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Liu Y, Tan J, Miao Y, Zhang Q. Neurogenesis, A Potential Target for Intermittent Hypoxia Leading to Cognitive Decline. Curr Stem Cell Res Ther 2024; 19:63-70. [PMID: 37005547 DOI: 10.2174/1574888x18666230330083206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Revised: 01/30/2023] [Accepted: 02/06/2023] [Indexed: 04/04/2023]
Abstract
As a sleep breathing disorder, characterized by intermittent hypoxia (IH) and Obstructive sleep apnea (OSA), is believed to decrease the cognitive function of patients. Many factors are thought to be responsible for cognitive decline in OSA patients. Neurogenesis, a process by which neural stem cells (NSCs) differentiate into new neurons in the brain, is a major determinant affecting cognitive function. However, there is no clear relationship between IH or OSA and neurogenesis. In recent years, increasing numbers of studies on IH and neurogenesis are documented. Therefore, this review summarizes the effects of IH on neurogenesis; then discusses the influencing factors that may cause these effects and the potential signaling pathways that may exist. Finally, based on this impact, we discuss potential methods and future directions for improving cognition.
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Affiliation(s)
- Yuxing Liu
- Department of Geriatrics, Tianjin Medical University General Hospital, Tianjin Geriatrics Institute, Tianjin, China
| | - Jin Tan
- Department of Geriatrics, Tianjin Medical University General Hospital, Tianjin Geriatrics Institute, Tianjin, China
| | - Yuyang Miao
- Department of Geriatrics, Tianjin Medical University General Hospital, Tianjin Geriatrics Institute, Tianjin, China
| | - Qiang Zhang
- Department of Geriatrics, Tianjin Medical University General Hospital, Tianjin Geriatrics Institute, Tianjin, China
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2
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Gozal D. Early life postnatal intermittent hypoxia: a case for (Mal)adaptive cardiorespiratory plasticity, inflammation, and epigenetics. Sleep 2023; 46:zsad065. [PMID: 36883695 PMCID: PMC10171623 DOI: 10.1093/sleep/zsad065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Indexed: 03/09/2023] Open
Affiliation(s)
- David Gozal
- Department of Child Health and Child Health Research Institute, MU Children’s Hospital, Columbia, MO, USA
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, USA
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Patodia S, Somani A, Thom M. Review: Neuropathology findings in autonomic brain regions in SUDEP and future research directions. Auton Neurosci 2021; 235:102862. [PMID: 34411885 PMCID: PMC8455454 DOI: 10.1016/j.autneu.2021.102862] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 07/16/2021] [Accepted: 07/24/2021] [Indexed: 12/21/2022]
Abstract
Autonomic dysfunction is implicated from clinical, neuroimaging and experimental studies in sudden and unexpected death in epilepsy (SUDEP). Neuropathological analysis in SUDEP series enable exploration of acquired, seizure-related cellular adaptations in autonomic and brainstem autonomic centres of relevance to dysfunction in the peri-ictal period. Alterations in SUDEP compared to control groups have been identified in the ventrolateral medulla, amygdala, hippocampus and central autonomic regions. These involve neuropeptidergic, serotonergic and adenosine systems, as well as specific regional astroglial and microglial populations, as potential neuronal modulators, orchestrating autonomic dysfunction. Future research studies need to extend to clinically and genetically characterized epilepsies, to explore if common or distinct pathways of autonomic dysfunction mediate SUDEP. The ultimate objective of SUDEP research is the identification of disease biomarkers for at risk patients, to improve post-mortem recognition and disease categorisation, but ultimately, for exposing potential treatment targets of pharmacologically modifiable and reversible cellular alterations.
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Affiliation(s)
- Smriti Patodia
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK
| | - Alyma Somani
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK
| | - Maria Thom
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK.
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Patodia S, Tachrount M, Somani A, Scheffer I, Yousry T, Golay X, Sisodiya SM, Thom M. MRI and pathology correlations in the medulla in sudden unexpected death in epilepsy (SUDEP): a postmortem study. Neuropathol Appl Neurobiol 2020; 47:157-170. [PMID: 32559314 DOI: 10.1111/nan.12638] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2020] [Accepted: 06/10/2020] [Indexed: 12/21/2022]
Abstract
AIMS Sudden unexpected death in epilepsy (SUDEP) likely arises as a result of autonomic dysfunction around the time of a seizure. In vivo MRI studies report volume reduction in the medulla and other brainstem autonomic regions. Our aim, in a pathology series, is to correlate regional quantitative features on 9.4T MRI with pathology measures in medullary regions. METHODS Forty-seven medullae from 18 SUDEP, 18 nonepilepsy controls and 11 epilepsy controls were studied. In 16 cases, representing all three groups, ex vivo 9.4T MRI of the brainstem was carried out. Five regions of interest (ROI) were delineated, including the reticular formation zone (RtZ), and actual and relative volumes (RV), as well as T1, T2, T2* and magnetization transfer ratio (MTR) measurements were evaluated on MRI. On serial sections, actual and RV estimates using Cavalieri stereological method and immunolabelling indices for myelin basic protein, synaptophysin and Microtubule associated protein 2 (MAP2) were carried out in similar ROI. RESULTS Lower relative RtZ volumes in the rostral medulla but higher actual volumes in the caudal medulla were observed in SUDEP (P < 0.05). No differences between groups for T1, T2, T2* and MTR values in any region was seen but a positive correlation between T1 values and MAP2 labelling index in RtZ (P < 0.05). Significantly lower MAP2 LI were noted in the rostral medulla RtZ in epilepsy cases (P < 0.05). CONCLUSIONS Rostro-caudal alterations of medullary volume in SUDEP localize with regions containing respiratory regulatory nuclei. They may represent seizure-related alterations, relevant to the pathophysiology of SUDEP.
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Affiliation(s)
- S Patodia
- Department of Neuropathology, UCL Queen Square Institute of Neurology, London, UK.,Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, UK
| | - M Tachrount
- Neuroradiology Academic Unit, Brain Repair and Rehabilitation, UCL Queen Square Institute of Neurology, London, UK.,FMRIB, Nuffield Department of Clinical Neurosciences, Wellcome Centre for Integrative Neuroimaging, University of Oxford, Oxford, UK
| | - A Somani
- Department of Neuropathology, UCL Queen Square Institute of Neurology, London, UK.,Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, UK
| | - I Scheffer
- Department of Medicine (Neurology), Epilepsy Research Centre, University of Melbourne, Melbourne, VIC, Australia
| | - T Yousry
- Neuroradiology Academic Unit, Brain Repair and Rehabilitation, UCL Queen Square Institute of Neurology, London, UK
| | - X Golay
- Neuroradiology Academic Unit, Brain Repair and Rehabilitation, UCL Queen Square Institute of Neurology, London, UK
| | - S M Sisodiya
- Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, UK.,Chalfont Centre for Epilepsy, Chalfont St Peter, UK
| | - M Thom
- Department of Neuropathology, UCL Queen Square Institute of Neurology, London, UK.,Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, UK
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Bittencourt‐Silva PG, Menezes MF, Mendonça‐Junior BA, Karlen‐Amarante M, Zoccal DB. Postnatal intermittent hypoxia enhances phrenic and reduces vagal upper airway motor activities in rats by epigenetic mechanisms. Exp Physiol 2019; 105:148-159. [DOI: 10.1113/ep087928] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Accepted: 10/08/2019] [Indexed: 11/08/2022]
Affiliation(s)
- Paloma G. Bittencourt‐Silva
- Department of Physiology and Pathology School of Dentistry of Araraquara São Paulo State University (UNESP) Araraquara Brazil
| | - Miguel Furtado Menezes
- Department of Physiology and Pathology School of Dentistry of Araraquara São Paulo State University (UNESP) Araraquara Brazil
| | - Bolival A. Mendonça‐Junior
- Department of Physiology and Pathology School of Dentistry of Araraquara São Paulo State University (UNESP) Araraquara Brazil
| | - Marlusa Karlen‐Amarante
- Department of Physiology and Pathology School of Dentistry of Araraquara São Paulo State University (UNESP) Araraquara Brazil
| | - Daniel B. Zoccal
- Department of Physiology and Pathology School of Dentistry of Araraquara São Paulo State University (UNESP) Araraquara Brazil
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Pancaro C, Boulanger-Bertolus J, Segal S, Watson CJ, St Charles I, Mashour GA, Marchand JE. Maternal Noninfectious Fever Enhances Cell Proliferation and Microglial Activation in the Neonatal Rat Dentate Gyrus. Anesth Analg 2019; 128:1190-1198. [PMID: 31094787 DOI: 10.1213/ane.0000000000004051] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Fever and increased maternal interleukin-6 (IL-6) plasma levels in labor are associated with an increased risk of adverse events in offspring, including neonatal seizures, cerebral palsy, and low intelligence scores at school age. However, the neural changes in the neonate that might mediate the adverse effects of maternal noninfectious fever are not fully characterized. This study was designed to test the hypothesis that induced maternal noninfectious fever alters neonatal neural progenitor cell proliferation and enhances microglial activation in the rat dentate gyrus of the hippocampus. METHODS Systemic vehicle or IL-6 was given 3 times to near-term pregnant rats (n = 7/group) every 90 minutes, and maternal core temperature was recorded. Neonatal brains were processed and analyzed for dentate gyrus cell proliferation (using Ki-67, n = 10/group, and glial fibrillary acidic protein, n = 6/group) and resident microglia activation (using ionized calcium-binding adaptor protein-1 [Iba-1], n = 6/group). In separate studies, the authors assessed microglia proliferation using Ki-67/Iba-1 costaining (n = 5/group). RESULTS Compared to controls, exposure to IL-6 resulted in significant maternal temperature increase [mean temperature difference 0.558°C (95% CI, 0.417-0.698; P < .0001)]. Following maternal IL-6, Ki-67 cell proliferation in the dentate gyrus was 55 % higher in neonates whose mother received IL-6 (38.8 ± 9.2) compared with those that received vehicle (25.1 ± 7.8); mean difference 13.7 (95% CI, 5.68-21.71); (P = .0021). Glial fibrillary acidic protein cell proliferation was 40% higher in the neonatal dentate gyrus whose mother received IL-6 when compared to controls (713 ± 85.52 vs 500 ± 115); mean difference 212 (95% CI, 82.2-343.4); (P = .004). Resident microglial activation was 90% higher in the dentate gyrus of neonates whose mother received IL-6 when compared to controls (71.8 ± 9.3 vs 37.8 ± 5.95); mean Iba-1 in stained cells was significantly different between IL-6 and vehicle groups 34 (95% CI, 23.94-44.05); (P < .0001). Proliferating microglia, determined by the colocalization of Ki-67 and Iba-1, were not different in the vehicle (8.8 % ± 3.19 %) and the IL-6 (5.6% ± 2.3%) groups (mean difference 3.2% (95% CI, -0.8-7.25) (P = .1063). CONCLUSIONS IL-6 is sufficient to induce maternal systemic temperature increases in near-term pregnant rats as well as neuronal, glial, and neuroinflammatory changes in the dentate gyrus of the neonatal hippocampus. These alterations might disrupt fetal neurodevelopment during a vulnerable period.
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Affiliation(s)
- Carlo Pancaro
- From the Department of Anesthesiology, University of Michigan Health System, Ann Arbor, Michigan
| | - Julie Boulanger-Bertolus
- From the Department of Anesthesiology, University of Michigan Health System, Ann Arbor, Michigan
| | - Scott Segal
- Department of Anesthesiology, Wake Forest University School of Medicine, Winston-Salem, North Carolina
| | - Chris J Watson
- From the Department of Anesthesiology, University of Michigan Health System, Ann Arbor, Michigan
| | - Irene St Charles
- From the Department of Anesthesiology, University of Michigan Health System, Ann Arbor, Michigan
| | - George A Mashour
- From the Department of Anesthesiology, University of Michigan Health System, Ann Arbor, Michigan
| | - James E Marchand
- Department of Anesthesiology, Tufts Medical Center, Boston, Massachusetts
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Vitelli O, Del Pozzo M, Baccari G, Rabasco J, Pietropaoli N, Barreto M, Villa MP. Autonomic imbalance during apneic episodes in pediatric obstructive sleep apnea. Clin Neurophysiol 2016; 127:551-555. [DOI: 10.1016/j.clinph.2015.05.025] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2015] [Revised: 05/18/2015] [Accepted: 05/27/2015] [Indexed: 11/26/2022]
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Serebrovskaya TV, Xi L. Intermittent hypoxia in childhood: the harmful consequences versus potential benefits of therapeutic uses. Front Pediatr 2015; 3:44. [PMID: 26042211 PMCID: PMC4436817 DOI: 10.3389/fped.2015.00044] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 05/07/2015] [Indexed: 12/04/2022] Open
Abstract
Intermittent hypoxia (IH) often occurs in early infancy in both preterm and term infants and especially at 36-44 weeks postmenstrual age. These episodes of IH could result from sleep-disordered breathing or may be temporally unrelated to apnea or bradycardia events. There are numerous reports indicating adverse effects of IH on development, behavior, academic achievement, and cognition in children with sleep apnea syndrome. It remains uncertain about the exact causative relationship between the neurocognitive and behavioral morbidities and IH and/or its associated sleep fragmentation. On the other hand, well-controlled and moderate IH conditioning/training has been used in sick children for treating their various forms of bronchial asthma, allergic dermatoses, autoimmune thyroiditis, cerebral palsy, and obesity. This review article provides an updated and impartial analysis on the currently available evidence in supporting either side of the seemingly contradictory scenarios. We wish to stimulate a comprehensive understanding of such a complex physiological phenomenon as intermittent hypoxia, which may be accompanied by other confounding factors (e.g., hypercapnia, polycythemia), in order to prevent or reduce its harmful consequences, while maximizing its potential utility as an effective therapeutic tool in pediatric patients.
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Affiliation(s)
| | - Lei Xi
- Department of Internal Medicine, Virginia Commonwealth University , Richmond, VA , USA
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Smith SMC, Friedle SA, Watters JJ. Chronic intermittent hypoxia exerts CNS region-specific effects on rat microglial inflammatory and TLR4 gene expression. PLoS One 2013; 8:e81584. [PMID: 24324707 PMCID: PMC3852519 DOI: 10.1371/journal.pone.0081584] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Accepted: 10/24/2013] [Indexed: 12/12/2022] Open
Abstract
Intermittent hypoxia (IH) during sleep is a hallmark of sleep apnea, causing significant neuronal apoptosis, and cognitive and behavioral deficits in CNS regions underlying memory processing and executive functions. IH-induced neuroinflammation is thought to contribute to cognitive deficits after IH. In the present studies, we tested the hypothesis that IH would differentially induce inflammatory factor gene expression in microglia in a CNS region-dependent manner, and that the effects of IH would differ temporally. To test this hypothesis, adult rats were exposed to intermittent hypoxia (2 min intervals of 10.5% O2) for 8 hours/day during their respective sleep cycles for 1, 3 or 14 days. Cortex, medulla and spinal cord tissues were dissected, microglia were immunomagnetically isolated and mRNA levels of the inflammatory genes iNOS, COX-2, TNFα, IL-1β and IL-6 and the innate immune receptor TLR4 were compared to levels in normoxia. Inflammatory gene expression was also assessed in tissue homogenates (containing all CNS cells). We found that microglia from different CNS regions responded to IH differently. Cortical microglia had longer lasting inflammatory gene expression whereas spinal microglial gene expression was rapid and transient. We also observed that inflammatory gene expression in microglia frequently differed from that in tissue homogenates from the same region, indicating that cells other than microglia also contribute to IH-induced neuroinflammation. Lastly, microglial TLR4 mRNA levels were strongly upregulated by IH in a region- and time-dependent manner, and the increase in TLR4 expression appeared to coincide with timing of peak inflammatory gene expression, suggesting that TLR4 may play a role in IH-induced neuroinflammation. Together, these data indicate that microglial-specific neuroinflammation may play distinct roles in the effects of intermittent hypoxia in different CNS regions.
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Affiliation(s)
- Stephanie M. C. Smith
- Department of Comparative Biosciences, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Scott A. Friedle
- Department of Comparative Biosciences, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Jyoti J. Watters
- Department of Comparative Biosciences, University of Wisconsin, Madison, Wisconsin, United States of America
- * E-mail:
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Hakim F, Gozal D, Kheirandish-Gozal L. Sympathetic and catecholaminergic alterations in sleep apnea with particular emphasis on children. Front Neurol 2012; 3:7. [PMID: 22319509 PMCID: PMC3268184 DOI: 10.3389/fneur.2012.00007] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Accepted: 01/10/2012] [Indexed: 01/04/2023] Open
Abstract
Sleep is involved in the regulation of major organ functions in the human body, and disruption of sleep potentially can elicit organ dysfunction. Obstructive sleep apnea (OSA) is the most prevalent sleep disorder of breathing in adults and children, and its manifestations reflect the interactions between intermittent hypoxia, intermittent hypercapnia, increased intra-thoracic pressure swings, and sleep fragmentation, as elicited by the episodic changes in upper airway resistance during sleep. The sympathetic nervous system is an important modulator of the cardiovascular, immune, endocrine and metabolic systems, and alterations in autonomic activity may lead to metabolic imbalance and organ dysfunction. Here we review how OSA and its constitutive components can lead to perturbation of the autonomic nervous system in general, and to altered regulation of catecholamines, both of which then playing an important role in some of the mechanisms underlying OSA-induced morbidities.
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Affiliation(s)
- Fahed Hakim
- Department of Pediatrics, Comer Children's Hospital, The University of Chicago Chicago, IL, USA
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11
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Autonomic alterations and endothelial dysfunction in pediatric obstructive sleep apnea. Sleep Med 2010; 11:714-20. [DOI: 10.1016/j.sleep.2009.12.013] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2009] [Revised: 12/06/2009] [Accepted: 12/12/2009] [Indexed: 11/21/2022]
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12
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Dean JB, Putnam RW. The caudal solitary complex is a site of central CO(2) chemoreception and integration of multiple systems that regulate expired CO(2). Respir Physiol Neurobiol 2010; 173:274-87. [PMID: 20670695 DOI: 10.1016/j.resp.2010.07.002] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2010] [Revised: 06/30/2010] [Accepted: 07/01/2010] [Indexed: 12/16/2022]
Abstract
The solitary complex is comprised of the nucleus tractus solitarius (NTS, sensory) and dorsal motor nucleus of the vagus (DMV, motor), which functions as an integrative center for neural control of multiple systems including the respiratory, cardiovascular and gastroesophageal systems. The caudal NTS-DMV is one of the several sites of central CO(2) chemoreception in the brain stem. CO(2) chemosensitive neurons are fully responsive to CO(2) at birth and their responsiveness seems to depend on pH-sensitive K(+) channels. In addition, chemosensitive neurons are highly sensitive to conditions such as hypoxia (e.g., neural plasticity) and hyperoxia (e.g., stimulation), suggesting they employ redox and nitrosative signaling mechanisms. Here we review the cellular and systems physiological evidence supporting our hypothesis that the caudal NTS-DMV is a site for integration of respiratory, cardiovascular and gastroesophageal systems that work together to eliminate CO(2) during acute and chronic respiratory acidosis to restore pH homeostasis.
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Affiliation(s)
- Jay B Dean
- Dept. of Molecular Pharmacology & Physiology, Hyperbaric Biomedical Research Laboratory, University of South Florida, Tampa, FL 33612, USA.
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Zoccal DB, Paton JFR, Machado BH. Do changes in the coupling between respiratory and sympathetic activities contribute to neurogenic hypertension? Clin Exp Pharmacol Physiol 2009; 36:1188-96. [DOI: 10.1111/j.1440-1681.2009.05202.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Zoccal DB, Bonagamba LGH, Paton JFR, Machado BH. Sympathetic-mediated hypertension of awake juvenile rats submitted to chronic intermittent hypoxia is not linked to baroreflex dysfunction. Exp Physiol 2009; 94:972-83. [PMID: 19578126 DOI: 10.1113/expphysiol.2009.048306] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In the present study, we evaluated the mechanisms underpinning the hypertension observed in freely moving juvenile rats submitted to chronic intermittent hypoxia (CIH). Male juvenile Wistar rats (20-21 days old) were submitted to CIH (6% O(2) for 40 s every 9 min, 8 h day(1)) for 10 days while control rats were maintained in normoxia. Prior to CIH, baseline systolic arterial pressure (SAP), measured indirectly, was similar between groups (86 +/- 1 versus 87 +/- 1 mmHg). After exposure to CIH, SAP recorded directly was higher in the CIH (n = 28) than in the control group (n = 29; 131 +/- 3 versus 115 +/- 2 mmHg, P < 0.05). This higher SAP of CIH rats presented an augmented power of oscillatory components at low (10.05 +/- 0.91 versus 5.02 +/- 0.63 mmHg(2), P < 0.05) and high (respiratory-related) frequencies (12.42 +/- 2.46 versus 3.28 +/- 0.61 mmHg(2), P < 0.05) in comparison with control animals. In addition, rats exposed to CIH also exhibited an increased cardiac baroreflex gain (3.11 +/- 0.08 versus 2.1 +/- 0.10 beats min(1) mmHg(1), P < 0.0001), associated with a shift to the right of the operating point, in comparison with control rats. Administration of hexamethonium (ganglionic blocker, i.v.), injected after losartan (angiotensin II type 1 receptor antagonist) and [beta-mercapto-beta,beta-cyclopenta-methylenepropionyl(1), O-Me-Tyr(2), Arg(8)]-vasopressin (vasopressin type 1a receptor antagonist), produced a larger depressor response in the CIH (n = 8) than in the control group (n = 9; 49 +/- 2 versus 39 +/- 2 mmHg, P < 0.05). Fifteen days after the cessation of exposure to CIH, the mean arterial pressure of CIH rats returned to normal levels. The data indicate that the sympathetic-mediated hypertension observed in conscious juvenile rats exposed to CIH is not secondary to a reduction in cardiac baroreflex gain and exhibits a higher respiratory modulation, indicating that an enhanced respiratory-sympathetic coupling seems to be the major factor contributing to hypertension in rats exposed to CIH.
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Affiliation(s)
- Daniel B Zoccal
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, 14049-900, Ribeirão Preto, SP, Brazil
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Soukhova GK, Nozdrachev AD, Gozal D. Neonatal intermittent hypoxia and hypertension. J EVOL BIOCHEM PHYS+ 2009. [DOI: 10.1134/s002209300902008x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Abstract
Data from animal and human studies provide a biological plausibility to the notion that obstructive sleep apnea activates pathways that lead to insulin resistance, atherosclerosis and hypertension. Sleep apnea thus activates the same pathways as does obesity. That obstructive sleep apnea is a risk factor for cardiovascular disease is supported by epidemiological association studies. Longitudinal cohort studies also provide evidence that patients with untreated severe sleep apnea have an increased rate of cardiovascular events. But these studies, while highly suggestive, do not provide the evidence needed to convince the skeptic. This would only be obtained by randomized treatment trials with hard cardiovascular endpoints such as cardiac events and deaths. While such studies are in the planning stages, they will be challenging. There are issues about randomizing individuals with severe sleep apnea and excessive sleepiness into no therapy, since they are at known increased risk for car crashes. Thus, lack of therapy puts others on the road at risk as well as the subject with sleep apnea. There is, moreover, the concern that treating obstructive sleep apnea in very obese individuals will have little impact, since any effect of therapy for OSA will be overwhelmed by the effects of obesity itself. Data from randomized treatment trials for cardiovascular endpoints will likely not be available for many years. In the interim, physicians need to consider how to treat such patients. It is proposed that given that CPAP treatment for obstructive sleep apnea is highly effective and essentially totally safe, and that the evidence is suggestive that sleep apnea is a risk factor for cardiovascular disease, then we propose all patients with severe sleep apnea should be treated to reduce cardiovascular risk.
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17
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Edge D, Skelly JR, Bradford A, O'Halloran KD. Ventilatory drive is enhanced in male and female rats following chronic intermittent hypoxia. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2009; 648:337-44. [PMID: 19536497 DOI: 10.1007/978-90-481-2259-2_38] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
Obstructive sleep apnoea is characterized by chronic intermittent hypoxia (CIH) due to recurrent apnoea. We have developed a rat model of CIH, which shows evidence of impaired respiratory muscle function. In this study, we wished to characterize the ventilatory effects of CIH in conscious male and female animals. Adult male (n=14) and female (n=8) Wistar rats were used. Animals were placed in chambers daily for 8 h with free access to food and water. The gas supply to one half of the chambers alternated between air and nitrogen every 90 s, for 8 h per day, reducing ambient oxygen concentration in the chambers to 5% at the nadir (intermittent hypoxia; n=7 male, n=4 female). Air supplying the other chambers was switched every 90 s to air from a separate source, at the same flow rates, and animals in these chambers served as controls (n=7 male, n=4 female). Ventilatory measurements were made in conscious animals (typically sleeping) after 10 days using whole-body plethysmography. Normoxic ventilation was increased in both male and female CIH-treated rats compared to controls but this did not achieve statistical significance. However, ventilatory drive was increased in CIH-treated rats of both sexes as evidenced by significant increases in mean and peak inspiratory flow. Ventilatory responses to acute hypoxia (F(I)O(2) = 0.10; 6 min) and hyperoxic hypercapnia (F(I)CO(2) = 0.05; 6 min) were unaffected by CIH treatment in male and female rats (P>0.05, ANOVA). We conclude that CIH increases respiratory drive in adult rats. We speculate that this represents a form of neural plasticity that may compensate for respiratory muscle impairment that occurs in this animal model.
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Affiliation(s)
- D Edge
- UCD School of Medicine and Medical Science, University College Dublin, Dublin 4, Ireland
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18
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Lin M, Ai J, Li L, Huang C, Chapleau MW, Liu R, Gozal D, Wead WB, Wurster RD, Cheng Z'J'. Structural remodeling of nucleus ambiguus projections to cardiac ganglia following chronic intermittent hypoxia in C57BL/6J mice. J Comp Neurol 2008; 509:103-17. [PMID: 18425809 DOI: 10.1002/cne.21732] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The baroreflex control of heart rate (HR) is reduced following chronic intermittent hypoxia (CIH). Since the nucleus ambiguus (NA) plays a key role in baroreflex control of HR, we examined whether CIH remodels vagal efferent projections to cardiac ganglia. C57BL/6J mice (3-4 months of age) were exposed to either room air (RA) or CIH for 3 months. Confocal microscopy was used to examine NA axons and terminals in cardiac ganglia following Fluoro-Gold (FG) injections to label cardiac ganglia, and microinjections of tracer DiI into the left NA to anterogradely label vagal efferents. We found that: 1) Cardiac ganglia were widely distributed on the dorsal surface of the atria. Although the total number of cardiac ganglia did not differ between RA and CIH mice, the size of ganglia and the somatic area of cardiac principal neurons (PNs) were significantly decreased (P < 0.01), and the size of the PN nuclei was increased following CIH (P < 0.01). 2) NA axons entered cardiac ganglia and innervated PNs with dense basket endings in both RA and CIH mice, and the percentage of innervated PNs was similar (RA: 50 +/- 1.0%; CIH: 49 +/- 1.0%; P > 0.10). In CIH mice, however, swollen cardiac axons and terminals without close contacts to PNs were found. Furthermore, varicose endings around PNs appeared swollen and the axonal varicose area around PNs was almost doubled in size (CIH: 163.1 +/- 6.4 microm(2); RA: 88 +/- 3.9 microm(2), P < 0.01). Thus, CIH significantly altered the structure of cardiac ganglia and resulted in reorganized vagal efferent projections to cardiac ganglia. Such remodeling of cardiac ganglia and vagal efferent projections provides new insight into the effects of CIH on the brain-heart circuitry of C57BL/6J mice.
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Affiliation(s)
- Min Lin
- Biomolecular Science Center, Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, Florida 32816, USA
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19
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Soukhova-O'Hare GK, Ortines RV, Gu Y, Nozdrachev AD, Prabhu SD, Gozal D. Postnatal Intermittent Hypoxia and Developmental Programming of Hypertension in Spontaneously Hypertensive Rats. Hypertension 2008; 52:156-62. [DOI: 10.1161/hypertensionaha.108.110296] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Obstructive and central apneas during sleep are associated with chronic intermittent hypoxia (CIH) and increased cardiovascular morbidity. Spontaneously hypertensive rats exposed to CIH during postnatal days 4 to 30 develop exaggerated hypertension as adults. We hypothesized that reactive oxygen species and altered L-Ca
2+
channel activity may underlie the postnatal programming of exaggerated blood pressure and cardiac remodeling. Newborn male spontaneously hypertensive rats were exposed to CIH (10% and 21% O
2
alternating every 90 seconds, 12 h/d, for postnatal days 4 to 30) or normoxia (room air). In each condition, spontaneously hypertensive rats received daily (SC) 1 of 3 treatments:
l
-calcium channel blocker nifedipine (5 mg/kg), superoxide dismutase mimetic MnTMPyP pentachloride (10 mg/kg), or vehicle (polyethylene glycol). Blood pressure was evaluated monthly for 6 months after birth, and echocardiographic assessments were conducted at 6 months of age. CIH vehicle-treated rats presented higher systolic blood pressure (187±5 mm Hg) as compared with normoxic vehicle treated controls (163±2 mm Hg;
P
<0.001). Postnatal CIH elicited marked increases in left ventricular wall thickness in a pattern of concentric hypertrophy with augmented systolic contractility. The treatment with nifedipine in the CIH group attenuated blood pressure (159±2 mm Hg;
P
<0.001) and normalized left ventricular wall thickness and systolic function, whereas the treatment with SOD mimetic decreased blood pressure (165±2 mm Hg;
P
<0.001) and reduced left ventricular wall thickness without changes in the systolic function. We conclude that Ca
2+
and reactive oxygen species–mediated signaling during intermittent hypoxia are critical mechanisms underlying postnatal programming of an increased severity of hypertension and hypertrophic cardiac remodeling in a genetically susceptible rodent model.
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Affiliation(s)
- Galia K. Soukhova-O'Hare
- From the Kosair Children’s Hospital Research Institute (G.K.S-O., D.G.), Department of Pediatrics, Institute of Molecular Cardiology (R.V.O., Y.G., S.D.P.), Department of Medicine, and Department of Pharmacology and Toxicology (D.G.), University of Louisville, Ky; Department of General Physiology (G.K.S-O., A.D.N.), St Petersburg State University, St Petersburg, Russia; Medical Service (S.D.P.), and the Louisville Veterans’ Affairs Medical Center, Louisville, Ky
| | - Roger V. Ortines
- From the Kosair Children’s Hospital Research Institute (G.K.S-O., D.G.), Department of Pediatrics, Institute of Molecular Cardiology (R.V.O., Y.G., S.D.P.), Department of Medicine, and Department of Pharmacology and Toxicology (D.G.), University of Louisville, Ky; Department of General Physiology (G.K.S-O., A.D.N.), St Petersburg State University, St Petersburg, Russia; Medical Service (S.D.P.), and the Louisville Veterans’ Affairs Medical Center, Louisville, Ky
| | - Yan Gu
- From the Kosair Children’s Hospital Research Institute (G.K.S-O., D.G.), Department of Pediatrics, Institute of Molecular Cardiology (R.V.O., Y.G., S.D.P.), Department of Medicine, and Department of Pharmacology and Toxicology (D.G.), University of Louisville, Ky; Department of General Physiology (G.K.S-O., A.D.N.), St Petersburg State University, St Petersburg, Russia; Medical Service (S.D.P.), and the Louisville Veterans’ Affairs Medical Center, Louisville, Ky
| | - Alexander D. Nozdrachev
- From the Kosair Children’s Hospital Research Institute (G.K.S-O., D.G.), Department of Pediatrics, Institute of Molecular Cardiology (R.V.O., Y.G., S.D.P.), Department of Medicine, and Department of Pharmacology and Toxicology (D.G.), University of Louisville, Ky; Department of General Physiology (G.K.S-O., A.D.N.), St Petersburg State University, St Petersburg, Russia; Medical Service (S.D.P.), and the Louisville Veterans’ Affairs Medical Center, Louisville, Ky
| | - Sumanth D. Prabhu
- From the Kosair Children’s Hospital Research Institute (G.K.S-O., D.G.), Department of Pediatrics, Institute of Molecular Cardiology (R.V.O., Y.G., S.D.P.), Department of Medicine, and Department of Pharmacology and Toxicology (D.G.), University of Louisville, Ky; Department of General Physiology (G.K.S-O., A.D.N.), St Petersburg State University, St Petersburg, Russia; Medical Service (S.D.P.), and the Louisville Veterans’ Affairs Medical Center, Louisville, Ky
| | - David Gozal
- From the Kosair Children’s Hospital Research Institute (G.K.S-O., D.G.), Department of Pediatrics, Institute of Molecular Cardiology (R.V.O., Y.G., S.D.P.), Department of Medicine, and Department of Pharmacology and Toxicology (D.G.), University of Louisville, Ky; Department of General Physiology (G.K.S-O., A.D.N.), St Petersburg State University, St Petersburg, Russia; Medical Service (S.D.P.), and the Louisville Veterans’ Affairs Medical Center, Louisville, Ky
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20
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Zoccal DB, Simms AE, Bonagamba LGH, Braga VA, Pickering AE, Paton JFR, Machado BH. Increased sympathetic outflow in juvenile rats submitted to chronic intermittent hypoxia correlates with enhanced expiratory activity. J Physiol 2008; 586:3253-65. [PMID: 18450774 DOI: 10.1113/jphysiol.2008.154187] [Citation(s) in RCA: 203] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Chronic intermittent hypoxia (CIH) in rats produces changes in the central regulation of cardiovascular and respiratory systems by unknown mechanisms. We hypothesized that CIH (6% O(2) for 40 s, every 9 min, 8 h day(-1)) for 10 days alters the central respiratory modulation of sympathetic activity. After CIH, awake rats (n = 14) exhibited higher levels of mean arterial pressure than controls (101 +/- 3 versus 89 +/- 3 mmHg, n = 15, P < 0.01). Recordings of phrenic, thoracic sympathetic, cervical vagus and abdominal nerves were performed in the in situ working heart-brainstem preparations of control and CIH juvenile rats. The data obtained in CIH rats revealed that: (i) abdominal (Abd) nerves exhibited an additional burst discharge in late expiration; (ii) thoracic sympathetic nerve activity (tSNA) was greater during late expiration than in controls (52 +/- 5 versus 40 +/- 3%; n = 11, P < 0.05; values expressed according to the maximal activity observed during inspiration and the noise level recorded at the end of each experiment), which was not dependent on peripheral chemoreceptors; (iii) the additional late expiratory activity in the Abd nerve correlated with the increased tSNA; (iv) the enhanced late expiratory activity in the Abd nerve unique to CIH rats was accompanied by reduced post-inspiratory activity in cervical vagus nerve compared to controls. The data indicate that CIH rats present an altered pattern of central sympathetic-respiratory coupling, with increased tSNA that correlates with enhanced late expiratory discharge in the Abd nerve. Thus, CIH alters the coupling between the central respiratory generator and sympathetic networks that may contribute to the induced hypertension in this experimental model.
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Affiliation(s)
- Daniel B Zoccal
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, 14049-900, Ribeirão Preto, SP, Brazil
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21
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Bavis RW, Mitchell GS. Long-term effects of the perinatal environment on respiratory control. J Appl Physiol (1985) 2008; 104:1220-9. [DOI: 10.1152/japplphysiol.01086.2007] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The respiratory control system exhibits considerable plasticity, similar to other regions of the nervous system. Plasticity is a persistent change in system behavior triggered by experiences such as changes in neural activity, hypoxia, and/or disease/injury. Although plasticity is observed in animals of all ages, some forms of plasticity appear to be unique to development (i.e., “developmental plasticity”). Developmental plasticity is an alteration in respiratory control induced by experiences during “critical” developmental periods; similar experiences outside the critical period will have little or no lasting effect. Thus complementary experiments on both mature and developing animals are generally needed to verify that the observed plasticity is unique to development. Frequently studied models of developmental plasticity in respiratory control include developmental manipulations of respiratory gas concentrations (O2and CO2). Environmental factors not specifically associated with breathing may also trigger developmental plasticity, however, including psychological stress or chemicals associated with maternal habits (e.g., nicotine, cocaine). Despite rapid advances in describing models of developmental plasticity in breathing, our understanding of fundamental mechanisms giving rise to such plasticity is poor; mechanistic studies of developmental plasticity are of considerable importance. Developmental plasticity may enable organisms to “fine tune” their phenotype to optimize the performance of this critical homeostatic regulatory system. On the other hand, developmental plasticity could also increase the risk of disease later in life. Future directions for studies concerning the mechanisms and functional implications of developmental plasticity in respiratory motor control are discussed.
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22
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Gu H, Lin M, Liu J, Gozal D, Scrogin KE, Wurster R, Chapleau MW, Ma X, Cheng ZJ. Selective impairment of central mediation of baroreflex in anesthetized young adult Fischer 344 rats after chronic intermittent hypoxia. Am J Physiol Heart Circ Physiol 2007; 293:H2809-18. [PMID: 17693540 DOI: 10.1152/ajpheart.00358.2007] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Baroreflex control of heart rate (HR) is impaired after chronic intermittent hypoxia (CIH). However, the location and nature of this response remain unclear. We examined baroreceptor afferent, vagal efferent, and central components of the baroreflex circuitry. Fischer 344 (F344) rats were exposed to room air (RA) or CIH for 35-50 days and were then anesthetized with isoflurane, ventilated, and catheterized for measurement of mean arterial blood pressure (MAP) and HR. Baroreceptor function was characterized by measuring percent changes of integrated aortic depressor nerve (ADN) activity (Int ADNA) relative to the baseline value in response to sodium nitroprusside- and phenylephrine-induced changes in MAP. Data were fitted to a sigmoid logistic function curve. HR responses to electrical stimulation of the left ADN and the right vagus nerve were assessed under ketamine-acepromazine anesthesia. Compared with RA controls, CIH significantly increased maximum baroreceptor gain or maximum slope, maximum Int ADNA, and Int ADNA range (maximum - minimum Int ADNA), whereas other parameters of the logistic function were unchanged. In addition, CIH increased the maximum amplitude of bradycardic response to vagal efferent stimulation and decreased the time from stimulus onset to peak response. In contrast, CIH significantly reduced the maximum amplitude of bradycardic response to left ADN stimulation and increased the time from stimulus onset to peak response. Therefore, CIH decreased central mediation of the baroreflex but augmented baroreceptor afferent function and vagal efferent control of HR.
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Affiliation(s)
- He Gu
- Biomolecular Science Center, Burnett College of Biomedical Sciences, University of Central Florida, Orlando, FL 32816, USA
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23
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Lin M, Liu R, Gozal D, Wead WB, Chapleau MW, Wurster R, Cheng ZJ. Chronic intermittent hypoxia impairs baroreflex control of heart rate but enhances heart rate responses to vagal efferent stimulation in anesthetized mice. Am J Physiol Heart Circ Physiol 2007; 293:H997-1006. [PMID: 17384123 DOI: 10.1152/ajpheart.01124.2006] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Chronic intermittent hypoxia (CIH) leads to increased sympathetic nerve activity and arterial hypertension. In this study, we tested the hypothesis that CIH impairs baroreflex (BR) control of heart rate (HR) in mice, and that decreased cardiac chronotropic responsiveness to vagal efferent activity contributes to such impairment. C57BL/6J mice were exposed to either room air (RA) or CIH (6-min alternations of 21% O(2) and 5.7% O(2), 12 h/day) for 90 days. After the treatment period, mice were anesthetized (Avertin) and arterial blood pressure (ABP) was measured from the femoral artery. Mean ABP (MABP) was significantly increased in mice exposed to CIH (98.7 +/- 2.5 vs. RA: 78.9 +/- 1.4 mmHg, P < 0.001). CIH increased HR significantly (584.7 +/- 8.9 beats/min; RA: 518.2 +/- 17.9 beats/min, P < 0.05). Sustained infusion of phenylephrine (PE) at different doses (0.1-0.4 microg/min) significantly increased MABP in both CIH and RA mice, but the ABP-mediated decreases in HR were significantly attenuated in mice exposed to CIH (P < 0.001). In contrast, decreases in HR in response to electrical stimulation of the left vagus nerve (30 microA, 2-ms pulses) were significantly enhanced in mice exposed to CIH compared with RA mice at low frequencies. We conclude that CIH elicits a sustained impairment of baroreflex control of HR in mice. The blunted BR-mediated bradycardia occurs despite enhanced cardiac chronotropic responsiveness to vagal efferent stimulation. This suggests that an afferent and/or a central defect is responsible for the baroreflex impairment following CIH.
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Affiliation(s)
- Min Lin
- Biomolecular Science Center, Burnett College of Biomedical Sciences, University of Central Florida, 4000 Central Florida Parkway, Orlando, FL 32816, USA
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24
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Reeves SR, Gozal D. Respiratory and metabolic responses to early postnatal chronic intermittent hypoxia and sustained hypoxia in the developing rat. Pediatr Res 2006; 60:680-6. [PMID: 17065578 DOI: 10.1203/01.pdr.0000246073.95911.18] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Exposure to sustained hypoxia (SH) differentially modifies the hypoxic ventilatory response (HVR) in adults and developing rats. We examined the possibility that postnatal intermittent hypoxia (IH), a more prevalent clinical condition than SH, may lead to significant modifications of ventilatory patterning during development. Sprague-Dawley rat pups were exposed as of the d 1 of life to either SH (10% O2) or IH [alternating room air (RA) and 10% O2 every 90 s] for up to 30 d; controls were exposed to normoxia. HVR (10% O2 for 20 min) was assessed in unrestrained pups at 5, 10, 15, and 30 d of age using whole-body plethysmography. IH pups displayed higher normoxic ventilation (VE) at all ages (p < 0.001 versus control; n = 12 per group), which was not observed in SH animals until 10 d of exposure (p < 0.001 versus control; n = 12 per group). Furthermore, both SH and IH modified properties of peak HVR (pHVR), as well as those of the ensuing hypoxic ventilatory decline (HVD); however, the ventilatory strategies adopted after SH and IH greatly differed. We conclude that both postnatal IH and SH modify normal ventilatory patterning and induce altered HVR, but differ in the ventilatory strategies adopted to mount HVR responses.
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Affiliation(s)
- Stephen R Reeves
- Department of Pediatrics, Kosair Children's Hospital Research Institute, University of Louisville School of Medicine, Louisville, Kentucky 40202, USA
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25
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Braga VA, Soriano RN, Machado BH. Sympathoexcitatory response to peripheral chemoreflex activation is enhanced in juvenile rats exposed to chronic intermittent hypoxia. Exp Physiol 2006; 91:1025-31. [PMID: 16959820 DOI: 10.1113/expphysiol.2006.034868] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In the present study, we tested the hypothesis that chronic intermittent hypoxia (CIH) produces changes in the autonomic and respiratory responses to acute peripheral chemoreflex activation. To attain this goal, 3-week-old rats were exposed to 10 days of CIH (6% O(2) for 40 s at 9 min intervals; 8 h day(-1)). They were then used to obtain a working heart-brainstem preparation and, using this unanaesthetized experimental preparation, the chemoreflex was activated with potassium cyanide (0.05%, injected via the perfusion system), and the thoracic sympathetic nerve activity (tSNA), heart rate and phrenic nerve discharge (PND) were recorded. Rats subjected to CIH (n = 12), when compared with control animals (n = 12), presented the following significant changes in response to chemoreflex activation: (a) an increase in tSNA (78 +/- 4 versus 48 +/- 3%); (b) a long-lasting increase in the frequency of the PND at 20 (0.52 +/- 0.03 versus 0.36 +/- 0.03 Hz) and 30 s (0.40 +/- 0.02 versus 0.31 +/- 0.02 Hz) after the stimulus; and (c) a greater bradycardic response (-218 +/- 20 versus -163 +/- 16 beats min(-1)). These results indicate that the autonomic and respiratory responses to chemoreflex activation in juvenile rats previously submitted to CIH are greatly increased.
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Affiliation(s)
- Valdir A Braga
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, 14049-900, Ribeirão Preto, SP, Brazil
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