1
|
Postnatal changes in O2 and CO2 sensitivity in rodents. Respir Physiol Neurobiol 2020; 272:103313. [DOI: 10.1016/j.resp.2019.103313] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2019] [Revised: 08/31/2019] [Accepted: 10/02/2019] [Indexed: 02/06/2023]
|
2
|
Furuya WI, Bassi M, Menani JV, Colombari E, Zoccal DB, Colombari DSA. Modulation of hypercapnic respiratory response by cholinergic transmission in the commissural nucleus of the solitary tract. Pflugers Arch 2019; 472:49-60. [PMID: 31884528 DOI: 10.1007/s00424-019-02341-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Revised: 11/28/2019] [Accepted: 12/11/2019] [Indexed: 01/16/2023]
Abstract
The nucleus of the solitary tract (NTS) is an important area of the brainstem that receives and integrates afferent cardiorespiratory sensorial information, including those from arterial chemoreceptors and baroreceptors. It was described that acetylcholine (ACh) in the commissural subnucleus of the NTS (cNTS) promotes an increase in the phrenic nerve activity (PNA) and antagonism of nicotinic receptors in the same region reduces the magnitude of tachypneic response to peripheral chemoreceptor stimulation, suggesting a functional role of cholinergic transmission within the cNTS in the chemosensory control of respiratory activity. In the present study, we investigated whether cholinergic receptor antagonism in the cNTS modifies the sympathetic and respiratory reflex responses to hypercapnia. Using an arterially perfused in situ preparation of juvenile male Holtzman rats, we found that the nicotinic antagonist (mecamylamine, 5 mM), but not the muscarinic antagonist (atropine, 5 mM), into the cNTS attenuated the hypercapnia-induced increase of hypoglossal activity. Furthermore, mecamylamine in the cNTS potentiated the generation of late-expiratory (late-E) activity in abdominal nerve induced by hypercapnia. None of the cholinergic antagonists microinjected in the cNTS changed either the sympathetic or the phrenic nerve responses to hypercapnia. Our data provide evidence for the role of cholinergic transmission in the cNTS, acting on nicotinic receptors, modulating the hypoglossal and abdominal responses to hypercapnia.
Collapse
Affiliation(s)
- Werner I Furuya
- Department of Physiology and Pathology, School of Dentistry, UNESP - São Paulo State University, Araraquara, SP, Brazil
| | - Mirian Bassi
- Department of Physiology and Pathology, School of Dentistry, UNESP - São Paulo State University, Araraquara, SP, Brazil
| | - José V Menani
- Department of Physiology and Pathology, School of Dentistry, UNESP - São Paulo State University, Araraquara, SP, Brazil
| | - Eduardo Colombari
- Department of Physiology and Pathology, School of Dentistry, UNESP - São Paulo State University, Araraquara, SP, Brazil
| | - Daniel B Zoccal
- Department of Physiology and Pathology, School of Dentistry, UNESP - São Paulo State University, Araraquara, SP, Brazil
| | - Débora S A Colombari
- Department of Physiology and Pathology, School of Dentistry, UNESP - São Paulo State University, Araraquara, SP, Brazil.
| |
Collapse
|
3
|
Lumb KJ, Schneider JM, Ibrahim T, Rigaux A, Hasan SU. Afferent neural feedback overrides the modulating effects of arousal, hypercapnia and hypoxaemia on neonatal cardiorespiratory control. J Physiol 2018; 596:6009-6019. [PMID: 29676798 PMCID: PMC6265552 DOI: 10.1113/jp275682] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 04/13/2018] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Evidence obtained at whole animal, organ-system, and cellular and molecular levels suggests that afferent volume feedback is critical for the establishment of adequate ventilation at birth. As a result of the irreversible nature of the vagal ablation studies performed to date, it was difficult to quantify the roles of afferent volume input, arousal and changes in blood gas tensions on neonatal respiratory control. During reversible perineural vagal block, profound apnoeas and hypoxaemia and hypercarbia were observed, necessitating the termination of perineural blockade. Respiratory depression and apnoeas were independent of sleep state. We demonstrate that profound apnoeas and life-threatening respiratory failure in vagally denervated animals do not result from a lack of arousal or hypoxaemia. A change in sleep state and concomitant respiratory depression result from a lack of afferent volume feedback, which appears to be critical for the maintenance of normal breathing patterns and adequate gas exchange during the early postnatal period. ABSTRACT Afferent volume feedback plays a vital role in neonatal respiratory control. Mechanisms for the profound respiratory depression and life-threatening apnoeas observed in vagally denervated neonatal animals remain unclear. We investigated the roles of sleep states, hypoxic-hypercapnia and afferent volume feedback on respiratory depression using reversible perineural vagal block during the early postnatal period. Seven lambs were instrumented during the first 48 h of life to record/analyse sleep states, diaphragmatic electromyograph, arterial blood gas tensions, systemic arterial blood pressure and rectal temperature. Perineural cuffs were placed around the vagi to attain reversible blockade. Postoperatively, during the awake state, both vagi were blocked using 2% xylocaine for up to 30 min. Compared to baseline values, pHa , P a o 2 and S a o 2 decreased and P ac o 2 increased during perineural blockade (P < 0.05). Four of seven animals exhibited apnoeas of ≥20 s requiring the immediate termination of perineural blockade. Breathing rates decreased from the baseline value of 53 ± 12 to 24 ± 20 breaths min-1 during blockade despite an increased P ac o 2 (P < 0.001). Following blockade, breathing patterns returned to baseline values despite marked hypocapnia ( P ac o 2 33 ± 3 torr; P = 0.03). Respiratory depression and apnoeas were independent of sleep states. The present study provides the much needed physiological evidence indicating that profound apnoeas and life-threatening respiratory failure in vagally denervated animals do not result from a lack of arousal or hypoxaemia. Rather, a change in sleep state and concomitant respiratory depression result from a lack of afferent volume feedback, which appears to be critical for the maintenance of normal breathing patterns and adequate gas exchange during the early postnatal period.
Collapse
Affiliation(s)
- Kathleen J. Lumb
- Department of PediatricsAlberta Children's Hospital Research Institute, Faculty of MedicineUniversity of CalgaryCalgaryAlbertaCanada
| | - Jennifer M. Schneider
- Department of PediatricsAlberta Children's Hospital Research Institute, Faculty of MedicineUniversity of CalgaryCalgaryAlbertaCanada
| | - Thowfique Ibrahim
- Department of PediatricsAlberta Children's Hospital Research Institute, Faculty of MedicineUniversity of CalgaryCalgaryAlbertaCanada
| | - Anita Rigaux
- Department of PediatricsAlberta Children's Hospital Research Institute, Faculty of MedicineUniversity of CalgaryCalgaryAlbertaCanada
| | - Shabih U. Hasan
- Department of PediatricsAlberta Children's Hospital Research Institute, Faculty of MedicineUniversity of CalgaryCalgaryAlbertaCanada
| |
Collapse
|
4
|
Tachikawa S, Nakayama K, Nakamura S, Mochizuki A, Iijima T, Inoue T. Coordinated Respiratory Motor Activity in Nerves Innervating the Upper Airway Muscles in Rats. PLoS One 2016; 11:e0166436. [PMID: 27832132 PMCID: PMC5104329 DOI: 10.1371/journal.pone.0166436] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 10/28/2016] [Indexed: 12/02/2022] Open
Abstract
Maintaining the patency of the upper airway during breathing is of vital importance. The activity of various muscles is related to the patency of the upper airway. In the present study, we examined the respiratory motor activity in the efferent nerves innervating the upper airway muscles to determine the movements of the upper airway during respiration under normocapnic conditions (pH = 7.4) and in hypercapnic acidosis (pH = 7.2). Experiments were performed on arterially perfused decerebrate rats aged between postnatal days 21–35. We recorded the efferent nerve activity in a branch of the cervical spinal nerve innervating the infrahyoid muscles (CN), the hypoglossal nerve (HGN), the external branch of the superior laryngeal nerve (SLN), and the recurrent laryngeal nerve (RLN) with the phrenic nerve (PN). Inspiratory nerve discharges were observed in all these nerves under normocapnic conditions. The onset of inspiratory discharges in the CN and HGN was slightly prior to those in the SLN and RLN. When the CO2 concentration in the perfusate was increased from 5% to 8% to prepare for hypercapnic acidosis, the peak amplitudes of the inspiratory discharges in all the recorded nerves were increased. Moreover, hypercapnic acidosis induced pre-inspiratory discharges in the CN, HGN, SLN, and RLN. The onset of pre-inspiratory discharges in the CN, HGN, and SLN was prior to that of discharges in the RLN. These results suggest that the securing of the airway that occurs a certain time before dilation of the glottis may facilitate ventilation and improve hypercapnic acidosis.
Collapse
Affiliation(s)
- Satoshi Tachikawa
- Department of Oral Physiology, Showa University School of Dentistry, Shinagawa-ku, Tokyo 142–8555, Japan
- Department of Perioperative Medicine, Division of Anesthesiology, Showa University School of Dentistry, Oota-ku, Tokyo 145–8515, Japan
| | - Kiyomi Nakayama
- Department of Oral Physiology, Showa University School of Dentistry, Shinagawa-ku, Tokyo 142–8555, Japan
- * E-mail:
| | - Shiro Nakamura
- Department of Oral Physiology, Showa University School of Dentistry, Shinagawa-ku, Tokyo 142–8555, Japan
| | - Ayako Mochizuki
- Department of Oral Physiology, Showa University School of Dentistry, Shinagawa-ku, Tokyo 142–8555, Japan
| | - Takehiko Iijima
- Department of Perioperative Medicine, Division of Anesthesiology, Showa University School of Dentistry, Oota-ku, Tokyo 145–8515, Japan
| | - Tomio Inoue
- Department of Oral Physiology, Showa University School of Dentistry, Shinagawa-ku, Tokyo 142–8555, Japan
| |
Collapse
|
5
|
Dzal YA, Jenkin SEM, Lague SL, Reichert MN, York JM, Pamenter ME. Oxygen in demand: How oxygen has shaped vertebrate physiology. Comp Biochem Physiol A Mol Integr Physiol 2015; 186:4-26. [PMID: 25698654 DOI: 10.1016/j.cbpa.2014.10.029] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2014] [Revised: 10/07/2014] [Accepted: 10/10/2014] [Indexed: 10/24/2022]
Abstract
In response to varying environmental and physiological challenges, vertebrates have evolved complex and often overlapping systems. These systems detect changes in environmental oxygen availability and respond by increasing oxygen supply to the tissues and/or by decreasing oxygen demand at the cellular level. This suite of responses is termed the oxygen transport cascade and is comprised of several components. These components include 1) chemosensory detectors that sense changes in oxygen, carbon dioxide, and pH in the blood, and initiate changes in 2) ventilation and 3) cardiac work, thereby altering the rate of oxygen delivery to, and carbon dioxide clearance from, the tissues. In addition, changes in 4) cellular and systemic metabolism alters tissue-level metabolic demand. Thus the need for oxygen can be managed locally when increasing oxygen supply is not sufficient or possible. Together, these mechanisms provide a spectrum of responses that facilitate the maintenance of systemic oxygen homeostasis in the face of environmental hypoxia or physiological oxygen depletion (i.e. due to exercise or disease). Bill Milsom has dedicated his career to the study of these responses across phylogenies, repeatedly demonstrating the power of applying the comparative approach to physiological questions. The focus of this review is to discuss the anatomy, signalling pathways, and mechanics of each step of the oxygen transport cascade from the perspective of a Milsomite. That is, by taking into account the developmental, physiological, and evolutionary components of questions related to oxygen transport. We also highlight examples of some of the remarkable species that have captured Bill's attention through their unique adaptations in multiple components of the oxygen transport cascade, which allow them to achieve astounding physiological feats. Bill's research examining the oxygen transport cascade has provided important insight and leadership to the study of the diverse suite of adaptations that maintain cellular oxygen content across vertebrate taxa, which underscores the value of the comparative approach to the study of physiological systems.
Collapse
Affiliation(s)
- Yvonne A Dzal
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Sarah E M Jenkin
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Sabine L Lague
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Michelle N Reichert
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Julia M York
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Matthew E Pamenter
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
| |
Collapse
|
6
|
Abstract
The evolution of the aspiration pump seen in tetrapod vertebrates from the buccal-pharyngeal force pump seen in air breathing fish and amphibians appears to have first involved the production of active expiration. Active inspiration arose later. This appears to have involved reconfiguration of a parafacial oscillator (now the parafacial respiratory group/retrotrapezoid nucleus (pFRG/RTN)) to produce active expiration, followed by reconfiguration of a paravagal oscillator (now the preBötC) to produce active inspiration. In the ancestral breathing cycle, inspiration follows expiration, which is in turn followed by glottal closure and breath holding. When both rhythms are expressed, as they are in reptiles and birds, and mammals under conditions of elevated respiratory drive, the pFRG/RTN appears to initiate the respiratory cycle. We propose that the coordinated output of this system is a ventilation cycle characterized by four phases. In reptiles, these consist of active inspiration (I), glottal closure (E1), a pause (an apnea or breath hold) (E2), and an active expiration (E3) that initiates the next cycle. In mammals under resting conditions, active expiration (E3) is suppressed and inspiration (I) is followed by airway constriction and diaphragmatic braking (E1) (rather than glottal closure) and a short pause at end-expiration (E2). As respiratory drive increases in mammals, expiratory muscle activity appears. Frequently, it first appears immediately preceding inspiration (E3) just as it does in reptiles. It can also appear in E1, however, and it is not yet clear what mechanisms underlie when and where in the cycle it appears. This may reflect whether the active expiration is recruited to enhance tidal volume, increase breathing frequency, or both.
Collapse
Affiliation(s)
- Sarah E M Jenkin
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - William K Milsom
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada.
| |
Collapse
|
7
|
Morris KF, Nuding SC, Segers LS, Baekey DM, Shannon R, Lindsey BG, Dick TE. Respiratory and Mayer wave-related discharge patterns of raphé and pontine neurons change with vagotomy. J Appl Physiol (1985) 2010; 109:189-202. [PMID: 20360432 DOI: 10.1152/japplphysiol.01324.2009] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previous models have attributed changes in respiratory modulation of pontine neurons after vagotomy to a loss of pulmonary stretch receptor "gating" of an efference copy of inspiratory drive. Recently, our group confirmed that pontine neurons change firing patterns and become more respiratory modulated after vagotomy, although average peak and mean firing rates of the sample did not increase (Dick et al., J Physiol 586: 4265-4282, 2008). Because raphé neurons are also elements of the brain stem respiratory network, we tested the hypotheses that after vagotomy raphé neurons have increased respiratory modulation and that alterations in their firing patterns are similar to those seen for pontine neurons during withheld lung inflation. Raphé and pontine neurons were recorded simultaneously before and after vagotomy in decerebrated cats. Before vagotomy, 14% of 95 raphé neurons had increased activity during single respiratory cycles prolonged by withholding lung inflation; 13% exhibited decreased activity. After vagotomy, the average index of respiratory modulation (eta(2)) increased (0.05 +/- 0.10 to 0.12 +/- 0.18 SD; Student's paired t-test, P < 0.01). Time series and frequency domain analyses identified pontine and raphé neuron firing rate modulations with a 0.1-Hz rhythm coherent with blood pressure Mayer waves. These "Mayer wave-related oscillations" (MWROs) were coupled with central respiratory drive and became synchronized with the central respiratory rhythm after vagotomy (7 of 10 animals). Cross-correlation analysis identified functional connectivity in 52 of 360 pairs of neurons with MWROs. Collectively, the results suggest that a distributed network participates in the generation of MWROs and in the coordination of respiratory and vasomotor rhythms.
Collapse
Affiliation(s)
- K F Morris
- Department of Molecular Pharmacology and Physiology, School of Biomedical Sciences, College of Medicine, University of South Florida, 12901 Bruce B. Downs Blvd., Tampa, FL 33612-4799, USA.
| | | | | | | | | | | | | |
Collapse
|
8
|
Abdala APL, Rybak IA, Smith JC, Paton JFR. Abdominal expiratory activity in the rat brainstem-spinal cord in situ: patterns, origins and implications for respiratory rhythm generation. J Physiol 2009; 587:3539-59. [PMID: 19491247 DOI: 10.1113/jphysiol.2008.167502] [Citation(s) in RCA: 154] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
We studied respiratory neural activity generated during expiration. Motoneuronal activity was recorded simultaneously from abdominal (AbN), phrenic (PN), hypoglossal (HN) and central vagus nerves from neonatal and juvenile rats in situ. During eupnoeic activity, low-amplitude post-inspiratory (post-I) discharge was only present in AbN motor outflow. Expression of AbN late-expiratory (late-E) activity, preceding PN bursts, occurred during hypercapnia. Biphasic expiratory (biphasic-E) activity with pre-inspiratory (pre-I) and post-I discharges occurred only during eucapnic anoxia or hypercapnic anoxia. Late-E activity generated during hypercapnia (7-10% CO(2)) was abolished with pontine transections or chemical suppression of retrotrapezoid nucleus/ventrolateral parafacial (RTN/vlPF). AbN late-E activity during hypercapnia is coupled with augmented pre-I discharge in HN, truncated PN burst, and was quiescent during inspiration. Our data suggest that the pons provides a necessary excitatory drive to an additional neural oscillatory mechanism that is only activated under conditions of high respiratory drive to generate late-E activity destined for AbN motoneurones. This mechanism may arise from neurons located in the RTN/vlPF or the latter may relay late-E activity generated elsewhere. We hypothesize that this oscillatory mechanism is not a necessary component of the respiratory central pattern generator but constitutes a defensive mechanism activated under critical metabolic conditions to provide forced expiration and reduced upper airway resistance simultaneously. Possible interactions of this oscillator with components of the brainstem respiratory network are discussed.
Collapse
Affiliation(s)
- A P L Abdala
- Department of Physiology and Pharmacology, Bristol Heart Institute, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
| | | | | | | |
Collapse
|
9
|
Harris MB, St-John WM. Phasic pulmonary stretch receptor feedback modulates both eupnea and gasping in an in situ rat preparation. Am J Physiol Regul Integr Comp Physiol 2005; 289:R450-R455. [PMID: 15831763 DOI: 10.1152/ajpregu.00750.2004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The perfused in situ juvenile rat preparation produces patterns of phrenic discharge comparable to eupnea and gasping in vivo. These ventilatory patterns differ in multiple aspects, including most prominently the rate of rise of inspiratory activity. Although we have recently demonstrated that both eupnea and gasping are similarly modulated by a Hering-Breuer expiratory-promoting reflex to tonic pulmonary stretch, it has generally been assumed that gasping was unresponsive to afferent stimuli from pulmonary stretch receptors. In the present study, we recorded eupneic and gasplike efferent activity of the phrenic nerve in the in situ juvenile rat perfused brain stem preparation, with and without phrenic-triggered phasic pulmonary inflation. We tested the hypothesis that phasic pulmonary inflation produces reflex responses in situ akin to those in vivo and that both eupnea and gasping are similarly modulated by phasic pulmonary stretch. In eupnea, we found that phasic pulmonary inflation decreases inspiratory burst duration and the period of expiration, thus increasing burst frequency of the phrenic neurogram. Phasic pulmonary inflation also decreases the duration of expiration and increases the burst frequency during gasping. Bilateral vagotomy eliminated these changes. We conclude that the neural substrate mediating the Hering-Breuer reflex is retained in the in situ preparation and that the brain stem circuitry generating the respiratory patterns respond to phasic activation of pulmonary stretch receptors in both eupnea and gasping. These findings support the homology of eupneic phrenic discharge patterns in the reduced in situ preparation and eupnea in vivo and disprove the common supposition that gasping is insensitive to vagal afferent feedback from pulmonary stretch receptor mechanisms.
Collapse
Affiliation(s)
- Michael B Harris
- Institute of Arctic Biology, Irving I, University of Alaska-Fairbanks, Fairbanks, AK 99775-7000, USA.
| | | |
Collapse
|
10
|
Harris MB, Milsom WK. Apneusis follows disruption of NMDA-type glutamate receptors in vagotomized ground squirrels. Respir Physiol Neurobiol 2003; 134:191-207. [PMID: 12660099 DOI: 10.1016/s1569-9048(02)00223-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The influences of N-methyl-D-aspartate (NMDA) type glutamate receptor antagonism, by (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5,10-imine maleate (MK-801), on breathing pattern and ventilatory chemoresponses, were assessed in anaesthetized vagotomized spontaneously breathing golden-mantled ground squirrels, Spermophilus lateralis. MK-801 was administered by either bilateral pressure micro-injection into a region of the rostral dorsolateral pons, containing the medial and lateral Parabrachial and Kölliker-Fuse nuclei (the Parabrachial complex, PbC), or by systemic injection. Both treatments induced apneusis. These data indicate that functional NMDA receptor-mediated processes located within the PbC terminate inspiration and actively prevent apneusis in vagotomized ground squirrels. Although both hypercapnia and hypoxia stimulated breathing during the apneusis, the responses were generally slight. The breathing frequency component of the hypercapnic ventilatory response was completely eliminated supporting the hypothesis that the PbC is an integral component of the control network for CO(2) chemoreflex responses. Differences in the results of systemic versus PbC MK-801 illustrate that NMDA receptor-mediated processes outside the PbC do influence ventilation. Our data also show that such processes outside the PbC lengthen both inspiration and expiration in this species, slowing ventilation, and are necessary for the expression of the hypoxic ventilatory response.
Collapse
Affiliation(s)
- Michael B Harris
- Department of Physiology, Dartmouth Hitchcock Medical Center, Dartmouth College, Borwell Building Hinman box, 7700, One Medical Center Drive, Lebanon, NH 03756, USA.
| | | |
Collapse
|
11
|
Lalani S, Remmers JE, MacKinnon Y, Ford GT, Hasan SU. Hypoxemia and low Crs in vagally denervated lambs result from reduced lung volume and not pulmonary edema. J Appl Physiol (1985) 2002; 93:601-10. [PMID: 12133870 DOI: 10.1152/japplphysiol.00949.2001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Vagal denervation performed in the intrathoracic region in newborn lambs leads to hypoxemia and decreased respiratory system compliance (Crs), which could result from atelectasis and/or pulmonary edema. The objective of the present study was to quantify the relative roles of alveolar derecruitment and pulmonary edema as underlying cause(s) of respiratory failure. Vagal denervation was performed in the intrathoracic region and below the recurrent laryngeal nerves in six newborn lambs within 24 h of birth, whereas six were sham operated. Pre- and postinflation Crs was measured to investigate the presence of alveolar derecruitment. Pulmonary edema was assessed with lung wet-dry-to-wet and lung tissue wet-to-dry ratios, total protein, and FITC-BSA recovery in lung tissue and bronchoalveolar lavage. Compared with that in the sham-operated animals, Crs was significantly lower in vagally denervated animals. However, postinflation, pulmonary system compliance obtained by quasi-static lung inflation and deflation to 30 cmH2O showed no significant difference between the sham-operated and denervated lambs. The lung wet-dry-to-wet and lung tissue wet-to-dry ratios, total protein, and FITC-BSA recovery in lung tissue and bronchoalveolar lavage were similar in denervated and sham-operated groups. We provide evidence that reduced lung volume and not pulmonary edema is associated with intrathoracic vagal denervation and is the likely underlying mechanism for hypoxemia and low Crs.
Collapse
Affiliation(s)
- Salim Lalani
- Department of Pediatrics, Respiratory Research Group, Faculty of Medicine, The University of Calgary, Calgary, Alberta, Canada T2N 4N1
| | | | | | | | | |
Collapse
|
12
|
Lalani S, Remmers JE, Hasan SU. Breathing patterns, pulmonary mechanics and gas exchange: role of vagal innervation in neonatal lamb. Exp Physiol 2001; 86:803-10. [PMID: 11698977 DOI: 10.1111/j.1469-445x.2001.tb00048.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- S Lalani
- Department of Paediatrics, Faculty of Medicine, The University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada.
| | | | | |
Collapse
|
13
|
Harris MB, Milsom WK. The influence of NMDA receptor-mediated processes on breathing pattern in ground squirrels. RESPIRATION PHYSIOLOGY 2001; 125:181-97. [PMID: 11282386 DOI: 10.1016/s0034-5687(00)00219-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The effects of blockade of N-methyl-D-aspartate (NMDA) type glutamate receptors by a non-competitive antagonist (MK-801) on cortical arousal, breathing pattern and ventilatory responses to hypoxia (10% O2 in N2) and hypercapnia (5% CO2 in air) were assessed in anesthetized (urethane) and unanesthetized golden-mantled ground squirrels (Spermophilus lateralis). Intra-cerebroventricular administration of MK-801 did not alter ventilation during wakefulness, although it did alter the pattern (breathing frequency and tidal volume components) of the hypercapnic ventilatory response, and suppressed the ventilatory response to hypoxia. Animals did not sleep following treatment with MK-801, and intravenous administration of MK-801 prevented expression of the sleep-like state normally observed in anesthetized animals. In anesthetized animals MK-801 elevated breathing frequency to levels observed without anesthesia, and suppressed the hypoxic ventilatory response. These data suggest that NMDA-type glutamatergic receptor-mediated processes influence cortical arousal and facilitate depression of breathing frequency during anesthesia and the hypoxic ventilatory response. Such processes are not essential for the hypercapnic ventilatory response.
Collapse
Affiliation(s)
- M B Harris
- Department of Zoology, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.
| | | |
Collapse
|