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Iyer SH, Hinman JE, Warren T, Matthews SA, Simeone TA, Simeone KA. Altered ventilatory responses to hypercapnia-hypoxia challenges in a preclinical SUDEP model involve orexin neurons. Neurobiol Dis 2024; 199:106592. [PMID: 38971479 DOI: 10.1016/j.nbd.2024.106592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 06/25/2024] [Accepted: 07/02/2024] [Indexed: 07/08/2024] Open
Abstract
Failure to recover from repeated hypercapnia and hypoxemia (HH) challenges caused by severe GCS and postictal apneas may contribute to sudden unexpected death in epilepsy (SUDEP). Our previous studies found orexinergic dysfunction contributes to respiratory abnormalities in a preclinical model of SUDEP, Kcna1-/- mice. Here, we developed two gas challenges consisting of repeated HH exposures and used whole body plethysmography to determine whether Kcna1-/- mice have detrimental ventilatory responses. Kcna1-/- mice exhibited an elevated ventilatory response to a mild repeated hypercapnia-hypoxia (HH) challenge compared to WT. Moreover, 71% of Kcna1-/- mice failed to survive a severe repeated HH challenge, whereas all WT mice recovered. We next determined whether orexin was involved in these differences. Pretreating Kcna1-/- mice with a dual orexin receptor antagonist rescued the ventilatory response during the mild challenge and all subjects survived the severe challenge. In ex vivo extracellular recordings in the lateral hypothalamus of coronal brain slices, we found reducing pH either inhibits or stimulates putative orexin neurons similar to other chemosensitive neurons; however, a significantly greater percentage of putative orexin neurons from Kcna1-/-mice were stimulated and the magnitude of stimulation was increased resulting in augmentation of the calculated chemosensitivity index relative to WT. Collectively, our data suggest that increased chemosensitive activity of orexin neurons may be pathologic in the Kcna1-/- mouse model of SUDEP, and contribute to elevated ventilatory responses. Our preclinical data suggest that those at high risk for SUDEP may be more sensitive to HH challenges, whether induced by seizures or other means; and the depth and length of the HH exposure could dictate the probability of survival.
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Affiliation(s)
- Shruthi H Iyer
- Department of Pharmacology and Neuroscience, Creighton University School of Medicine, Omaha, NE 68178, USA
| | - Jillian E Hinman
- Department of Pharmacology and Neuroscience, Creighton University School of Medicine, Omaha, NE 68178, USA
| | - Ted Warren
- Department of Pharmacology and Neuroscience, Creighton University School of Medicine, Omaha, NE 68178, USA
| | - Stephanie A Matthews
- Department of Pharmacology and Neuroscience, Creighton University School of Medicine, Omaha, NE 68178, USA
| | - Timothy A Simeone
- Department of Pharmacology and Neuroscience, Creighton University School of Medicine, Omaha, NE 68178, USA
| | - Kristina A Simeone
- Department of Pharmacology and Neuroscience, Creighton University School of Medicine, Omaha, NE 68178, USA.
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Bhagavan H, Wei AD, Oliveira LM, Aldinger KA, Ramirez JM. Chronic intermittent hypoxia elicits distinct transcriptomic responses among neurons and oligodendrocytes within the brainstem of mice. Am J Physiol Lung Cell Mol Physiol 2024; 326:L698-L712. [PMID: 38591125 DOI: 10.1152/ajplung.00320.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Revised: 01/22/2024] [Accepted: 03/26/2024] [Indexed: 04/10/2024] Open
Abstract
Chronic intermittent hypoxia (CIH) is a prevalent condition characterized by recurrent episodes of oxygen deprivation, linked to respiratory and neurological disorders. Prolonged CIH is known to have adverse effects, including endothelial dysfunction, chronic inflammation, oxidative stress, and impaired neuronal function. These factors can contribute to serious comorbidities, including metabolic disorders and cardiovascular diseases. To investigate the molecular impact of CIH, we examined male C57BL/6J mice exposed to CIH for 21 days, comparing with normoxic controls. We used single-nucleus RNA sequencing to comprehensively examine the transcriptomic impact of CIH on key cell classes within the brainstem, specifically excitatory neurons, inhibitory neurons, and oligodendrocytes. These cell classes regulate essential physiological functions, including autonomic tone, cardiovascular control, and respiration. Through analysis of 10,995 nuclei isolated from pontine-medullary tissue, we identified seven major cell classes, further subdivided into 24 clusters. Our findings among these cell classes, revealed significant differential gene expression, underscoring their distinct responses to CIH. Notably, neurons exhibited transcriptional dysregulation of genes associated with synaptic transmission, and structural remodeling. In addition, we found dysregulated genes encoding ion channels and inflammatory response. Concurrently, oligodendrocytes exhibited dysregulated genes associated with oxidative phosphorylation and oxidative stress. Utilizing CellChat network analysis, we uncovered CIH-dependent altered patterns of diffusible intercellular signaling. These insights offer a comprehensive transcriptomic cellular atlas of the pons-medulla and provide a fundamental resource for the analysis of molecular adaptations triggered by CIH.NEW & NOTEWORTHY This study on chronic intermittent hypoxia (CIH) from pons-medulla provides initial insights into the molecular effects on excitatory neurons, inhibitory neurons, and oligodendrocytes, highlighting our unbiased approach, in comparison with earlier studies focusing on single target genes. Our findings reveal that CIH affects cell classes distinctly, and the dysregulated genes in distinct cell classes are associated with synaptic transmission, ion channels, inflammation, oxidative stress, and intercellular signaling, advancing our understanding of CIH-induced molecular responses.
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Affiliation(s)
- Hemalatha Bhagavan
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington, United States
| | - Aguan D Wei
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington, United States
| | - Luiz M Oliveira
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington, United States
| | - Kimberly A Aldinger
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington, United States
- Department of Pediatrics, University of Washington, Seattle, Washington, United States
- Department of Neurology, University of Washington, Seattle, Washington, United States
| | - Jan-Marino Ramirez
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington, United States
- Department of Pediatrics, University of Washington, Seattle, Washington, United States
- Department of Neurological Surgery, University of Washington, Seattle, Washington, United States
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Yavuz M, İyiköşker P, Mutlu N, Kiliçparlar S, Şalci ÖH, Dolu G, Kaymakçilar EN, Akkol S, Onat F. Dexmedetomidine, an alpha 2A receptor agonist, triggers seizures unilaterally in GAERS during the pre-epileptic phase: does the onset of spike-and-wave discharges occur in a focal manner? Front Neurol 2023; 14:1231736. [PMID: 38146441 PMCID: PMC10749324 DOI: 10.3389/fneur.2023.1231736] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Accepted: 11/13/2023] [Indexed: 12/27/2023] Open
Abstract
Introduction The genetic absence epilepsy rat from Strasbourg (GAERS) is a rat model for infantile absence epilepsy with spike-and-wave discharges (SWDs). This study aimed to investigate the potential of alpha 2A agonism to induce seizures during the pre-epileptic period in GAERS rats. Methods Stereotaxic surgery was performed on male pups and adult GAERS rats to implant recording electrodes in the frontoparietal cortices (right/left) under anesthesia (PN23-26). Following the recovery period, pup GAERS rats were subjected to electroencephalography (EEG) recordings for 2 h. Before the injections, pup epileptiform activity was examined using baseline EEG data. Dexmedetomidine was acutely administered at 0.6 mg/kg to pup GAERS rats 2-3 days after the surgery and once during the post-natal (PN) days 25-29. Epileptiform activities before injections triggered unilateral SWDs and induced sleep durations, and power spectral density was evaluated based on EEG traces. Results The most prominent finding of this study is that unilateral SWD-like activities were induced in 47% of the animals with the intraperitoneal dexmedetomidine injection. The baseline EEGs of pup GAERS rats had no SWDs as expected since they are in the pre-epileptic period but showed low-amplitude non-rhythmic epileptiform activity. There was no difference in the duration of epileptiform activities between the basal EEG groups and DEX-injected unilateral SWD-like-exhibiting and non-SWD-like activities groups; however, the sleep duration of the unilateral SWD-like-exhibiting group was shorter. Power spectrum density (PSD) results revealed that the 1.75-Hz power in the left hemisphere peaks significantly higher than in the right. Discussion As anticipated, pup GAERS rats in the pre-epileptic stage showed no SWDs. Nevertheless, they exhibited sporadic epileptiform activities. Specifically, dexmedetomidine induced SWD-like activities solely within the left hemisphere. These observations imply that absence seizures might originate unilaterally in the left cortex due to α2AAR agonism. Additional research is necessary to explore the precise cortical focal point of this activity.
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Affiliation(s)
- Melis Yavuz
- Department of Pharmacology, Faculty of Pharmacy, Acibadem Mehmet Ali Aydinlar University, Istanbul, Türkiye
| | - Pelin İyiköşker
- Faculty of Pharmacy, Acibadem Mehmet Ali Aydinlar University, Istanbul, Türkiye
| | - Nursima Mutlu
- Department of Biotechnology and Genetics, Institute of Science, Istanbul University, Istanbul, Türkiye
| | - Serra Kiliçparlar
- Faculty of Pharmacy, Acibadem Mehmet Ali Aydinlar University, Istanbul, Türkiye
| | - Öykü Hazal Şalci
- Faculty of Pharmacy, Acibadem Mehmet Ali Aydinlar University, Istanbul, Türkiye
| | - Gökçen Dolu
- Faculty of Pharmacy, Acibadem Mehmet Ali Aydinlar University, Istanbul, Türkiye
| | | | - Serdar Akkol
- Department of Neurology, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Filiz Onat
- Department of Medical Pharmacology, School of Medicine, Acibadem Mehmet Ali Aydinlar University, Istanbul, Türkiye
- Institute of Neurosciences, Acibadem Mehmet Ali Aydinlar University, Istanbul, Türkiye
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Guluzade NA, Huggard JD, Duffin J, Keir DA. A test of the interaction between central and peripheral respiratory chemoreflexes in humans. J Physiol 2023; 601:4591-4609. [PMID: 37566804 DOI: 10.1113/jp284772] [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: 03/30/2023] [Accepted: 07/25/2023] [Indexed: 08/13/2023] Open
Abstract
How central and peripheral chemoreceptor drives to breathe interact in humans remains contentious. We measured the peripheral chemoreflex sensitivity to hypoxia (PChS) at various isocapnic CO2 tensions (P C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ) to determine the form of the relationship between PChS and centralP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ . Twenty participants (10F) completed three repetitions of modified rebreathing tests with end-tidalP O 2 ${P_{{{\mathrm{O}}_{\mathrm{2}}}}}$ (P ET O 2 ${P_{{\mathrm{ET}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ) clamped at 150, 70, 60 and 45 mmHg. End-tidalP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ (P ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ),P ET O 2 ${P_{{\mathrm{ET}}{{\mathrm{O}}_{\mathrm{2}}}}}$ , ventilation (V ̇ $\dot{V}$ E ) and calculated oxygen saturation (SC O2 ) were measured breath-by-breath by gas-analyser and pneumotach. TheV ̇ $\dot{V}$ E -P ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ relationship of repeat-trials were linear-interpolated, combined, averaged into 1 mmHg bins, and fitted with a double-linear function (V ̇ $\dot{V}$ E S, L min-1 mmHg-1 ). PChS was computed at intervals of 1 mmHg ofP ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ as follows: the difference inV ̇ $\dot{V}$ E between the three hypoxic profiles and the hyperoxic profile (∆V ̇ $\dot{V}$ E ) was calculated; three ∆V ̇ $\dot{V}$ E values were plotted against corresponding SC O2 ; and linear regression determined PChS (Lmin-1 mmHg-1 %SC O2 -1 ). These processing steps were repeated at eachP ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ to produce the PChS vs. isocapnicP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ relationship. These were fitted with linear and polynomial functions, and Akaike information criterion identified the best-fit model. One-way repeated measures analysis of variance assessed between-condition differences.V ̇ $\dot{V}$ E S increased (P < 0.0001) with isoxicP ET O 2 ${P_{{\mathrm{ET}}{{\mathrm{O}}_{\mathrm{2}}}}}$ from 3.7 ± 1.5 L min-1 mmHg-1 at 150 mmHg to 4.4 ± 1.8, 5.0 ± 1.6 and 6.0 ± 2.2 Lmin-1 mmHg-1 at 70, 60 and 45 mmHg, respectively. Mean SC O2 fell progressively (99.3 ± 0%, 93.7 ± 0.1%, 90.4 ± 0.1% and 80.5 ± 0.1%; P < 0.0001). In all individuals, PChS increased withP ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ , and this relationship was best described by a linear model in 75%. Despite increasing central chemoreflex activation, PChS increased linearly withP ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ indicative of an additive central-peripheral chemoreflex response. KEY POINTS: How central and peripheral chemoreceptor drives to breathe interact in humans remains contentious. We measured peripheral chemoreflex sensitivity to hypoxia (PChS) at various isocapnic carbon dioxide tensions (P C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ) to determine the form of the relationship between PChS and centralP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ . Participants performed three repetitions of modified rebreathing with end-tidalP O 2 ${P_{{{\mathrm{O}}_{\mathrm{2}}}}}$ fixed at 150, 70, 60 and 45 mmHg. PChS was computed at intervals of 1 mmHg of end-tidalP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ (P ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ) as follows: the difference inV ̇ $\dot{V}$ E between the three hypoxic profiles and the hyperoxic profile (∆V ̇ $\dot{V}$ E ) was calculated; three ∆V ̇ $\dot{V}$ E values were plotted against corresponding calculated oxygen saturation (SC O2 ); and linear regression determined PChS (Lmin-1 mmHg-1 %SC O2 -1 ). In all individuals, PChS increased withP ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ , and this relationship was best described by a linear (rather than polynomial) model in 15 of 20. Most participants did not exhibit a hypo- or hyper-additive effect of central chemoreceptors on the peripheral chemoreflex indicating that the interaction was additive.
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Affiliation(s)
- Nasimi A Guluzade
- School of Kinesiology, The University of Western Ontario, London, ON, Canada
| | - Joshua D Huggard
- School of Kinesiology, The University of Western Ontario, London, ON, Canada
| | - James Duffin
- Department of Anaesthesia and Pain Management, University of Toronto, Toronto, ON, Canada
- Department of Physiology, University of Toronto, Toronto, ON, Canada
- Thornhill Research Inc., Toronto, ON, Canada
| | - Daniel A Keir
- School of Kinesiology, The University of Western Ontario, London, ON, Canada
- Toronto General Research Institute, Toronto General Hospital, Toronto, ON, Canada
- Lawson Health Research Institute, London, ON, Canada
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Marciante AB, Lurk C, Mata L, Lewis J, Reznikov LR, Mitchell GS. Progressive tauopathy disrupts breathing stability and chemoreflexes during presumptive sleep in mice. Front Physiol 2023; 14:1272980. [PMID: 37811498 PMCID: PMC10551153 DOI: 10.3389/fphys.2023.1272980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Accepted: 09/11/2023] [Indexed: 10/10/2023] Open
Abstract
Rationale: Although sleep apnea occurs in over 50% of individuals with Alzheimer's Disease (AD) or related tauopathies, little is known concerning the potential role of tauopathy in the pathogenesis of sleep apnea. Here, we tested the hypotheses that, during presumptive sleep, a murine model of tauopathy (rTg4510) exhibits: 1) increased breathing instability; 2) impaired chemoreflex function; and 3) exacerbation of these effects with tauopathy progression. Methods: rTg4510 mice initially develop robust tauopathy in the hippocampus and cortex, and eventually progresses to the brainstem. Type I and II post-sigh apnea, Type III (spontaneous) apnea, sigh, and hypopnea incidence were measured in young adult (5-6 months; n = 10-14/group) and aged (13-15 months; n = 22-24/group) non-transgenic (nTg), monogenic control tetracycline transactivator, and bigenic rTg4510 mice using whole-body plethysmography during presumptive sleep (i.e., eyes closed, curled/laying posture, stable breathing for >200 breaths) while breathing room air (21% O2). Peripheral and central chemoreceptor sensitivity were assessed with transient exposures (5 min) to hyperoxia (100% O2) or hypercapnia (3% and 5% CO2 in 21% O2), respectively. Results: We report significant increases in Type I, II, and III apneas (all p < 0.001), sighs (p = 0.002) and hypopneas (p < 0.001) in aged rTg4510 mice, but only Type III apneas in young adult rTg4510 mice (p < 0.001) versus age-matched nTg controls. Aged rTg4510 mice exhibited profound chemoreflex impairment versus age matched nTg and tTA mice. In rTg4510 mice, breathing frequency, tidal volume and minute ventilation were not affected by hyperoxic or hypercapnic challenges, in striking contrast to controls. Histological examination revealed hyperphosphorylated tau in brainstem regions involved in the control of breathing (e.g., pons, medullary respiratory column, retrotrapezoid nucleus) in aged rTg4510 mice. Neither breathing instability nor hyperphosphorylated tau in brainstem tissues were observed in young adult rTg4510 mice. Conclusion: Older rTg4510 mice exhibit profound impairment in the neural control of breathing, with greater breathing instability and near absence of oxygen and carbon-dioxide chemoreflexes. Breathing impairments paralleled tauopathy progression into brainstem regions that control breathing. These findings are consistent with the idea that tauopathy per se undermines chemoreflexes and promotes breathing instability during sleep.
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Affiliation(s)
- Alexandria B. Marciante
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Carter Lurk
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Luz Mata
- Department of Physiological Sciences, University of Florida, Gainesville, FL, United States
| | - Jada Lewis
- Center for Translational Research in Neurodegenerative Diseases, Department of Neuroscience, University of Florida, Gainesville, FL, United States
| | - Leah R. Reznikov
- Department of Physiological Sciences, University of Florida, Gainesville, FL, United States
| | - Gordon S. Mitchell
- Breathing Research and Therapeutics Center, Department of Physical Therapy and McKnight Brain Institute, University of Florida, Gainesville, FL, United States
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Getsy PM, Davis J, Coffee GA, Lewis THJ, Lewis SJ. Hypercapnic signaling influences hypoxic signaling in the control of breathing in C57BL6 mice. J Appl Physiol (1985) 2023; 134:1188-1206. [PMID: 36892890 PMCID: PMC10151047 DOI: 10.1152/japplphysiol.00548.2022] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 02/28/2023] [Accepted: 02/28/2023] [Indexed: 03/10/2023] Open
Abstract
Interactions between hypoxic and hypercapnic signaling pathways, expressed as ventilatory changes occurring during and following a simultaneous hypoxic-hypercapnic gas challenge (HH-C) have not been determined systematically in mice. This study in unanesthetized male C57BL6 mice addressed the hypothesis that hypoxic (HX) and hypercapnic (HC) signaling events display an array of interactions indicative of coordination by peripheral and central respiratory mechanisms. We evaluated the ventilatory responses elicited by hypoxic (HX-C, 10%, O2, 90% N2), hypercapnic (HC-C, 5% CO2, 21%, O2, 90% N2), and HH-C (10% O2, 5%, CO2, 85% N2) challenges to determine whether ventilatory responses elicited by HH-C were simply additive of responses elicited by HX-C and HC-C, or whether other patterns of interactions existed. Responses elicited by HH-C were additive for tidal volume, minute ventilation and expiratory time, among others. Responses elicited by HH-C were hypoadditive of the HX-C and HC-C responses (i.e., HH-C responses were less than expected by simple addition of HX-C and HC-C responses) for frequency of breathing, inspiratory time and relaxation time, among others. In addition, end-expiratory pause increased during HX-C, but decreased during HC-C and HH-C, therefore showing that HC-C responses influenced the HX-C responses when given simultaneously. Return to room-air responses was additive for tidal volume and minute ventilation, among others, whereas they were hypoadditive for frequency of breathing, inspiratory time, peak inspiratory flow, apneic pause, inspiratory and expiratory drives, and rejection index. These data show that HX-C and HH-C signaling pathways interact with one another in additive and often hypoadditive processes.NEW & NOTEWORTHY We present data showing that the ventilatory responses elicited by a hypoxic gas challenge in male C57BL6 mice are markedly altered by coexposure to hypercapnic gas challenge with hypercapnic responses often dominating the hypoxic responses. These data suggest that hypercapnic signaling processes activated within brainstem regions, such as the retrotrapezoid nuclei, may directly modulate the signaling processes within the nuclei tractus solitarius resulting from hypoxic-induced increase in carotid body chemoreceptor input to these nuclei.
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Affiliation(s)
- Paulina M Getsy
- Department of Pediatrics, Case Western Reserve University, Cleveland, Ohio, United States
| | - Jesse Davis
- Department of Pediatrics, Case Western Reserve University, Cleveland, Ohio, United States
| | - Gregory A Coffee
- Department of Pediatrics, Case Western Reserve University, Cleveland, Ohio, United States
| | - Tristan H J Lewis
- Department of Pediatrics, Case Western Reserve University, Cleveland, Ohio, United States
| | - Stephen J Lewis
- Department of Pediatrics, Case Western Reserve University, Cleveland, Ohio, United States
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio, United States
- Functional Electrical Stimulation Center, Case Western Reserve University, Cleveland, Ohio, United States
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Carotid body stimulation as a potential intervention in sudden death in epilepsy. Epilepsy Behav 2022; 136:108918. [PMID: 36202052 PMCID: PMC10187768 DOI: 10.1016/j.yebeh.2022.108918] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2021] [Revised: 09/09/2022] [Accepted: 09/11/2022] [Indexed: 12/14/2022]
Abstract
OBJECTIVE To investigate carotid body (CB) mechanisms related to sudden death during seizure. Ictal activation of oxygen-conserving reflexes (OCRs) can trigger fatal cardiorespiratory collapse in seizing rats, which presents like human sudden unexpected death in epilepsy (SUDEP). The CB is strongly implicated in OCR pathways; we hypothesize that modulating CB activity will provide insight into these mechanisms of death. METHODS Long-Evans rats were anesthetized with urethane. Recordings included: electrocorticography, electrocardiography, respiration via nasal thermocouple, and blood pressure (BP). The mammalian diving reflex (MDR) was activated by cold water delivered through a nasal cannula. Reflex and stimulation trials were repeated up to 16 times (4 pre-intervention, 12 post-intervention) or until death. In some animals, one or both carotid bodies were denervated. In some animals, the CB was electrically stimulated, both with and without MDR. Seizures were induced with kainic acid (KA). RESULTS Animals without seizure and with no CB modulation survived all reflexes. Non-seizing animals with CB denervation survived 7.1 ± 5.4 reflexes before death, and only 1 of 7 survived past the 12-trial threshold. Electrical CB stimulation without seizure and without reflex caused significant tachypnea and hypotension. Electrical CB stimulation with seizure and without reflex required higher amplitudes to replicate the physiological responses seen outside seizure. Seizing animals without CB intervention survived 3.2 ± 3.6 trials (per-reflex survival rate 42.0% ± 44.4%), and 0 of 7 survived past the 12-trial threshold. Seizing animals with electrical CB stimulation survived 10.5 ± 4.7 ictal trials (per-reflex survival rate 86.3% ± 35.0%), and 6 of 8 survived past the 12-trial threshold. SIGNIFICANCE These results suggest that, during seizure, the ability of the CB to stimulate a restart of respiration is impaired. The CB and its afferents may be relevant to fatal ictal apnea and SUDEP in humans, and CB stimulation may be a relevant intervention technique in these deaths.
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Molecular Organization and Patterning of the Medulla Oblongata in Health and Disease. Int J Mol Sci 2022; 23:ijms23169260. [PMID: 36012524 PMCID: PMC9409237 DOI: 10.3390/ijms23169260] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 08/15/2022] [Accepted: 08/16/2022] [Indexed: 11/17/2022] Open
Abstract
The medulla oblongata, located in the hindbrain between the pons and the spinal cord, is an important relay center for critical sensory, proprioceptive, and motoric information. It is an evolutionarily highly conserved brain region, both structural and functional, and consists of a multitude of nuclei all involved in different aspects of basic but vital functions. Understanding the functional anatomy and developmental program of this structure can help elucidate potential role(s) of the medulla in neurological disorders. Here, we have described the early molecular patterning of the medulla during murine development, from the fundamental units that structure the very early medullary region into 5 rhombomeres (r7–r11) and 13 different longitudinal progenitor domains, to the neuronal clusters derived from these progenitors that ultimately make-up the different medullary nuclei. By doing so, we developed a schematic overview that can be used to predict the cell-fate of a progenitor group, or pinpoint the progenitor domain of origin of medullary nuclei. This schematic overview can further be used to help in the explanation of medulla-related symptoms of neurodevelopmental disorders, e.g., congenital central hypoventilation syndrome, Wold–Hirschhorn syndrome, Rett syndrome, and Pitt–Hopkins syndrome. Based on the genetic defects seen in these syndromes, we can use our model to predict which medullary nuclei might be affected, which can be used to quickly direct the research into these diseases to the likely affected nuclei.
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Abstract
The clinical term dyspnea (a.k.a. breathlessness or shortness of breath) encompasses at least three qualitatively distinct sensations that warn of threats to breathing: air hunger, effort to breathe, and chest tightness. Air hunger is a primal homeostatic warning signal of insufficient alveolar ventilation that can produce fear and anxiety and severely impacts the lives of patients with cardiopulmonary, neuromuscular, psychological, and end-stage disease. The sense of effort to breathe informs of increased respiratory muscle activity and warns of potential impediments to breathing. Most frequently associated with bronchoconstriction, chest tightness may warn of airway inflammation and constriction through activation of airway sensory nerves. This chapter reviews human and functional brain imaging studies with comparison to pertinent neurorespiratory studies in animals to propose the interoceptive networks underlying each sensation. The neural origins of their distinct sensory and affective dimensions are discussed, and areas for future research are proposed. Despite dyspnea's clinical prevalence and impact, management of dyspnea languishes decades behind the treatment of pain. The neurophysiological bases of current therapeutic approaches are reviewed; however, a better understanding of the neural mechanisms of dyspnea may lead to development of novel therapies and improved patient care.
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Affiliation(s)
- Andrew P Binks
- Department of Basic Science Education, Virginia Tech Carilion School of Medicine, Roanoke, VA, United States; Faculty of Health Sciences, Virginia Tech, Blacksburg, VA, United States.
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Batista LA, Cabral LM, Moreira TS, Takakura AC. Inhibition of anandamide hydrolysis does not rescue respiratory abnormalities observed in an animal model of Parkinson's disease. Exp Physiol 2021; 107:161-174. [PMID: 34907627 DOI: 10.1113/ep089249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Accepted: 12/08/2021] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? The respiratory frequency to hypercapnia is attenuated in an animal model of Parkinson's disease (PD): what is the therapeutic potential of inhibition of anandamide hydrolysis for this respiratory deficit? What is the main finding and its importance? In an animal model of PD there is an increased variability in resting respiratory frequency and an impaired tachypnoeic response to hypercapnia, which is accompanied by diminished expression of Phox2b immunoreactivity in the retrotrapezoid nucleus (RTN). Inhibition of anandamide hydrolysis also impaired the response to hypercapnia and decreased the number of Phox2b immunoreactive cells in the RTN. This strategy does not reverse the respiratory deficits observed in an animal model of PD. ABSTRACT Parkinson's disease (PD) is characterized by severe classic motor symptoms along with various non-classic symptoms. Among the non-classic symptoms, respiratory dysfunctions are increasingly recognized as contributory factors to complications in PD. The endocannabinoid system has been proposed as a target to treat PD and other neurodegenerative disorders. Since symptom management of PD is mainly focused on the classic motor symptoms, in this work we aimed to test the hypothesis that increasing the actions of the endocannabinoid anandamide by inhibiting its hydrolysis with URB597 reverses the respiratory deficits observed in an animal model of PD. Results show that bilateral injection of 6-hydroxydopamine hydrochloride (6-OHDA) in the dorsal striatum leads to neurodegeneration of the substantia nigra, accompanied by reduced expression of Phox2b in the retrotrapezoid nucleus (RTN), an increase in resting respiratory frequency variability and an impaired tachypnoeic response to hypercapnia. URB597 treatment in control animals was associated with an impaired tachypnoeic response to hypercapnia and a reduced expression of Phox2b in the RTN, whereas treatment of 6-OHDA-lesioned animals with URB597 was not able to reverse the deficits observed. These results suggest that targeting anandamide may not be a suitable strategy to treat PD since this treatment mimics the respiratory deficits observed in the 6-OHDA model of PD.
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Affiliation(s)
- Luara A Batista
- Department of Pharmacology, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, SP, Brazil
| | - Laís M Cabral
- Department of Pharmacology, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, SP, Brazil
| | - Thiago S Moreira
- Department of Physiology and Biophysics, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, SP, Brazil
| | - Ana C Takakura
- Department of Pharmacology, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, SP, Brazil
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11
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Wu Y, Cui N, Xing H, Zhong W, Arrowood C, Johnson CM, Jiang C. In vivo evidence for the cellular basis of central hypoventilation of Rett syndrome and pharmacological correction in the rat model. J Cell Physiol 2021; 236:8082-8098. [PMID: 34077559 DOI: 10.1002/jcp.30462] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2020] [Revised: 04/13/2021] [Accepted: 05/08/2021] [Indexed: 12/29/2022]
Abstract
Rett syndrome (RTT) is a neurodevelopmental disorder caused mostly by mutations in the MECP2 gene. RTT patients show periodical hypoventilation attacks. The breathing disorder contributing to the high incidence of sudden death is thought to be due to depressed central inspiratory (I) activity via unknown cellular processes. Demonstration of such processes may lead to targets for pharmacological control of the RTT-type hypoventilation. We performed in vivo recordings from medullary respiratory neurons on the RTT rat model. To our surprise, both I and expiratory (E) neurons in the ventral respiratory column (VRC) increased their firing activity in Mecp2-null rats with severe hypoventilation. These I neurons including E-I phase-spanning and other I neurons remained active during apneas. Consistent with enhanced central I drive, ectopic phrenic discharges during expiration as well as apnea were observed in the Mecp2-null rats. Considering the increased I neuronal firing and ectopic phrenic activity, the RTT-type hypoventilation does not seem to be caused by depression in central I activity, neither reduced medullary I premotor output. This as well as excessive E neuronal firing as shown in our previous studies suggests inadequate synaptic inhibition for phase transition. We found that the abnormal respiratory neuronal firing, ectopic phrenic discharge as well as RTT-type hypoventilation all can be corrected by enhancing GABAergic inhibition. More strikingly, Mecp2-null rats reaching humane endpoints with severe hypoventilation can be rescued by GABAergic augmentation. Thus, defective GABAergic inhibition among respiratory neurons is likely to play a role in the RTT-type hypoventilation, which can be effectively controlled with pharmacological agents.
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Affiliation(s)
- Yang Wu
- Department of Biology, Georgia State University, Atlanta, Georgia, USA
| | - Ningren Cui
- Department of Biology, Georgia State University, Atlanta, Georgia, USA
| | - Hao Xing
- Department of Biology, Georgia State University, Atlanta, Georgia, USA
| | - Weiwei Zhong
- Department of Biology, Georgia State University, Atlanta, Georgia, USA
| | - Colin Arrowood
- Department of Biology, Georgia State University, Atlanta, Georgia, USA
| | | | - Chun Jiang
- Department of Biology, Georgia State University, Atlanta, Georgia, USA
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12
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Ventilatory responses during and following hypercapnic gas challenge are impaired in male but not female endothelial NOS knock-out mice. Sci Rep 2021; 11:20557. [PMID: 34663876 PMCID: PMC8523677 DOI: 10.1038/s41598-021-99922-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 09/24/2021] [Indexed: 11/28/2022] Open
Abstract
The roles of endothelial nitric oxide synthase (eNOS) in the ventilatory responses during and after a hypercapnic gas challenge (HCC, 5% CO2, 21% O2, 74% N2) were assessed in freely-moving female and male wild-type (WT) C57BL6 mice and eNOS knock-out (eNOS-/-) mice of C57BL6 background using whole body plethysmography. HCC elicited an array of ventilatory responses that were similar in male and female WT mice, such as increases in breathing frequency (with falls in inspiratory and expiratory times), and increases in tidal volume, minute ventilation, peak inspiratory and expiratory flows, and inspiratory and expiratory drives. eNOS-/- male mice had smaller increases in minute ventilation, peak inspiratory flow and inspiratory drive, and smaller decreases in inspiratory time than WT males. Ventilatory responses in female eNOS-/- mice were similar to those in female WT mice. The ventilatory excitatory phase upon return to room-air was similar in both male and female WT mice. However, the post-HCC increases in frequency of breathing (with decreases in inspiratory times), and increases in tidal volume, minute ventilation, inspiratory drive (i.e., tidal volume/inspiratory time) and expiratory drive (i.e., tidal volume/expiratory time), and peak inspiratory and expiratory flows in male eNOS-/- mice were smaller than in male WT mice. In contrast, the post-HCC responses in female eNOS-/- mice were equal to those of the female WT mice. These findings provide the first evidence that the loss of eNOS affects the ventilatory responses during and after HCC in male C57BL6 mice, whereas female C57BL6 mice can compensate for the loss of eNOS, at least in respect to triggering ventilatory responses to HCC.
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13
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Randelman M, Zholudeva LV, Vinit S, Lane MA. Respiratory Training and Plasticity After Cervical Spinal Cord Injury. Front Cell Neurosci 2021; 15:700821. [PMID: 34621156 PMCID: PMC8490715 DOI: 10.3389/fncel.2021.700821] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Accepted: 08/11/2021] [Indexed: 12/30/2022] Open
Abstract
While spinal cord injuries (SCIs) result in a vast array of functional deficits, many of which are life threatening, the majority of SCIs are anatomically incomplete. Spared neural pathways contribute to functional and anatomical neuroplasticity that can occur spontaneously, or can be harnessed using rehabilitative, electrophysiological, or pharmacological strategies. With a focus on respiratory networks that are affected by cervical level SCI, the present review summarizes how non-invasive respiratory treatments can be used to harness this neuroplastic potential and enhance long-term recovery. Specific attention is given to "respiratory training" strategies currently used clinically (e.g., strength training) and those being developed through pre-clinical and early clinical testing [e.g., intermittent chemical stimulation via altering inhaled oxygen (hypoxia) or carbon dioxide stimulation]. Consideration is also given to the effect of training on non-respiratory (e.g., locomotor) networks. This review highlights advances in this area of pre-clinical and translational research, with insight into future directions for enhancing plasticity and improving functional outcomes after SCI.
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Affiliation(s)
- Margo Randelman
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, United States.,Marion Murray Spinal Cord Research Center, Drexel University College of Medicine, Philadelphia, PA, United States
| | - Lyandysha V Zholudeva
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, United States.,Marion Murray Spinal Cord Research Center, Drexel University College of Medicine, Philadelphia, PA, United States.,Gladstone Institutes, San Francisco, CA, United States
| | - Stéphane Vinit
- INSERM, END-ICAP, Université Paris-Saclay, UVSQ, Versailles, France
| | - Michael A Lane
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA, United States.,Marion Murray Spinal Cord Research Center, Drexel University College of Medicine, Philadelphia, PA, United States
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14
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Getsy PM, Sundararajan S, May WJ, von Schill GC, McLaughlin DK, Palmer LA, Lewis SJ. Short-term facilitation of breathing upon cessation of hypoxic challenge is impaired in male but not female endothelial NOS knock-out mice. Sci Rep 2021; 11:18346. [PMID: 34526532 PMCID: PMC8443732 DOI: 10.1038/s41598-021-97322-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 08/09/2021] [Indexed: 02/08/2023] Open
Abstract
Decreases in arterial blood oxygen stimulate increases in minute ventilation via activation of peripheral and central respiratory structures. This study evaluates the role of endothelial nitric oxide synthase (eNOS) in the expression of the ventilatory responses during and following a hypoxic gas challenge (HXC, 10% O2, 90% N2) in freely moving male and female wild-type (WT) C57BL6 and eNOS knock-out (eNOS-/-) mice. Exposure to HXC caused an array of responses (of similar magnitude and duration) in both male and female WT mice such as, rapid increases in frequency of breathing, tidal volume, minute ventilation and peak inspiratory and expiratory flows, that were subject to pronounced roll-off. The responses to HXC in male eNOS-/- mice were similar to male WT mice. In contrast, several of the ventilatory responses in female eNOS-/- mice (e.g., frequency of breathing, and expiratory drive) were greater compared to female WT mice. Upon return to room-air, male and female WT mice showed similar excitatory ventilatory responses (i.e., short-term potentiation phase). These responses were markedly reduced in male eNOS-/- mice, whereas female eNOS-/- mice displayed robust post-HXC responses that were similar to those in female WT mice. Our data demonstrates that eNOS plays important roles in (1) ventilatory responses to HXC in female compared to male C57BL6 mice; and (2) expression of post-HXC responses in male, but not female C57BL6 mice. These data support existing evidence that sex, and the functional roles of specific proteins (e.g., eNOS) have profound influences on ventilatory processes, including the responses to HXC.
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Affiliation(s)
- Paulina M. Getsy
- grid.67105.350000 0001 2164 3847Department of Pediatrics, Biomedical Research Building BRB 319, Case Western Reserve University, 10900 Euclid Avenue Mail Stop 1714, Cleveland, OH 44106-1714 USA ,grid.67105.350000 0001 2164 3847Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH USA
| | - Sripriya Sundararajan
- grid.27755.320000 0000 9136 933XPediatric Respiratory Medicine, University of Virginia School of Medicine, Charlottesville, VA USA ,grid.411024.20000 0001 2175 4264Present Address: Division of Neonatology, Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD 21201 USA
| | - Walter J. May
- grid.27755.320000 0000 9136 933XPediatric Respiratory Medicine, University of Virginia School of Medicine, Charlottesville, VA USA
| | - Graham C. von Schill
- grid.27755.320000 0000 9136 933XPediatric Respiratory Medicine, University of Virginia School of Medicine, Charlottesville, VA USA
| | - Dylan K. McLaughlin
- grid.27755.320000 0000 9136 933XPediatric Respiratory Medicine, University of Virginia School of Medicine, Charlottesville, VA USA
| | - Lisa A. Palmer
- grid.27755.320000 0000 9136 933XPediatric Respiratory Medicine, University of Virginia School of Medicine, Charlottesville, VA USA
| | - Stephen J. Lewis
- grid.67105.350000 0001 2164 3847Department of Pediatrics, Biomedical Research Building BRB 319, Case Western Reserve University, 10900 Euclid Avenue Mail Stop 1714, Cleveland, OH 44106-1714 USA ,grid.67105.350000 0001 2164 3847Department of Pharmacology, Case Western Reserve University, Cleveland, OH USA ,grid.67105.350000 0001 2164 3847Functional Electrical Stimulation Center, Case Western Reserve University, Cleveland, OH USA
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15
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Getsy PM, Sundararajan S, Lewis SJ. Carotid sinus nerve transection abolishes the facilitation of breathing that occurs upon cessation of a hypercapnic gas challenge in male mice. J Appl Physiol (1985) 2021; 131:821-835. [PMID: 34236243 DOI: 10.1152/japplphysiol.01031.2020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Arterial pCO2 elevations increase minute ventilation via activation of chemosensors within the carotid body (CB) and brainstem. Although the roles of CB chemoafferents in the hypercapnic (HC) ventilatory response have been investigated, there are no studies reporting the role of these chemoafferents in the ventilatory responses to a HC challenge or the responses that occur upon return to room air, in freely moving mice. This study found that an HC challenge (5% CO2, 21% O2, 74% N2 for 15 min) elicited an array of responses, including increases in frequency of breathing (accompanied by decreases in inspiratory and expiratory times), and increases in tidal volume, minute ventilation, peak inspiratory and expiratory flows, and inspiratory and expiratory drives in sham-operated (SHAM) adult male C57BL6 mice, and that return to room air elicited a brief excitatory phase followed by gradual recovery of all parameters toward baseline values over a 15-min period. The array of ventilatory responses to the HC challenge in mice with bilateral carotid sinus nerve transection (CSNX) performed 7 days previously occurred more slowly but reached similar maxima as SHAM mice. A major finding was responses upon return to room air were dramatically lower in CSNX mice than SHAM mice, and the parameters returned to baseline values within 1-2 min in CSNX mice, whereas it took much longer in SHAM mice. These findings are the first evidence that CB chemoafferents play a key role in initiating the ventilatory responses to HC challenge in C57BL6 mice and are essential for the expression of post-HC ventilatory responses.NEW & NOTEWORTHY This study presents the first evidence that carotid body chemoafferents play a key role in initiating the ventilatory responses, such as increases in frequency of breathing, tidal volume, and minute ventilation that occur in response to a hypercapnic gas challenge in freely moving C57BL6 mice. Our study also demonstrates for the first time that these chemoafferents are essential for the expression of the ventilatory responses that occur upon return to room air in these mice.
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Affiliation(s)
- Paulina M Getsy
- Department of Pediatrics, Case Western University, Cleveland, Ohio
| | - Sripriya Sundararajan
- Pediatric Respiratory Medicine, University of Virginia School of Medicine, Charlottesville, Virginia
| | - Stephen J Lewis
- Department of Pediatrics, Case Western University, Cleveland, Ohio.,Department of Pharmacology, Case Western University, Cleveland, Ohio
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16
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Cinelli E, Mutolo D, Pantaleo T, Bongianni F. Neural mechanisms underlying respiratory regulation within the preBötzinger complex of the rabbit. Respir Physiol Neurobiol 2021; 293:103736. [PMID: 34224867 DOI: 10.1016/j.resp.2021.103736] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 07/01/2021] [Accepted: 07/01/2021] [Indexed: 11/29/2022]
Abstract
The preBötzinger complex (preBötC) is a medullary area essential for normal breathing and widely recognized as necessary and sufficient to generate the inspiratory phase of respiration. It has been studied mainly in rodents. Here we report the main results of our studies revealing the characteristics of the rabbit preBötC identified by means of neuronal recordings, D,L-homocysteic acid microinjections and histological controls. A crucial role in the respiratory rhythmogenesis within this neural substrate is played by excitatory amino acids, but also GABA and glycine display important contributions. Increases in respiratory frequency are induced by microinjections of neurokinins, somatostatin as well by serotonin (5-HT) through an action on 5-HT1A and 5-HT3 receptors or the disinhibition of a GABAergic circuit. Respiratory depression is observed in response to microinjections of the μ-opioid receptor agonist DAMGO. Our results show similarities and differences with the rodent preBötC and emphasize the importance of comparative studies on the mechanisms underlying respiratory rhythmogenesis in different animal species.
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Affiliation(s)
- Elenia Cinelli
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università Degli Studi di Firenze, Viale G.B. Morgagni 63, Firenze, 50134, Italy
| | - Donatella Mutolo
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università Degli Studi di Firenze, Viale G.B. Morgagni 63, Firenze, 50134, Italy
| | - Tito Pantaleo
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università Degli Studi di Firenze, Viale G.B. Morgagni 63, Firenze, 50134, Italy
| | - Fulvia Bongianni
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università Degli Studi di Firenze, Viale G.B. Morgagni 63, Firenze, 50134, Italy.
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17
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Fink AM, Burke LA, Sharma K. Lesioning of the pedunculopontine nucleus reduces rapid eye movement sleep, but does not alter cardiorespiratory activities during sleep, under hypoxic conditions in rats. Respir Physiol Neurobiol 2021; 288:103653. [PMID: 33716095 PMCID: PMC8112452 DOI: 10.1016/j.resp.2021.103653] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 12/21/2020] [Accepted: 03/09/2021] [Indexed: 11/17/2022]
Abstract
To determine how partial lesioning of the pedunculopontine nucleus (PPT) affects sleep, breathing, and blood pressure in rats, ibotenic acid (IBO) was injected bilaterally into the PPT. Sham-injected (saline) and IBO-lesioned rats were first studied under normoxic conditions (40 recordings were obtained from 15 rats, with each recording lasting for 6 daytime hours). Rats were then exposed to intermittent hypoxia for 4 ± 2 days (51 recordings from 12 rats, each lasting 6 daytime hours). The intermittent hypoxia protocol involved an oxygen decline lasting 35 s (to a nadir of 10 %) followed by a 50 s increase to normoxia. The IBO caused an estimated 53 % reduction in PPT neurons. When normoxic, IBO-lesioned rats had remarkedly normal sleep architecture, respiratory rates, and mean arterial pressure. The exposure to intermittent hypoxia evoked tachypnea in both the IBO-lesioned and sham-injected rats. When intermittently hypoxic, IBO-lesioned rats demonstrated a significant reduction in the duration of rapid eye movement (REM) sleep. We conclude that partial lesions of the PPT do not disrupt cardiorespiratory activities, but a reduction in PPT neurons impairs the ability to sustain REM sleep under hypoxic conditions.
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Affiliation(s)
- Anne M Fink
- Center for Sleep and Health Research, University of Illinois Chicago, 845 S. Damen Ave (MC 802), Room 750, Chicago, IL, 60612, United States.
| | - Larisa A Burke
- Office of Research Facilitation, University of Illinois Chicago, 845 S. Damen Ave (MC 802), Room 615, Chicago, IL, 60612, United States.
| | - Kamal Sharma
- Department of Anatomy and Cell Biology, University of Illinois Chicago, 808 S Wood St (MC 512), Room 666, Chicago, IL, United States.
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18
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Dhaibar HA, Hamilton KA, Glasscock E. Kv1.1 subunits localize to cardiorespiratory brain networks in mice where their absence induces astrogliosis and microgliosis. Mol Cell Neurosci 2021; 113:103615. [PMID: 33901631 DOI: 10.1016/j.mcn.2021.103615] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 04/14/2021] [Accepted: 04/16/2021] [Indexed: 12/27/2022] Open
Abstract
Cardiorespiratory collapse following a seizure is a suspected cause of sudden unexpected death in epilepsy (SUDEP), the leading cause of epilepsy-related mortality. In the commonly used Kcna1 gene knockout (Kcna1-/-) mouse model of SUDEP, cardiorespiratory profiling reveals an array of aberrant breathing patterns that could contribute to risk of seizure-related mortality. However, the brain structures mediating these respiratory abnormalities remain unknown. We hypothesize that Kv1.1 deficiency in respiratory control centers of the brain contribute to respiratory dysfunction in Kcna1-/- mice leading to increased SUDEP risk. Thus, in this study, we first used immunohistochemistry to map expression of Kv1.1 protein in cardiorespiratory brain regions of wild-type Kcna1+/+ (WT) mice. Next, GFAP and Iba1 immunostaining was used to test for the presence of astrogliosis and microgliosis, respectively, in the cardiorespiratory centers of Kcna1-/- mice, which could be indicative of seizure-related brain injury that could impair breathing. In WT mice, we detected Kv1.1 protein in all cardiorespiratory centers examined, including the basolateral amygdala, dorsal respiratory group, dorsal motor nucleus of vagus, nucleus ambiguus, ventral respiratory column, and pontine respiratory group, as well as chemosensory centers including the retrotrapezoid and median raphae nuclei. Extensive gliosis was observed in the same areas in Kcna1-/- mice suggesting that seizure-associated brain injury could contribute to respiratory abnormalities.
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Affiliation(s)
- Hemangini A Dhaibar
- Department of Cellular Biology & Anatomy, Louisiana State University Health Sciences Center, Shreveport, LA, USA.
| | - Kathryn A Hamilton
- Department of Cellular Biology & Anatomy, Louisiana State University Health Sciences Center, Shreveport, LA, USA.
| | - Edward Glasscock
- Department of Cellular Biology & Anatomy, Louisiana State University Health Sciences Center, Shreveport, LA, USA; Department of Biological Sciences, Southern Methodist University, Dallas, TX, USA.
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19
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Adult-onset congenital central hypoventilation syndrome due to PHOX2B mutation. Acta Neurol Belg 2021; 121:23-35. [PMID: 32335870 DOI: 10.1007/s13760-020-01363-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Accepted: 04/16/2020] [Indexed: 01/29/2023]
Abstract
Central hypoventilation in adult patients is a rare life-threatening condition characterised by the loss of automatic breathing, more pronounced during sleep. In most cases, it is secondary to a brainstem lesion or to a primary pulmonary, cardiac or neuromuscular disease. More rarely, it can be a manifestation of congenital central hypoventilation syndrome (CCHS). We here describe a 25-year-old woman with severe central hypoventilation triggered by analgesics. Genetic analysis confirmed the diagnosis of adult-onset CCHS caused by a heterozygous de novo poly-alanine repeat expansion of the PHOX2B gene. She was treated with nocturnal non-invasive ventilation. We reviewed the literature and found 21 genetically confirmed adult-onset CCHS cases. Because of the risk of deleterious respiratory complications, adult-onset CCHS is an important differential diagnosis in patients with central hypoventilation.
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20
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Pietrancosta N, Djibo M, Daumas S, El Mestikawy S, Erickson JD. Molecular, Structural, Functional, and Pharmacological Sites for Vesicular Glutamate Transporter Regulation. Mol Neurobiol 2020; 57:3118-3142. [PMID: 32474835 PMCID: PMC7261050 DOI: 10.1007/s12035-020-01912-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Accepted: 03/30/2020] [Indexed: 12/11/2022]
Abstract
Vesicular glutamate transporters (VGLUTs) control quantal size of glutamatergic transmission and have been the center of numerous studies over the past two decades. VGLUTs contain two independent transport modes that facilitate glutamate packaging into synaptic vesicles and phosphate (Pi) ion transport into the synaptic terminal. While a transmembrane proton electrical gradient established by a vacuolar-type ATPase powers vesicular glutamate transport, recent studies indicate that binding sites and flux properties for chloride, potassium, and protons within VGLUTs themselves regulate VGLUT activity as well. These intrinsic ionic binding and flux properties of VGLUTs can therefore be modulated by neurophysiological conditions to affect levels of glutamate available for release from synapses. Despite their extraordinary importance, specific and high-affinity pharmacological compounds that interact with these sites and regulate VGLUT function, distinguish between the various modes of transport, and the different isoforms themselves, are lacking. In this review, we provide an overview of the physiologic sites for VGLUT regulation that could modulate glutamate release in an over-active synapse or in a disease state.
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Affiliation(s)
- Nicolas Pietrancosta
- Neuroscience Paris Seine - Institut de Biologie Paris Seine (NPS - IBPS) INSERM, CNRS, Sorbonne Université, Paris, France. .,Laboratoire des Biomolécules, Sorbonne Université, CNRS, ENS, LBM, 75005, Paris, France.
| | - Mahamadou Djibo
- Sorbonne Paris Cité, Université Paris Descartes, LCBPT, UMR 8601, 75006, Paris, France
| | - Stephanie Daumas
- Neuroscience Paris Seine - Institut de Biologie Paris Seine (NPS - IBPS) INSERM, CNRS, Sorbonne Université, Paris, France
| | - Salah El Mestikawy
- Neuroscience Paris Seine - Institut de Biologie Paris Seine (NPS - IBPS) INSERM, CNRS, Sorbonne Université, Paris, France. .,Douglas Hospital Research Center, Department of Psychiatry, McGill University, 6875 boulevard Lasalle, Verdun, Montreal, QC, Canada.
| | - Jeffrey D Erickson
- Neuroscience Center, Louisiana State University, New Orleans, LA, 70112, USA. .,Department of Pharmacology, Louisiana State University, New Orleans, LA, 70112, USA.
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21
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Zavhorodnia VA, Androshchuk OI, Kharchenko TH, Kudii LI, Kovalenko SO. Haemodynamic effects of hyperventilation on healthy men with different levels of autonomic tone. REGULATORY MECHANISMS IN BIOSYSTEMS 2020. [DOI: 10.15421/022002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
The topicality of the research is stipulated by insufficient study of the correlation between the functional state of the cardiorespiratory system and autonomic tone. The goal of the research was to analyze the changes of central haemodynamics with 10-minute regulated breathing at the rate of 30 cycles per minute and within 40 minutes of recovery after the test in healthy young men with different levels of autonomic tone. Records of the chest rheoplethysmogram were recorded on a rheograph KhAI-medica standard (KhAI-medica, Kharkiv, Ukraine), a capnogram - in a lateral flow on a infrared capnograph (Datex, Finland), and the duration of R-R intervals was determined by a Polar WIND Link in the program of Polar Protrainer 5.0 (Polar Electro OY, Finland). Systolic and diastolic blood pressure were measured by Korotkov’s auscultatory method by mercury tonometer (Riester, Germany). The indicator of the normalized power of the spectrum in the range of 0.15–0.40 Hz was evaluated by 5-minute records; three groups of persons were distinguished according to its distribution at rest by the method of signal deviation, namely, sympathicotonic, normotonic and parasympathicotonic. The initial level of autonomic tone was found to impact the dynamics of СО2 level in alveolar air during hyperventilation and during recovery thereafter. Thus, PetCО2 was higher (41.3 mm Hg) in parasympathicotonic than in sympathicotonic (39.3 mm Hg) and normotonic (39.5 mm Hg) persons. During the test, R-R interval duration decreased being more expressed in normotonic persons. At the same time, the heart index was found to increase in three groups, and general peripheral resistance – to decrease mostly in normo- and parasympathicotonic persons. In addition, the reliable increase of stroke index and heart index was found in these groups. In the recovery period after hyperventilation, the decrease of tension index and ejection speed was found in normo- and, particularly, parasympathicotonic compared with sympathicotonic men and the increase of tension phase and ejection phase duration.
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Keir DA, Duffin J, Millar PJ, Floras JS. Simultaneous assessment of central and peripheral chemoreflex regulation of muscle sympathetic nerve activity and ventilation in healthy young men. J Physiol 2019; 597:3281-3296. [DOI: 10.1113/jp277691] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Accepted: 05/13/2019] [Indexed: 12/20/2022] Open
Affiliation(s)
- Daniel A. Keir
- University Health Network and Mount Sinai Hospital Division of CardiologyDepartment of Medicine, University of Toronto Toronto Ontario Canada
| | - James Duffin
- Departments of Anaesthesia and PhysiologyUniversity of Toronto Toronto Ontario Canada
- Thornhill Research Inc. Toronto Ontario Canada
| | - Philip J. Millar
- University Health Network and Mount Sinai Hospital Division of CardiologyDepartment of Medicine, University of Toronto Toronto Ontario Canada
- Human Health and Nutritional ScienceUniversity of Guelph Guelph Ontario Canada
| | - John S. Floras
- University Health Network and Mount Sinai Hospital Division of CardiologyDepartment of Medicine, University of Toronto Toronto Ontario Canada
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23
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Ramirez JM, Baertsch N. Defining the Rhythmogenic Elements of Mammalian Breathing. Physiology (Bethesda) 2019; 33:302-316. [PMID: 30109823 DOI: 10.1152/physiol.00025.2018] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Breathing's remarkable ability to adapt to changes in metabolic, environmental, and behavioral demands stems from a complex integration of its rhythm-generating network within the wider nervous system. Yet, this integration complicates identification of its specific rhythmogenic elements. Based on principles learned from smaller rhythmic networks of invertebrates, we define criteria that identify rhythmogenic elements of the mammalian breathing network and discuss how they interact to produce robust, dynamic breathing.
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Affiliation(s)
- Jan-Marino Ramirez
- Center for Integrative Brain Research, Seattle Children's Research Institute, University of Washington School of Medicine , Seattle, Washington
| | - Nathan Baertsch
- Center for Integrative Brain Research, Seattle Children's Research Institute, University of Washington School of Medicine , Seattle, Washington
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24
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Bishara J, Keens TG, Perez IA. The genetics of congenital central hypoventilation syndrome: clinical implications. APPLICATION OF CLINICAL GENETICS 2018; 11:135-144. [PMID: 30532577 PMCID: PMC6241683 DOI: 10.2147/tacg.s140629] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Congenital central hypoventilation syndrome (CCHS) is a rare genetic disorder of the autonomic nervous system (ANS) and respiratory control. This disorder, formerly referred to as Ondine’s curse, is due to a mutation in the PHOX2B gene that affects the development of the neural crest cells. CCHS has an autosomal dominant pattern of inheritance. Majority of the patients have a polyalanine repeat mutation (PARM) of the PHOX2B, while a small group has non-PARM (NPARM). Knowledge of the patient’s PHOX2B gene mutation helps predict a patient’s clinical presentation and outcome and aids in anticipatory management of the respiratory and ANS dysfunction.
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Affiliation(s)
- John Bishara
- Division of Pediatric Pulmonology and Sleep Medicine, Children's Hospital Los Angeles, Los Angeles, CA, USA,
| | - Thomas G Keens
- Division of Pediatric Pulmonology and Sleep Medicine, Children's Hospital Los Angeles, Los Angeles, CA, USA, .,Department of Pediatrics, Keck School of Medicine of USC, Los Angeles, CA, USA,
| | - Iris A Perez
- Division of Pediatric Pulmonology and Sleep Medicine, Children's Hospital Los Angeles, Los Angeles, CA, USA, .,Department of Pediatrics, Keck School of Medicine of USC, Los Angeles, CA, USA,
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25
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Andrade DC, Haine L, Toledo C, Diaz HS, Quintanilla RA, Marcus NJ, Iturriaga R, Richalet JP, Voituron N, Del Rio R. Ventilatory and Autonomic Regulation in Sleep Apnea Syndrome: A Potential Protective Role for Erythropoietin? Front Physiol 2018; 9:1440. [PMID: 30374309 PMCID: PMC6196773 DOI: 10.3389/fphys.2018.01440] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Accepted: 09/21/2018] [Indexed: 12/20/2022] Open
Abstract
Obstructive sleep apnea (OSA) is the most common form of sleep disordered breathing and is associated with wide array of cardiovascular morbidities. It has been proposed that during OSA, the respiratory control center (RCC) is affected by exaggerated afferent signals coming from peripheral/central chemoreceptors which leads to ventilatory instability and may perpetuate apnea generation. Treatments focused on decreasing hyperactivity of peripheral/central chemoreceptors may be useful to improving ventilatory instability in OSA patients. Previous studies indicate that oxidative stress and inflammation are key players in the increased peripheral/central chemoreflex drive associated with OSA. Recent data suggest that erythropoietin (Epo) could also be involved in modulating chemoreflex activity as functional Epo receptors are constitutively expressed in peripheral and central chemoreceptors cells. Additionally, there is some evidence that Epo has anti-oxidant/anti-inflammatory effects. Accordingly, we propose that Epo treatment during OSA may reduce enhanced peripheral/central chemoreflex drive and normalize the activity of the RCC which in turn may help to abrogate ventilatory instability. In this perspective article we discuss the potential beneficial effects of Epo administration on ventilatory regulation in the setting of OSA.
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Affiliation(s)
- David C Andrade
- Laboratory of Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Investigación en Fisiología del Ejercicio, Facultad de Ciencias, Universidad Mayor, Santiago, Chile
| | - Liasmine Haine
- Laboratoire Hypoxie and Poumon - EA2363, Université Paris 13, Paris, France
| | - Camilo Toledo
- Laboratory of Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Envejecimiento y Regeneración (CARE), Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Hugo S Diaz
- Laboratory of Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Investigación Biomédica, Universidad Autónoma de Chile, Santiago, Chile
| | | | - Noah J Marcus
- Department of Physiology and Pharmacology, Des Moines University, Des Moines, IA, United States
| | - Rodrigo Iturriaga
- Laboratorio de Neurobiología, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Jean-Paul Richalet
- Laboratoire Hypoxie and Poumon - EA2363, Université Paris 13, Paris, France
| | - Nicolas Voituron
- Laboratoire Hypoxie and Poumon - EA2363, Université Paris 13, Paris, France
| | - Rodrigo Del Rio
- Laboratory of Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Envejecimiento y Regeneración (CARE), Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Excelencia en Biomedicina de Magallanes (CEBIMA), Universidad de Magallanes, Punta Arenas, Chile
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26
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Cardani S, Di Lascio S, Belperio D, Di Biase E, Ceccherini I, Benfante R, Fornasari D. Desogestrel down-regulates PHOX2B and its target genes in progesterone responsive neuroblastoma cells. Exp Cell Res 2018; 370:671-679. [PMID: 30036539 DOI: 10.1016/j.yexcr.2018.07.032] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 07/18/2018] [Accepted: 07/19/2018] [Indexed: 10/28/2022]
Abstract
The paired-like homeobox 2B gene (PHOX2B) encodes a key transcription factor that plays a role in the development of the autonomic nervous system and the neural structures involved in controlling breathing. In humans, PHOX2B over-expression plays a role in the pathogenesis of tumours arising from the sympathetic nervous system such as neuroblastomas, and heterozygous PHOX2B mutations cause Congenital Central Hypoventilation Syndrome (CCHS), a life-threatening neurocristopathy characterised by the defective autonomic control of breathing and involving altered CO2/H+ chemosensitivity. The recovery of CO2/H+ chemosensitivity and increased ventilation have been observed in two CCHS patients using the potent contraceptive progestin desogestrel. Given the central role of PHOX2B in the pathogenesis of CCHS, and the progesterone-mediated effects observed in the disease, we generated progesterone-responsive neuroblastoma cells, and evaluated the effects of 3-Ketodesogestrel (3-KDG), the biologically active metabolite of desogestrel, on the expression of PHOX2B and its target genes. Our findings demonstrate that, through progesterone nuclear receptor PR-B, 3-KDG down-regulates PHOX2B gene expression, by a post-transcriptional mechanism, and its target genes and open up the possibility that this mechanism may contribute to the positive effects observed in some CCHS patients.
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Affiliation(s)
- Silvia Cardani
- Dept. of Medical Biotechnology and Translational Medicine (BIOMETRA), Università degli Studi di Milano, via Vanvitelli 32, 2019 Milan, Italy
| | - Simona Di Lascio
- Dept. of Medical Biotechnology and Translational Medicine (BIOMETRA), Università degli Studi di Milano, via Vanvitelli 32, 2019 Milan, Italy
| | - Debora Belperio
- Dept. of Medical Biotechnology and Translational Medicine (BIOMETRA), Università degli Studi di Milano, via Vanvitelli 32, 2019 Milan, Italy
| | - Erika Di Biase
- Dept. of Medical Biotechnology and Translational Medicine (BIOMETRA), Università degli Studi di Milano, via Vanvitelli 32, 2019 Milan, Italy
| | - Isabella Ceccherini
- Laboratorio di Genetica Molecolare, Istituto Giannina Gaslini, Largo G. Gaslini 5, 16148 Genoa, Italy
| | - Roberta Benfante
- Dept. of Medical Biotechnology and Translational Medicine (BIOMETRA), Università degli Studi di Milano, via Vanvitelli 32, 2019 Milan, Italy; CNR -Neuroscience Institute, via Vanvitelli 32, 20129 Milan, Italy.
| | - Diego Fornasari
- Dept. of Medical Biotechnology and Translational Medicine (BIOMETRA), Università degli Studi di Milano, via Vanvitelli 32, 2019 Milan, Italy; CNR -Neuroscience Institute, via Vanvitelli 32, 20129 Milan, Italy.
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27
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Gonçalves CM, Mulkey DK. Bicarbonate directly modulates activity of chemosensitive neurons in the retrotrapezoid nucleus. J Physiol 2018; 596:4033-4042. [PMID: 29873079 DOI: 10.1113/jp276104] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 05/14/2018] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Changes in CO2 result in corresponding changes in both H+ and HCO3- and despite evidence that HCO3- can function as an independent signalling molecule, there is little evidence suggesting HCO3- contributes to respiratory chemoreception. We show that HCO3- directly activates chemosensitive retrotrapezoid nucleus (RTN) neurons. Identifying all relevant signalling molecules is essential for understanding how chemoreceptors function, and because HCO3- and H+ are buffered by separate cellular mechanisms, having the ability to sense both modalities adds additional information regarding changes in CO2 that are not necessarily reflected by pH alone. HCO3- may be particularly important for regulating activity of RTN chemoreceptors during sustained intracellular acidifications when TASK-2 channels, which appear to be the sole intracellular pH sensor, are minimally active. ABSTRACT Central chemoreception is the mechanism by which the brain regulates breathing in response to changes in tissue CO2 /H+ . The retrotrapezoid nucleus (RTN) is an important site of respiratory chemoreception. Mechanisms underlying RTN chemoreception involve H+ -mediated activation of chemosensitive neurons and CO2 /H+ -evoked ATP-purinergic signalling by local astrocytes, which activates chemosensitive neurons directly and indirectly by maintaining vascular tone when CO2 /H+ levels are high. Although changes in CO2 result in corresponding changes in both H+ and HCO3- and despite evidence that HCO3- can function as an independent signalling molecule, there is little evidence suggesting HCO3- contributes to respiratory chemoreception. Therefore, the goal of this study was to determine whether HCO3- regulates activity of chemosensitive RTN neurons independent of pH. Cell-attached recordings were used to monitor activity of chemosensitive RTN neurons in brainstem slices (300 μm thick) isolated from rat pups (postnatal days 7-11) during exposure to low or high concentrations of HCO3- . In a subset of experiments, we also included 2',7'-bis(2carboxyethyl)-5-(and 6)-carboxyfluorescein (BCECF) in the internal solution to measure pHi under each experimental condition. We found that HCO3- activates chemosensitive RTN neurons by mechanisms independent of intracellular or extracellular pH, glutamate, GABA, glycine or purinergic signalling, soluble adenylyl cyclase activity, nitric oxide or KCNQ channels. These results establish HCO3- as a novel independent modulator of chemoreceptor activity, and because the levels of HCO3- along with H+ are buffered by independent cellular mechanisms, these results suggest HCO3- chemoreception adds additional information regarding changes in CO2 that are not necessarily reflected by pH.
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Affiliation(s)
| | - Daniel K Mulkey
- Department of Physiology and Neurobiology, University of Connecticut, Storrs CT, USA
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28
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Mehboob R, Kabir M, Ahmed N, Ahmad FJ. Towards Better Understanding of the Pathogenesis of Neuronal Respiratory Network in Sudden Perinatal Death. Front Neurol 2017; 8:320. [PMID: 28729852 PMCID: PMC5498558 DOI: 10.3389/fneur.2017.00320] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Accepted: 06/19/2017] [Indexed: 01/16/2023] Open
Abstract
Sudden perinatal death that includes the victims of sudden infant death syndrome, sudden intrauterine death syndrome, and stillbirth are heartbreaking events in the life of parents. Most of the studies about sudden perinatal death were reported from Italy, highlighting two main etiological factors: prone sleeping position and smoking. Other probable contributory factors are prematurity, male gender, lack of breastfeeding, respiratory tract infections, use of pacifiers, infant botulism, extensive use of pesticides and insecticides, etc. However, extensive studies across the world are required to establish the role of these factors in a different subset of populations. Previous studies confirmed the widely accepted hypothesis that neuropathology of the brainstem is one of the main cause of sudden perinatal death. This study is an effort to summarize the neuropathological evaluation of the brainstems and their association to sudden perinatal death. Brainstem nuclei in vulnerable infants undergo certain changes that may alter the sleep arousal cycle, cardiorespiratory control, and ultimately culminate in death. This review focuses on the roles of different brainstem nuclei, their pathologies, and the established facts in this regard in terms of it's link to such deaths. This study will also help to understand the role of brainstem nuclei in controlling the cardiorespiratory cycles in sudden perinatal death and may provide a better understanding to resolve the mystery of these deaths in future. It is also found that a global initiative to deal with perinatal death is required to facilitate the diagnosis and prevention in developed and as well as developing countries.
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Affiliation(s)
- Riffat Mehboob
- Biomedical Sciences, King Edward Medical University, Lahore, Pakistan.,Faculty of Allied Health Sciences, University of Lahore, Lahore, Pakistan
| | - Mahvish Kabir
- Department of Chemistry, School of Science, University of Management and Technology (UMT), Lahore, Pakistan
| | - Naseer Ahmed
- Department of Cardiac Surgery, University of Verona Medical School, Verona, Italy.,Section of Pharmacology, University of Verona Medical School, Verona, Italy
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29
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Alerted microglia and the sympathetic nervous system: A novel form of microglia in the development of hypertension. Respir Physiol Neurobiol 2016; 226:51-62. [DOI: 10.1016/j.resp.2015.11.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 11/24/2015] [Accepted: 11/25/2015] [Indexed: 02/07/2023]
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30
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Saiyed R, Rand CM, Carroll MS, Koliboski CM, Stewart TM, Brogadir CD, Kenny AS, Petersen EKE, Carley DW, Weese-Mayer DE. Congenital central hypoventilation syndrome (CCHS): Circadian temperature variation. Pediatr Pulmonol 2016; 51:300-7. [PMID: 26086998 DOI: 10.1002/ppul.23236] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Accepted: 04/01/2015] [Indexed: 01/21/2023]
Abstract
BACKGROUND Congenital central hypoventilation syndrome (CCHS) is a rare neurocristopathy, which includes a control of breathing deficit and features of autonomic nervous system (ANS) dysregulation. In recognition of the fundamental role of the ANS in temperature regulation and rhythm and the lack of any prior characterization of circadian temperature rhythms in CCHS, we sought to explore peripheral and core temperatures and circadian patterning. We hypothesized that CCHS patients would exhibit lower peripheral skin temperatures (PST), variability, and circadian rhythmicity (vs. controls), as well as a disrupted relationship between core body temperature (CBT) and PST. METHODS PST was sampled every 3 min over four 24-hr periods in CCHS cases and similarly aged controls. CBT was sampled in a subset of these recordings. RESULTS PST was recorded from 25 CCHS cases (110,664 measures/230 days) and 39 controls (78,772 measures/164 days). Simultaneous CBT measurements were made from 23 CCHS patients. In CCHS, mean PST was lower overall (P = 0.03) and at night (P = 0.02), and PST variability (interquartile range) was higher at night (P = 0.05) (vs. controls). PST circadian rhythm remained intact but the phase relationship of PST to CBT rhythm was extremely variable in CCHS. CONCLUSIONS PST alterations in CCHS likely reflect altered autonomic control of peripheral vascular tone. These alterations represent a previously unreported manifestation of CCHS and may provide an opportunity for therapeutic intervention. The relationship between temperature dysregulation and CCHS may also offer insight into basic mechanisms underlying thermoregulation.
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Affiliation(s)
- Rehan Saiyed
- Center for Autonomic Medicine in Pediatrics (CAMP), Ann & Robert H. Lurie Children's Hospital of Chicago, Stanley Manne Children's Research Institute, Chicago, Illinois
| | - Casey M Rand
- Center for Autonomic Medicine in Pediatrics (CAMP), Ann & Robert H. Lurie Children's Hospital of Chicago, Stanley Manne Children's Research Institute, Chicago, Illinois
| | - Michael S Carroll
- Center for Autonomic Medicine in Pediatrics (CAMP), Ann & Robert H. Lurie Children's Hospital of Chicago, Stanley Manne Children's Research Institute, Chicago, Illinois.,Northwestern University Feinberg School of Medicine, Chicago, Illinois
| | - Cynthia M Koliboski
- Center for Autonomic Medicine in Pediatrics (CAMP), Ann & Robert H. Lurie Children's Hospital of Chicago, Stanley Manne Children's Research Institute, Chicago, Illinois
| | - Tracey M Stewart
- Center for Autonomic Medicine in Pediatrics (CAMP), Ann & Robert H. Lurie Children's Hospital of Chicago, Stanley Manne Children's Research Institute, Chicago, Illinois
| | - Cindy D Brogadir
- Center for Autonomic Medicine in Pediatrics (CAMP), Ann & Robert H. Lurie Children's Hospital of Chicago, Stanley Manne Children's Research Institute, Chicago, Illinois
| | - Anna S Kenny
- Center for Autonomic Medicine in Pediatrics (CAMP), Ann & Robert H. Lurie Children's Hospital of Chicago, Stanley Manne Children's Research Institute, Chicago, Illinois
| | - Emily K E Petersen
- Cardiovascular Thoracic Surgery, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois
| | - David W Carley
- Center for Narcolepsy, Sleep and Health Research (CNSHR), University of Illinois at Chicago, Chicago, Illinois
| | - Debra E Weese-Mayer
- Center for Autonomic Medicine in Pediatrics (CAMP), Ann & Robert H. Lurie Children's Hospital of Chicago, Stanley Manne Children's Research Institute, Chicago, Illinois.,Northwestern University Feinberg School of Medicine, Chicago, Illinois
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31
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Jones SE, Dutschmann M. Testing the hypothesis of neurodegeneracy in respiratory network function with a priori transected arterially perfused brain stem preparation of rat. J Neurophysiol 2016; 115:2593-607. [PMID: 26888109 DOI: 10.1152/jn.01073.2015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Accepted: 02/12/2016] [Indexed: 11/22/2022] Open
Abstract
Degeneracy of respiratory network function would imply that anatomically discrete aspects of the brain stem are capable of producing respiratory rhythm. To test this theory we a priori transected brain stem preparations before reperfusion and reoxygenation at 4 rostrocaudal levels: 1.5 mm caudal to obex (n = 5), at obex (n = 5), and 1.5 (n = 7) and 3 mm (n = 6) rostral to obex. The respiratory activity of these preparations was assessed via recordings of phrenic and vagal nerves and lumbar spinal expiratory motor output. Preparations with a priori transection at level of the caudal brain stem did not produce stable rhythmic respiratory bursting, even when the arterial chemoreceptors were stimulated with sodium cyanide (NaCN). Reperfusion of brain stems that preserved the pre-Bötzinger complex (pre-BötC) showed spontaneous and sustained rhythmic respiratory bursting at low phrenic nerve activity (PNA) amplitude that occurred simultaneously in all respiratory motor outputs. We refer to this rhythm as the pre-BötC burstlet-type rhythm. Conserving circuitry up to the pontomedullary junction consistently produced robust high-amplitude PNA at lower burst rates, whereas sequential motor patterning across the respiratory motor outputs remained absent. Some of the rostrally transected preparations expressed both burstlet-type and regular PNA amplitude rhythms. Further analysis showed that the burstlet-type rhythm and high-amplitude PNA had 1:2 quantal relation, with burstlets appearing to trigger high-amplitude bursts. We conclude that no degenerate rhythmogenic circuits are located in the caudal medulla oblongata and confirm the pre-BötC as the primary rhythmogenic kernel. The absence of sequential motor patterning in a priori transected preparations suggests that pontine circuits govern respiratory pattern formation.
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Affiliation(s)
- Sarah E Jones
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia
| | - Mathias Dutschmann
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia
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32
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Nobuta H, Cilio MR, Danhaive O, Tsai HH, Tupal S, Chang SM, Murnen A, Kreitzer F, Bravo V, Czeisler C, Gokozan HN, Gygli P, Bush S, Weese-Mayer DE, Conklin B, Yee SP, Huang EJ, Gray PA, Rowitch D, Otero JJ. Dysregulation of locus coeruleus development in congenital central hypoventilation syndrome. Acta Neuropathol 2015; 130:171-83. [PMID: 25975378 PMCID: PMC4503865 DOI: 10.1007/s00401-015-1441-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Revised: 05/01/2015] [Accepted: 05/02/2015] [Indexed: 12/29/2022]
Abstract
Human congenital central hypoventilation syndrome (CCHS), resulting from mutations in transcription factor PHOX2B, manifests with impaired responses to hypoxemia and hypercapnia especially during sleep. To identify brainstem structures developmentally affected in CCHS, we analyzed two postmortem neonatal-lethal cases with confirmed polyalanine repeat expansion (PARM) or Non-PARM (PHOX2B∆8) mutation of PHOX2B. Both human cases showed neuronal losses within the locus coeruleus (LC), which is important for central noradrenergic signaling. Using a conditionally active transgenic mouse model of the PHOX2B∆8 mutation, we found that early embryonic expression (<E10.5) caused failure of LC neuronal specification and perinatal respiratory lethality. In contrast, later onset (E11.5) of PHOX2B∆8 expression was not deleterious to LC development and perinatal respiratory lethality was rescued, despite failure of chemosensor retrotrapezoid nucleus formation. Our findings indicate that early-onset mutant PHOX2B expression inhibits LC neuronal development in CCHS. They further suggest that such mutations result in dysregulation of central noradrenergic signaling, and therefore, potential for early pharmacologic intervention in humans with CCHS.
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33
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Holloway BB, Viar KE, Stornetta RL, Guyenet PG. The retrotrapezoid nucleus stimulates breathing by releasing glutamate in adult conscious mice. Eur J Neurosci 2015; 42:2271-82. [PMID: 26096172 DOI: 10.1111/ejn.12996] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Revised: 06/10/2015] [Accepted: 06/17/2015] [Indexed: 11/30/2022]
Abstract
The retrotrapezoid nucleus (RTN) is a bilateral cluster of neurons located at the ventral surface of the brainstem below the facial nucleus. The RTN is activated by hypercapnia and stabilises arterial Pco2 by adjusting lung ventilation in a feedback manner. RTN neurons contain vesicular glutamate transporter-2 (Vglut2) transcripts (Slc17a6), and their synaptic boutons are Vglut2-immunoreactive. Here, we used optogenetics to test whether the RTN increases ventilation in conscious adult mice by releasing glutamate. Neurons located below the facial motor nucleus were transduced unilaterally to express channelrhodopsin-2 (ChR2)-enhanced yellow fluorescent protein, with lentiviral vectors that employ the Phox2b-activated artificial promoter PRSx8. The targeted population consisted of two types of Phox2b-expressing neuron: non-catecholaminergic neurons (putative RTN chemoreceptors) and catecholaminergic (C1) neurons. Opto-activation of a mix of ChR2-expressing RTN and C1 neurons produced a powerful stimulus frequency-dependent (5-15 Hz) stimulation of breathing in control conscious mice. Respiratory stimulation was comparable in mice in which dopamine-β-hydroxylase (DβH)-positive neurons no longer expressed Vglut2 (DβH(C) (re/0);;Vglut2(fl/fl)). In a third group of mice, i.e. DβH(+/+);;Vglut2(fl/fl) mice, we injected a mixture of PRSx8-Cre lentiviral vector and Cre-dependent ChR2 adeno-associated virus 2 unilaterally into the RTN; this procedure deleted Vglut2 from ChR2-expressing neurons regardless of whether or not they were catecholaminergic. The ventilatory response elicited by photostimulation of ChR2-positive neurons was almost completely absent in these mice. Resting ventilatory parameters were identical in the three groups of mice, and their brains contained similar numbers of ChR2-positive catecholaminergic and non-catecholaminergic neurons. From these results, we conclude that RTN neurons increase breathing in conscious adult mice by releasing glutamate.
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Affiliation(s)
- Benjamin B Holloway
- Department of Pharmacology, University of Virginia Health System, P.O. Box 800735, 1340 Jefferson Park Avenue, Charlottesville, VA, 22908-0735, USA
| | - Kenneth E Viar
- Department of Pharmacology, University of Virginia Health System, P.O. Box 800735, 1340 Jefferson Park Avenue, Charlottesville, VA, 22908-0735, USA
| | - Ruth L Stornetta
- Department of Pharmacology, University of Virginia Health System, P.O. Box 800735, 1340 Jefferson Park Avenue, Charlottesville, VA, 22908-0735, USA
| | - Patrice G Guyenet
- Department of Pharmacology, University of Virginia Health System, P.O. Box 800735, 1340 Jefferson Park Avenue, Charlottesville, VA, 22908-0735, USA
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Silva NT, Nalivaiko E, da Silva LG, Haibara AS. Excitatory amino acid receptors in the dorsomedial hypothalamic area contribute to the chemoreflex tachypneic response. Respir Physiol Neurobiol 2015; 212-214:1-8. [DOI: 10.1016/j.resp.2015.04.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 03/12/2015] [Accepted: 04/05/2015] [Indexed: 10/23/2022]
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Jerath R, Crawford MW, Barnes VA, Harden K. Widespread depolarization during expiration: A source of respiratory drive? Med Hypotheses 2015; 84:31-7. [DOI: 10.1016/j.mehy.2014.11.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 10/23/2014] [Accepted: 11/08/2014] [Indexed: 12/21/2022]
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Ben-Tal A, Tawhai MH. Integrative approaches for modeling regulation and function of the respiratory system. WILEY INTERDISCIPLINARY REVIEWS. SYSTEMS BIOLOGY AND MEDICINE 2013; 5:687-99. [PMID: 24591490 PMCID: PMC4048368 DOI: 10.1002/wsbm.1244] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 08/02/2013] [Accepted: 08/05/2013] [Indexed: 11/08/2022]
Abstract
Mathematical models have been central to understanding the interaction between neural control and breathing. Models of the entire respiratory system-which comprises the lungs and the neural circuitry that controls their ventilation-have been derived using simplifying assumptions to compartmentalize each component of the system and to define the interactions between components. These full system models often rely-through necessity-on empirically derived relationships or parameters, in addition to physiological values. In parallel with the development of whole respiratory system models are mathematical models that focus on furthering a detailed understanding of the neural control network, or of the several functions that contribute to gas exchange within the lung. These models are biophysically based, and rely on physiological parameters. They include single-unit models for a breathing lung or neural circuit, through to spatially distributed models of ventilation and perfusion, or multicircuit models for neural control. The challenge is to bring together these more recent advances in models of neural control with models of lung function, into a full simulation for the respiratory system that builds upon the more detailed models but remains computationally tractable. This requires first understanding the mathematical models that have been developed for the respiratory system at different levels, and which could be used to study how physiological levels of O2 and CO2 in the blood are maintained.
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Affiliation(s)
- Alona Ben-Tal
- Institute of Natural and Mathematical Sciences, Massey University, Albany, Auckland, New Zealand
| | - Merryn H. Tawhai
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
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Abstract
Central respiratory chemoreceptors sense changes in CO2/H(+) and initiate the adjustments to ventilation required to preserve brain and tissue pH. The cellular nature of the sensors (neurons and/or glia) and their CNS location are not conclusively established but the glutamatergic, Phox2b-expressing neurons located in the retrotrapezoid nucleus (RTN) are strong candidates. However, a direct demonstration that RTN neurons are intrinsically sensitive to CO2/H(+), required for designation as a chemosensor, has been lacking. To address this, we tested the pH sensitivity of RTN neurons that were acutely dissociated from two lines of Phox2b-GFP BAC transgenic mice. All GFP-labeled cells assayed by reverse transcriptase-PCR (n = 40) were Phox2b+, VGlut2+, TH-, and ChAT-, the neurochemical phenotype previously defined for chemosensitive RTN neurons in vivo. We found that most dissociated RTN neurons from both lines of mice were CO2/H(+)-sensitive (∼79%), with discharge increasing during acidification and decreasing during alkalization. The pH-sensitive cells could be grouped into two populations characterized by similar pH sensitivity but different basal firing rates, as previously observed in recordings from GFP-labeled RTN neurons in slice preparations. In conclusion, these data indicate that RTN neurons are inherently pH-sensitive, as expected for a respiratory chemoreceptor.
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