirão Preto SP 14049-900 Brazil
| | - The Late Leni G. H. Bonagamba
- Department of Physiology, School of Medicine of Ribeirão Preto; University of São Paulo; Ribeirão Preto SP 14049-900 Brazil
| | - Benedito H. Machado
- Department of Physiology, School of Medicine of Ribeirão Preto; University of São Paulo; Ribeirão Preto SP 14049-900 Brazil
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64
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Possible Breathing Influences on the Control of Arterial Pressure After Sino-aortic Denervation in Rats. Curr Hypertens Rep 2018; 20:2. [PMID: 29356918 DOI: 10.1007/s11906-018-0800-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
PURPOSE OF REVIEW Surgical removal of the baroreceptor afferents [sino-aortic denervation (SAD)] leads to a lack of inhibitory feedback to sympathetic outflow, which in turn is expected to result in a large increase in mean arterial pressure (MAP). However, few days after surgery, the sympathetic nerve activity (SNA) and MAP of SAD rats return to a range similar to that observed in control rats. In this review, we present experimental evidence suggesting that breathing contributes to control of SNA and MAP following SAD.The purpose of this review was to discuss studies exploring SNA and MAP regulation in SAD rats, highlighting the possible role of breathing in the neural mechanisms of this modulation of SNA. RECENT FINDINGS Recent studies show that baroreceptor afferent stimulation or removal (SAD) results in changes in the respiratory pattern. Changes in the neural respiratory network and in the respiratory pattern must be considered among mechanisms involved in the modulation of the MAP after SAD.
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Guyenet PG, Bayliss DA, Stornetta RL, Kanbar R, Shi Y, Holloway BB, Souza GMPR, Basting TM, Abbott SBG, Wenker IC. Interdependent feedback regulation of breathing by the carotid bodies and the retrotrapezoid nucleus. J Physiol 2017; 596:3029-3042. [PMID: 29168167 DOI: 10.1113/jp274357] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 11/02/2017] [Indexed: 12/13/2022] Open
Abstract
The retrotrapezoid nucleus (RTN) regulates breathing in a CO2 - and state-dependent manner. RTN neurons are glutamatergic and innervate principally the respiratory pattern generator; they regulate multiple aspects of breathing, including active expiration, and maintain breathing automaticity during non-REM sleep. RTN neurons encode arterial PCO2 /pH via cell-autonomous and paracrine mechanisms, and via input from other CO2 -responsive neurons. In short, RTN neurons are a pivotal structure for breathing automaticity and arterial PCO2 homeostasis. The carotid bodies stimulate the respiratory pattern generator directly and indirectly by activating RTN via a neuronal projection originating within the solitary tract nucleus. The indirect pathway operates under normo- or hypercapnic conditions; under respiratory alkalosis (e.g. hypoxia) RTN neurons are silent and the excitatory input from the carotid bodies is suppressed. Also, silencing RTN neurons optogenetically quickly triggers a compensatory increase in carotid body activity. Thus, in conscious mammals, breathing is subject to a dual and interdependent feedback regulation by chemoreceptors. Depending on the circumstance, the activity of the carotid bodies and that of RTN vary in the same or the opposite directions, producing additive or countervailing effects on breathing. These interactions are mediated either via changes in blood gases or by brainstem neuronal connections, but their ultimate effect is invariably to minimize arterial PCO2 fluctuations. We discuss the potential relevance of this dual chemoreceptor feedback to cardiorespiratory abnormalities present in diseases in which the carotid bodies are hyperactive at rest, e.g. essential hypertension, obstructive sleep apnoea and heart failure.
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Affiliation(s)
- Patrice G Guyenet
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Douglas A Bayliss
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Ruth L Stornetta
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Roy Kanbar
- Department of Pharmaceutical Sciences, Lebanese American University, Beyrouth, Lebanon
| | - Yingtang Shi
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Benjamin B Holloway
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - George M P R Souza
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Tyler M Basting
- Department of Pharmacology & Experimental Therapeutics, Louisiana State University, New Orleans, Louisiana 70112, USA
| | - Stephen B G Abbott
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Ian C Wenker
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
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de Brito Alves JL, Costa-Silva JH. Maternal protein malnutrition induced-hypertension: New evidence about the autonomic and respiratory dysfunctions and epigenetic mechanisms. Clin Exp Pharmacol Physiol 2017; 45:422-429. [PMID: 29164748 DOI: 10.1111/1440-1681.12892] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Revised: 11/10/2017] [Accepted: 11/13/2017] [Indexed: 12/21/2022]
Abstract
Maternal protein malnutrition during the critical stages of development (pregnancy, lactation and first infancy) can lead to adult hypertension. Studies have shown that renal and cardiovascular dysfunctions can be associated to the development of hypertension in humans and rats exposed to maternal protein malnutrition. The etiology of hypertension, however, includes a complex network involved in central and peripheral blood pressure control. Recently, the hyperactivity of the sympathetic nervous system in protein-restricted rats has been reported. Studies have shown that protein malnutrition during pregnancy and/or lactation alters blood pressure control through mechanisms that include central sympathetic-respiratory dysfunctions and epigenetic modifications, which may contribute to adult hypertension. Thus, this review will discuss the historical context, new evidences of neurogenic disruption in respiratory-sympathetic activities and possible epigenetic mechanisms involved in maternal protein malnutrition induced- hypertension.
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Affiliation(s)
- José Luiz de Brito Alves
- Department of Nutrition, Health Sciences Center, Federal University of Paraíba, UFPB, João Pessoa, Brazil
| | - João Henrique Costa-Silva
- Department of Physical Education and Sport Sciences, Federal University of Pernambuco, UFPE, Vitória de Santo Antão-PE, Brazil
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67
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Role of ventral medullary catecholaminergic neurons for respiratory modulation of sympathetic outflow in rats. Sci Rep 2017; 7:16883. [PMID: 29203815 PMCID: PMC5715015 DOI: 10.1038/s41598-017-17113-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Accepted: 11/22/2017] [Indexed: 02/07/2023] Open
Abstract
Sympathetic activity displays rhythmic oscillations generated by brainstem inspiratory and expiratory neurons. Amplification of these rhythmic respiratory-related oscillations is observed in rats under enhanced central respiratory drive or during development of neurogenic hypertension. Herein, we evaluated the involvement of ventral medullary sympatho-excitatory catecholaminergic C1 neurons, using inhibitory Drosophila allatostatin receptors, for the enhanced expiratory-related oscillations in sympathetic activity in rats submitted to chronic intermittent hypoxia (CIH) and following activation of both peripheral (hypoxia) and central chemoreceptors (hypercapnia). Pharmacogenetic inhibition of C1 neurons bilaterally resulted in reductions of their firing frequency and amplitude of inspiratory-related sympathetic activity in rats in normocapnia, hypercapnia or after CIH. In contrast, hypercapnia or hypoxia-induced enhanced expiratory-related sympathetic oscillations were unaffected by C1 neuronal inhibition. Inhibition of C1 neurons also resulted in a significant fall in arterial pressure and heart rate that was similar in magnitude between normotensive and CIH hypertensive rats, but basal arterial pressure in CIH rats remained higher compared to controls. C1 neurons play a key role in regulating inspiratory modulation of sympathetic activity and arterial pressure in both normotensive and CIH hypertensive rats, but they are not involved in the enhanced late-expiratory-related sympathetic activity triggered by activation of peripheral or central chemoreceptors.
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68
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Effect of maternal dyslipidaemia on the cardiorespiratory physiology and biochemical parameters in male rat offspring. Br J Nutr 2017; 118:930-941. [DOI: 10.1017/s0007114517003014] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractThe present study evaluated the effects of maternal dyslipidaemia on blood pressure (BP), cardiorespiratory physiology and biochemical parameters in male offspring. Wistar rat dams were fed either a control (CTL) or a dyslipidaemic (DLP) diet during pregnancy and lactation. After weaning, both CTL and DLP offspring received standard diet. On the 30th and 90th day of life, blood samples were collected for metabolic analyses. Direct measurements of BP, respiratory frequency (RF), tidal volume (VT) and ventilation (VE) under baseline condition, as well as during hypercapnia (7 % CO2) and hypoxia (KCN, 0·04 %), were recorded from awake 90-d-old male offspring. DLP dams exhibited raised serum levels of total cholesterol (TC) (4·0-fold), TAG (2·0-fold), VLDL+LDL (7·7-fold) and reduced HDL-cholesterol (2·4-fold), insulin resistance and hepatic steatosis at the end of lactation. At 30 d of age, the DLP offspring showed an increase in the serum levels of TC (P<0·05) and VLDL+LDL (P<0·05) in comparison with CTL offspring. At 90 d of age, DLP offspring exhibited higher mean arterial pressure (MAP, approximately 34 %). In the spectral analysis, the DLP group showed augmented low-frequency (LF) power and LF:high-frequency (HF) ratio when compared with CTL offspring. In addition, the DLP animals showed a larger delta variation in arterial pressure after administration of the ganglionic blocker (P=0·0003). We also found that cardiorespiratory response to hypercapnia and hypoxia was augmented in DLP offspring. In conclusion, the present data show that maternal dyslipidaemia alters cardiorespiratory physiology and may be a predisposing factor for hypertension at adulthood.
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69
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Holbein WW, Blackburn MB, Andrade MA, Toney GM. Burst patterning of hypothalamic paraventricular nucleus-driven sympathetic nerve activity in ANG II-salt hypertension. Am J Physiol Heart Circ Physiol 2017; 314:H530-H541. [PMID: 29167122 DOI: 10.1152/ajpheart.00560.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
ANG II-salt hypertension selectively increases splanchnic sympathetic nerve activity (sSNA), but the extent to which this reflects increased respiratory versus cardiac rhythmic bursting is unknown. Here, integrated sSNA was elevated in ANG II-infused rats fed a high-salt (2% NaCl) diet (ANG II-HSD) compared with vehicle-infused rats fed a normal-salt (0.4% NaCl) diet (Veh-NSD; P < 0.01). Increased sSNA was not accompanied by increased inspiratory or expiratory bursting, consistent with no group difference in central inspiratory drive. Consistent with preserved inhibitory baroreflex entrainment of elevated sSNA in ANG II-HSD rats, the time integral ( P < 0.05) and amplitude ( P < 0.01) of cardiac rhythmic sSNA were increased. Consistent with activity of hypothalamic paraventricular nucleus (PVN) neurons supporting basal SNA in ANG II-salt hypertension, inhibition of PVN with the GABA-A receptor agonist muscimol reduced mean arterial pressure (MAP) and integrated sSNA only in the ANG II-HSD group ( P < 0.001). PVN inhibition had no effect on respiratory rhythmic sSNA bursting in either group but reduced cardiac rhythmic sSNA in ANG II-HSD rats only ( P < 0.01). The latter likely reflected reduced inhibitory baroreflex entrainment subsequent to the fall of MAP. Of note is that MAP as well as integrated and rhythmic burst patterns of sSNA were similar in vehicle-infused rats whether they were fed a normal or high-salt diet. Findings indicate that PVN neurons support elevated sSNA in ANG II-HSD rats by driving a tonic component of activity without altering respiratory or cardiac rhythmic bursting. Because sSNA was unchanged in Veh-HSD rats, activation of PVN-driven tonic sSNA appears to require central actions of ANG II. NEW & NOTEWORTHY ANG II-salt hypertension is strongly neurogenic and depends on hypothalamic paraventricular nucleus (PVN)-driven splanchnic sympathetic nerve activity (sSNA). Here, respiratory and cardiac bursts of sSNA were preserved in ANG II-salt rats and unaltered by PVN inhibition, suggesting that PVN neurons drive a tonic component of sSNA rather than modulating dominant patterns of burst discharge.
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Affiliation(s)
- Walter W Holbein
- Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio , San Antonio, Texas
| | - Megan B Blackburn
- Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio , San Antonio, Texas
| | - Mary Ann Andrade
- Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio , San Antonio, Texas
| | - Glenn M Toney
- Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio , San Antonio, Texas.,Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio , San Antonio, Texas
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70
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Liu H, Zheng X, Zhang L, Yang X, Shao Y, Zhang S. Bilateral superior cervical ganglionectomy attenuates the progression of β-aminopropionitrile-induced aortic dissection in rats. Life Sci 2017; 193:200-206. [PMID: 29104105 DOI: 10.1016/j.lfs.2017.10.043] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Revised: 10/20/2017] [Accepted: 10/31/2017] [Indexed: 12/15/2022]
Abstract
AIMS Aortic dissection (AD) represents one of the most common aortic emergencies with high incidence of morbidity and mortality. Clinical studies have shown that the increased excitability of the sympathetic nerve may be associated with the formation of AD. In this study, we examined the effects of bilateral superior cervical sympathectomy (SCGx) on the progression of β-aminopropionitrile (BAPN)-induced AD in rats. MAIN METHODS Sprague-Dawley rats were randomly divided into three groups, including BAPN, BAPN+SCGx and control groups. For terminal measurements, the mean arterial pressure (MAP) and heart rate (HR) were monitored and the basal sympathetic nerve activity (SNA) was assessed through recording the variation in arterial pressure in response to hexamethonium application. Pathological changes in the aortic wall were observed by histological staining. Matrix metalloproteinase-2 (MMP-2) and MMP-9 concentrations within the aortic wall were analyzed by western blot. KEY FINDINGS The results show that BAPN administration could elevate SNA and cause the formation of AD in rats with a high incidence (67.7%), while SCGx treatment inhibited the elevation of SNA and significantly reduced the incidence (20%). SCGx may suppress the formation of BAPN-induced AD via restraining the rise of HR and reducing the MMP-9 concentration in aortic wall. SIGNIFICANCE These results indicate that surgical techniques such as sympathetic nerve block may be a potentially useful therapy for the prevention of AD.
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Affiliation(s)
- Huan Liu
- Department of Cardiovascular Surgery, The First Affiliated Hospital, Nanjing Medical University, Nanjing, Jiangsu, China
| | - Xiangxiang Zheng
- Department of Cardiovascular Surgery, The First Affiliated Hospital, Nanjing Medical University, Nanjing, Jiangsu, China
| | - Linfei Zhang
- Department of Cardiovascular Surgery, The First Affiliated Hospital, Nanjing Medical University, Nanjing, Jiangsu, China
| | - Xuechao Yang
- Department of Cardiovascular Surgery, The First Affiliated Hospital, Nanjing Medical University, Nanjing, Jiangsu, China
| | - Yongfeng Shao
- Department of Cardiovascular Surgery, The First Affiliated Hospital, Nanjing Medical University, Nanjing, Jiangsu, China
| | - Shijiang Zhang
- Department of Cardiovascular Surgery, The First Affiliated Hospital, Nanjing Medical University, Nanjing, Jiangsu, China.
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71
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Barnett WH, Jenkin SEM, Milsom WK, Paton JFR, Abdala AP, Molkov YI, Zoccal DB. The Kölliker-Fuse nucleus orchestrates the timing of expiratory abdominal nerve bursting. J Neurophysiol 2017; 119:401-412. [PMID: 29070631 DOI: 10.1152/jn.00499.2017] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Coordination of respiratory pump and valve muscle activity is essential for normal breathing. A hallmark respiratory response to hypercapnia and hypoxia is the emergence of active exhalation, characterized by abdominal muscle pumping during the late one-third of expiration (late-E phase). Late-E abdominal activity during hypercapnia has been attributed to the activation of expiratory neurons located within the parafacial respiratory group (pFRG). However, the mechanisms that control emergence of active exhalation, and its silencing in restful breathing, are not completely understood. We hypothesized that inputs from the Kölliker-Fuse nucleus (KF) control the emergence of late-E activity during hypercapnia. Previously, we reported that reversible inhibition of the KF reduced postinspiratory (post-I) motor output to laryngeal adductor muscles and brought forward the onset of hypercapnia-induced late-E abdominal activity. Here we explored the contribution of the KF for late-E abdominal recruitment during hypercapnia by pharmacologically disinhibiting the KF in in situ decerebrate arterially perfused rat preparations. These data were combined with previous results and incorporated into a computational model of the respiratory central pattern generator. Disinhibition of the KF through local parenchymal microinjections of gabazine (GABAA receptor antagonist) prolonged vagal post-I activity and inhibited late-E abdominal output during hypercapnia. In silico, we reproduced this behavior and predicted a mechanism in which the KF provides excitatory drive to post-I inhibitory neurons, which in turn inhibit late-E neurons of the pFRG. Although the exact mechanism proposed by the model requires testing, our data confirm that the KF modulates the formation of late-E abdominal activity during hypercapnia. NEW & NOTEWORTHY The pons is essential for the formation of the three-phase respiratory pattern, controlling the inspiratory-expiratory phase transition. We provide functional evidence of a novel role for the Kölliker-Fuse nucleus (KF) controlling the emergence of abdominal expiratory bursts during active expiration. A computational model of the respiratory central pattern generator predicts a possible mechanism by which the KF interacts indirectly with the parafacial respiratory group and exerts an inhibitory effect on the expiratory conditional oscillator.
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Affiliation(s)
- William H Barnett
- Department of Mathematics and Statistics, Georgia State University , Atlanta, Georgia
| | - Sarah E M Jenkin
- Department of Zoology, University of British Columbia , Vancouver, British Columbia , Canada
| | - William K Milsom
- Department of Zoology, University of British Columbia , Vancouver, British Columbia , Canada
| | - Julian F R Paton
- School of Physiology, Pharmacology and Neuroscience, Faculty of Biomedical Sciences, University of Bristol , Bristol , United Kingdom.,Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland , Auckland , New Zealand
| | - Ana P Abdala
- School of Physiology, Pharmacology and Neuroscience, Faculty of Biomedical Sciences, University of Bristol , Bristol , United Kingdom
| | - Yaroslav I Molkov
- Department of Mathematics and Statistics, Georgia State University , Atlanta, Georgia.,Neuroscience Institute, Georgia State University , Atlanta, Georgia
| | - Daniel B Zoccal
- Department of Physiology and Pathology, São Paulo State University , Araraquara , Brazil
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72
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de Brito Alves JL, de Oliveira JMD, Ferreira DJS, Barros MADV, Nogueira VO, Alves DS, Vidal H, Leandro CG, Lagranha CJ, Pirola L, da Costa-Silva JH. Maternal protein restriction induced-hypertension is associated to oxidative disruption at transcriptional and functional levels in the medulla oblongata. Clin Exp Pharmacol Physiol 2017; 43:1177-1184. [PMID: 27612187 DOI: 10.1111/1440-1681.12667] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Revised: 08/31/2016] [Accepted: 09/06/2016] [Indexed: 01/11/2023]
Abstract
Maternal protein restriction during pregnancy and lactation predisposes the adult offspring to sympathetic overactivity and arterial hypertension. Although the underlying mechanisms are poorly understood, dysregulation of the oxidative balance has been proposed as a putative trigger of neural-induced hypertension. The aim of the study was to evaluate the association between the oxidative status at transcriptional and functional levels in the medulla oblongata and maternal protein restriction induced-hypertension. Wistar rat dams were fed a control (normal protein; 17% protein) or a low protein ((Lp); 8% protein) diet during pregnancy and lactation, and male offspring was studied at 90 days of age. Direct measurements of baseline arterial blood pressure (ABP) and heart rate (HR) were recorded in awakened offspring. In addition, quantitative RT-PCR was used to assess the mRNA expression of superoxide dismutase 1 (SOD1) and 2 (SOD2), catalase (CAT), glutathione peroxidase (GPx), Glutamatergic receptors (Grin1, Gria1 and Grm1) and GABA(A)-receptor-associated protein like 1 (Gabarapl1). Malondialdehyde (MDA) levels, CAT and SOD activities were examined in ventral and dorsal medulla. Lp rats exhibited higher ABP. The mRNA expression levels of SOD2, GPx and Gabarapl1 were down regulated in medullary tissue of Lp rats (P<.05, t test). In addition, we observed that higher MDA levels were associated to decreased SOD (approximately 45%) and CAT (approximately 50%) activities in ventral medulla. Taken together, our data suggest that maternal protein restriction induced-hypertension is associated with medullary oxidative dysfunction at transcriptional level and with impaired antioxidant capacity in the ventral medulla.
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Affiliation(s)
- José L de Brito Alves
- Department of Physical Education and Sport Sciences, Federal University of Pernambuco, Vitoria de Santo Antão, Pernambuco, Brazil.,Carmen (Cardiology, Metabolism and Nutrition) Laboratory, INSERM U1060, South Lyon Medical Faculty, Lyon-1 University, Oullins, France
| | - Jéssica M D de Oliveira
- Department of Physical Education and Sport Sciences, Federal University of Pernambuco, Vitoria de Santo Antão, Pernambuco, Brazil
| | - Diorginis J S Ferreira
- Department of Physical Education and Sport Sciences, Federal University of Pernambuco, Vitoria de Santo Antão, Pernambuco, Brazil
| | - Monique A de V Barros
- Department of Physical Education and Sport Sciences, Federal University of Pernambuco, Vitoria de Santo Antão, Pernambuco, Brazil
| | - Viviane O Nogueira
- Department of Physical Education and Sport Sciences, Federal University of Pernambuco, Vitoria de Santo Antão, Pernambuco, Brazil
| | - Débora S Alves
- Department of Physical Education and Sport Sciences, Federal University of Pernambuco, Vitoria de Santo Antão, Pernambuco, Brazil
| | - Hubert Vidal
- Carmen (Cardiology, Metabolism and Nutrition) Laboratory, INSERM U1060, South Lyon Medical Faculty, Lyon-1 University, Oullins, France
| | - Carol G Leandro
- Department of Physical Education and Sport Sciences, Federal University of Pernambuco, Vitoria de Santo Antão, Pernambuco, Brazil
| | - Cláudia J Lagranha
- Department of Physical Education and Sport Sciences, Federal University of Pernambuco, Vitoria de Santo Antão, Pernambuco, Brazil
| | - Luciano Pirola
- Carmen (Cardiology, Metabolism and Nutrition) Laboratory, INSERM U1060, South Lyon Medical Faculty, Lyon-1 University, Oullins, France
| | - João H da Costa-Silva
- Department of Physical Education and Sport Sciences, Federal University of Pernambuco, Vitoria de Santo Antão, Pernambuco, Brazil
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Visualizing Carotid Bodies With Doppler Ultrasound Versus CT Angiography: Preliminary Study. AJR Am J Roentgenol 2017; 209:1348-1352. [PMID: 28871807 DOI: 10.2214/ajr.17.18079] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OBJECTIVE The purpose of this article is to evaluate the utility of ultrasound in identifying carotid bodies (CBs) in patients with drug-resistant arterial hypertension. SUBJECTS AND METHODS We enrolled 13 patients with drug-resistant hypertension into a trial for surgical CB excision. CT angiography (CTA) and Doppler ultrasound (DUS) of the cervical arteries were performed before surgery. CBs were identified in a blind manner at both CTA and DUS. CBs were defined at CTA as ovoid avidly enhancing structures at the inferomedial aspect of the carotid bifurcation. At DUS, CBs were defined as ovoid solid structures in the inferomedial aspect of the bifurcation. RESULTS CBs were identified in 12 of 13 patients (23/26 sides) using CTA and in 11 of 13 patients (18/26 sides) using DUS. Identification of CB with DUS and CTA correlated in 17 of 18 cases; in one instance, CB was identified with DUS but not CTA. There was no statistically significant difference in size and volume of CB measured by both methods. CONCLUSION Noncarcinogenic CBs can be visualized using DUS, with good correlation of size and location compared with CTA. The findings show that DUS can be reliably used to further examine the role of CBs in cardiovascular disorders and can be used in conjunction with therapies that target CBs.
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Amorim MR, Bonagamba LGH, Souza GMPR, Moraes DJA, Machado BH. Changes in the inspiratory pattern contribute to modulate the sympathetic activity in sino-aortic denervated rats. Exp Physiol 2017. [PMID: 28639723 DOI: 10.1113/ep086353] [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] [Indexed: 01/15/2023]
Abstract
NEW FINDINGS What is the central question of this study? Sino-aortic denervated (SAD) rats present normal levels of sympathetic activity and mean arterial pressure. However, neural mechanisms regulating the sympathetic activity in the absence of arterial baroreceptors remain unclear. Considering that respiration modulates the sympathetic activity, we hypothesize that changes in the respiratory network contribute to keep the sympathetic outflow in the normal range after removal of arterial baroreceptors. What is the main finding and its importance? Despite longer inspiration observed in SAD rats, the respiratory-sympathetic coupling is working within a normal range of variation. These findings suggest that in the absence of arterial baroreceptors the respiratory modulation of sympathetic activity is maintained within the normal range. The activity of presympathetic neurons is under respiratory modulation, and changes in the central respiratory network may impact on the baseline sympathetic activity and mean arterial pressure. It is well known that after removal of baroreceptor afferents [sino-aortic denervation (SAD)], rats present an unexpected normal level of mean arterial pressure. We hypothesized that changes in the respiratory pattern and in the respiratory modulation of the sympathetic activity contribute to keep the sympathetic outflow within a normal range of variation in the absence of arterial baroreceptors in rats. To study these mechanisms, we recorded perfusion pressure and the activities of phrenic and thoracic sympathetic nerves in male juvenile rats using the working heart-brainstem preparation. The time of inspiration significantly increased in SAD rats, and this change was not dependent on the carotid bodies or on the vagal afferents. However, no changes were observed in the perfusion pressure or in the baseline thoracic sympathetic nerves in all phases of the respiratory cycle in SAD rats. Our data show that despite longer inspiratory activity, the baseline sympathetic activity is maintained at a normal level in SAD rats. These findings indicate that the respiratory-sympathetic coupling is normal after SAD and suggest that the respiratory modulation of sympathetic activity is maintained within the normal range after the removal of arterial baroreceptors.
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Affiliation(s)
- Mateus R Amorim
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Leni G H Bonagamba
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - George M P R Souza
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Davi J A Moraes
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Benedito H Machado
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
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75
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Tipton MJ, Harper A, Paton JFR, Costello JT. The human ventilatory response to stress: rate or depth? J Physiol 2017. [PMID: 28650070 DOI: 10.1113/jp274596] [Citation(s) in RCA: 105] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Many stressors cause an increase in ventilation in humans. This is predominantly reported as an increase in minute ventilation (V̇E). But, the same V̇E can be achieved by a wide variety of changes in the depth (tidal volume, VT ) and number of breaths (respiratory frequency, ƒR ). This review investigates the impact of stressors including: cold, heat, hypoxia, pain and panic on the contributions of ƒR and VT to V̇E to see if they differ with different stressors. Where possible we also consider the potential mechanisms that underpin the responses identified, and propose mechanisms by which differences in ƒR and VT are mediated. Our aim being to consider if there is an overall differential control of ƒR and VT that applies in a wide range of conditions. We consider moderating factors, including exercise, sex, intensity and duration of stimuli. For the stressors reviewed, as the stress becomes extreme V̇E generally becomes increased more by ƒR than VT . We also present some tentative evidence that the pattern of ƒR and VT could provide some useful diagnostic information for a variety of clinical conditions. In The Physiological Society's year of 'Making Sense of Stress', this review has wide-ranging implications that are not limited to one discipline, but are integrative and relevant for physiology, psychophysiology, neuroscience and pathophysiology.
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Affiliation(s)
- Michael J Tipton
- Extreme Environments Laboratory, Department of Sport and Exercise Science, University of Portsmouth, Portsmouth, PO1 2ER, UK
| | - Abbi Harper
- Clinical Fellow in Intensive Care Medicine, Southmead Hospital, Bristol, BS10 5NB, UK
| | - Julian F R Paton
- School of Physiology, Pharmacology and Neuroscience, Biomedical Sciences, University Walk, University of Bristol, Bristol, BS8 1TD, UK
| | - Joseph T Costello
- Extreme Environments Laboratory, Department of Sport and Exercise Science, University of Portsmouth, Portsmouth, PO1 2ER, UK
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Taxini CL, Moreira TS, Takakura AC, Bícego KC, Gargaglioni LH, Zoccal DB. Role of A5 noradrenergic neurons in the chemoreflex control of respiratory and sympathetic activities in unanesthetized conditions. Neuroscience 2017; 354:146-157. [PMID: 28461215 DOI: 10.1016/j.neuroscience.2017.04.033] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 03/21/2017] [Accepted: 04/21/2017] [Indexed: 01/04/2023]
Abstract
The A5 area at the ventrolateral pons contains noradrenergic neurons connected with other medullary areas involved in the cardiorespiratory control. Its contribution to the cardiorespiratory regulation was previously evidenced in anesthetized conditions. In the present study, we investigated the involvement of the A5 noradrenergic neurons to the basal and chemoreflex control of the sympathetic and respiratory activities in unanesthetized conditions. A5 noradrenergic neurons were lesioned using microinjections of anti-dopamine β-hydroxylase saporin (anti-DβH-SAP). After 7-8days, we evaluated the arterial pressure levels, heart rate and minute ventilation in freely moving adult rats (280-350g) as well as recorded from thoracic sympathetic (tSN) and phrenic nerves (PN) using the arterially perfused in situ preparation of juvenile rats (80-90g). Baseline cardiovascular, sympathetic and respiratory parameters were similar between control (n=7-8) and A5-lesioned rats (n=5-6) in both experimental preparations. In adult rats, lesions of A5 noradrenergic neurons did not modify the reflex cardiorespiratory adjustments to hypoxia (7% O2) and hypercapnia (7% CO2). In the in situ preparations, the sympatho-excitation, but not the PN reflex response, elicited by either the stimulation of peripheral chemoreceptors (ΔtSN: 110±12% vs 58±8%, P<0.01) or hypercapnia (ΔtSN: 9.5±1.4% vs 3.9±1.7%, P<0.05) was attenuated in A5-lesioned rats compared to controls. Our data demonstrated that A5 noradrenergic neurons are part of the circuitry recruited for the processing of sympathetic response to hypoxia and hypercapnia in unanesthetized conditions.
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Affiliation(s)
- Camila L Taxini
- Department of Morphology and Animal Physiology, São Paulo State University (UNESP), Jaboticabal, SP, Brazil
| | - Thiago S Moreira
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo (USP), São Paulo, SP, Brazil
| | - Ana C Takakura
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo (USP), São Paulo, SP, Brazil
| | - Kênia C Bícego
- Department of Morphology and Animal Physiology, São Paulo State University (UNESP), Jaboticabal, SP, Brazil
| | - Luciane H Gargaglioni
- Department of Morphology and Animal Physiology, São Paulo State University (UNESP), Jaboticabal, SP, Brazil.
| | - Daniel B Zoccal
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, SP, Brazil.
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78
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Machado BH, Zoccal DB, Moraes DJA. Neurogenic hypertension and the secrets of respiration. Am J Physiol Regul Integr Comp Physiol 2017; 312:R864-R872. [PMID: 28438764 DOI: 10.1152/ajpregu.00505.2016] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 04/12/2017] [Accepted: 04/13/2017] [Indexed: 11/22/2022]
Abstract
Despite recent advances in the knowledge of the neural control of cardiovascular function, the cause of sympathetic overactivity in neurogenic hypertension remains unknown. Studies from our laboratory point out that rats submitted to chronic intermittent hypoxia (CIH), an experimental model of neurogenic hypertension, present changes in the central respiratory network that impact the pattern of sympathetic discharge and the levels of arterial pressure. In addition to the fine coordination of respiratory muscle contraction and relaxation, which is essential for O2 and CO2 pulmonary exchanges, neurons of the respiratory network are connected precisely to the neurons controlling the sympathetic activity in the brain stem. This respiratory-sympathetic neuronal interaction provides adjustments in the sympathetic outflow to the heart and vasculature during each respiratory phase according to the metabolic demands. Herein, we report that CIH-induced sympathetic over activity and mild hypertension are associated with increased frequency discharge of ventral medullary presympathetic neurons. We also describe that their increased frequency discharge is dependent on synaptic inputs, mostly from neurons of the brain stem respiratory network, rather than changes in their intrinsic electrophysiological properties. In perspective, we are taking into consideration the possibility that changes in the central respiratory rhythm/pattern generator contribute to increased sympathetic outflow and the development of neurogenic hypertension. Our experimental evidence provides support for the hypothesis that changes in the coupling of respiratory and sympathetic networks might be one of the unrevealed secrets of neurogenic hypertension in rats.
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Affiliation(s)
- Benedito H Machado
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, São Paulo, Brazil; and
| | - Daniel B Zoccal
- Department of Physiology and Pathology, School of Dentistry of Araraquara, São Paulo State University, Araraquara, São Paulo, Brazil
| | - Davi J A Moraes
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, São Paulo, Brazil; and
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79
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Jenkin SEM, Milsom WK, Zoccal DB. The Kölliker-Fuse nucleus acts as a timekeeper for late-expiratory abdominal activity. Neuroscience 2017; 348:63-72. [PMID: 28188852 PMCID: PMC5759332 DOI: 10.1016/j.neuroscience.2017.01.050] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Revised: 01/27/2017] [Accepted: 01/31/2017] [Indexed: 10/20/2022]
Abstract
While the transition from the inspiratory to the post-inspiratory (post-I) phase is dependent on the pons, little attention has been paid to understanding the role of the pontine respiratory nuclei, specifically the Kölliker-Fuse nucleus (KF), in transitioning from post-I to the late expiratory (late-E) activity seen with elevated respiratory drive. To elucidate this, we used the in situ working heart-brainstem preparation of juvenile male Holtzman rats and recorded from the vagus (cVN), phrenic (PN) and abdominal nerves (AbN) during baseline conditions and during chemoreflex activation [with potassium cyanide (KCN; n=13) or hypercapnia (8% CO2; n=10)] to recruit active expiration. Chemoreflex activation with KCN increased PN frequency and cVN post-I and AbN activities. The inhibition of KF with isoguvacine microinjections (10mM) attenuated the typical increase in PN frequency and cVN post-I activity, and amplified the AbN response. During hypercapnia, AbN late-E activity emerged in association with a significant reduction in expiratory time. KF inhibition during hypercapnia significantly decreased PN frequency and reduced the duration and amplitude of post-I cVN activity, while the onset of the AbN late-E bursts occurred significantly earlier. Our data reveal a negative relationship between KF-induced post-I and AbN late-E activities, suggesting that the KF coordinates the transition between post-I to late-E activity during conditions of elevated respiratory drive.
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Affiliation(s)
- Sarah E M Jenkin
- Department of Zoology, The University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada.
| | - William K Milsom
- Department of Zoology, The University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
| | - Daniel B Zoccal
- School of Dentistry of Araraquara, São Paulo State University, Araraquara, Brazil
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80
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Menuet C, Le S, Dempsey B, Connelly AA, Kamar JL, Jancovski N, Bassi JK, Walters K, Simms AE, Hammond A, Fong AY, Goodchild AK, McMullan S, Allen AM. Excessive Respiratory Modulation of Blood Pressure Triggers Hypertension. Cell Metab 2017; 25:739-748. [PMID: 28215844 DOI: 10.1016/j.cmet.2017.01.019] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Revised: 12/09/2016] [Accepted: 01/28/2017] [Indexed: 02/07/2023]
Abstract
The etiology of hypertension, the world's biggest killer, remains poorly understood, with treatments targeting the established symptom, not the cause. The development of hypertension involves increased sympathetic nerve activity that, in experimental hypertension, may be driven by excessive respiratory modulation. Using selective viral and cell lesion techniques, we identify adrenergic C1 neurons in the medulla oblongata as critical for respiratory-sympathetic entrainment and the development of experimental hypertension. We also show that a cohort of young, normotensive humans, selected for an exaggerated blood pressure response to exercise and thus increased hypertension risk, has enhanced respiratory-related blood pressure fluctuations. These studies pinpoint a specific neuronal target for ameliorating excessive sympathetic activity during the developmental phase of hypertension and identify a group of pre-hypertensive subjects that would benefit from targeting these cells.
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Affiliation(s)
- Clément Menuet
- Department of Physiology, University of Melbourne, Parkville, VIC 3010, Australia
| | - Sheng Le
- Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW 2109, Australia
| | - Bowen Dempsey
- Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW 2109, Australia
| | - Angela A Connelly
- Department of Physiology, University of Melbourne, Parkville, VIC 3010, Australia
| | - Jessica L Kamar
- Department of Physiology, University of Melbourne, Parkville, VIC 3010, Australia
| | - Nikola Jancovski
- Department of Physiology, University of Melbourne, Parkville, VIC 3010, Australia
| | - Jaspreet K Bassi
- Department of Physiology, University of Melbourne, Parkville, VIC 3010, Australia
| | - Keryn Walters
- Department of Physiology, University of Melbourne, Parkville, VIC 3010, Australia
| | - Annabel E Simms
- Department of Physiology, University of Melbourne, Parkville, VIC 3010, Australia
| | - Andrew Hammond
- Department of Physiology, University of Melbourne, Parkville, VIC 3010, Australia
| | - Angelina Y Fong
- Department of Physiology, University of Melbourne, Parkville, VIC 3010, Australia
| | - Ann K Goodchild
- Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW 2109, Australia
| | - Simon McMullan
- Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW 2109, Australia
| | - Andrew M Allen
- Department of Physiology, University of Melbourne, Parkville, VIC 3010, Australia; Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, VIC 3010, Australia.
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81
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de Britto AA, Moraes DJA. Non-chemosensitive parafacial neurons simultaneously regulate active expiration and airway patency under hypercapnia in rats. J Physiol 2017; 595:2043-2064. [PMID: 28004411 DOI: 10.1113/jp273335] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 11/30/2016] [Indexed: 01/01/2023] Open
Abstract
KEY POINTS Hypercapnia or parafacial respiratory group (pFRG) disinhibition at normocapnia evokes active expiration in rats by recruitment of pFRG late-expiratory (late-E) neurons. We show that hypercapnia simultaneously evoked active expiration and exaggerated glottal dilatation by late-E synaptic excitation of abdominal, hypoglossal and laryngeal motoneurons. Simultaneous rhythmic expiratory activity in previously silent pFRG late-E neurons, which did not express the marker of ventral medullary CO2 -sensitive neurons (transcription factor Phox2b), was also evoked by hypercapnia. Hypercapnia-evoked active expiration, neural and neuronal late-E activities were eliminated by pFRG inhibition, but not after blockade of synaptic excitation. Hypercapnia produces disinhibition of non-chemosensitive pFRG late-E neurons to evoke active expiration and concomitant cranial motor respiratory responses controlling the oropharyngeal and upper airway patency. ABSTRACT Hypercapnia produces active expiration in rats and the recruitment of late-expiratory (late-E) neurons located in the parafacial respiratory group (pFRG) of the ventral medullary brainstem. We tested the hypothesis that hypercapnia produces active expiration and concomitant cranial respiratory motor responses controlling the oropharyngeal and upper airway patency by disinhibition of pFRG late-E neurons, but not via synaptic excitation. Phrenic nerve, abdominal nerve (AbN), cranial respiratory motor nerves, subglottal pressure, and medullary and spinal neurons/motoneurons were recorded in in situ preparations of juvenile rats. Hypercapnia evoked AbN active expiration, exaggerated late-E discharges in cranial respiratory motor outflows, and glottal dilatation via late-E synaptic excitation of abdominal, hypoglossal and laryngeal motoneurons. Simultaneous rhythmic late-E activity in previously silent pFRG neurons, which did not express the marker of ventral medullary CO2 -sensitive neurons (transcription factor Phox2b), was also evoked by hypercapnia. In addition, hypercapnia-evoked AbN active expiration, neural and neuronal late-E activities were eliminated by pFRG inhibition, but not after blockade of synaptic excitation. On the other hand, pFRG inhibition did not affect either hypercapnia-induced inspiratory increases in respiratory motor outflows or CO2 sensitivity of the more medial Phox2b-positive neurons in the retrotrapezoid nucleus (RTN). Our data suggest that neither RTN Phox2b-positive nor other CO2 -sensitive brainstem neurons activate Phox2b-negative pFRG late-E neurons under hypercapnia to produce AbN active expiration and concomitant cranial motor respiratory responses controlling the oropharyngeal and upper airway patency. Hypercapnia produces disinhibition of non-chemosensitive pFRG late-E neurons in in situ preparations of juvenile rats to activate abdominal, hypoglossal and laryngeal motoneurons.
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Affiliation(s)
- Alan A de Britto
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Davi J A Moraes
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil
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82
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Molkov YI, Rubin JE, Rybak IA, Smith JC. Computational models of the neural control of breathing. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2016; 9. [PMID: 28009109 DOI: 10.1002/wsbm.1371] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2016] [Revised: 10/06/2016] [Accepted: 10/25/2016] [Indexed: 11/10/2022]
Abstract
The ongoing process of breathing underlies the gas exchange essential for mammalian life. Each respiratory cycle ensues from the activity of rhythmic neural circuits in the brainstem, shaped by various modulatory signals, including mechanoreceptor feedback sensitive to lung inflation and chemoreceptor feedback dependent on gas composition in blood and tissues. This paper reviews a variety of computational models designed to reproduce experimental findings related to the neural control of breathing and generate predictions for future experimental testing. The review starts from the description of the core respiratory network in the brainstem, representing the central pattern generator (CPG) responsible for producing rhythmic respiratory activity, and progresses to encompass additional complexities needed to simulate different metabolic challenges, closed-loop feedback control including the lungs, and interactions between the respiratory and autonomic nervous systems. The integrated models considered in this review share a common framework including a distributed CPG core network responsible for generating the baseline three-phase pattern of rhythmic neural activity underlying normal breathing. WIREs Syst Biol Med 2017, 9:e1371. doi: 10.1002/wsbm.1371 For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
- Yaroslav I Molkov
- Department of Mathematics and Statistics, Georgia State University, Atlanta, GA, USA
| | - Jonathan E Rubin
- Department of Mathematics, University of Pittsburgh, Pittsburgh, PA, USA
| | - Ilya A Rybak
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, USA
| | - Jeffrey C Smith
- Cellular and Systems Neurobiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
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83
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Korkmaz B, Benbir Şenel G, Kızıltan ME, Karadeniz D. Demonstration of sympathetic dysfunction in patients with obstructive sleep apnea syndrome by measuring sympathetic skin responses from the neck. Sleep Med 2016; 25:13-15. [PMID: 27823705 DOI: 10.1016/j.sleep.2016.06.030] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 06/06/2016] [Accepted: 06/13/2016] [Indexed: 10/21/2022]
Abstract
OBJECTIVE We aimed to study the sympathetic sudomotor responses via the sympathetic skin responses (SSR) from bilateral hands and right and left sides of the neck in patients with obstructive sleep apnea syndrome (OSAS). METHODS A total of 31 patients with OSAS diagnosed by whole-night polysomnography and 18 healthy volunteers were consecutively enrolled into this prospective study. RESULTS The SSRs from hands were not obtained in two patients with OSAS (6.4%) and in one volunteer (5.5%); the attainability of SSRs from hands was similar between patients and healthy controls (p = 0.698). The SSRs from neck were not obtained in 22 patients with OSAS (70.9%), but only in two healthy volunteers (11.1%, p <0.001). The mean amplitudes of SSRs from both right and left sides of neck were significantly lower in patients with OSAS than those in controls (p <0.001). After effective treatment of OSAS, the SSRs from hands were obtained in all patients (100% vs 93.6% before treatment, p = 0.560). The attainability of SSRs from bilateral sides of the neck was significantly improved after treatment (80%) in compared to before treatment (29.1%, p <0.001). The amplitudes of SSRs obtained from the neck were also significantly increased after treatment (p <0.004). CONCLUSIONS Our results show that there is sympathetic dysfunction in OSAS, which could be demonstrated by sudomotor response abnormalities from neck area and reversed following effective treatment of OSAS. SSR studies from the neck area may therefore be accepted as an easy and effective method for demonstrating the sympathetic dysfunction in OSAS and for monitoring the efficacy of OSAS treatment.
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Affiliation(s)
- Bektaş Korkmaz
- Department of Neurology, Sleep and Disorders Unit, Istanbul University Cerrahpasa Faculty of Medicine, Istanbul, Turkey.
| | - Gülçin Benbir Şenel
- Department of Neurology, Sleep and Disorders Unit, Istanbul University Cerrahpasa Faculty of Medicine, Istanbul, Turkey
| | - Meral E Kızıltan
- Department of Neurology, Sleep and Disorders Unit, Istanbul University Cerrahpasa Faculty of Medicine, Istanbul, Turkey
| | - Derya Karadeniz
- Department of Neurology, Sleep and Disorders Unit, Istanbul University Cerrahpasa Faculty of Medicine, Istanbul, Turkey
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84
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Murphy DJ. Apneic events – A proposed new target for respiratory safety pharmacology. Regul Toxicol Pharmacol 2016; 81:194-200. [DOI: 10.1016/j.yrtph.2016.07.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 06/30/2016] [Accepted: 07/02/2016] [Indexed: 10/21/2022]
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85
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Amorim MR, Bonagamba LGH, Souza GMPR, Moraes DJA, Machado BH. Role of respiratory changes in the modulation of arterial pressure in rats submitted to sino-aortic denervation. Exp Physiol 2016; 101:1359-1370. [DOI: 10.1113/ep085897] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Accepted: 09/09/2016] [Indexed: 11/08/2022]
Affiliation(s)
- Mateus R. Amorim
- 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
| | - George M. P. R. Souza
- Department of Physiology, School of Medicine of Ribeirão Preto; University of São Paulo; Ribeirão Preto 14049-900 SP Brazil
| | - Davi J. A. Moraes
- 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
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Santisteban MM, Qi Y, Zubcevic J, Kim S, Yang T, Shenoy V, Cole-Jeffrey CT, Lobaton GO, Stewart DC, Rubiano A, Simmons CS, Garcia-Pereira F, Johnson RD, Pepine CJ, Raizada MK. Hypertension-Linked Pathophysiological Alterations in the Gut. Circ Res 2016; 120:312-323. [PMID: 27799253 DOI: 10.1161/circresaha.116.309006] [Citation(s) in RCA: 335] [Impact Index Per Article: 41.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Revised: 10/24/2016] [Accepted: 10/31/2016] [Indexed: 12/24/2022]
Abstract
RATIONALE Sympathetic nervous system control of inflammation plays a central role in hypertension. The gut receives significant sympathetic innervation, is densely populated with a diverse microbial ecosystem, and contains immune cells that greatly impact overall inflammatory homeostasis. Despite this uniqueness, little is known about the involvement of the gut in hypertension. OBJECTIVE Test the hypothesis that increased sympathetic drive to the gut is associated with increased gut wall permeability, increased inflammatory status, and microbial dysbiosis and that these gut pathological changes are linked to hypertension. METHODS AND RESULTS Gut epithelial integrity and wall pathology were examined in spontaneously hypertensive rat and chronic angiotensin II infusion rat models. The increase in blood pressure in spontaneously hypertensive rat was associated with gut pathology that included increased intestinal permeability and decreased tight junction proteins. These changes in gut pathology in hypertension were associated with alterations in microbial communities relevant in blood pressure control. We also observed enhanced gut-neuronal communication in hypertension originating from paraventricular nucleus of the hypothalamus and presenting as increased sympathetic drive to the gut. Finally, angiotensin-converting enzyme inhibition (captopril) normalized blood pressure and was associated with reversal of gut pathology. CONCLUSIONS A dysfunctional sympathetic-gut communication is associated with gut pathology, dysbiosis, and inflammation and plays a key role in hypertension. Thus, targeting of gut microbiota by innovative probiotics, antibiotics, and fecal transplant, in combination with the current pharmacotherapy, may be a novel strategy for hypertension treatment.
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Affiliation(s)
- Monica M Santisteban
- From the Department of Physiology and Functional Genomics, College of Medicine (M.M.S., S.K., C.T.C.-J., G.O.L., M.K.R.), Division of Cardiovascular Medicine, Department of Medicine (Y.Q., C.S.S., C.J.P.), Department of Physiological Sciences, College of Veterinary Medicine (J.Z., T.Y., F.G.-P., R.D.J.), Department of Pharmacodynamics, College of Pharmacy (V.S.), J. Crayton Pruitt Family Department of Biomedical Engineering (D.C.S., C.S.S.); Mechanical and Aerospace Engineering, Herbert Wertheim College of Engineering (A.R., C.S.S.), University of Florida, Gainesville
| | - Yanfei Qi
- From the Department of Physiology and Functional Genomics, College of Medicine (M.M.S., S.K., C.T.C.-J., G.O.L., M.K.R.), Division of Cardiovascular Medicine, Department of Medicine (Y.Q., C.S.S., C.J.P.), Department of Physiological Sciences, College of Veterinary Medicine (J.Z., T.Y., F.G.-P., R.D.J.), Department of Pharmacodynamics, College of Pharmacy (V.S.), J. Crayton Pruitt Family Department of Biomedical Engineering (D.C.S., C.S.S.); Mechanical and Aerospace Engineering, Herbert Wertheim College of Engineering (A.R., C.S.S.), University of Florida, Gainesville.
| | - Jasenka Zubcevic
- From the Department of Physiology and Functional Genomics, College of Medicine (M.M.S., S.K., C.T.C.-J., G.O.L., M.K.R.), Division of Cardiovascular Medicine, Department of Medicine (Y.Q., C.S.S., C.J.P.), Department of Physiological Sciences, College of Veterinary Medicine (J.Z., T.Y., F.G.-P., R.D.J.), Department of Pharmacodynamics, College of Pharmacy (V.S.), J. Crayton Pruitt Family Department of Biomedical Engineering (D.C.S., C.S.S.); Mechanical and Aerospace Engineering, Herbert Wertheim College of Engineering (A.R., C.S.S.), University of Florida, Gainesville
| | - Seungbum Kim
- From the Department of Physiology and Functional Genomics, College of Medicine (M.M.S., S.K., C.T.C.-J., G.O.L., M.K.R.), Division of Cardiovascular Medicine, Department of Medicine (Y.Q., C.S.S., C.J.P.), Department of Physiological Sciences, College of Veterinary Medicine (J.Z., T.Y., F.G.-P., R.D.J.), Department of Pharmacodynamics, College of Pharmacy (V.S.), J. Crayton Pruitt Family Department of Biomedical Engineering (D.C.S., C.S.S.); Mechanical and Aerospace Engineering, Herbert Wertheim College of Engineering (A.R., C.S.S.), University of Florida, Gainesville
| | - Tao Yang
- From the Department of Physiology and Functional Genomics, College of Medicine (M.M.S., S.K., C.T.C.-J., G.O.L., M.K.R.), Division of Cardiovascular Medicine, Department of Medicine (Y.Q., C.S.S., C.J.P.), Department of Physiological Sciences, College of Veterinary Medicine (J.Z., T.Y., F.G.-P., R.D.J.), Department of Pharmacodynamics, College of Pharmacy (V.S.), J. Crayton Pruitt Family Department of Biomedical Engineering (D.C.S., C.S.S.); Mechanical and Aerospace Engineering, Herbert Wertheim College of Engineering (A.R., C.S.S.), University of Florida, Gainesville
| | - Vinayak Shenoy
- From the Department of Physiology and Functional Genomics, College of Medicine (M.M.S., S.K., C.T.C.-J., G.O.L., M.K.R.), Division of Cardiovascular Medicine, Department of Medicine (Y.Q., C.S.S., C.J.P.), Department of Physiological Sciences, College of Veterinary Medicine (J.Z., T.Y., F.G.-P., R.D.J.), Department of Pharmacodynamics, College of Pharmacy (V.S.), J. Crayton Pruitt Family Department of Biomedical Engineering (D.C.S., C.S.S.); Mechanical and Aerospace Engineering, Herbert Wertheim College of Engineering (A.R., C.S.S.), University of Florida, Gainesville
| | - Colleen T Cole-Jeffrey
- From the Department of Physiology and Functional Genomics, College of Medicine (M.M.S., S.K., C.T.C.-J., G.O.L., M.K.R.), Division of Cardiovascular Medicine, Department of Medicine (Y.Q., C.S.S., C.J.P.), Department of Physiological Sciences, College of Veterinary Medicine (J.Z., T.Y., F.G.-P., R.D.J.), Department of Pharmacodynamics, College of Pharmacy (V.S.), J. Crayton Pruitt Family Department of Biomedical Engineering (D.C.S., C.S.S.); Mechanical and Aerospace Engineering, Herbert Wertheim College of Engineering (A.R., C.S.S.), University of Florida, Gainesville
| | - Gilberto O Lobaton
- From the Department of Physiology and Functional Genomics, College of Medicine (M.M.S., S.K., C.T.C.-J., G.O.L., M.K.R.), Division of Cardiovascular Medicine, Department of Medicine (Y.Q., C.S.S., C.J.P.), Department of Physiological Sciences, College of Veterinary Medicine (J.Z., T.Y., F.G.-P., R.D.J.), Department of Pharmacodynamics, College of Pharmacy (V.S.), J. Crayton Pruitt Family Department of Biomedical Engineering (D.C.S., C.S.S.); Mechanical and Aerospace Engineering, Herbert Wertheim College of Engineering (A.R., C.S.S.), University of Florida, Gainesville
| | - Daniel C Stewart
- From the Department of Physiology and Functional Genomics, College of Medicine (M.M.S., S.K., C.T.C.-J., G.O.L., M.K.R.), Division of Cardiovascular Medicine, Department of Medicine (Y.Q., C.S.S., C.J.P.), Department of Physiological Sciences, College of Veterinary Medicine (J.Z., T.Y., F.G.-P., R.D.J.), Department of Pharmacodynamics, College of Pharmacy (V.S.), J. Crayton Pruitt Family Department of Biomedical Engineering (D.C.S., C.S.S.); Mechanical and Aerospace Engineering, Herbert Wertheim College of Engineering (A.R., C.S.S.), University of Florida, Gainesville
| | - Andres Rubiano
- From the Department of Physiology and Functional Genomics, College of Medicine (M.M.S., S.K., C.T.C.-J., G.O.L., M.K.R.), Division of Cardiovascular Medicine, Department of Medicine (Y.Q., C.S.S., C.J.P.), Department of Physiological Sciences, College of Veterinary Medicine (J.Z., T.Y., F.G.-P., R.D.J.), Department of Pharmacodynamics, College of Pharmacy (V.S.), J. Crayton Pruitt Family Department of Biomedical Engineering (D.C.S., C.S.S.); Mechanical and Aerospace Engineering, Herbert Wertheim College of Engineering (A.R., C.S.S.), University of Florida, Gainesville
| | - Chelsey S Simmons
- From the Department of Physiology and Functional Genomics, College of Medicine (M.M.S., S.K., C.T.C.-J., G.O.L., M.K.R.), Division of Cardiovascular Medicine, Department of Medicine (Y.Q., C.S.S., C.J.P.), Department of Physiological Sciences, College of Veterinary Medicine (J.Z., T.Y., F.G.-P., R.D.J.), Department of Pharmacodynamics, College of Pharmacy (V.S.), J. Crayton Pruitt Family Department of Biomedical Engineering (D.C.S., C.S.S.); Mechanical and Aerospace Engineering, Herbert Wertheim College of Engineering (A.R., C.S.S.), University of Florida, Gainesville
| | - Fernando Garcia-Pereira
- From the Department of Physiology and Functional Genomics, College of Medicine (M.M.S., S.K., C.T.C.-J., G.O.L., M.K.R.), Division of Cardiovascular Medicine, Department of Medicine (Y.Q., C.S.S., C.J.P.), Department of Physiological Sciences, College of Veterinary Medicine (J.Z., T.Y., F.G.-P., R.D.J.), Department of Pharmacodynamics, College of Pharmacy (V.S.), J. Crayton Pruitt Family Department of Biomedical Engineering (D.C.S., C.S.S.); Mechanical and Aerospace Engineering, Herbert Wertheim College of Engineering (A.R., C.S.S.), University of Florida, Gainesville
| | - Richard D Johnson
- From the Department of Physiology and Functional Genomics, College of Medicine (M.M.S., S.K., C.T.C.-J., G.O.L., M.K.R.), Division of Cardiovascular Medicine, Department of Medicine (Y.Q., C.S.S., C.J.P.), Department of Physiological Sciences, College of Veterinary Medicine (J.Z., T.Y., F.G.-P., R.D.J.), Department of Pharmacodynamics, College of Pharmacy (V.S.), J. Crayton Pruitt Family Department of Biomedical Engineering (D.C.S., C.S.S.); Mechanical and Aerospace Engineering, Herbert Wertheim College of Engineering (A.R., C.S.S.), University of Florida, Gainesville
| | - Carl J Pepine
- From the Department of Physiology and Functional Genomics, College of Medicine (M.M.S., S.K., C.T.C.-J., G.O.L., M.K.R.), Division of Cardiovascular Medicine, Department of Medicine (Y.Q., C.S.S., C.J.P.), Department of Physiological Sciences, College of Veterinary Medicine (J.Z., T.Y., F.G.-P., R.D.J.), Department of Pharmacodynamics, College of Pharmacy (V.S.), J. Crayton Pruitt Family Department of Biomedical Engineering (D.C.S., C.S.S.); Mechanical and Aerospace Engineering, Herbert Wertheim College of Engineering (A.R., C.S.S.), University of Florida, Gainesville
| | - Mohan K Raizada
- From the Department of Physiology and Functional Genomics, College of Medicine (M.M.S., S.K., C.T.C.-J., G.O.L., M.K.R.), Division of Cardiovascular Medicine, Department of Medicine (Y.Q., C.S.S., C.J.P.), Department of Physiological Sciences, College of Veterinary Medicine (J.Z., T.Y., F.G.-P., R.D.J.), Department of Pharmacodynamics, College of Pharmacy (V.S.), J. Crayton Pruitt Family Department of Biomedical Engineering (D.C.S., C.S.S.); Mechanical and Aerospace Engineering, Herbert Wertheim College of Engineering (A.R., C.S.S.), University of Florida, Gainesville.
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87
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Souza GMPR, Bonagamba LGH, Amorim MR, Moraes DJA, Machado BH. Inspiratory modulation of sympathetic activity is increased in female rats exposed to chronic intermittent hypoxia. Exp Physiol 2016; 101:1345-1358. [DOI: 10.1113/ep085850] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2016] [Accepted: 09/01/2016] [Indexed: 11/08/2022]
Affiliation(s)
- George Miguel P. R. Souza
- 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
| | - Mateus R. Amorim
- Department of Physiology; School of Medicine of Ribeirão Preto; University of São Paulo; Ribeirão Preto 14049-900 SP Brazil
| | - Davi J. A. Moraes
- 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
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88
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Moraes DJ, Bonagamba LG, da Silva MP, Mecawi AS, Antunes-Rodrigues J, Machado BH. Respiratory Network Enhances the Sympathoinhibitory Component of Baroreflex of Rats Submitted to Chronic Intermittent Hypoxia. Hypertension 2016; 68:1021-30. [DOI: 10.1161/hypertensionaha.116.07731] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Accepted: 07/09/2016] [Indexed: 11/16/2022]
Abstract
Chronic intermittent hypoxia (CIH) produces respiratory-related sympathetic overactivity and hypertension in rats. In this study, we tested the hypothesis that the enhanced central respiratory modulation of sympathetic activity after CIH also decreases the sympathoinhibitory component of baroreflex of rats, which may contribute to the development of hypertension. Wistar rats were exposed to CIH or normoxia (control group) for 10 days. Phrenic nerve, thoracic sympathetic nerve, and neurons in the rostral ventrolateral medulla and caudal ventrolateral medulla were recorded in in situ preparations of rats. Baroreflex regulation of thoracic sympathetic nerve, rostral ventrolateral medulla, and caudal ventrolateral medulla neurons activities were evaluated in different phases of respiration in response to either aortic depressor nerve stimulation or pressure stimuli. CIH rats presented higher respiratory-related thoracic sympathetic nerve and rostral ventrolateral medulla presympathetic neurons activities at the end of expiration in relation to control rats, which are indexes of respiratory-related sympathetic overactivity. Baroreflex-evoked thoracic sympathetic nerve inhibition during expiration, but not during inspiration, was enhanced in CIH when compared with control rats. In addition, CIH selectively enhanced the expiratory-related baroreceptor inputs, probably through caudal ventrolateral medulla neurons, to the respiratory-modulated bulbospinal rostral ventrolateral medulla presympathetic neurons. These findings support the concept that the onset of hypertension, mediated by sympathetic overactivity, after 10 days of CIH is not secondary to a reduction in sympathoinhibitory component of baroreflex. Instead, it was observed an increase in the gain of sympathoinhibitory component in in situ preparations of rats, suggesting that changes in the respiratory-related sympathetic network after CIH also play a key role in preventing greater increase in arterial pressure.
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Affiliation(s)
- Davi J.A. Moraes
- From the Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Brazil
| | - Leni G.H. Bonagamba
- From the Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Brazil
| | - Melina P. da Silva
- From the Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Brazil
| | - André S. Mecawi
- From the Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Brazil
| | - José Antunes-Rodrigues
- From the Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Brazil
| | - Benedito H. Machado
- From the Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Brazil
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89
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Lemes EV, Colombari E, Zoccal DB. Generation of active expiration by serotoninergic mechanisms of the ventral medulla of rats. J Appl Physiol (1985) 2016; 121:1135-1144. [PMID: 27660299 DOI: 10.1152/japplphysiol.00470.2016] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 09/19/2016] [Accepted: 09/19/2016] [Indexed: 01/16/2023] Open
Abstract
Abdominal expiratory activity is absent at rest and is evoked during metabolic challenges, such as hypercapnia and hypoxia, or after the exposure to intermittent hypoxia (IH). The mechanisms engaged during this process are not completely understood. In this study, we hypothesized that serotonin (5-HT), acting in the retrotrapezoid nucleus/parafacial respiratory group (RTN/pFRG), is able to generate active expiration. In anesthetized (urethane, ip), tracheostomized, spontaneously-breathing adult male Holtzman rats we microinjected a serotoninergic agonist and antagonist bilaterally in the RTN/pFRG and recorded diaphragm and abdominal muscle activities. We found that episodic (3 times, 5 min apart), but not single microinjections of 5-HT (1 mM) in the RTN/pFRG elicited an enduring (>30 min) increase in abdominal activity. This response was amplified in vagotomized rats and blocked by previous 5-HT receptor antagonism with ketanserin (10 µM). Episodic 5-HT microinjections in the RTN/pFRG also potentiated the inspiratory and expiratory reflex responses to hypercapnia. The antagonism of 5-HT receptors in the RTN/pFRG also prevented the long-term facilitation (>30 min) of abdominal activity in response to acute IH exposure (10 × 6-7% O for 45 s every 5 min). Our findings indicate the activation of serotoninergic mechanisms in the RTN/pFRG is sufficient to increase abdominal expiratory activity at resting conditions and required for the emergence of active expiration after IH in anesthetized animals.
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Affiliation(s)
- Eduardo V Lemes
- Department of Physiology and Pathology, School of Dentistry of Araraquara, São Paulo State University (UNESP), Araraquara, SP, Brazil
| | - Eduardo Colombari
- Department of Physiology and Pathology, School of Dentistry of Araraquara, São Paulo State University (UNESP), Araraquara, SP, Brazil
| | - Daniel B Zoccal
- Department of Physiology and Pathology, School of Dentistry of Araraquara, São Paulo State University (UNESP), Araraquara, SP, Brazil
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90
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Niewinski P, Janczak D, Rucinski A, Tubek S, Engelman ZJ, Piesiak P, Jazwiec P, Banasiak W, Fudim M, Sobotka PA, Javaheri S, Hart EC, Paton JF, Ponikowski P. Carotid body resection for sympathetic modulation in systolic heart failure: results from first-in-man study. Eur J Heart Fail 2016; 19:391-400. [DOI: 10.1002/ejhf.641] [Citation(s) in RCA: 80] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Revised: 07/10/2016] [Accepted: 07/25/2016] [Indexed: 12/30/2022] Open
Affiliation(s)
- Piotr Niewinski
- Department of Cardiology, Centre for Heart Disease; 4th Military Hospital; Wroclaw Poland
| | - Dariusz Janczak
- Department of Vascular Surgery; 4th Military Hospital; Wroclaw Poland
| | - Artur Rucinski
- Department of Vascular Surgery; 4th Military Hospital; Wroclaw Poland
| | - Stanislaw Tubek
- Department of Cardiology, Centre for Heart Disease; 4th Military Hospital; Wroclaw Poland
- Department of Heart Diseases, Faculty of Health Sciences; Wroclaw Medical University; Wroclaw Poland
| | | | - Pawel Piesiak
- Department of Pulmonology and Lung Cancer; Medical University; Wroclaw Poland
| | - Przemyslaw Jazwiec
- Department of Radiology and Diagnostics Imaging; 4th Military Hospital; Wroclaw Poland
| | - Waldemar Banasiak
- Department of Cardiology, Centre for Heart Disease; 4th Military Hospital; Wroclaw Poland
| | - Marat Fudim
- Department of Cardiology; Duke University School of Medicine; Durham NC USA
| | - Paul A. Sobotka
- Cibiem Inc.; Los Altos CA USA
- The Ohio State University; Columbus OH USA
| | - Shahrokh Javaheri
- Bethesda North Hospital; Cincinnati OH USA
- University of Cincinnati; Cincinnati OH USA
| | - Emma C.J. Hart
- School of Physiology and Pharmacology, Clinical Research & Imaging Centre; University of Bristol; Bristol UK
| | - Julian F.R. Paton
- School of Physiology and Pharmacology, Clinical Research & Imaging Centre; University of Bristol; Bristol UK
| | - Piotr Ponikowski
- Department of Cardiology, Centre for Heart Disease; 4th Military Hospital; Wroclaw Poland
- Department of Heart Diseases, Faculty of Health Sciences; Wroclaw Medical University; Wroclaw Poland
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91
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Purinergic receptors in the carotid body as a new drug target for controlling hypertension. Nat Med 2016; 22:1151-1159. [PMID: 27595323 DOI: 10.1038/nm.4173] [Citation(s) in RCA: 135] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Accepted: 07/27/2016] [Indexed: 11/09/2022]
Abstract
In view of the high proportion of individuals with resistance to antihypertensive medication and/or poor compliance or tolerance of this medication, new drugs to treat hypertension are urgently needed. Here we show that peripheral chemoreceptors generate aberrant signaling that contributes to high blood pressure in hypertension. We discovered that purinergic receptor P2X3 (P2rx3, also known as P2x3) mRNA expression is upregulated substantially in chemoreceptive petrosal sensory neurons in rats with hypertension. These neurons generate both tonic drive and hyperreflexia in hypertensive (but not normotensive) rats, and both phenomena are normalized by the blockade of P2X3 receptors. Antagonism of P2X3 receptors also reduces arterial pressure and basal sympathetic activity and normalizes carotid body hyperreflexia in conscious rats with hypertension; no effect was observed in rats without hypertension. We verified P2X3 receptor expression in human carotid bodies and observed hyperactivity of carotid bodies in individuals with hypertension. These data support the identification of the P2X3 receptor as a potential new target for the control of human hypertension.
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92
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Microcircuits in respiratory rhythm generation: commonalities with other rhythm generating networks and evolutionary perspectives. Curr Opin Neurobiol 2016; 41:53-61. [PMID: 27589601 DOI: 10.1016/j.conb.2016.08.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2016] [Revised: 08/16/2016] [Accepted: 08/17/2016] [Indexed: 02/07/2023]
Abstract
Rhythmicity is critical for the generation of rhythmic behaviors and higher brain functions. This review discusses common mechanisms of rhythm generation, including the role of synaptic inhibition and excitation, with a focus on the mammalian respiratory network. This network generates three phases of breathing and is highly integrated with brain regions associated with numerous non-ventilatory behaviors. We hypothesize that during evolution multiple rhythmogenic microcircuits were recruited to accommodate the generation of each breathing phase. While these microcircuits relied primarily on excitatory mechanisms, synaptic inhibition became increasingly important to coordinate the different microcircuits and to integrate breathing into a rich behavioral repertoire that links breathing to sensory processing, arousal, and emotions as well as learning and memory.
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93
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Abstract
Sleep apnea (SA) is increasing in prevalence and is commonly comorbid with hypertension. Chronic intermittent hypoxia is used to model the arterial hypoxemia seen in SA, and through this paradigm, the mechanisms that underlie SA-induced hypertension are becoming clear. Cyclic hypoxic exposure during sleep chronically stimulates the carotid chemoreflexes, inducing sensory long-term facilitation, and drives sympathetic outflow from the hindbrain. The elevated sympathetic tone drives hypertension and renal sympathetic activity to the kidneys resulting in increased plasma renin activity and eventually angiotensin II (Ang II) peripherally. Upon waking, when respiration is normalized, the sympathetic activity does not diminish. This is partially because of adaptations leading to overactivation of the hindbrain regions controlling sympathetic outflow such as the nucleus tractus solitarius (NTS), and rostral ventrolateral medulla (RVLM). The sustained sympathetic activity is also due to enhanced synaptic signaling from the forebrain through the paraventricular nucleus (PVN). During the waking hours, when the chemoreceptors are not exposed to hypoxia, the forebrain circumventricular organs (CVOs) are stimulated by peripherally circulating Ang II from the elevated plasma renin activity. The CVOs and median preoptic nucleus chronically activate the PVN due to the Ang II signaling. All together, this leads to elevated nocturnal mean arterial pressure (MAP) as a response to hypoxemia, as well as inappropriately elevated diurnal MAP in response to maladaptations.
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Affiliation(s)
- Brent Shell
- Institute for Cardiovascular and Metabolic Diseases, University of North Texas Health Science Center, EAD 332B, 3500 Camp Bowie Blvd, Fort Worth, TX, 76107, USA
| | - Katelynn Faulk
- Institute for Cardiovascular and Metabolic Diseases, University of North Texas Health Science Center, EAD 332B, 3500 Camp Bowie Blvd, Fort Worth, TX, 76107, USA
| | - J Thomas Cunningham
- Institute for Cardiovascular and Metabolic Diseases, University of North Texas Health Science Center, EAD 332B, 3500 Camp Bowie Blvd, Fort Worth, TX, 76107, USA.
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94
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Kim SJ, Pilowsky PM, Farnham MMJ. Intrathecal Intermittent Orexin-A Causes Sympathetic Long-Term Facilitation and Sensitizes the Peripheral Chemoreceptor Response to Hypoxia in Rats. J Pharmacol Exp Ther 2016; 358:492-501. [PMID: 27384072 DOI: 10.1124/jpet.116.234443] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Accepted: 07/05/2016] [Indexed: 11/22/2022] Open
Abstract
Intermittent hypoxia causes a persistent increase in sympathetic nerve activity (SNA), which progresses to hypertension in conditions such as obstructive sleep apnea. Orexins (A and B) are hypothalamic neurotransmitters with arousal-promoting and sympathoexcitatory effects. We investigated whether the sustained elevation of SNA, termed sympathetic long-term facilitation, after acute intermittent hypoxia (AIH) is caused by endogenous orexin acting on spinal sympathetic preganglionic neurons. The role of orexin in the increased SNA response to AIH was investigated in urethane-anesthetized, vagotomized, and artificially ventilated Sprague-Dawley rats (n = 58). A spinally infused subthreshold dose of orexin-A (intermittent; 0.1 nmol × 10) produced long-term enhancement in SNA (41.4% ± 6.9%) from baseline. This phenomenon was not produced by the same dose of orexin-A administered as a bolus intrathecal infusion (1 nmol; 7.3% ± 2.3%). The dual orexin receptor blocker, Almorexant, attenuated the effect of sympathetic long-term facilitation generated by intermittent orexin-A (20.7% ± 4.5% for Almorexant at 30 mg∙kg(-1) and 18.5% ± 1.2% for 75 mg∙kg(-1)), but not in AIH. The peripheral chemoreflex sympathoexcitatory response to hypoxia was greatly enhanced by intermittent orexin-A and AIH. In both cases, the sympathetic chemoreflex sensitization was reduced by Almorexant. Taken together, spinally acting orexin-A is mechanistically sufficient to evoke sympathetic long-term facilitation. However, AIH-induced sympathetic long-term facilitation appears to rely on mechanisms that are independent of orexin neurotransmission. Our findings further reveal that the activation of spinal orexin receptors is critical to enhance peripheral chemoreceptor responses to hypoxia after AIH.
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Affiliation(s)
- Seung Jae Kim
- Department of Physiology, Sydney Medical School, University of Sydney, and Heart Research Institute, Sydney, New South Wales, Australia
| | - Paul M Pilowsky
- Department of Physiology, Sydney Medical School, University of Sydney, and Heart Research Institute, Sydney, New South Wales, Australia
| | - Melissa M J Farnham
- Department of Physiology, Sydney Medical School, University of Sydney, and Heart Research Institute, Sydney, New South Wales, Australia
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95
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Affiliation(s)
- Julian F R Paton
- School of Physiology, Pharmacology, and Neuroscience, Biomedical Sciences, University of Bristol, Bristol, United Kingdom.
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96
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Del Rio R, Andrade DC, Lucero C, Arias P, Iturriaga R. Carotid Body Ablation Abrogates Hypertension and Autonomic Alterations Induced by Intermittent Hypoxia in Rats. Hypertension 2016; 68:436-45. [PMID: 27381902 DOI: 10.1161/hypertensionaha.116.07255] [Citation(s) in RCA: 89] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 05/06/2016] [Indexed: 01/12/2023]
Abstract
Chronic intermittent hypoxia (CIH), the main feature of obstructive sleep apnea, enhances carotid body (CB) chemosensory responses to hypoxia and produces autonomic dysfunction, cardiac arrhythmias, and hypertension. We tested whether autonomic alterations, arrhythmogenesis, and the progression of hypertension induced by CIH depend on the enhanced CB chemosensory drive, by ablation of the CB chemoreceptors. Male Sprague-Dawley rats were exposed to control (Sham) conditions for 7 days and then to CIH (5% O2, 12/h 8 h/d) for a total of 28 days. At 21 days of CIH exposure, rats underwent bilateral CB ablation and then exposed to CIH for 7 additional days. Arterial blood pressure and ventilatory chemoreflex response to hypoxia were measured in conscious rats. In addition, cardiac autonomic imbalance, cardiac baroreflex gain, and arrhythmia score were assessed during the length of the experiments. In separate experimental series, we measured extracellular matrix remodeling content in cardiac atrial tissue and systemic oxidative stress. CIH induced hypertension, enhanced ventilatory response to hypoxia, induced autonomic imbalance toward sympathetic preponderance, reduced baroreflex gain, and increased arrhythmias and atrial fibrosis. CB ablation normalized blood pressure, reduced ventilatory response to hypoxia, and restored cardiac autonomic and baroreflex function. In addition, CB ablation reduced the number of arrhythmias, but not extracellular matrix remodeling or systemic oxidative stress, suggesting that reductions in arrhythmia incidence during CIH were related to normalization of cardiac autonomic balance. Present results show that autonomic alterations induced by CIH are critically dependent on the CB and support a main role for the CB in the CIH-induced hypertension.
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Affiliation(s)
- Rodrigo Del Rio
- From the Laboratory of Cardiorespiratory Control, Center of Biomedical Research, Universidad Autónoma de Chile, Santiago, Chile (R.D.R., C.L.); and Laboratorio de Neurobiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile (D.C.A., P.A., R.I.)
| | - David C Andrade
- From the Laboratory of Cardiorespiratory Control, Center of Biomedical Research, Universidad Autónoma de Chile, Santiago, Chile (R.D.R., C.L.); and Laboratorio de Neurobiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile (D.C.A., P.A., R.I.)
| | - Claudia Lucero
- From the Laboratory of Cardiorespiratory Control, Center of Biomedical Research, Universidad Autónoma de Chile, Santiago, Chile (R.D.R., C.L.); and Laboratorio de Neurobiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile (D.C.A., P.A., R.I.)
| | - Paulina Arias
- From the Laboratory of Cardiorespiratory Control, Center of Biomedical Research, Universidad Autónoma de Chile, Santiago, Chile (R.D.R., C.L.); and Laboratorio de Neurobiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile (D.C.A., P.A., R.I.)
| | - Rodrigo Iturriaga
- From the Laboratory of Cardiorespiratory Control, Center of Biomedical Research, Universidad Autónoma de Chile, Santiago, Chile (R.D.R., C.L.); and Laboratorio de Neurobiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile (D.C.A., P.A., R.I.).
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97
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Lemes EV, Aiko S, Orbem CB, Formentin C, Bassi M, Colombari E, Zoccal DB. Long-term facilitation of expiratory and sympathetic activities following acute intermittent hypoxia in rats. Acta Physiol (Oxf) 2016; 217:254-66. [PMID: 26910756 DOI: 10.1111/apha.12661] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 01/14/2016] [Accepted: 02/15/2016] [Indexed: 12/20/2022]
Abstract
AIM Acute intermittent hypoxia (AIH) promotes persistent increases in ventilation and sympathetic activity, referred as long-term facilitation (LTF). Augmented inspiratory activity is suggested as a major component of respiratory LTF. In this study, we hypothesized that AIH also elicits a sustained increase in expiratory motor activity. We also investigated whether the expiratory LTF contributes to the development of sympathetic LTF after AIH. METHODS Rats were exposed to AIH (10 × 6-7% O2 for 45 s, every 5 min), and the cardiorespiratory parameters were evaluated during 60 min using in vivo and in situ approaches. RESULTS In unanesthetized conditions (n = 9), AIH elicited a modest but sustained increase in baseline mean arterial pressure (MAP, 104 ± 2 vs. 111 ± 3 mmHg, P < 0.05) associated with enhanced sympathetic and respiratory-related variabilities. In the in situ preparations (n = 9), AIH evoked LTF in phrenic (33 ± 12%), thoracic sympathetic (75 ± 25%) and abdominal nerve activities (69 ± 14%). The sympathetic overactivity after AIH was phase-locked with the emergence of bursts in abdominal activity during the late-expiratory phase. In anesthetized vagus-intact animals, AIH increased baseline MAP (113 ± 3 vs. 122 ± 2 mmHg, P < 0.05) and abdominal muscle activity (535 ± 94%), which were eliminated after pharmacological inhibition of the retrotrapezoid nucleus/parafacial respiratory group (RTN/pFRG). CONCLUSION These findings indicate that increased expiratory activity is also an important component of AIH-elicited respiratory LTF. Moreover, the development of sympathetic LTF after AIH is linked to the emergence of active expiratory pattern and depends on the integrity of the neurones of the RTN/pFRG.
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Affiliation(s)
- E. V. Lemes
- Department of Physiology and Pathology; School of Dentistry of Araraquara; São Paulo State University (UNESP); Araraquara SP Brazil
| | - S. Aiko
- Department of Physiological Sciences; Centre of Biological Sciences; Federal University of Santa Catarina (UFSC); Florianópolis SC Brazil
| | - C. B. Orbem
- Department of Physiological Sciences; Centre of Biological Sciences; Federal University of Santa Catarina (UFSC); Florianópolis SC Brazil
| | - C. Formentin
- Department of Physiological Sciences; Centre of Biological Sciences; Federal University of Santa Catarina (UFSC); Florianópolis SC Brazil
| | - M. Bassi
- Department of Physiology and Pathology; School of Dentistry of Araraquara; São Paulo State University (UNESP); Araraquara SP Brazil
| | - E. Colombari
- Department of Physiology and Pathology; School of Dentistry of Araraquara; São Paulo State University (UNESP); Araraquara SP Brazil
| | - D. B. Zoccal
- Department of Physiology and Pathology; School of Dentistry of Araraquara; São Paulo State University (UNESP); Araraquara SP Brazil
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98
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Toledo C, Andrade DC, Lucero C, Schultz HD, Marcus N, Retamal M, Madrid C, Del Rio R. Contribution of peripheral and central chemoreceptors to sympatho-excitation in heart failure. J Physiol 2016; 595:43-51. [PMID: 27218485 DOI: 10.1113/jp272075] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Accepted: 04/20/2016] [Indexed: 12/18/2022] Open
Abstract
Chronic heart failure (CHF) is a major public health problem. Tonic hyper-activation of sympathetic neural outflow is commonly observed in patients with CHF. Importantly, sympatho-excitation in CHF exacerbates its progression and is strongly related to poor prognosis and high mortality risk. Increases in both peripheral and central chemoreflex drive are considered markers of the severity of CHF. The principal peripheral chemoreceptors are the carotid bodies (CBs) and alteration in their function has been described in CHF. Mainly, during CHF the CB chemosensitivity is enhanced leading to increases in ventilation and sympathetic outflow. In addition to peripheral control of breathing, central chemoreceptors (CCs) are considered a dominant mechanism in ventilatory regulation. Potentiation of the ventilatory and sympathetic drive in response to CC activation has been shown in patients with CHF as well as in animal models. Therefore, improving understanding of the contribution of the peripheral and central chemoreflexes to augmented sympathetic discharge in CHF could help in developing new therapeutic approaches intended to attenuate the progression of CHF. Accordingly, the main focus of this review is to discuss recent evidence that peripheral and central chemoreflex function are altered in CHF and that they contribute to autonomic imbalance and progression of CHF.
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Affiliation(s)
- Camilo Toledo
- Laboratory of Cardiorespiratory Control, Center of Biomedical Research, Universidad Autónoma de Chile, Santiago, Chile
| | - David C Andrade
- Laboratory of Cardiorespiratory Control, Center of Biomedical Research, Universidad Autónoma de Chile, Santiago, Chile
| | - Claudia Lucero
- Laboratory of Cardiorespiratory Control, Center of Biomedical Research, Universidad Autónoma de Chile, Santiago, Chile
| | - Harold D Schultz
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE, USA
| | - Noah Marcus
- Department of Physiology and Pharmacology, Des Moines University, Des Moines, IA, USA
| | - Mauricio Retamal
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana-Universidad del Desarrollo, Santiago, Chile
| | - Carlos Madrid
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana-Universidad del Desarrollo, Santiago, Chile
| | - Rodrigo Del Rio
- Laboratory of Cardiorespiratory Control, Center of Biomedical Research, Universidad Autónoma de Chile, Santiago, Chile
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99
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Perim RR, Bonagamba LGH, Machado BH. Cardiovascular and respiratory outcome of preconditioned rats submitted to chronic intermittent hypoxia. Exp Physiol 2016. [PMID: 26195236 DOI: 10.1113/ep085237] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
NEW FINDINGS What is the central question of this study? What are the effects of hypoxic preconditioning upon the cardiovascular and respiratory responses to subsequent episodes of chronic intermittent hypoxia? What is the main finding and its importance? The cardiovascular and respiratory responses to a chronic intermittent hypoxia protocol were not altered by previous exposure to intermittent or sustained hypoxia. These findings show that preconditioning to hypoxia produced neither facilitation nor protection from the cardiovascular and respiratory dysfunctions in response to subsequent episodes of chronic intermittent hypoxia in juvenile rats. Rats exposed to chronic intermittent hypoxia (CIH) develop hypertension, which is associated with changes in the coupling of sympathetic and respiratory activities. In this study, we hypothesized that previous preconditioning to intermittent or sustained hypoxia would affect cardiovascular and respiratory changes produced by subsequent protocols of CIH. To test this hypothesis, male Wistar rats were preconditioned to either 10 days of CIH or 24 h of sustained hypoxia (SH). After the initial exposure to hypoxia, rats were maintained in normoxic conditions for 15 days before a new protocol of CIH during 10 days. Cardiovascular and respiratory variables obtained from groups of preconditioned rats were compared with a group of rats exposed to CIH for the first time and also to a group of rats maintained in normoxic conditions throughout the period of time of the respective preconditioning protocol. The data show that CIH produced a similar increase in arterial pressure and heart rate in both CIH and SH preconditioning protocols. Respiratory parameters during basal conditions were also not affected by preconditioning to either CIH or SH. We conclude that previous exposure to CIH or SH preconditioning does not facilitate or prevent the cardiovascular changes produced by CIH.
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Affiliation(s)
- Raphael R Perim
- 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
| | - Benedito H Machado
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, 14049-900, SP, Brazil
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100
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Barnett WH, Abdala AP, Paton JFR, Rybak IA, Zoccal DB, Molkov YI. Chemoreception and neuroplasticity in respiratory circuits. Exp Neurol 2016; 287:153-164. [PMID: 27240520 DOI: 10.1016/j.expneurol.2016.05.036] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 04/22/2016] [Accepted: 05/26/2016] [Indexed: 12/20/2022]
Abstract
The respiratory central pattern generator must respond to chemosensory cues to maintain oxygen (O2) and carbon dioxide (CO2) homeostasis in the blood and tissues. To do this, sensorial cells located in the periphery and central nervous system monitor the arterial partial pressure of O2 and CO2 and initiate respiratory and autonomic reflex adjustments in conditions of hypoxia and hypercapnia. In conditions of chronic intermittent hypoxia (CIH), repeated peripheral chemoreceptor input mediated by the nucleus of the solitary tract induces plastic changes in respiratory circuits that alter baseline respiratory and sympathetic motor outputs and result in chemoreflex sensitization, active expiration, and arterial hypertension. Herein, we explored the hypothesis that the CIH-induced neuroplasticity primarily consists of increased excitability of pre-inspiratory/inspiratory neurons in the pre-Bötzinger complex. To evaluate this hypothesis and elucidate neural mechanisms for the emergence of active expiration and sympathetic overactivity in CIH-treated animals, we extended a previously developed computational model of the brainstem respiratory-sympathetic network to reproduce experimental data on peripheral and central chemoreflexes post-CIH. The model incorporated neuronal connections between the 2nd-order NTS neurons and peripheral chemoreceptors afferents, the respiratory pattern generator, and sympathetic neurons in the rostral ventrolateral medulla in order to capture key features of sympathetic and respiratory responses to peripheral chemoreflex stimulation. Our model identifies the potential neuronal groups recruited during peripheral chemoreflex stimulation that may be required for the development of inspiratory, expiratory and sympathetic reflex responses. Moreover, our model predicts that pre-inspiratory neurons in the pre-Bötzinger complex experience plasticity of channel expression due to excessive excitation during peripheral chemoreflex. Simulations also show that, due to positive interactions between pre-inspiratory neurons in the pre-Bötzinger complex and expiratory neurons in the retrotrapezoid nucleus, increased excitability of the former may lead to the emergence of the active expiratory pattern at normal CO2 levels found after CIH exposure. We conclude that neuronal type specific neuroplasticity in the pre-Bötzinger complex induced by repetitive episodes of peripheral chemoreceptor activation by hypoxia may contribute to the development of sympathetic over-activity and hypertension.
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Affiliation(s)
| | - Ana P Abdala
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, UK
| | - Julian F R Paton
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, UK
| | - Ilya A Rybak
- Drexel University College of Medicine, Philadelphia, PA, United States
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