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Cinelli E, Iovino L, Bongianni F, Pantaleo T, Mutolo D. Essential Role of the cVRG in the Generation of Both the Expiratory and Inspiratory Components of the Cough Reflex. Physiol Res 2020; 69:S19-S27. [PMID: 32228008 DOI: 10.33549/physiolres.934396] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
As stated by Korpáš and Tomori (1979), cough is the most important airway protective reflex which provides airway defensive responses to nociceptive stimuli. They recognized that active expiratory efforts, due to the activation of caudal ventral respiratory group (cVRG) expiratory premotoneurons, are the prominent component of coughs. Here, we discuss data suggesting that neurons located in the cVRG have an essential role in the generation of both the inspiratory and expiratory components of the cough reflex. Some lines of evidence indicate that cVRG expiratory neurons, when strongly activated, may subserve the alternation of inspiratory and expiratory cough bursts, possibly owing to the presence of axon collaterals. Of note, experimental findings such as blockade or impairment of glutamatergic transmission to the cVRG neurons lead to the view that neurons located in the cVRG are crucial for the production of the complete cough motor pattern. The involvement of bulbospinal expiratory neurons seems unlikely since their activation affects differentially expiratory and inspiratory muscles, while their blockade does not affect baseline inspiratory activity. Thus, other types of cVRG neurons with their medullary projections should have a role and possibly contribute to the fine tuning of the intensity of inspiratory and expiratory efforts.
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Affiliation(s)
- E Cinelli
- Department of Experimental and Clinical Medicine, Physiological Sciences Section, University of Florence, Florence, Italy.
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2
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Brainstem mechanisms underlying the cough reflex and its regulation. Respir Physiol Neurobiol 2017; 243:60-76. [DOI: 10.1016/j.resp.2017.05.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 05/16/2017] [Accepted: 05/17/2017] [Indexed: 12/12/2022]
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Cinelli E, Mutolo D, Contini M, Pantaleo T, Bongianni F. Inhibitory control of ascending glutamatergic projections to the lamprey respiratory rhythm generator. Neuroscience 2016; 326:126-140. [PMID: 27058146 DOI: 10.1016/j.neuroscience.2016.03.063] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Revised: 03/29/2016] [Accepted: 03/30/2016] [Indexed: 10/22/2022]
Abstract
Neurons within the vagal motoneuron region of the lamprey have been shown to modulate respiratory activity via ascending excitatory projections to the paratrigeminal respiratory group (pTRG), the proposed respiratory rhythm generator. The present study was performed on in vitro brainstem preparations of the lamprey to provide a characterization of ascending projections within the whole respiratory motoneuron column with regard to the distribution of neurons projecting to the pTRG and related neurochemical markers. Injections of Neurobiotin were performed into the pTRG and the presence of glutamate, GABA and glycine immunoreactivity was investigated by double-labeling experiments. Interestingly, retrogradely labeled neurons were found not only in the vagal region, but also in the facial and glossopharyngeal motoneuron regions. They were also present within the sensory octavolateral area (OLA). The results show for the first time that neurons projecting to the pTRG are immunoreactive for glutamate, surrounded by GABA-immunoreactive structures and associated with the presence of glycinergic cells. Consistently, GABAA or glycine receptor blockade within the investigated regions increased the respiratory frequency. Furthermore, microinjections of agonists and antagonists of ionotropic glutamate receptors and of the GABAA receptor agonist muscimol showed that OLA neurons do not contribute to respiratory rhythm generation. The results provide evidence that glutamatergic ascending pathways to the pTRG are subject to a potent inhibitory control and suggest that disinhibition is one important mechanism subserving their function. The general characteristics of inhibitory control involved in rhythmic activities, such as respiration, appear to be highly conserved throughout vertebrate evolution.
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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, 50134 Firenze, Italy
| | - Donatella Mutolo
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università degli Studi di Firenze, Viale G.B. Morgagni 63, 50134 Firenze, Italy
| | - Massimo Contini
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università degli Studi di Firenze, Viale G.B. Morgagni 63, 50134 Firenze, Italy
| | - Tito Pantaleo
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università degli Studi di Firenze, Viale G.B. Morgagni 63, 50134 Firenze, Italy
| | - Fulvia Bongianni
- Dipartimento di Medicina Sperimentale e Clinica, Sezione Scienze Fisiologiche, Università degli Studi di Firenze, Viale G.B. Morgagni 63, 50134 Firenze, Italy.
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Andrews CG, Pagliardini S. Expiratory activation of abdominal muscle is associated with improved respiratory stability and an increase in minute ventilation in REM epochs of adult rats. J Appl Physiol (1985) 2015; 119:968-74. [PMID: 26338455 DOI: 10.1152/japplphysiol.00420.2015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Accepted: 09/01/2015] [Indexed: 01/08/2023] Open
Abstract
Breathing is more vulnerable to apneas and irregular breathing patterns during rapid eye movement (REM) sleep in both humans and rodents. We previously reported that robust and recurrent recruitment of expiratory abdominal (ABD) muscle activity is present in rats during REM epochs despite ongoing REM-induced muscle atonia in skeletal musculature. To develop a further understanding of the characteristics of ABD recruitment during REM epochs and their relationship with breathing patterns and irregularities, we sought to compare REM epochs that displayed ABD muscle recruitment with those that did not, within the same rats. Specifically, we investigated respiratory characteristics that preceded and followed recruitment. We hypothesized that ABD muscle recruitment would be likely to occur following respiratory irregularities and would subsequently contribute to respiratory stability and the maintenance of good ventilation following recruitment. Our data demonstrate that epochs of REM sleep containing ABD recruitments (REM(ABD+)) were characterized by increased respiratory rate variability and increased presence of spontaneous brief central apneas. Within these epochs, respiratory events that displayed ABD muscle activation were preceded by periods of increased respiratory rate variability. Onset of ABD muscle activity increased tidal volume, amplitude of diaphragmatic contractions, and minute ventilation compared with the periods preceding ABD muscle activation. These results show that expiratory muscle activity is more likely recruited when respiration is irregular and its recruitment is subsequently associated with an increase in minute ventilation and a more regular respiratory rhythm.
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Affiliation(s)
- Colin G Andrews
- Department of Physiology, Women and Children's Health Research Institute, Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Silvia Pagliardini
- Department of Physiology, Women and Children's Health Research Institute, Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
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Cinelli E, Bongianni F, Pantaleo T, Mutolo D. Modulation of the cough reflex by GABA(A) receptors in the caudal ventral respiratory group of the rabbit. Front Physiol 2012; 3:403. [PMID: 23087651 PMCID: PMC3475209 DOI: 10.3389/fphys.2012.00403] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Accepted: 10/01/2012] [Indexed: 11/16/2022] Open
Abstract
We have previously shown that the caudal ventral respiratory group (cVRG) is a possible site of action of some antitussive drugs and plays a crucial role in determining both the expiratory and inspiratory components of the cough motor pattern. In addition, it has been reported that medullary expiratory neurons of the cVRG are subject to potent GABAergic gain modulation. This study was devoted to investigate the role of cVRG GABAA receptors in the control of baseline respiratory activity and cough responses to mechanical and chemical (citric acid) stimulation of the tracheobronchial tree. To this purpose, bilateral microinjections (30–50 nl) of bicuculline or muscimol were performed into the cVRG of pentobarbital sodium-anesthetized, spontaneously breathing rabbits. Bicuculline (1 mM) increased peak abdominal activity and respiratory frequency due to decreases in TE. Cough responses were potentiated mainly owing to increases in the cough number. The recovery was observed within ~2 h. On the contrary, muscimol (0.3 mM) abolished abdominal activity and decreased respiratory frequency due to increases in TE. In addition, cough responses were progressively reduced and completely suppressed within ~20 min. Partial recovery of cough responses was achieved after ~3 h or within ~5 min following bicuculline microinjections at the same locations. The sneeze reflex induced by mechanical stimulation of the nasal mucosa persisted following bicuculline and muscimol microinjections. However, the number and intensity of expiratory thrusts were enhanced by bicuculline and suppressed by muscimol. The results provide evidence that a potent GABAA-mediated inhibitory modulation is exerted at the level of the cVRG not only on respiratory activity, but also on cough and sneeze reflex responses.
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Affiliation(s)
- Elenia Cinelli
- Dipartimento di Scienze Fisiologiche, Università degli Studi di Firenze Firenze, Italy
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Jones SE, Saad M, Lewis DI, Subramanian HH, Dutschmann M. The nucleus retroambiguus as possible site for inspiratory rhythm generation caudal to obex. Respir Physiol Neurobiol 2012; 180:305-10. [PMID: 22210466 PMCID: PMC3282833 DOI: 10.1016/j.resp.2011.12.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2011] [Revised: 12/14/2011] [Accepted: 12/14/2011] [Indexed: 11/17/2022]
Abstract
We investigated whether spinalized animals can produce inspiratory rhythm. We recorded spinal inspiratory phrenic (PNA) and cranial inspiratory hypoglossal (HNA) nerve activity in the perfused brainstem preparation of rat. Complete transverse transections were performed at 1.5 (pyramidal decussation) or 2mm (first cervical spinal segment) caudal to obex. Excitatory drive was enhanced by either extracellular potassium, hypercapnia or by stimulating arterial chemoreceptors. Caudal transections immediately eliminated descending network drive for PNA, while the cranial inspiratory HNA remained unaffected. After transection, PNA bursting remained sporadic even during enhanced excitatory drive. This implies, cervical spinal circuits lack intrinsic rhythmogenic capacity. Rostral transections also abolished PNA immediately. However, HNA also progressively lost its amplitude and rhythm. Chemoreceptor activation only triggered tonic, non-rhythmic HNA. Thus the integrity of ponto-medullary circuitry was maintained. Our results suggest that an area overlapping the caudal nucleus retroambiguus provides critical ascending input to the ponto-medullary respiratory network for inspiratory rhythm generation.
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Affiliation(s)
- Sarah E. Jones
- Institute of Membrane and Systems Biology, Garstang Building, University of Leeds, Leeds LS2 9JT
| | - Mona Saad
- Institute of Membrane and Systems Biology, Garstang Building, University of Leeds, Leeds LS2 9JT
| | - David I. Lewis
- Institute of Membrane and Systems Biology, Garstang Building, University of Leeds, Leeds LS2 9JT
| | - Hari H. Subramanian
- Florey Neurosciences Institutes, Gate 11, Royal Parade, University of Melbourne, Victoria, 3052, Australia
| | - Mathias Dutschmann
- Institute of Membrane and Systems Biology, Garstang Building, University of Leeds, Leeds LS2 9JT
- Florey Neurosciences Institutes, Gate 11, Royal Parade, University of Melbourne, Victoria, 3052, Australia
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Mutolo D, Bongianni F, Cinelli E, Pantaleo T. Depression of cough reflex by microinjections of antitussive agents into caudal ventral respiratory group of the rabbit. J Appl Physiol (1985) 2010; 109:1002-10. [PMID: 20651222 DOI: 10.1152/japplphysiol.00406.2010] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
We have previously shown that the caudal nucleus tractus solitarii is a site of action of some antitussive drugs and that the caudal ventral respiratory group (cVRG) region has a crucial role in determining both the expiratory and inspiratory components of the cough motor pattern. These findings led us to suggest that the cVRG region, and possibly other neural substrates involved in cough regulation, may be sites of action of antitussive drugs. To address this issue, we investigated changes in baseline respiratory activity and cough responses to tracheobronchial mechanical stimulation following microinjections (30-50 nl) of some antitussive drugs into the cVRG of pentobarbital-anesthetized, spontaneously breathing rabbits. [D-Ala(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin (DAMGO) and baclofen at the lower concentrations (0.5 mM and 0.1 mM, respectively) decreased cough number, peak abdominal activity, and peak tracheal pressure and increased cough-related total cycle duration (Tt). At the higher concentrations (5 mM and 1 mM, respectively), both drugs abolished the cough reflex. DAMGO and baclofen also affected baseline respiratory activity. Both drugs reduced peak abdominal activity, while only DAMGO increased Tt, owing to increases in expiratory time. The neurokinin-1 (NK(1)) receptor antagonist CP-99,994 (10 mM) decreased cough number, peak abdominal activity, and peak tracheal pressure, without affecting baseline respiration. The NK(2) receptor antagonist MEN 10376 (5 mM) had no effect. The results indicate that the cVRG is a site of action of some antitussive agents and support the hypothesis that several neural substrates involved in cough regulation may share this characteristic.
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Affiliation(s)
- Donatella Mutolo
- Dipartimento di Scienze Fisiologiche, Viale G. B. Morgagni 63, 50134 Florence, Italy
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Poliacek I, Wang C, Corrie LWC, Rose MJ, Bolser DC. Microinjection of codeine into the region of the caudal ventral respiratory column suppresses cough in anesthetized cats. J Appl Physiol (1985) 2010; 108:858-65. [PMID: 20093669 DOI: 10.1152/japplphysiol.00783.2009] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We investigated the influence of microinjection of codeine into the caudal ventral respiratory column (cVRC) on the cough reflex. Experiments were performed on 36 anesthetized spontaneously breathing cats. Electromyograms (EMGs) were recorded bilaterally from inspiratory parasternal and expiratory transversus abdominis (ABD) muscles and unilaterally from laryngeal posterior cricoarytenoid and thyroarytenoid muscles. Repetitive coughing was elicited by mechanical stimulation of the intrathoracic airways. The unilateral microinjection of codeine (3.3 mM, 20-32 nl) in the cVRC reduced cough number by 29% (P < 0.01) and expiratory cough amplitudes of esophageal pressure by 33% (P < 0.05) as well as both ipsilateral and contralateral ABD EMGs by 35% and 48% (P < 0.01 and P < 0.01, respectively). No cough depression was observed after microinjections of vehicle. There was no significant effect of microinjection of codeine in the cVRC (3.3 mM, 30-40 nl) on ABD activity induced by a microinjection of D,L-homocysteic acid (30 mM, 27-40 nl) in the same location. However, a cumulative dose of codeine (0.1 mg/kg, 330 nmol/kg) applied into the brain stem circulation through the vertebral artery reduced the ABD motor response to cVRC D,L-homocysteic acid microinjection (30 mM, 28-32 nl) by 47% (P < 0.01). These results suggest that 1) codeine can act within the cVRC to suppress cough and 2) expiratory premotoneurons within the cVRC are relatively insensitive to this opioid.
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Affiliation(s)
- Ivan Poliacek
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida, USA.
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Poster discussion: summary. Fifth International Cough Symposium. Pulm Pharmacol Ther 2008; 22:163-5. [PMID: 19026758 DOI: 10.1016/j.pupt.2008.10.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2008] [Accepted: 10/22/2008] [Indexed: 11/22/2022]
Abstract
At the Fifth International Cough Symposium 16 posters were presented and, as well as discussions at the poster sites, were considered in a formal symposium session. Here they are divided into groups and we summarize the discussions.
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Panneton WM, Sun W, Gan Q. Pressor responses to nasal stimulation are unaltered after disrupting the CPA. Auton Neurosci 2008; 144:13-21. [PMID: 18809361 DOI: 10.1016/j.autneu.2008.08.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Revised: 07/30/2008] [Accepted: 08/10/2008] [Indexed: 12/26/2022]
Abstract
Stimulation of either the caudal pressor area (CPA) in the most caudal ventrolateral medulla with glutamate, or the nasal mucosa with ammonia vapors, induces an increase in mean arterial blood pressure (MABP). In the present study, we determined if neurons in the CPA serve as a relay for the increase in MABP seen after nasal stimulation. Ammonia vapors stimulated the nasal mucosa of rats anesthetized with either urethane alone or ketamine/xylazine and urethane to induce an increase in MABP, a bradycardia, and an apnea. Bilateral injections (50 nl) of glycine (1 M) or muscimol (2 mM) were placed in the CPA and the nasal mucosa again stimulated. The increases in MABP, the bradycardia and the duration of apnea to nasal stimulation were unchanged after either injection. However, resting MABP and HR were decreased significantly after glycine injections and resting MABP and resting respiratory rate were decreased after muscimol injections. The increase in MABP seen with nasal stimulation also did not change after multiple bilateral injections (3x40 nl) of ibotenate (5 microg/microl) in the CPA, but the bradycardia was eliminated and the duration of apnea was significantly shorter. These results suggest that the increase in MABP induced by nasal stimulation is via routes that do not include neurons in the CPA.
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Affiliation(s)
- W Michael Panneton
- Department of Anatomy and Neurobiology, St. Louis University School of Medicine, 1402 S. Grand Blvd., St. Louis, MO 63104-1028, United States
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Poliacek I, Corrie LWC, Wang C, Rose MJ, Bolser DC. Microinjection of DLH into the region of the caudal ventral respiratory column in the cat: evidence for an endogenous cough-suppressant mechanism. J Appl Physiol (1985) 2006; 102:1014-21. [PMID: 17138836 PMCID: PMC1817661 DOI: 10.1152/japplphysiol.00616.2006] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The caudal ventral respiratory column (cVRC) contains premotor expiratory neurons that play an important role in cough-related expiratory activity of chest wall and abdominal muscles. Microinjection of d,l-homocysteic acid (DLH) was used to test the hypothesis that local activation of cVRC neurons can suppress the cough reflex. DLH (20-50 mM, 10-30 nl) was injected into the region of cVRC in nine anesthetized spontaneously breathing cats. Repetitive coughing was elicited by mechanical stimulation of the intrathoracic airways. Electromyograms (EMG) were recorded bilaterally from inspiratory parasternal and expiratory transversus abdominis (ABD) and unilaterally from laryngeal posterior cricoarytenoid and thyroarytenoid muscles. Unilateral microinjection of DLH (1-1.5 nmol) elicited bilateral increases in tonic and phasic respiratory ABD EMG activity, and it altered the respiratory pattern and laryngeal motor activities. However, DLH also decreased cough frequency by 51 +/- 7% compared with control (P < 0.001) and the amplitude of the contralateral (-35 +/- 3%; P < 0.001) and ipsilateral (-34 +/- 5%; P < 0.001) ABD EMGs during postinjection coughs compared with control. The cough alterations were much less pronounced after microinjection of a lower dose of DLH (0.34-0.8 nmol). No cough depression was observed after microinjections of vehicle. These results suggest that an endogenous cough suppressant neuronal network in the region of the cVRC may exist, and this network may be involved in the control of cough reflex excitability.
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Affiliation(s)
- Ivan Poliacek
- Dept. of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610-0144, USA
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Bongianni F, Mutolo D, Nardone F, Pantaleo T. Ionotropic glutamate receptors mediate excitatory drive to caudal medullary expiratory neurons in the rabbit. Brain Res 2005; 1056:145-57. [PMID: 16122708 DOI: 10.1016/j.brainres.2005.07.019] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2005] [Revised: 07/13/2005] [Accepted: 07/13/2005] [Indexed: 01/06/2023]
Abstract
Most of the neurons of the caudal ventral respiratory group (cVRG) are bulbospinal expiratory neurons that receive their main excitatory drive from more rostral, but not yet defined regions. This study was devoted to investigate the functional role of ionotropic excitatory amino acid (EAA) receptors in the excitatory drive transmission to cVRG expiratory neurons during eupnoeic breathing and some respiratory reflexes including cough induced by mechanical stimulation of the tracheobronchial tree. The experiments were performed on spontaneously breathing rabbits under pentobarbitone anesthesia making use of microinjections (30--50 nl) of EAA receptor antagonists into the cVRG. Phrenic nerve and abdominal muscle activities were recorded. Bilateral microinjections of 50 mM kynurenic acid (KYN), a broad-spectrum EAA antagonist, and 10 mM 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), a non-NMDA antagonist, or 5 mM 6-nitro-7-sulphamoylbenzo(f)quinoxaline-2,3-dione (NBQX), a more specific non-NMDA antagonist, completely suppressed spontaneous rhythmic abdominal activity and reflex expiratory responses either to tracheal occlusion at end-inspiration (Breuer-Hering inflation reflex) or to expiratory threshold loading (5 cm H(2)O); they also suppressed both the inspiratory and expiratory components of the cough reflex. Spontaneous rhythmic abdominal activity and the reflex respiratory responses were strongly reduced, but not completely abolished by microinjections of 10 mM d(-)-2-amino-5-phosphonopentanoic acid (D-AP5), an NMDA antagonist. The results provide evidence that the excitatory drive to cVRG bulbospinal expiratory neurons during eupnoeic breathing and the investigated respiratory reflexes is mediated by EAA receptors. They also support the view that neurons located in the cVRG are not merely elements of the expiratory output system.
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Affiliation(s)
- Fulvia Bongianni
- Dipartimento di Scienze Fisiologiche, Università degli Studi di Firenze, Viale G.B. Morgagni 63, I-50134 Firenze, Italy.
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Dick TE, Shannon R, Lindsey BG, Nuding SC, Segers LS, Baekey DM, Morris KF. Arterial pulse modulated activity is expressed in respiratory neural output. J Appl Physiol (1985) 2005; 99:691-8. [PMID: 15761086 DOI: 10.1152/japplphysiol.01124.2004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Although it is well-established that sympathetic activity is modulated with respiration, it is unknown whether neural control of respiration is reciprocally influenced by cardiovascular function. Even though previous studies have suggested the existence of pulse modulation in respiratory neurons, they could not exclude the possibility that such cells were involved in cardiovascular rather than respiratory motor control, owing to neuroanatomic and functional overlaps between brain stem neurons involved in respiratory and cardiovascular control. The aim of this study was to test the hypothesis that respiratory motoneurons and putative premotoneurons are modulated by arterial pulse. An existing data set composed of 72 well-characterized, respiratory-modulated brain stem motoneurons and putative premotoneurons was analyzed using delta(2), a recently described statistic that quantifies the magnitude of arterial pulse-modulated spike activity [Dick TE and Morris KF. J Physiol 556: 959-970, 2004]. Neuronal activity was recorded in the rostral and caudal ventral respiratory groups of 19 decerebrate, neuromuscular-blocked, ventilated cats. Axonal projections were identified by rectified and unrectified spike-triggered averages of recurrent laryngeal nerve activity or by antidromic activation from spinal stimulation electrodes. The firing rates of approximately 30% of these neurons were modulated in phase with both the respiratory and cardiac cycles. Furthermore, arterial pulse modulation occurred preferentially in the expiratory phase in that only expiratory neurons had high delta(2) values and only expiratory activity had significant delta(2) values after partitioning tonic activity into the inspiratory and expiratory phases. The results demonstrate that both respiratory motoneurons and putative premotoneuronal activity can be pulse modulated. We conclude that a cardiac cycle-related modulation is expressed in respiratory motor activity, complementing the long-recognized respiratory modulation of sympathetic nerve activity.
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Affiliation(s)
- Thomas E Dick
- Division of Pulmonary and Critical Care Medicine, Dept. of Medicine, Case Western Reserve University, Biomedical Research Bldg. BRB B55, 10900 Euclid Avenue, Cleveland, OH 44106-4941, USA.
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Abstract
Cough is an airway defensive reflex substantially consisting in a modified respiratory act. Transection experiments have shown that the fundamental structures responsible for this reflex are located within the medulla oblongata. Electrical stimulation applied to the medulla failed to provide convincing evidence of a cough centre distinct from the brainstem respiratory network. In fact, electrical stimuli affect not only neuronal somata, but also intramedullary cough-related pathways. Studies on the behaviour of medullary respiratory neurones have led to the conclusion that the same respiratory neurones involved in the generation of the eupnoeic pattern of breathing also participate in the production of the cough motor pattern. These findings support the existence of multifunctional neural networks in the mammal brainstem. Bötzinger complex expiratory neurones with augmenting discharge patterns have been suggested to convey an excitatory drive to the expiratory bulbospinal neurones of the caudal ventral respiratory group and, hence, to expiratory motoneurones. The excitatory drive to caudal medullary expiratory neurones is mediated by ionotropic glutamate receptors. Recent lines of evidence indicate that the Bötzinger complex and the caudal ventral respiratory group have a crucial role in determining both the inspiratory and the expiratory components of the cough motor pattern.
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Affiliation(s)
- Tito Pantaleo
- Dipartimento di Scienze Fisiologiche, Università degli Studi di Firenze, Viale G.B. Morgagni 63, Firenze, I-50134, Italy.
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Mutolo D, Bongianni F, Carfì M, Pantaleo T. Respiratory changes induced by kainic acid lesions in rostral ventral respiratory group of rabbits. Am J Physiol Regul Integr Comp Physiol 2002; 283:R227-42. [PMID: 12069949 DOI: 10.1152/ajpregu.00579.2001] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The role played by the Bötzinger complex (BötC), the pre-Bötzinger complex (pre-BötC), and the more rostral extent of the inspiratory portion of the ventral respiratory group (iVRG) in the genesis of the eupneic pattern of breathing was investigated in anesthetized, vagotomized, paralyzed, and artificially ventilated rabbits by means of kainic acid (KA, 4.7 mM) microinjections (20-30 nl). Unilateral KA microinjections into all of the investigated VRG subregions caused increases in respiratory frequency associated with moderate decreases in peak phrenic amplitude in the BötC and pre-BötC regions. Bilateral KA microinjections into either the BötC or pre-BötC transiently eliminated respiratory rhythmicity and caused the appearance of tonic phrenic activity ("tonic apnea"), whereas injections into the rostral iVRG completely suppressed inspiratory activity. Rhythmic activity resumed as low-amplitude, high-frequency oscillations and displayed a progressive, although incomplete, recovery. Combined bilateral KA microinjections (BötC and pre-BötC) caused persistent (>3 h) tonic apnea. Results show that all of the investigated VRG subregions exert a potent control on both the intensity and frequency of inspiratory activity, thus suggesting that these areas play a major role in the genesis of the eupneic pattern of breathing.
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Affiliation(s)
- Donatella Mutolo
- Dipartimento di Scienze Fisiologiche, Università degli Studi di Firenze, Viale G.B. Morgagni 63, I-50134 Florence, Italy
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Solomon IC. Modulation of expiratory motor output evoked by chemical activation of pre-Bötzinger complex in vivo. Respir Physiol Neurobiol 2002; 130:235-51. [PMID: 12093621 DOI: 10.1016/s0034-5687(02)00004-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
We have previously demonstrated that chemical stimulation of the pre-Bötzinger complex (pre-BötC) in the anesthetized cat produces either phasic or tonic excitation of phrenic nerve discharge. This region is characterized by a mixture of inspiratory-modulated, expiratory-modulated, and phase-spanning (including pre-inspiratory (pre-I)) neurons; however, its influence on expiratory motor output is unknown. We, therefore, examined the effects of chemical stimulation of the pre-BötC on expiratory motor output recorded from the caudal iliohypogastric (lumbar, L(2)) nerve. We found that unilateral microinjection of DL-homocysteic acid (DLH; 10 mM; 10-20 nl) into 16 sites in the pre-BötC enhanced lumbar nerve discharge, including changes in timing and patterning similar to those previously reported for phrenic motor output. Both increased peak amplitude and frequency of phasic lumbar bursts as well as tonic excitation of lumbar motor activity were observed. In some cases, evoked phasic lumbar nerve activity was synchronized in phase with phrenic nerve discharge. These findings demonstrate that chemical stimulation of the pre-BötC not only excites inspiratory motor activity but also excites expiratory motor output, suggesting a role for the pre-BötC in generation and modulation of inspiratory and expiratory rhythm and pattern.
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Affiliation(s)
- Irene C Solomon
- Department of Physiology and Biophysics, State University of New York at Stony Brook, Stony Brook, NY 11794-8661, USA.
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Mutolo D, Bongianni F, Carfì M, Pantaleo T. Respiratory responses to thyrotropin-releasing hormone microinjected into the rabbit medulla oblongata. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:R1331-8. [PMID: 10564204 DOI: 10.1152/ajpregu.1999.277.5.r1331] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We investigated the respiratory role of thyrotropin-releasing hormone (TRH) input to medullary structures involved in the control of breathing in anesthetized, vagotomized, paralyzed, and artificially ventilated rabbits. Microinjections (10-20 nl) of 1 or 10 mM TRH were performed in different regions of the ventral respiratory group (VRG), namely the rostral expiratory portion or Bötzinger complex (Böt. c.), the inspiratory portion, the transition zone between these two neuronal pools, and the caudal expiratory component. TRH microinjections were also performed in the dorsal respiratory group (DRG) and the area postrema (AP). Injection sites were localized by using stereotaxic coordinates and extracellular recordings of neuronal activity; their locations were confirmed by subsequent histological control. TRH microinjections in the Böt. c. and the directly caudally located region where a mix of inspiratory and expiratory neurons were encountered elicited depressant respiratory responses. TRH microinjections were completely ineffective at sites within the inspiratory and the caudal expiratory components of the VRG. TRH microinjections in either the DRG or the AP induced excitatory effects on inspiratory activity. The results show for the first time that TRH may exert inhibitory influences on respiration at medullary levels by acting on rostral expiratory neurons and that not only the DRG, as previously suggested, but also the AP may mediate TRH-induced excitatory effects on respiration.
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Affiliation(s)
- D Mutolo
- Dipartimento di Scienze Fisiologiche, Università degli Studi di Firenze, I-50134 Firenze, Italy
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Anderson MK, Speck DF. Differential effects of excitatory amino acid receptor antagonism in the ventral respiratory group. Brain Res 1999; 829:69-76. [PMID: 10350531 DOI: 10.1016/s0006-8993(99)01340-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
This study tested the hypothesis that selective antagonism of excitatory amino acid (EAA) receptors within the ventral respiratory group (VRG) would induce changes in both respiratory rhythm and pattern. In the paralyzed, decerebrate, vagotomized and ventilated cat, baseline values for respiratory (Ttot), inspiratory (Ti), and expiratory (Te) durations and peak integrated phrenic nerve (integralPN) amplitude were established. Microinjection of the non-NMDA (N-methyl-d-aspartate) receptor antagonist NBQX (2, 3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline) into rostral/inspiratory-modulated (iVRG) or caudal/expiratory-modulated VRG elicited an immediate apnea. When PN activity resumed, Ttot was significantly decreased, and integralPN amplitude was attenuated. NMDA receptor antagonism with microinjections of AP5 (2-amino-5-phosphonopentanoic acid) into iVRG decreased Te for more than 30 min. NMDA receptor antagonism in inspiratory/expiratory-modulated VRG (level of obex, transitional VRG) yielded either apnea or a significant reduction in Ttot, Ti and integralPN amplitude. Our data suggest that endogenous EAA receptor-mediated neurotransmission throughout the VRG is active in the determination of both respiratory timing and pattern. Our data further suggest that tVRG serves a unique function within the respiratory network.
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Affiliation(s)
- M K Anderson
- Department of Physiology, University of Kentucky, MS 515 Chandler Medical Center, Lexington, KY 40536-0298, USA
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Chitravanshi VC, Sapru HN. Phrenic nerve responses to chemical stimulation of the subregions of ventral medullary respiratory neuronal group in the rat. Brain Res 1999; 821:443-60. [PMID: 10064832 DOI: 10.1016/s0006-8993(99)01139-7] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Phrenic nerve (PN) responses to unilateral microinjections of L-glutamate (L-Glu, 5 mM) or N-methyl-D-aspartic acid (NMDA, 1 mM) into different subregions of ventral respiratory neuronal group (VRG) were studied in urethane-anesthetized, immobilized, and artificially ventilated, adult male Wistar rats. A 50-nl volume of microinjection was used in all the subregions of VRG except in Pre-Bötzinger complex (Pre-BötC) where a 20-nl volume was used. Unilateral microinjections of L-Glu or NMDA into the Bötzinger complex (BötC) and caudal VRG (cVRG), caused a transient cessation of phrenic nerve (PN) activity. Expiratory neurons, abundant in BötC and cVRG, were excited by stimulation of cardiopulmonary receptors while their responses to carotid chemoreceptor stimulation were variable. Microinjections of L-Glu or NMDA into the Pre-BötC caused an increase in the PN background discharge (this response was unique to Pre-BötC) superimposed on which was an increase in the PN burst frequency. Microinjections of L-Glu or NMDA into the rostral VRG (rVRG) caused an increase in the frequency and amplitude of PN bursts. Inspiratory neurons, abundant in Pre-BötC and rVRG, were excited and inhibited by activation of carotid chemoreceptors and cardiopulmonary receptors, respectively. The coordinates for the location of different subregions of VRG were as follows (reference points are listed in parentheses). BötC: 1.6-2.6 mm rostral (calamus scriptorius), 1.7-2.7 mm lateral (midline), and 2.3-2.8 mm deep (dorsal surface of medulla); Pre-BötC: 1.4-1.6 mm rostral, 1. 8-2.5 mm lateral, and 2.3-2.8 mm deep; rVRG: 0.4-1.4 mm rostral, 1. 6-2.5 mm lateral, and 2.3-2.8 mm deep; and cVRG: 0.5 mm caudal to 0. 5 mm rostral, 1.0-2.2 mm lateral, and 2.1-2.6 mm deep. A detailed map of the subregions of VRG, functionally identified by L-Glu and NMDA-microinjections, has been presented. These data are likely to prove useful in future studies on respiratory reflex mechanisms.
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Affiliation(s)
- V C Chitravanshi
- Section of Neurological Surgery, MSB H-586, New Jersey Medical School, 185 South Orange Ave., Newark, NJ 07103-2757, USA
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Orem J. Augmenting expiratory neuronal activity in sleep and wakefulness and in relation to duration of expiration. J Appl Physiol (1985) 1998; 85:1260-6. [PMID: 9760314 DOI: 10.1152/jappl.1998.85.4.1260] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Augmenting expiratory cells (n = 23) were recorded in the rostral medulla of five cats in sleep and wakefulness. The objective was to determine the relationship of their activity to the duration of expiration (TE) and, particularly, to TE in rapid-eye-movement (REM) sleep, when expirations are short and may even cause fractionated breathing. Correlation analysis (Kendall's tau) showed no consistent relationship in any state between the breath-by-breath mean activity of augmenting expiratory cells and TE. This result contradicts predications of an inverse relationship between augmenting expiratory activity and TE. Some cells (11 of 23) were more active in REM than in non-REM sleep and were active during fractionated breathing. This suggests that fractionated breathing in REM sleep is caused by short expiratory phases and not by intermittent inhibition of an ongoing inspiration.
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Affiliation(s)
- J Orem
- Department of Physiology, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA.
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Abstract
Normal respiration, termed eupnea, is characterized by periodic filling and emptying of the lungs. Eupnea can occur 'automatically' without conscious effort. Such automatic ventilation is controlled by the brainstem respiratory centers of pons and medulla. Following removal of the pons, eupnea is replaced by gasping, marked by brief but maximal inspiratory efforts. The mechanisms by which the respiratory rhythms are generated have been examined intensively. Evidence is discussed that ventilatory activity can be generated in multiple regions of pons and medulla. Eupnea and gasping represent fundamentally different ventilatory patterns. Only for gasping has a critical region for neurogenesis been identified, in the rostral medulla. Gasping may be generated by the discharge of 'pacemaker' neurons. In eupnea, this pacemaker activity is suppressed and incorporated into the pontile and medullary neuronal circuit responsible for the neurogenesis of eupnea. Evidence for ventilatory neurogenesis which has been obtained from a number of in vitro preparations is discussed. A much-used preparation is that of a 'superfused' brainstem of the neonatal rat. However, activities of this preparation differ greatly from those of eupnea, as recorded in vitro or in arterially perfused in vitro preparations. Activities of this 'superfused' preparation are identical with gasping and, hence, results must be reinterpreted accordingly. The possibility is present that mechanisms responsible for generating respiratory rhythms may differ from those responsible for shaping respiratory-modulated discharge patterns of cranial and spinal nerves. The importance of pontile mechanisms in the neurogenesis and control of eupnea is reemphasized.
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Affiliation(s)
- W M St-John
- Department of Physiology, Dartmouth-Hitchcock Medical Center, Dartmouth Medical School, Lebanon, NH 03756, USA
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Hedrick MS, Ryan ML, Bisgard GE. Recurrent laryngeal nerve activation by alpha 2 adrenergic agonists in goats. RESPIRATION PHYSIOLOGY 1995; 101:129-37. [PMID: 8570915 DOI: 10.1016/0034-5687(95)00030-h] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The purpose of this study was to test the hypothesis that respiratory and apneas induced by alpha 2 agonists in anesthetized goats are associated with an increase of upper airway expiratory-related activity, rather than a general depression of breathing. Activities of phrenic (Phr) and recurrent laryngeal nerves (RLN) were recorded in response to the alpha 2 agonists clonidine (0.5-3.0 microgram.kg-1 i.v.) or guanabenz (7.0-20.0 micrograms.kg-1 i.v.) in ten chloralose-anesthetized goats. Injection of either alpha 2 agonist resulted in respiratory arrhythmias with a greater than seven-fold increase in TE and a 30% reduction in TI. During apneas RLN expiratory-related activity remained tonic until the next Phr burst, consistent with our hypothesis. Cessation of Phr activity during hypocapnia also resulted in a tonic increase of RLN expiratory activity; and injection of NaCN (50 micrograms.kg-1 i.v.) increased Phr and RLN inspiratory activities, while attenuating RLN expiratory-related activity. Inspiratory and expiratory-related activity of RLN motoneurons appear to be reciprocally modulated by alpha 2 agonists or changes in central or peripheral chemoreceptor drive. The results indicate that central apneas and respiratory arrhythmias may be associated with alpha 2-adrenoceptor modulation of laryngeal expiratory-related activity.
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Affiliation(s)
- M S Hedrick
- Dept. of Biological Sciences, California State University, Hayward 94542, USA
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