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Khalilpour J, Zangbar HS, Alipour MR, Pakdel FQ, Zavari Z, Shahabi P. Chronic Sustained Hypoxia Leads to Brainstem Tauopathy and Declines the Power of Rhythms in the Ventrolateral Medulla: Shedding Light on a Possible Mechanism. Mol Neurobiol 2024; 61:3121-3143. [PMID: 37976025 DOI: 10.1007/s12035-023-03763-4] [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: 11/23/2022] [Accepted: 10/31/2023] [Indexed: 11/19/2023]
Abstract
Hypoxia, especially the chronic type, leads to disruptive results in the brain that may contribute to the pathogenesis of some neurodegenerative diseases such as Alzheimer's disease (AD). The ventrolateral medulla (VLM) contains clusters of interneurons, such as the pre-Bötzinger complex (preBötC), that generate the main respiratory rhythm drive. We hypothesized that exposing animals to chronic sustained hypoxia (CSH) might develop tauopathy in the brainstem, consequently changing the rhythmic manifestations of respiratory neurons. In this study, old (20-22 months) and young (2-3 months) male rats were subjected to CSH (10 ± 0.5% O2) for ten consecutive days. Western blotting and immunofluorescence (IF) staining were used to evaluate phosphorylated tau. Mitochondrial membrane potential (MMP or ∆ψm) and reactive oxygen species (ROS) production were measured to assess mitochondrial function. In vivo diaphragm's electromyography (dEMG) and local field potential (LFP) recordings from preBötC were employed to assess the respiratory factors and rhythmic representation of preBötC, respectively. Findings showed that ROS production increased significantly in hypoxic groups, associated with a significant decline in ∆ψm. In addition, tau phosphorylation elevated in the brainstem of hypoxic groups. On the other hand, the power of rhythms declined significantly in the preBötC of hypoxic rats, parallel with changes in the respiratory rate, total respiration time, and expiration time. Moreover, there was a positive and statistically significant correlation between LFP rhythm's power and inspiration time. Our data showed that besides CSH, aging also contributed to mitochondrial dysfunction, tau hyperphosphorylation, LFP rhythms' power decline, and changes in respiratory factors.
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Affiliation(s)
- Jamal Khalilpour
- Drug Applied Research Center, Tabriz University of Medical Sciences, Golgasht Street, Tabriz, East Azerbaijan, Iran
| | - Hamid Soltani Zangbar
- Department of Neuroscience, Faculty of Advanced Medical Sciences, Tabriz University of Medical Sciences, Golgasht Street, Tabriz, East Azerbaijan, Iran.
| | - Mohammad Reza Alipour
- Drug Applied Research Center, Tabriz University of Medical Sciences, Golgasht Street, Tabriz, East Azerbaijan, Iran
| | - Firouz Qaderi Pakdel
- Department of Physiology, Faculty of Medicine, Urmia University of Medical Sciences, Urmia, Iran
| | - Zohre Zavari
- Drug Applied Research Center, Tabriz University of Medical Sciences, Golgasht Street, Tabriz, East Azerbaijan, Iran
| | - Parviz Shahabi
- Drug Applied Research Center, Tabriz University of Medical Sciences, Golgasht Street, Tabriz, East Azerbaijan, Iran.
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2
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Kawamura K, Sasaki K, Sasaki SI, Tomita K. Axonal projection of the medullary expiratory neurons in the feline thoracic spinal cord. Respir Physiol Neurobiol 2024; 322:104218. [PMID: 38237882 DOI: 10.1016/j.resp.2024.104218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 01/12/2024] [Accepted: 01/13/2024] [Indexed: 01/26/2024]
Abstract
Expiratory neurons in the caudal ventral respiratory group extend descending axons to the lumbar and sacral spinal cord, and they possess axon collaterals, the distribution of which has been well-documented. Likewise, these expiratory neurons extend axons to the thoracic spinal cord and innervate thoracic expiratory motoneurons. These axons also give rise to collaterals, and their distribution may influence the strength of synaptic connectivity between the axons and the thoracic expiratory motoneurons. We investigated the distribution of axon collaterals in the thoracic spinal cord using a microstimulation technique. This study was performed on cats; one cat was used to make an anatomical atlas and six were used in the experiment. Extracellular spikes of expiratory neurons were recorded in artificially ventilated cats. The thoracic spinal gray matter was microstimulated from dorsal to ventral sites at 100-μm intervals using a glass-insulated tungsten microelectrode with a current of 150-250 μA. The stimulation tracks were made at 1 mm intervals along the spinal cord in segments Th9 to Th13, and the effective stimulating sites of antidromic activation in axon collaterals were systematically mapped. The effective stimulating sites in the contralateral thoracic spinal cord with expiratory neurons in the caudal ventral respiratory group (cVRG) occupied 14.4% of the total length of the thoracic spinal cord examined. The mean percentage of effective stimulating tracks per unit was 18.6 ± 4.4%. The distribution of axon collaterals of expiratory neurons in the feline thoracic spinal cord indeed resembled that reported in the upper lumbar spinal cord. We propose that a single medullary expiratory neuron exerts excitatory effects across multiple segments of the thoracic spinal cord via its collaterals.
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Affiliation(s)
- Kenta Kawamura
- Department of Physical Therapy, Ibaraki Prefectural University of Health Sciences, 4669-2 Ami, Ami-machi, Inashiki-gun, Ibaraki 300-0394, Japan.
| | - Kazumasa Sasaki
- Department of Anatomy, Toho University, 5-21-16 Ohmorinishi, Ohta-ku, Tokyo 143-8540, Japan
| | - Sei-Ichi Sasaki
- Toyo Public Health College, 6-21-7 Honmachi, Shibuya-ku, Tokyo 151-0071, Japan
| | - Kazuhide Tomita
- Department of Physical Therapy, Ibaraki Prefectural University of Health Sciences, 4669-2 Ami, Ami-machi, Inashiki-gun, Ibaraki 300-0394, Japan
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3
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Thakre PP, Rana S, Benevides ES, Fuller DD. Targeting drug or gene delivery to the phrenic motoneuron pool. J Neurophysiol 2023; 129:144-158. [PMID: 36416447 PMCID: PMC9829468 DOI: 10.1152/jn.00432.2022] [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: 10/13/2022] [Revised: 11/19/2022] [Accepted: 11/19/2022] [Indexed: 11/24/2022] Open
Abstract
Phrenic motoneurons (PhrMNs) innervate diaphragm myofibers. Located in the ventral gray matter (lamina IX), PhrMNs form a column extending from approximately the third to sixth cervical spinal segment. Phrenic motor output and diaphragm activation are impaired in many neuromuscular diseases, and targeted delivery of drugs and/or genetic material to PhrMNs may have therapeutic application. Studies of phrenic motor control and/or neuroplasticity mechanisms also typically require targeting of PhrMNs with drugs, viral vectors, or tracers. The location of the phrenic motoneuron pool, however, poses a challenge. Selective PhrMN targeting is possible with molecules that move retrogradely upon uptake into phrenic axons subsequent to diaphragm or phrenic nerve delivery. However, nonspecific approaches that use intrathecal or intravenous delivery have considerably advanced the understanding of PhrMN control. New opportunities for targeted PhrMN gene expression may be possible with intersectional genetic methods. This article provides an overview of methods for targeting the phrenic motoneuron pool for studies of PhrMNs in health and disease.
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Affiliation(s)
- Prajwal P Thakre
- Department of Physical Therapy, University of Florida, Gainesville, Florida
- McKnight Brain Institute, University of Florida, Gainesville, Florida
- Breathing Research and Therapeutics Center, Gainesville, Florida
| | - Sabhya Rana
- Department of Physical Therapy, University of Florida, Gainesville, Florida
- McKnight Brain Institute, University of Florida, Gainesville, Florida
- Breathing Research and Therapeutics Center, Gainesville, Florida
| | - Ethan S Benevides
- Department of Physical Therapy, University of Florida, Gainesville, Florida
- McKnight Brain Institute, University of Florida, Gainesville, Florida
- Breathing Research and Therapeutics Center, Gainesville, Florida
| | - David D Fuller
- Department of Physical Therapy, University of Florida, Gainesville, Florida
- McKnight Brain Institute, University of Florida, Gainesville, Florida
- Breathing Research and Therapeutics Center, Gainesville, Florida
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4
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Asan AS, McIntosh JR, Carmel JB. Targeting Sensory and Motor Integration for Recovery of Movement After CNS Injury. Front Neurosci 2022; 15:791824. [PMID: 35126040 PMCID: PMC8813971 DOI: 10.3389/fnins.2021.791824] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2021] [Accepted: 12/27/2021] [Indexed: 12/18/2022] Open
Abstract
The central nervous system (CNS) integrates sensory and motor information to acquire skilled movements, known as sensory-motor integration (SMI). The reciprocal interaction of the sensory and motor systems is a prerequisite for learning and performing skilled movement. Injury to various nodes of the sensorimotor network causes impairment in movement execution and learning. Stimulation methods have been developed to directly recruit the sensorimotor system and modulate neural networks to restore movement after CNS injury. Part 1 reviews the main processes and anatomical interactions responsible for SMI in health. Part 2 details the effects of injury on sites critical for SMI, including the spinal cord, cerebellum, and cerebral cortex. Finally, Part 3 reviews the application of activity-dependent plasticity in ways that specifically target integration of sensory and motor systems. Understanding of each of these components is needed to advance strategies targeting SMI to improve rehabilitation in humans after injury.
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Affiliation(s)
| | | | - Jason B. Carmel
- Departments of Neurology and Orthopedics, Columbia University, New York, NY, United States
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Fuller DD, Rana S, Smuder AJ, Dale EA. The phrenic neuromuscular system. HANDBOOK OF CLINICAL NEUROLOGY 2022; 188:393-408. [PMID: 35965035 PMCID: PMC11135908 DOI: 10.1016/b978-0-323-91534-2.00012-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The phrenic neuromuscular system consists of the phrenic motor nucleus in the mid-cervical spinal cord, the phrenic nerve, and the diaphragm muscle. This motor system helps sustain breathing throughout life, while also contributing to posture, coughing, swallowing, and speaking. The phrenic nerve contains primarily efferent phrenic axons and afferent axons from diaphragm sensory receptors but is also a conduit for autonomic fibers. On a breath-by-breath basis, rhythmic (inspiratory) depolarization of phrenic motoneurons occurs due to excitatory bulbospinal synaptic pathways. Further, a complex propriospinal network innervates phrenic motoneurons and may serve to coordinate postural, locomotor, and respiratory movements. The phrenic neuromuscular system is impacted in a wide range of neuromuscular diseases and injuries. Contemporary research is focused on understanding how neuromuscular plasticity occurs in the phrenic neuromuscular system and using this information to optimize treatments and rehabilitation strategies to improve breathing and related behaviors.
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Affiliation(s)
- David D Fuller
- Department of Physical Therapy, University of Florida, Gainesville, FL, United States; McKnight Brain Institute, University of Florida, Gainesville, FL, United States; Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL, United States.
| | - Sabhya Rana
- Department of Physical Therapy, University of Florida, Gainesville, FL, United States; McKnight Brain Institute, University of Florida, Gainesville, FL, United States; Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL, United States
| | - Ashley J Smuder
- Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL, United States; Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL, United States
| | - Erica A Dale
- McKnight Brain Institute, University of Florida, Gainesville, FL, United States; Breathing Research and Therapeutics Center, University of Florida, Gainesville, FL, United States; Department of Physiology and Functional Genomics, University of Florida, Gainesville, FL, United States
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6
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Kowalski KE, Romaniuk JR, Kirkwood PA, DiMarco AF. Inspiratory muscle activation via ventral lower thoracic high-frequency spinal cord stimulation. J Appl Physiol (1985) 2019; 126:977-983. [DOI: 10.1152/japplphysiol.01054.2018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In animals, high-frequency spinal cord stimulation (HF-SCS) applied on the ventral epidural surface at the T2 level results in negative airway pressure generation consistent with inspiratory muscle activation. In the present study, in anesthetized dogs, we found that ventral HF-SCS (500 Hz) applied at all thoracic levels resulted in negative airway pressure generation. In the region of the lower thoracic spinal cord, negative airway pressure generation was most pronounced at the T9 level. At this level, airway pressure generation was monitored: 1) during ventral HF-SCS over a wide range of stimulus amplitudes (0.5–15 mA) and frequencies (50–1,000 Hz) and 2) following spinal sections at C8 (to assess potential diaphragm activation) and subsequently at T6 (to assess potential intercostal muscle activation). The application of low stimulus currents between 1 and 2 mA and high stimulus frequencies (>300 Hz) resulted in the development of large negative airway pressure generation. Stimulation with 1 mA, 500 Hz resulted in a highest negative airway pressure generation of 47 ± 2 cmH2O. Increasing stimulus current was associated with progressive reductions in the magnitude of negative airway pressure generation. HF-SCS (500 Hz) with 15 mA resulted in a negative airway pressure generation of 7 ± 3 cmH2O. C8 section markedly reduced negative airway pressure generation, and subsequent T6 section resulted in positive airway pressure generation after HF-SCS. Our results indicate the existence of pathways with connections to both the phrenic and inspiratory intercostal motoneuron pools in the ventral part of the lower thoracic spinal cord. We speculate that the circuits mediating the previously described excitatory intercostal-to-phrenic reflex mediate the observed responses. NEW & NOTEWORTHY This study suggests that, in contrast to dorsal high-frequency spinal cord stimulation at the T9 spinal level, which results in positive pressure generation, ventral high-frequency spinal cord stimulation at the same spinal level results in large negative airway pressure generation with low stimulus currents. This method, therefore, may provide an alternative method to restore ventilation in ventilator-dependent spinal cord-injured patients.
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Affiliation(s)
- Krzysztof E. Kowalski
- Research Service, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio
- Department of Medicine, Case Western Reserve University, Cleveland, Ohio
- MetroHealth Research Institute, MetroHealth Medical Center, Cleveland, Ohio
| | | | - Peter A. Kirkwood
- UCL Queen Square Institute of Neurology, Queen Square, London, United Kingdom
| | - Anthony F. DiMarco
- Department of Physical Medicine and Rehabilitation, Case Western Reserve University, Cleveland, Ohio
- MetroHealth Research Institute, MetroHealth Medical Center, Cleveland, Ohio
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Structural and functional identification of two distinct inspiratory neuronal populations at the level of the phrenic nucleus in the rat cervical spinal cord. Brain Struct Funct 2018; 224:57-72. [PMID: 30251026 PMCID: PMC6373374 DOI: 10.1007/s00429-018-1757-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 09/18/2018] [Indexed: 11/22/2022]
Abstract
The diaphragm is driven by phrenic motoneurons that are located in the cervical spinal cord. Although the anatomical location of the phrenic nucleus and the function of phrenic motoneurons at a single cellular level have been extensively analyzed, the spatiotemporal dynamics of phrenic motoneuron group activity have not been fully elucidated. In the present study, we analyzed the functional and structural characteristics of respiratory neuron population in the cervical spinal cord at the level of the phrenic nucleus by voltage imaging, together with histological analysis of neuronal and astrocytic distribution in the cervical spinal cord. We found spatially distinct two cellular populations that exhibited synchronized inspiratory activity on the transversely cut plane at C4–C5 levels and on the ventral surface of the mid cervical spinal cord in the isolated brainstem–spinal cord preparation of the neonatal rat. Inspiratory activity of one group emerged in the central portion of the ventral horn that corresponded to the central motor column, and the other appeared in the medial portion of the ventral horn that corresponded to the medial motor column. We identified by retrogradely labeling study that the anatomical distributions of phrenic and scalene motoneurons coincided with optically detected central and medial motor regions, respectively. Furthermore, we anatomically demonstrated closely located features of putative motoneurons, interneurons and astrocytes in these regions. Collectively, we report that phrenic and scalene motoneuron populations show synchronized inspiratory activities with distinct anatomical locations in the mid cervical spinal cord.
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8
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Kowalski KE, Romaniuk JR, Kowalski T, DiMarco AF. Effects of expiratory muscle activation via high-frequency spinal cord stimulation. J Appl Physiol (1985) 2017; 123:1525-1531. [PMID: 28935824 DOI: 10.1152/japplphysiol.00402.2017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In persons with spinal cord injury, lower thoracic low-frequency spinal cord stimulation (LF-SCS; 50 Hz, 15 mA) is a useful method to restore an effective cough. Unfortunately, the high-stimulus-amplitude requirements and potential activation of pain fibers significantly limit this application in persons with intact sensation. In this study, the mechanism of the expiratory muscle activation, via high-frequency SCS (HF-SCS; 500 Hz, 1 mA) was evaluated in dogs. In group 1, the effects of electrode placement on airway pressure generation (P) was evaluated. Maximal P occurred at the T9-T10 level with progressive decrements in P at more rostral and caudal levels for both LF-SCS and HF-SCS. In group 2, electromyographic (EMG) latencies of internal intercostal muscle (II) activation were evaluated before and after spinal root section and during direct motor root stimulation. Onset time of II EMG activity during HF-SCS was significantly longer (3.84 ± 1.16 ms) than obtained during direct motor root activation (1.61 ± 0.10 ms). In group 3, P and external oblique (EO) EMG activity, before and after sequential spinal section at the T11-T12 level, were evaluated. Bilateral dorsal column section significantly reduced EO EMG activity below the section and resulted in a substantial fall in P. Subsequent lateral funiculi section completely abolished those activities and resulted in further reductions in P. We conclude that 1) activation of the expiratory muscles via HF-SCS is dependent entirely on synaptic spinal cord pathways, and 2) HF-SCS at the T9 level produces a comparable level of muscle activation with that achieved with LF-SCS but with much lower stimulus amplitudes. NEW & NOTEWORTHY The findings in the present study suggest that lower thoracic high-frequency spinal cord stimulation with low stimulus currents results in sufficient activation of the expiratory muscles via spinal circuitry to produce large positive airway pressures sufficient to generate an effective cough mechanism. This method, therefore, may be applied in patient populations with intact sensation such as stroke and amyotrophic lateral sclerosis to restore an effective cough.
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Affiliation(s)
- K E Kowalski
- Research Service, Louis Stokes Cleveland Veterans Affairs Medical Center , Cleveland, Ohio.,Department of Medicine, Case Western Reserve University , Cleveland, Ohio.,MetroHealth Research Institute, MetroHealth Medical Center , Cleveland, Ohio
| | - J R Romaniuk
- Research Service, Louis Stokes Cleveland Veterans Affairs Medical Center , Cleveland, Ohio
| | - T Kowalski
- MetroHealth Research Institute, MetroHealth Medical Center , Cleveland, Ohio
| | - A F DiMarco
- Department of Physical Medicine and Rehabilitation, Case Western Reserve University , Cleveland, Ohio.,MetroHealth Research Institute, MetroHealth Medical Center , Cleveland, Ohio
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Hachmann JT, Calvert JS, Grahn PJ, Drubach DI, Lee KH, Lavrov IA. Review of Epidural Spinal Cord Stimulation for Augmenting Cough after Spinal Cord Injury. Front Hum Neurosci 2017; 11:144. [PMID: 28400726 PMCID: PMC5368218 DOI: 10.3389/fnhum.2017.00144] [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: 10/21/2016] [Accepted: 03/13/2017] [Indexed: 12/13/2022] Open
Abstract
Spinal cord injury (SCI) remains a debilitating condition for which there is no cure. In addition to loss of somatic sensorimotor functions, SCI is also commonly associated with impairment of autonomic function. Importantly, cough dysfunction due to paralysis of expiratory muscles in combination with respiratory insufficiency can render affected individuals vulnerable to respiratory morbidity. Failure to clear sputum can aggravate both risk for and severity of respiratory infections, accounting for frequent hospitalizations and even mortality. Recently, epidural stimulation of the lower thoracic spinal cord has been investigated as novel means for restoring cough by evoking expiratory muscle contraction to generate large positive airway pressures and expulsive air flow. This review article discusses available preclinical and clinical evidence, current challenges and clinical potential of lower thoracic spinal cord stimulation (SCS) for restoring cough in individuals with SCI.
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Affiliation(s)
- Jan T Hachmann
- Department of Neurologic Surgery, Mayo Clinic Rochester, MN, USA
| | | | - Peter J Grahn
- Department of Neurologic Surgery, Mayo Clinic Rochester, MN, USA
| | - Dina I Drubach
- Department of Neurologic Surgery, Mayo Clinic Rochester, MN, USA
| | - Kendall H Lee
- Department of Neurologic Surgery, Mayo ClinicRochester, MN, USA; Department of Physiology and Biomedical Engineering, Mayo ClinicRochester, MN, USA; Department of Physical Medicine and Rehabilitation, Mayo ClinicRochester, MN, USA
| | - Igor A Lavrov
- Department of Neurologic Surgery, Mayo Clinic Rochester, MN, USA
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10
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Villiere SM, Nakase K, Kollmar R, Silverman J, Sundaram K, Stewart M. Seizure-associated central apnea in a rat model: Evidence for resetting the respiratory rhythm and activation of the diving reflex. Neurobiol Dis 2017; 101:8-15. [PMID: 28153424 DOI: 10.1016/j.nbd.2017.01.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2016] [Revised: 01/02/2017] [Accepted: 01/25/2017] [Indexed: 12/18/2022] Open
Abstract
Respiratory derangements, including irregular, tachypnic breathing and central or obstructive apnea can be consequences of seizure activity in epilepsy patients and animal models. Periods of seizure-associated central apnea, defined as periods >1s with rapid onset and offset of no airflow during plethysmography, suggest that seizures spread to brainstem respiratory regions to disrupt breathing. We sought to characterize seizure-associated central apneic episodes as an indicator of seizure impact on the respiratory rhythm in rats anesthetized with urethane and given parenteral kainic acid to induce recurring seizures. We measured central apneic period onsets and offsets to determine if onset-offset relations were a consequence of 1) a reset of the respiratory rhythm, 2) a transient pausing of the respiratory rhythm, resuming from the pause point at the end of the apneic period, 3) a transient suppression of respiratory behavior with apnea offset predicted by a continuation of the breathing pattern preceding apnea, or 4) a random re-entry into the respiratory cycle. Animals were monitored with continuous ECG, EEG, and plethysmography. One hundred ninety central apnea episodes (1.04 to 36.18s, mean: 3.2±3.7s) were recorded during seizure activity from 7 rats with multiple apneic episodes. The majority of apneic period onsets occurred during expiration (125/161 apneic episodes, 78%). In either expiration or inspiration, apneic onsets tended to occur late in the cycle, i.e. between the time of the peak and end of expiration (82/125, 66%) or inspiration (34/36, 94%). Apneic period offsets were more uniformly distributed between early and late expiration (27%, 34%) and inspiration (16%, 23%). Differences between the respiratory phase at the onset of apnea and the corresponding offset phase varied widely, even within individual animals. Each central apneic episode was associated with a high frequency event in EEG or ECG records at onset. High frequency events that were not associated with flatline plethysmographs revealed a constant plethysmograph pattern within each animal, suggesting a clear reset of the respiratory rhythm. The respiratory rhythm became highly variable after about 1s, however, accounting for the unpredictability of the offset phase. The dissociation of respiratory rhythm reset from the cessation of airflow also suggested that central apneic periods involved activation of brainstem regions serving the diving reflex to eliminate the expression of respiratory movements. This conclusion was supported by the decreased heart rate as a function of apnea duration. We conclude that seizure-associated central apnea episodes are associated with 1) a reset of the respiratory rhythm, and 2) activation of brainstem regions serving the diving reflex to suppress respiratory behavior. The significance of these conclusions is that these details of seizure impact on brainstem circuitry represent metrics for assessing seizure spread and potentially subclassifying seizure patterns.
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Affiliation(s)
- S M Villiere
- Department of Physiology & Pharmacology, State University of New York Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, United States; Research Initiative for Scientific Enhancement (RISE) Program, City University of New York Medgar Evers College, 1638 Bedford Avenue, Brooklyn, NY 11225, United States
| | - K Nakase
- Department of Physiology & Pharmacology, State University of New York Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, United States
| | - R Kollmar
- Department of Cell Biology, State University of New York Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, United States; Department of Otolaryngology, State University of New York Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, United States
| | - J Silverman
- Department of Otolaryngology, State University of New York Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, United States
| | - K Sundaram
- Department of Otolaryngology, State University of New York Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, United States
| | - M Stewart
- Department of Physiology & Pharmacology, State University of New York Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, United States; Department of Neurology, State University of New York Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, United States.
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11
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Eippert F, Kong Y, Winkler AM, Andersson JL, Finsterbusch J, Büchel C, Brooks JCW, Tracey I. Investigating resting-state functional connectivity in the cervical spinal cord at 3T. Neuroimage 2016; 147:589-601. [PMID: 28027960 PMCID: PMC5315056 DOI: 10.1016/j.neuroimage.2016.12.072] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Revised: 12/20/2016] [Accepted: 12/23/2016] [Indexed: 12/12/2022] Open
Abstract
The study of spontaneous fluctuations in the blood-oxygen-level-dependent (BOLD) signal has recently been extended from the brain to the spinal cord. Two ultra-high field functional magnetic resonance imaging (fMRI) studies in humans have provided evidence for reproducible resting-state connectivity between the dorsal horns as well as between the ventral horns, and a study in non-human primates has shown that these resting-state signals are impacted by spinal cord injury. As these studies were carried out at ultra-high field strengths using region-of-interest (ROI) based analyses, we investigated whether such resting-state signals could also be observed at the clinically more prevalent field strength of 3 T. In a reanalysis of a sample of 20 healthy human participants who underwent a resting-state fMRI acquisition of the cervical spinal cord, we were able to observe significant dorsal horn connectivity as well as ventral horn connectivity, but no consistent effects for connectivity between dorsal and ventral horns, thus replicating the human 7 T results. These effects were not only observable when averaging along the acquired length of the spinal cord, but also when we examined each of the acquired spinal segments separately, which showed similar patterns of connectivity. Finally, we investigated the robustness of these resting-state signals against variations in the analysis pipeline by varying the type of ROI creation, temporal filtering, nuisance regression and connectivity metric. We observed that – apart from the effects of band-pass filtering – ventral horn connectivity showed excellent robustness, whereas dorsal horn connectivity showed moderate robustness. Together, our results provide evidence that spinal cord resting-state connectivity is a robust and spatially consistent phenomenon that could be a valuable tool for investigating the effects of pathology, disease progression, and treatment response in neurological conditions with a spinal component, such as spinal cord injury.
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Affiliation(s)
- Falk Eippert
- Oxford Centre for Functional Magnetic Resonance Imaging of the Brain, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.
| | - Yazhuo Kong
- Oxford Centre for Functional Magnetic Resonance Imaging of the Brain, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK; Magnetic Resonance Imaging Research Centre, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
| | - Anderson M Winkler
- Oxford Centre for Functional Magnetic Resonance Imaging of the Brain, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Jesper L Andersson
- Oxford Centre for Functional Magnetic Resonance Imaging of the Brain, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Jürgen Finsterbusch
- Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Christian Büchel
- Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | | | - Irene Tracey
- Oxford Centre for Functional Magnetic Resonance Imaging of the Brain, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
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12
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Abstract
Many neurologic diseases can cause acute respiratory decompensation, therefore a familiarity with these diseases is critical for any clinician managing patients with respiratory dysfunction. In this article, we review the anatomy of the respiratory system, focusing on the neurologic control of respiration. We discuss general mechanisms by which diseases of the peripheral and central nervous systems can cause acute respiratory dysfunction, and review the neurologic diseases which can adversely affect respiration. Lastly, we discuss the diagnosis and general management of acute respiratory impairment due to neurologic disease.
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Affiliation(s)
- Rachel A. Nardin
- From the Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
| | - Frank W. Drislane
- From the Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
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13
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Bautista TG, Dutschmann M. Inhibition of the pontine Kölliker-Fuse nucleus abolishes eupneic inspiratory hypoglossal motor discharge in rat. Neuroscience 2014; 267:22-9. [PMID: 24603053 DOI: 10.1016/j.neuroscience.2014.02.027] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Revised: 02/17/2014] [Accepted: 02/19/2014] [Indexed: 11/28/2022]
Abstract
The pontine Kölliker-Fuse nucleus (KF) has established functions in the regulation of inspiratory-expiratory phase transition and the regulation of upper airway patency via laryngeal valving mechanisms. Here we studied the role of the KF in the gating and modulation of eupneic hypoglossal motor activity (HNA) using the in situ perfused brainstem preparation, which displays robust inspiratory HNA. Microinjection of glutamate into the KF area triggered complex and often biphasic modulation (excitation/inhibition or inhibition/excitation) of HNA. Subsequent transient pharmacological inhibition of KF by unilateral microinjection of GABA-A receptor agonist isoguvacine reduced HNA and while bilateral microinjections completely abolished HNA. Our results indicate that mixed and overlapping KF pre-motor neurons provide eupneic drive for inspiratory HNA and postinspiratory vagal nerve activity. Both motor activities have important functions in the regulation of upper airway patency during eupnea but also during various oro-pharyngeal behaviors. These results have potential implications in the contribution of state-dependent modulation of KF hypoglossal pre-motor neurons during sleep-wake cycle to obstructive sleep apnea.
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Affiliation(s)
- T G Bautista
- Florey Institute of Neuroscience and Mental Health, Gate 11, Royal Parade, University of Melbourne, Victoria 3052, Australia
| | - M Dutschmann
- Florey Institute of Neuroscience and Mental Health, Gate 11, Royal Parade, University of Melbourne, Victoria 3052, Australia.
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14
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Abstract
There is a growing public awareness that hormones can have a significant impact on most biological systems, including the control of breathing. This review will focus on the actions of two broad classes of hormones on the neuronal control of breathing: sex hormones and stress hormones. The majority of these hormones are steroids; a striking feature is that both groups are derived from cholesterol. Stress hormones also include many peptides which are produced primarily within the paraventricular nucleus of the hypothalamus (PVN) and secreted into the brain or into the circulatory system. In this article we will first review and discuss the role of sex hormones in respiratory control throughout life, emphasizing how natural fluctuations in hormones are reflected in ventilatory metrics and how disruption of their endogenous cycle can predispose to respiratory disease. These effects may be mediated directly by sex hormone receptors or indirectly by neurotransmitter systems. Next, we will discuss the origins of hypothalamic stress hormones and their relationship with the respiratory control system. This relationship is 2-fold: (i) via direct anatomical connections to brainstem respiratory control centers, and (ii) via steroid hormones released from the adrenal gland in response to signals from the pituitary gland. Finally, the impact of stress on the development of neural circuits involved in breathing is evaluated in animal models, and the consequences of early stress on respiratory health and disease is discussed.
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Affiliation(s)
- Mary Behan
- Department of Comparative Biosciences, University of Wisconsin, Madison, Wisconsin, USA.
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15
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Abstract
Pontine respiratory nuclei provide synaptic input to medullary rhythmogenic circuits to shape and adapt the breathing pattern. An understanding of this statement depends on appreciating breathing as a behavior, rather than a stereotypic rhythm. In this review, we focus on the pontine-mediated inspiratory off-switch (IOS) associated with postinspiratory glottal constriction. Further, IOS is examined in the context of pontine regulation of glottal resistance in response to multimodal sensory inputs and higher commands, which in turn rules timing, duration, and patterning of respiratory airflow. In addition, network plasticity in respiratory control emerges during the development of the pons. Synaptic plasticity is required for dynamic and efficient modulation of the expiratory breathing pattern to cope with rapid changes from eupneic to adaptive breathing linked to exploratory (foraging and sniffing) and expulsive (vocalizing, coughing, sneezing, and retching) behaviors, as well as conveyance of basic emotions. The speed and complexity of changes in the breathing pattern of behaving animals implies that "learning to breathe" is necessary to adjust to changing internal and external states to maintain homeostasis and survival.
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Affiliation(s)
- Mathias Dutschmann
- Florey Neurosciences Institutes, University of Melbourne, Victoria, Australia.
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16
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Azabou E, Roche N, Sharshar T, Bussel B, Lofaso F, Petitjean M. Transcranial direct-current stimulation reduced the excitability of diaphragmatic corticospinal pathways whatever the polarity used. Respir Physiol Neurobiol 2013; 189:183-7. [PMID: 23933029 DOI: 10.1016/j.resp.2013.07.024] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 06/10/2013] [Accepted: 07/22/2013] [Indexed: 10/26/2022]
Abstract
We investigated effects of transcranial direct-current stimulation (tDCS) on the diaphragmatic corticospinal pathways in healthy human. Anodal, cathodal, and sham tDCS were randomly applied upon the left diaphragmatic motor cortex in twelve healthy right-handed men. Corticospinal pathways excitability was assessed by means of transcranial magnetic stimulation (TMS) elicited motor-evoked-potential (MEP). For each tDCS condition, MEPs were recorded before (Pre) tDCS then after 10 min (Post1, at tDCS discontinuation in the anodal and cathodal sessions) and 20 min (Post2). As result, both anodal and cathodal tDCS significantly decreased MEP amplitude of the right hemidiaphragm at both Post1 and Post2, versus Pre. MEP amplitude was unchanged versus Pre during the sham condition. The effects of cathodal and anodal tDCS applied to the diaphragm motor cortex differ from those observed during tDCS of the limb motor cortex. These differences may be related to specific characteristics of the diaphragmatic corticospinal pathways as well as to the diaphragm's functional peculiarities compared with the limb muscles.
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Affiliation(s)
- Eric Azabou
- Department of Physiology, Raymond Poincaré Hospital (AP-HP), Garches, Paris, France; Department of Critical Care Medicine, Raymond Poincaré Hospital (AP-HP), Garches, Paris, France; EA 4497 Group for Clinical and Technical Research on Disability, INSERM CIC-IT 805, University of Versailles Saint-Quentin-En-Yvelines, Versailles, France.
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17
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Hoh DJ, Mercier LM, Hussey SP, Lane MA. Respiration following spinal cord injury: evidence for human neuroplasticity. Respir Physiol Neurobiol 2013; 189:450-64. [PMID: 23891679 DOI: 10.1016/j.resp.2013.07.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 07/01/2013] [Accepted: 07/01/2013] [Indexed: 12/17/2022]
Abstract
Respiratory dysfunction is one of the most devastating consequences of cervical spinal cord injury (SCI) with impaired breathing being a leading cause of morbidity and mortality in this population. However, there is mounting experimental and clinical evidence for moderate spontaneous respiratory recovery, or "plasticity", after some spinal cord injuries. Pre-clinical models of respiratory dysfunction following SCI have demonstrated plasticity at neural and behavioral levels that result in progressive recovery of function. Temporal changes in respiration after human SCI have revealed some functional improvements suggesting plasticity paralleling that seen in experimental models-a concept that has been previously under-appreciated. While the extent of spontaneous recovery remains limited, it is possible that enhancing or facilitating neuroplastic mechanisms may have significant therapeutic potential. The next generation of treatment strategies for SCI and related respiratory dysfunction should aim to optimize these recovery processes of the injured spinal cord for lasting functional restoration.
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Affiliation(s)
- Daniel J Hoh
- Department of Neuroscience, College of Medicine, University of Florida, McKnight Brain Institute, Gainesville, FL 32611, USA; Neurological Surgery, College of Medicine, University of Florida, McKnight Brain Institute, Gainesville, FL, 32611, USA
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18
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de Almeida ATR, Kirkwood PA. Specificity in monosynaptic and disynaptic bulbospinal connections to thoracic motoneurones in the rat. J Physiol 2013; 591:4043-63. [PMID: 23774278 DOI: 10.1113/jphysiol.2013.256503] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The respiratory activity in the intercostal nerves of the rat is unusual, in that motoneurones of both branches of the intercostal nerves, internal and external, are activated during expiration. Here, the pathways involved in that activation were investigated in anaesthetised and in decerebrate rats by cross-correlation and by intracellular spike-triggered averaging from expiratory bulbospinal neurones (EBSNs), with a view to revealing specific connections that could be used in studies of experimental spinal cord injury. Decerebrate preparations, which showed the strongest expiratory activity, were found to be the most suitable for these measurements. Cross-correlations in these preparations showed monosynaptic connections from 16/19 (84%) of EBSNs, but only to internal intercostal nerve motoneurones (24/37, 65% of EBSN/nerve pairs), whereas disynaptic connections were seen for external intercostal nerve motoneurones (4/19, 21% of EBSNs or 7/25, 28% of EBSN/nerve pairs). There was evidence for additional disynaptic connections to internal intercostal nerve motoneurones. Intracellular spike-triggered averaging revealed excitatory postsynaptic potentials, which confirmed these connections. This is believed to be the first report of single descending fibres that participate in two different pathways to two different groups of motoneurones. It is of interest compared with the cat, where only one group of motoneurones is activated during expiration and only one of the pathways has been detected. The specificity of the connections could be valuable in studies of plasticity in pathological situations, but care will be needed in studying connections in such situations, because their strength was found here to be relatively weak.
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Affiliation(s)
- Anoushka T R de Almeida
- Sobell Department for Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK
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19
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McLean J, Bricault S, Schmidt MF. Characterization of respiratory neurons in the rostral ventrolateral medulla, an area critical for vocal production in songbirds. J Neurophysiol 2012; 109:948-57. [PMID: 23175802 DOI: 10.1152/jn.00595.2012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Much is known about the neuronal cell types and circuitry of the mammalian respiratory brainstem and its role in normal, quiet breathing. Our understanding of the role of respiration in the context of vocal production, however, is very limited. Songbirds contain a well-defined neural circuit, known as the song system, which is necessary for song production and is strongly coupled to the respiratory system. A major target of this system is nucleus parambigualis (PAm) in the ventrolateral medulla, a structure that controls inspiration by way of its bulbospinal projections but is also an integral part of the song-pattern generation circuit by way of its "thalamocortical" projections to song-control nuclei in the telencephalon. We have mapped out PAm to characterize the cell types and its functional organization. Extracellular single units were obtained in anesthetized adult male zebra finches while measuring air sac pressure to monitor respiration. Single units were characterized by their discharge patterns and the phase of the activity in the respiratory cycle. Several classes of neurons were identified and were analogous to those reported for mammalian medullary respiratory neurons. The majority of the neurons in PAm was classified as inspiratory augmenting or preinspiratory, although other basic discharge patterns were observed as well. The well-characterized connectivity of PAm within the vocal motor circuit and the similarity of its neural firing patterns to the rostral ventral respiratory group and pre-Bötzinger complex of mammals make it an ideal system for investigating the integration of breathing and vocalization.
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Affiliation(s)
- Judith McLean
- Department of Biology, Mahoney Institute of Neurological Sciences, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6018, USA
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20
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Enríquez Denton M, Wienecke J, Zhang M, Hultborn H, Kirkwood PA. Voltage-dependent amplification of synaptic inputs in respiratory motoneurones. J Physiol 2012; 590:3067-90. [PMID: 22495582 PMCID: PMC3406391 DOI: 10.1113/jphysiol.2011.225789] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Accepted: 04/05/2012] [Indexed: 11/08/2022] Open
Abstract
The role of persistent inward currents (PICs) in cat respiratory motoneurones (phrenic inspiratory and thoracic expiratory) was investigated by studying the voltage-dependent amplification of central respiratory drive potentials (CRDPs), recorded intracellularly, with action potentials blocked with the local anaesthetic derivative, QX-314. Decerebrate unanaesthetized or barbiturate-anaesthetized preparations were used. In expiratory motoneurones, plateau potentials were observed in the decerebrates, but not under anaesthesia. For phrenic motoneurones, no plateau potentials were observed in either state (except in one motoneurone after the abolition of the respiratory drive by means of a medullary lesion), but all motoneurones showed voltage-dependent amplification of the CRDPs, over a wide range of membrane potentials, too wide to result mainly from PIC activation. The measurements of the amplification were restricted to the phase of excitation, thus excluding the inhibitory phase. Amplification was found to be greatest for the smallest CRDPs in the lowest resistance motoneurones and was reduced or abolished following intracellular injection of the NMDA channel blocker, MK-801. Plateau potentials were readily evoked in non-phrenic cervical motoneurones in the same (decerebrate) preparations. We conclude that the voltage-dependent amplification of synaptic excitation in phrenic motoneurones is mainly the result of NMDA channel modulation rather than the activation of Ca2+ channel mediated PICs, despite phrenic motoneurones being strongly immunohistochemically labelled for CaV1.3 channels. The differential PIC activation in different motoneurones, all of which are CaV1.3 positive, leads us to postulate that the descending modulation of PICs is more selective than has hitherto been believed.
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Affiliation(s)
- M Enríquez Denton
- Sobell Department for Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK
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21
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Isolated in vitro brainstem-spinal cord preparations remain important tools in respiratory neurobiology. Respir Physiol Neurobiol 2011; 180:1-7. [PMID: 22015642 DOI: 10.1016/j.resp.2011.10.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Accepted: 10/06/2011] [Indexed: 11/22/2022]
Abstract
Isolated in vitro brainstem-spinal cord preparations are used extensively in respiratory neurobiology because the respiratory network in the pons and medulla is intact, monosynaptic descending inputs to spinal motoneurons can be activated, brainstem and spinal cord tissue can be bathed with different solutions, and the responses of cervical, thoracic, and lumbar spinal motoneurons to experimental perturbations can be compared. The caveats and limitations of in vitro brainstem-spinal cord preparations are well-documented. However, isolated brainstem-spinal cords are still valuable experimental preparations that can be used to study neuronal connectivity within the brainstem, development of motor networks with lethal genetic mutations, deleterious effects of pathological drugs and conditions, respiratory spinal motor plasticity, and interactions with other motor behaviors. Our goal is to show how isolated brainstem-spinal cord preparations still have a lot to offer scientifically and experimentally to address questions within and outside the field of respiratory neurobiology.
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22
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Lane MA. Spinal respiratory motoneurons and interneurons. Respir Physiol Neurobiol 2011; 179:3-13. [DOI: 10.1016/j.resp.2011.07.004] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Revised: 07/03/2011] [Accepted: 07/07/2011] [Indexed: 01/30/2023]
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23
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Lee KZ, Fuller DD. Neural control of phrenic motoneuron discharge. Respir Physiol Neurobiol 2011; 179:71-9. [PMID: 21376841 DOI: 10.1016/j.resp.2011.02.014] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Revised: 02/23/2011] [Accepted: 02/25/2011] [Indexed: 01/09/2023]
Abstract
Phrenic motoneurons (PMNs) provide a synaptic relay between bulbospinal respiratory pathways and the diaphragm muscle. PMNs also receive propriospinal inputs, although the functional role of these interneuronal projections has not been established. Here we review the literature regarding PMN discharge patterns during breathing and the potential mechanisms that underlie PMN recruitment. Anatomical and neurophysiological studies indicate that PMNs form a heterogeneous pool, with respiratory-related PMN discharge and recruitment patterns likely determined by a balance between intrinsic MN properties and extrinsic synaptic inputs. We also review the limited literature regarding PMN bursting during respiratory plasticity. Differential recruitment or rate modulation of PMN subtypes may underlie phrenic motor plasticity following neural injury and/or respiratory stimulation; however, this possibility remains relatively unexplored.
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Affiliation(s)
- Kun-Ze Lee
- University of Florida, College of Public Health and Health Professions, McKnight Brain Institute, Department of Physical Therapy, PO Box 100154, 100 S. Newell Dr, Gainesville, FL 32610, United States
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24
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Hilaire G, Voituron N, Menuet C, Ichiyama RM, Subramanian HH, Dutschmann M. The role of serotonin in respiratory function and dysfunction. Respir Physiol Neurobiol 2010; 174:76-88. [PMID: 20801236 PMCID: PMC2993113 DOI: 10.1016/j.resp.2010.08.017] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Revised: 08/18/2010] [Accepted: 08/20/2010] [Indexed: 01/11/2023]
Abstract
Serotonin (5-HT) is a neuromodulator-transmitter influencing global brain function. Past and present findings illustrate a prominent role for 5-HT in the modulation of ponto-medullary autonomic circuits. 5-HT is also involved in the control of neurotrophic processes during pre- and postnatal development of neural circuits. The functional implications of 5-HT are particularly illustrated in the alterations to the serotonergic system, as seen in a wide range of neurological disorders. This article reviews the role of 5-HT in the development and control of respiratory networks in the ponto-medullary brainstem. The review further examines the role of 5-HT in breathing disorders occurring at different stages of life, in particular, the neonatal neurodevelopmental diseases such as Rett, sudden infant death and Prader-Willi syndromes, adult diseases such as sleep apnoea and mental illness linked to neurodegeneration.
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Affiliation(s)
- Gérard Hilaire
- Mp3-respiration team, Centre de Recherche en Neurobiologie et Neurophysiologie de Marseille (CRN2M), Unité Mixte de Recherche 6231, CNRS - Université Aix-Marseille II & III, Faculté Saint Jérôme 13397 Marseille Cedex 20, France
| | - Nicolas Voituron
- Mp3-respiration team, Centre de Recherche en Neurobiologie et Neurophysiologie de Marseille (CRN2M), Unité Mixte de Recherche 6231, CNRS - Université Aix-Marseille II & III, Faculté Saint Jérôme 13397 Marseille Cedex 20, France
| | - Clément Menuet
- Mp3-respiration team, Centre de Recherche en Neurobiologie et Neurophysiologie de Marseille (CRN2M), Unité Mixte de Recherche 6231, CNRS - Université Aix-Marseille II & III, Faculté Saint Jérôme 13397 Marseille Cedex 20, France
| | - Ronaldo M. Ichiyama
- Institute of Membrane and Systems Biology, Garstang Building, University of Leeds, Leeds LS2 9JT
| | - Hari H. Subramanian
- Institute of Membrane and Systems Biology, Garstang Building, University of Leeds, Leeds LS2 9JT
| | - Mathias Dutschmann
- Institute of Membrane and Systems Biology, Garstang Building, University of Leeds, Leeds LS2 9JT
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25
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Early breathing defects after moderate hypoxia or hypercapnia in a mouse model of Rett syndrome. Respir Physiol Neurobiol 2009; 168:109-18. [DOI: 10.1016/j.resp.2009.05.013] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2009] [Revised: 05/29/2009] [Accepted: 05/29/2009] [Indexed: 12/21/2022]
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26
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Binder MD, Hirokawa N, Windhorst U. R. ENCYCLOPEDIA OF NEUROSCIENCE 2009. [PMCID: PMC7163931 DOI: 10.1007/978-3-540-29678-2_18] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Marc D. Binder
- Department of Physiology & Biophysics, University of Washington School of Medicine, Seattle Washington, USA
| | - Nobutaka Hirokawa
- Department of Cell Biology and Anatomy, Graduate School of Medicine University of Tokyo Hongo, Bunkyo‐ku Tokyo, Japan
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27
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Abstract
Each of the descending pathways involved in motor control has a number of anatomical, molecular, pharmacological, and neuroinformatic characteristics. They are differentially involved in motor control, a process that results from operations involving the entire motor network rather than from the brain commanding the spinal cord. A given pathway can have many functional roles. This review explores to what extent descending pathways are highly conserved across species and concludes that there are actually rather widespread species differences, for example, in the transmission of information from the corticospinal tract to upper limb motoneurons. The significance of direct, cortico-motoneuronal (CM) connections, which were discovered a little more than 50 years ago, is reassessed. I conclude that although these connections operate in parallel with other less direct linkages to motoneurons, CM influence is significant and may subserve some special functions including adaptive motor behaviors involving the distal extremities.
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Affiliation(s)
- Roger N Lemon
- Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London, WC1N 3BG, United Kingdom.
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28
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Giraudin A, Cabirol-Pol MJ, Simmers J, Morin D. Intercostal and abdominal respiratory motoneurons in the neonatal rat spinal cord: spatiotemporal organization and responses to limb afferent stimulation. J Neurophysiol 2008; 99:2626-40. [PMID: 18337363 DOI: 10.1152/jn.01298.2007] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Respiration requires the coordinated rhythmic contractions of diverse muscles to produce ventilatory movements adapted to organismal requirements. During fast locomotion, locomotory and respiratory movements are coordinated to reduce mechanical conflict between these functions. Using semi-isolated and isolated in vitro brain stem-spinal cord preparations from neonatal rats, we have characterized for the first time the respiratory patterns of all spinal intercostal and abdominal motoneurons and explored their functional relationship with limb sensory inputs. Neuroanatomical and electrophysiological procedures were initially used to locate intercostal and abdominal motoneurons in the cord. Intercostal motoneuron somata are distributed rostrocaudally from C(7)-T(13) segments. Abdominal motoneuron somata lie between T(8) and L(2). In accordance with their soma distributions, inspiratory intercostal motoneurons are recruited in a rostrocaudal sequence during each respiratory cycle. Abdominal motoneurons express expiratory-related discharge that alternates with inspiration. Lesioning experiments confirmed the pontine origin of this expiratory activity, which was abolished by a brain stem transection at the rostral boundary of the VII nucleus, a critical area for respiratory rhythmogenesis. Entrainment of fictive respiratory rhythmicity in intercostal and abdominal motoneurons was elicited by periodic low-threshold dorsal root stimulation at lumbar (L(2)) or cervical (C(7)) levels. These effects are mediated by direct ascending fibers to the respiratory centers and a combination of long-projection and polysynaptic descending pathways. Therefore the isolated brain stem-spinal cord in vitro generates a complex pattern of respiratory activity in which alternating inspiratory and expiratory discharge occurs in functionally identified spinal motoneuron pools that are in turn targeted by both forelimb and hindlimb somatic afferents to promote locomotor-respiratory coupling.
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Affiliation(s)
- Aurore Giraudin
- Université Victor Segalen Bordeaux 2, UMR CNRS 5227, Laboratoire Mouvement-Adaptation-Cognition, Bâtiment 2A, 146 Rue Léo Saignat, Bordeaux, France
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29
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Butler JE. Drive to the human respiratory muscles. Respir Physiol Neurobiol 2007; 159:115-26. [PMID: 17660051 DOI: 10.1016/j.resp.2007.06.006] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2007] [Revised: 06/07/2007] [Accepted: 06/07/2007] [Indexed: 11/24/2022]
Abstract
The motor control of the respiratory muscles differs in some ways from that of the limb muscles. Effectively, the respiratory muscles are controlled by at least two descending pathways: from the medulla during normal quiet breathing and from the motor cortex during behavioural or voluntary breathing. Neurophysiological studies of single motor unit activity in human subjects during normal and voluntary breathing indicate that the neural drive is not uniform to all muscles. The distribution of neural drive depends on a principle of neuromechanical matching. Those motoneurones that innervate intercostal muscles with greater mechanical advantage are active earlier in the breath and to a greater extent. Inspiratory drive is also distributed differently across different inspiratory muscles, possibly also according to their mechanical effectiveness in developing airway negative pressure. Genioglossus, a muscle of the upper airway, receives various types of neural drive (inspiratory, expiratory and tonic) distributed differentially across the hypoglossal motoneurone pool. The integration of the different inputs results in the overall activity in the muscle to keep the upper airway patent throughout respiration. Integration of respiratory and non-respiratory postural drive can be demonstrated in respiratory muscles, and respiratory drive can even be observed in limb muscles under certain circumstances. Recordings of motor unit activity from the human diaphragm during voluntary respiratory tasks have shown that depending on the task there can be large changes in recruitment threshold and recruitment order of motor units. This suggests that descending drive across the phrenic motoneurone pool is not necessarily consistent. Understanding the integration and distribution of drive to respiratory muscles in automatic breathing and voluntary tasks may have implications for limb motor control.
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Affiliation(s)
- Jane E Butler
- Prince of Wales Medical Research Institute, University of New South Wales, Sydney, NSW 2031, Australia.
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30
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Yelmen N, Sahin G, Oruc T, Guner I. The reflex effects on the respiratory regulation of the CO2 at the different flow rate and concentration. Yonsei Med J 2007; 48:856-64. [PMID: 17963345 PMCID: PMC2628154 DOI: 10.3349/ymj.2007.48.5.856] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
PURPOSE The purpose of this study was to investigate the activation of the respiratory centers during insufflation of the larynx with CO2 at different flow rates and concentrations. MATERIALS AND METHODS The experiments were carried out in spontaneous air breathing rabbits, anesthetized with thiopental sodium (25 mg kg(-1) i.v.). The larynx was separated from the oropharyngeal cavity and the trachea. The tidal volume (VT) and respiratory frequency (f min(-1)) were recorded from the lower tracheal cannula. The respiratory minute volume (VE) was calculated, the action potentials from the right phrenic nerve were recorded and the inspiratory (TI) and expiratory (TE) periods and the mean inspiratory flow rate (VT/TI) were calculated. The larynx was insufflated at flow rates of 500 mL min(-1) and 750 mL min(-1), with 7 and 12% CO2-Air by means of a respiratory pump. RESULTS Insufflation of the larynx, with both gas mixtures, decreased the f and VT significantly. The TI and TE were found to increase significantly due to the decreasing in f. There was a significant decrease in VT/TI ratio. Following bilateral midcervical vagotomy, on the passing of both gas mixtures, significant decreases were observed in the VT, and the responses of f, TI and TE were abolished. After cutting the superior laryngeal nerve, the responses of the VT to both gas mixtures were abolished. CONCLUSION In conclusion, the results of this study purpose that the stimulation of the laryngeal mechanoreceptors by the effect of hypercapnia decreases the activation of the respiratory center.
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Affiliation(s)
- Nermin Yelmen
- Department of Physiology, Istanbul University, Cerrahpaşa Medical School, 34098 Fatih-Istanbul, Turkey.
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31
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Taccola G, Secchia L, Ballanyi K. Anoxic persistence of lumbar respiratory bursts and block of lumbar locomotion in newborn rat brainstem spinal cords. J Physiol 2007; 585:507-24. [PMID: 17932145 DOI: 10.1113/jphysiol.2007.143594] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The tolerance of breathing in neonates to oxygen depletion is reflected by persistence of inspiratory-related motor output during sustained anoxia in newborn rat brainstem preparations. It is not known whether lumbar motor networks innervating expiratory abdominal muscles are, in contrast, inhibited by anoxia similar to locomotor networks in neonatal mouse lumbar cords. To test this, we recorded inspiratory-related cervical/hypoglossal plus pre/postinspiratory lumbar/facial nerve activities and, sometimes simultaneously, locomotor rhythms in newborn rat brainstem-spinal cords. Chemical anoxia slowed 1 : 1-coupled cervical and lumbar respiratory rhythms and induced cervical burst doublets associated with depressed preinspiratory and augmented postinspiratory lumbar activities. Similarly, anoxia evoked repetitive hypoglossal bursts and shifted facial activity toward augmented postinspiratory bursting in medullas without spinal cord. Selective lumbar anoxia augmented pre/postinspiratory lumbar bursting without slowing the rhythm. This suggests a medullary origin of both anoxic inspiratory double bursts and preinspiratory depression, but a mixed medullary/lumbar origin of boosted postinspiratory lumbar activity. Lumbar respiratory rhythm is likely to be generated by the parafacial respiratory group expiratory centre as indicated by lack of normoxic and anoxic bursting following brainstem transection between the facial motonucleus and the more caudal pre-Bötzinger complex inspiratory centre. Opposed to sustained respiratory activities, anoxia reversibly abolished non-rhythmic spinal discharges and electrically or chemically evoked lumbar locomotor activities, followed by pronounced postanoxic spinal hyperexcitability. We hypothesize that (i) the anoxia tolerance of neonatal breathing includes pFRG-driven lumbar expiratory networks, (ii) the anoxic respiratory pattern transformation is due to disturbed inspiratory-expiratory centre interactions, and (iii) postanoxic lumbar hyperexcitability contributes to spasticity in cerebral palsy.
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Affiliation(s)
- Giuliano Taccola
- Perinatal Research Centre, Department of Physiology, University of Alberta, Edmonton, AB, Canada T6G 2S2
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Boulenguez P, Gauthier P, Kastner A. Respiratory neuron subpopulations and pathways potentially involved in the reactivation of phrenic motoneurons after C2 hemisection. Brain Res 2007; 1148:96-104. [DOI: 10.1016/j.brainres.2007.02.060] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2007] [Revised: 02/14/2007] [Accepted: 02/14/2007] [Indexed: 12/21/2022]
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Saywell SA, Anissimova NP, Ford TW, Meehan CF, Kirkwood PA. The respiratory drive to thoracic motoneurones in the cat and its relation to the connections from expiratory bulbospinal neurones. J Physiol 2007; 579:765-82. [PMID: 17204500 PMCID: PMC2151366 DOI: 10.1113/jphysiol.2006.122481] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2006] [Accepted: 01/03/2007] [Indexed: 01/01/2023] Open
Abstract
The descending control of respiratory-related motoneurones in the thoracic spinal cord remains the subject of some debate. In this study, direct connections from expiratory bulbospinal neurones to identified motoneurones were investigated using spike-triggered averaging and the strengths of connection revealed were related to the presence and size of central respiratory drive potentials in the same motoneurones. Intracellular recordings were made from motoneurones in segments T5-T9 of the spinal cord of anaesthetized cats. Spike-triggered averaging from expiratory bulbospinal neurones in the caudal medulla revealed monosynaptic EPSPs in all groups of motoneurones, with the strongest connections to expiratory motoneurones with axons in the internal intercostal nerve. In the latter, connection strength was similar irrespective of the target muscle (e.g. external abdominal oblique or internal intercostal) and the EPSP amplitude was positively correlated with the amplitude of the central respiratory drive potential of the motoneurone. For this group, EPSPs were found in 45/83 bulbospinal neurone/motoneurone pairs, with a mean amplitude of 40.5 microV. The overall strength of the connection supports previous measurements made by cross-correlation, but is about 10 times stronger than that reported in the only previous similar survey to use spike-triggered averaging. Calculations are presented to suggest that this input alone is sufficient to account for all the expiratory depolarization seen in the recorded motoneurones. However, extra sources of input, or amplification of this one, are likely to be necessary to produce a useful motoneurone output.
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Affiliation(s)
- S A Saywell
- Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK
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Falgairolle M, Cazalets JR. Metachronal coupling between spinal neuronal networks during locomotor activity in newborn rat. J Physiol 2006; 580:87-102. [PMID: 17185345 PMCID: PMC2075426 DOI: 10.1113/jphysiol.2006.115709] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
In the present study, we investigate spinal cord neuronal network interactions in the neonatal rat during locomotion. The behavioural and physiological relevance of metachronally propagated locomotor activity were inferred from kinematic, anatomical and in vitro electrophysiological data. Kinematic analysis of freely behaving animals indicated that there is a rhythmic sequential change in trunk curvature during the step cycle. The motoneurons innervating back and tail muscles were identified along the spinal cord using retrograde labelling. Systematic multiple recordings from ventral roots were made to determine the precise intrinsic pattern of coordination in the isolated spinal cord. During locomotor-like activity, rhythmic ventral root motor bursts propagate caudo-rostrally in the sacral and the thoracic spinal cord regions. Plotting the latency as a function of the cycle period revealed that the system adapts the intersegmental latency to the ongoing motor period in order to maintain a constant phase relationship along the spinal axis. The thoracic, lumbar and sacral regions were capable of generating right and left alternating motor bursts when isolated. Longitudinal sections of the spinal cord revealed that both the bilateral antiphase pattern observed for the sacral region with respect to the lumbar segment 2 as well as the intersegmental phase lag were due to cross-cord connections. Together, these results provide physiological evidence that the dynamic changes observed in trunk bending during locomotion are determined by the intrinsic organization of spinal cord networks and their longitudinal and transverse interactions. Similarities between this organization, and that of locomotor pattern generation in more primitive vertebrates, suggest that the circuits responsible for metachronal propagation of motor patterns during locomotion are highly conserved.
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Affiliation(s)
- Mélanie Falgairolle
- CNRS Unité Mixte de Recherche 5227, Université Bordeaux 2, Zone nord Bat 2, 146, rue Léo Saignat, 33076 Bordeaux Cedex, France
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Ford TW, Kirkwood PA. Respiratory drive in hindlimb motoneurones of the anaesthetized female cat. Brain Res Bull 2006; 70:450-6. [PMID: 17027781 DOI: 10.1016/j.brainresbull.2006.07.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2006] [Revised: 06/27/2006] [Accepted: 07/03/2006] [Indexed: 10/24/2022]
Abstract
Anatomical studies have shown a monosynaptic projection from nucleus retroambiguus (NRA) to semimembranosus (Sm) motor nucleus in female cats, which is stronger in oestrus. Expiratory bulbospinal neurones are the best documented functional cell type in the NRA. If these cells participate in this projection, an expiratory drive would be expected in Sm motoneurones and this drive would be expected to be stronger in oestrus. In anaesthetized, paralyzed, ovariohysterectomized female cats, artificially ventilated to produce a strong respiratory drive (as monitored by phrenic nerve discharges), intracellular recordings were made from Sm motoneurones and from motoneurones in the surrounding hindlimb motor nuclei that are outside the focus of the NRA projection. The animals comprised two groups: either treated for 7 days with oestradiol benzoate (oestrous) or untreated (non-oestrous). Central respiratory drive potentials (CRDPs) were observed in most motoneurones of both groups, with amplitudes larger for the oestrous than for the non-oestrous group (1.58+/-1.34 mV versus 0.89+/-0.79 mV, mean+/-S.D.). However, the CRDPs most often consisted of a maximum depolarization in early expiration, which declined in late expiration and into inspiration. This pattern is different from the incrementing firing pattern of most expiratory bulbospinal neurones. The CRDPs in Sm and semitendinosus motoneurones (located in the same motor column) were of similar size and frequency to CRDPs in motoneurones outside that column. The hypothesis that expiratory bulbospinal neurones are significantly involved in the projection was rejected. Alternative sources and possible functional roles for the CRDPs are discussed.
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Affiliation(s)
- T W Ford
- University of Nottingham School of Nursing, Queen's Medical Centre, Nottingham NG7 2UH, United Kingdom
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Choi H, Liao WL, Newton KM, Onario RC, King AM, Desilets FC, Woodard EJ, Eichler ME, Frontera WR, Sabharwal S, Teng YD. Respiratory abnormalities resulting from midcervical spinal cord injury and their reversal by serotonin 1A agonists in conscious rats. J Neurosci 2006; 25:4550-9. [PMID: 15872102 PMCID: PMC6725034 DOI: 10.1523/jneurosci.5135-04.2005] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Respiratory dysfunction after cervical spinal cord injury (SCI) has not been examined experimentally using conscious animals, although clinical SCI most frequently occurs in midcervical segments. Here, we report a C5 hemicontusion SCI model in rats with abnormalities that emulate human post-SCI pathophysiology, including spontaneous recovery processes. Post-C5 SCI rats demonstrated deficits in minute ventilation (Ve) responses to a 7% CO2 challenge that correlated significantly with lesion severities (no injury or 12.5, 25, or 50 mm x 10 g weight drop; New York University impactor; p < 0.001) and ipsilateral motor neuron loss (p = 0.016). Importantly, C5 SCI resulted in at least 4 weeks of respiratory abnormalities that ultimately recovered afterward. Because serotonin is involved in respiration-related neuroplasticity, we investigated the impact of activating 5-HT1A receptors on post-C5 SCI respiratory dysfunction. Treatment with the 5-HT1A agonist 8-hydroxy-2-(di-n-propylmino)tetralin (8-OH DPAT) (250 microg/kg, i.p.) restored hypercapnic Ve at 2 and 4 weeks after injury (i.e., approximately 39.2% increase vs post-SCI baseline; p < or = 0.033). Improvements in hypercapnic Ve response after single administration of 8-OH DPAT were dose dependent and lasted for approximately 4 h(p < or = 0.038 and p < or = 0.024, respectively). Treatment with another 5-HT1A receptor agonist, buspirone (1.5 mg/kg, i.p.), replicated the results, whereas pretreatment with a 5-HT1A-specific antagonist, 4-iodo-N-[2-[4(methoxyphenyl)-1-piperazinyl]ethyl]-N-2-pyridinyl-benzamide (3 mg/kg, i.p.) given 20 min before 8-OH DPAT negated the effect of 8-OH DPAT. These results imply a potential clinical use of 5-HT1A agonists for post-SCI respiratory disorders.
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Affiliation(s)
- Howard Choi
- Department of Neurosurgery, Harvard Medical School, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA
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Achard P, Zanella S, Rodriguez R, Hilaire G. Perinatal maturation of the respiratory rhythm generator in mammals: from experimental results to computational simulation. Respir Physiol Neurobiol 2005; 149:17-27. [PMID: 16203211 DOI: 10.1016/j.resp.2005.01.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2004] [Revised: 01/24/2005] [Accepted: 01/24/2005] [Indexed: 01/20/2023]
Abstract
The survival of neonatal mammals requires a correct function of the respiratory rhythm generator (RRG), and therefore, the processes that control its prenatal maturation are of vital importance. In humans, lambs and rodents, foetal breathing movements (FBMs) occur early during gestation, are episodic, sensitive to bioamines, central hypoxia and inputs from CNS upper structures, and evolve with developmental age. In vitro, the foetal rodent RRG studied in preparations where the upper CNS structures are lacking continuously produces a rhythmic command, which is sensitive to hypoxia and bioaminergic inputs. The rhythm is slow with variable periods 4 days before birth. It becomes faster 2 days before birth, similar to the postnatal rhythm. Compelling evidence suggests that a region of the RRG called the preBötzinger complex (PBC) contains respiratory pacemaker neurones which play a primary role in perinatal rhythmogenesis. Although the RRG functions during early gestation, no pacemakers are found in the putative PBC area and its electrical stimulation and lesion do not affect the early foetal rhythm. To know whether the early foetal and perinatal rhythms originate from either pacemaker neurones or network connection properties, and to know which maturational processes might explain the appearance of PBC pacemakers and the rhythm increase during perinatal development, we computationally modelled maturing RRG. Our model shows that both network noise and persistent sodium conductance are crucial for rhythmogenesis and that a slight increase in the persistent sodium conductance can solve the pacemaker versus network dilemma in a noisy network.
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Affiliation(s)
- Pablo Achard
- CNRS UMR 6207, Centre de Physique Théorique, Case 907, 13288 Marseille cedex 9, France
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Greer JJ, Funk GD. Perinatal development of respiratory motoneurons. Respir Physiol Neurobiol 2005; 149:43-61. [PMID: 15951250 DOI: 10.1016/j.resp.2005.03.017] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2005] [Revised: 03/09/2005] [Accepted: 03/09/2005] [Indexed: 01/19/2023]
Abstract
Breathing movements require the coordinated recruitment of cranial and spinal motoneurons innervating muscles of the upper airway and ribcage. A significant part of respiratory motoneuron development and maturation occurs prenatally to support the generation of fetal breathing movements in utero and sustained breathing at birth. Postnatally, motoneuron properties are further refined and match changes in the maturing respiratory musculoskeletal system. In this review, we outline developmental changes in key respiratory motoneuronal populations occurring from the time of motoneuron birth in the embryo through the postnatal period. We will also bring attention to major deficiencies in the current knowledge of perinatal respiratory motoneuron development. To date, our understanding of processes occurring during the prenatal period comes primarily from analysis of phrenic motoneurons (PMNs), whereas information about postnatal development derives largely from studies of PMN and hypoglossal motoneuron properties.
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Affiliation(s)
- John J Greer
- Department of Physiology, Division of Neuroscience, 513 HMRC, Perinatal Research Centre, University of Alberta, Edmonton, Alta., Canada T6G 2S2.
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Abstract
The mechanical advantages of the external and internal intercostals depend partly on the orientation of the muscle but mostly on interspace number and the position of the muscle within each interspace. Thus the external intercostals in the dorsal portion of the rostral interspaces have a large inspiratory mechanical advantage, but this advantage decreases ventrally and caudally such that in the ventral portion of the caudal interspaces, it is reversed into an expiratory mechanical advantage. The internal interosseous intercostals in the caudal interspaces also have a large expiratory mechanical advantage, but this advantage decreases cranially and, for the upper interspaces, ventrally as well. The intercartilaginous portion of the internal intercostals (the so-called parasternal intercostals), therefore, has an inspiratory mechanical advantage, whereas the triangularis sterni has a large expiratory mechanical advantage. These rostrocaudal gradients result from the nonuniform coupling between rib displacement and lung expansion, and the dorsoventral gradients result from the three-dimensional configuration of the rib cage. Such topographic differences in mechanical advantage imply that the functions of the muscles during breathing are largely determined by the topographic distributions of neural drive. The distributions of inspiratory and expiratory activity among the muscles are strikingly similar to the distributions of inspiratory and expiratory mechanical advantages, respectively. As a result, the external intercostals and the parasternal intercostals have an inspiratory function during breathing, whereas the internal interosseous intercostals and the triangularis sterni have an expiratory function.
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Affiliation(s)
- André De Troyer
- Laboratory of Cardiorespiratory Physiology, Brussels School of Medicine and Chest Service, Erasme University Hospital, Belgium.
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Juvin L, Morin D. Descending respiratory polysynaptic inputs to cervical and thoracic motoneurons diminish during early postnatal maturation in rat spinal cord. Eur J Neurosci 2005; 21:808-13. [PMID: 15733100 DOI: 10.1111/j.1460-9568.2005.03910.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Isolated brainstem-spinal cord preparations were used to explore the coexistence of a direct and an indirect descending drive from the brainstem respiratory centre to cervical and thoracic respiratory motoneurons in the neonatal Sprague-Dawley rat. Polysynaptic spinal relay pathways from the respiratory centre were suppressed by selectively perfusing the cord with mephenesin (1 mM) or a solution enriched with Ca2+ and Mg2+. At birth, both direct and spinally relayed pathways are functional and contribute equally to the global descending respiratory drive. However, during the first postnatal week, significant maturational changes appear in the way the respiratory centre controls its target respiratory motoneurons in the cervical and thoracic spinal cord, with the direct respiratory drive becoming progressively predominant with maturation (from 50% to around 75% of the global descending command). The relative contributions of the monosynaptic and the polysynaptic spinal pathways may therefore have important implications for effective respiratory control during early postnatal development.
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Affiliation(s)
- Laurent Juvin
- Universités Bordeaux 1 & Victor Segalen Bordeaux 2, Laboratoire Physiologie et Physiopathologie de la Signalisation Cellulaire, UMR CNRS 5543, Equipe Neurobiologie Adaptative des Systèmes Moteurs, 33076 Bordeaux Cedex, France
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Polentes J, Stamegna JC, Nieto-Sampedro M, Gauthier P. Phrenic rehabilitation and diaphragm recovery after cervical injury and transplantation of olfactory ensheathing cells. Neurobiol Dis 2004; 16:638-53. [PMID: 15262276 DOI: 10.1016/j.nbd.2004.04.009] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2004] [Revised: 04/06/2004] [Accepted: 04/12/2004] [Indexed: 11/29/2022] Open
Abstract
Functional respiratory recovery was evaluated by recording diaphragm and phrenic nerve activity several months after cervical cord hemisection followed by olfactory ensheathing cell (OEC) transplantation. The intact side was taken as a control in each rat. Sham-transplanted rats did not recover respiratory activity from the ipsilateral lesioned side. By contrast, ipsilateral phrenic and diaphragmatic activities recovered in transplanted rats amounted to 80.7% and 73% of their controls, respectively. After contralateral acute C1 section eliminating any contralateral influence from crossed compensatory pathways, the ipsilateral phrenic activity remained at 57.5% of the control, indicating that the phrenic recovery originated from the ipsilateral side. Supralesional stimulation in these rats elicited sublesional ipsilateral postsynaptic phrenic responses showing that transplantation helped ipsilateral fibers to again transmit nervous messages to the phrenic target, leading to substantial functional recovery. The origin of mechanisms involved in respiratory recovery (regeneration, resurrection, sprouting, sparing, demasking of latent pathways) is discussed.
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Affiliation(s)
- J Polentes
- Physiologie Neurovégétative, UMR CNRS 6153 INRA 1147, Faculté des Sciences et Techniques de Saint-Jérôme (Aix-Marseille III), 13397 Marseille 20, France
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Meehan CF, Ford TW, Road JD, Donga R, Saywell SA, Anissimova NP, Kirkwood PA. Rostrocaudal distribution of motoneurones and variation in ventral horn area within a segment of the feline thoracic spinal cord. J Comp Neurol 2004; 472:281-91. [PMID: 15065124 DOI: 10.1002/cne.20096] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Retrograde transport of horseradish peroxidase, applied to cut peripheral nerves, was used to determine the rostrocaudal distribution of motoneurones supplying different branches of the ventral ramus for a single mid- or caudal thoracic segment in the cat. The motoneurones occupied a length of spinal cord equal to the segmental length but displaced rostrally from the segment as defined by the dorsal roots, with the number of motoneurones per unit length of cord higher in the rostral part of a segment (close to the entry of the most rostral dorsal root) than in the caudal part. The cross-sectional area of the ventral horn showed a rostrocaudal variation that closely paralleled the motoneurone distribution. The ratio between the number of motoneurones per unit length in the caudal and rostral regions of a segment (0.70) was similar to the ratio previously reported for the strength of functional projections of expiratory bulbospinal neurones (0.63). This is consistent with the motoneurones being the main targets of the bulbospinal neurones.
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Affiliation(s)
- Claire F Meehan
- Sobell Department for Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London WC1N 3BG, United Kingdom
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Blanchi B, Kelly LM, Viemari JC, Lafon I, Burnet H, Bévengut M, Tillmanns S, Daniel L, Graf T, Hilaire G, Sieweke MH. MafB deficiency causes defective respiratory rhythmogenesis and fatal central apnea at birth. Nat Neurosci 2003; 6:1091-100. [PMID: 14513037 DOI: 10.1038/nn1129] [Citation(s) in RCA: 135] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2003] [Accepted: 08/22/2003] [Indexed: 11/08/2022]
Abstract
The genetic basis for the development of brainstem neurons that generate respiratory rhythm is unknown. Here we show that mice deficient for the transcription factor MafB die from central apnea at birth and are defective for respiratory rhythmogenesis in vitro. MafB is expressed in a subpopulation of neurons in the preBötzinger complex (preBötC), a putative principal site of rhythmogenesis. Brainstems from Mafb(-/-) mice are insensitive to preBötC electrolytic lesion or stimulation and modulation of rhythmogenesis by hypoxia or peptidergic input. Furthermore, in Mafb(-/-) mice the preBötC, but not major neuromodulatory groups, presents severe anatomical defects with loss of cellularity. Our results show an essential role of MafB in central respiratory control, possibly involving the specification of rhythmogenic preBötC neurons.
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Affiliation(s)
- Bruno Blanchi
- Centre d'Immunologie de Marseille-Luminy, CNRS-INSERM-Université Mediterrané, Campus de Luminy, Case 906, 13288 Marseille Cedex 09, France
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Lonergan T, Goodchild AK, Christie MJ, Pilowsky PM. Presynaptic Δ opioid receptors differentially modulate rhythm and pattern generation in the ventral respiratory group of the rat. Neuroscience 2003; 121:959-73. [PMID: 14580946 DOI: 10.1016/s0306-4522(03)00591-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The specific role of the Delta opioid receptor (DOR), in opioid-induced respiratory depression in the ventral respiratory group (VRG) is largely unknown. Here, we sought to determine (1) the relationship between DOR-immunoreactive (ir) boutons, bulbospinal and functionally identified respiratory neurons in the VRG and (2) the effects of microinjection of the selective DOR agonist, D-Pen 2,5-enkephalin (DPDPE), into different subdivisions of the VRG, on phrenic nerve discharge and mean arterial pressure. Following injections of retrograde tracer into the spinal cord or intracellular labelling of respiratory neurons, in Sprague-Dawley rats, brainstem sections were processed for retrograde or intracellular labelling and DOR-ir. Bulbospinal neurons were apposed by DOR-ir boutons regardless of whether they projected to single (cervical or thoracic ventral horn) or multiple (cervical and thoracic ventral horn) targets in the spinal cord. In the VRG, a total of 24 +/- 5% (67 +/- 13/223 +/- 49) of neurons projecting to the cervical ventral horn, and 37 +/- 3% (96 +/- 22/255 +/- 37) of neurons projecting to the thoracic ventral horn, received close appositions from DOR-ir boutons. Furthermore, DOR-ir boutons closely apposed six of seven intracellularly labelled neurons, whilst the remaining neuron itself possessed boutons that were DOR-ir. DPDPE was microinjected (10 mM, 60 nl, unilateral) into regions of respiratory field activity in the VRG of anaesthetised, vagotomised rats, and the effects on phrenic nerve discharge and mean arterial pressure were recorded. DPDPE depressed phrenic nerve amplitude, with little effect on phrenic nerve frequency in the Bötzinger complex, pre-Bötzinger complex and rVRG, the greatest effects occurring in the Bötzinger complex. The results indicate that the DOR is located on afferent inputs to respiratory neurons in the VRG. Activation of the DOR in the VRG is likely to inhibit the release of neurotransmitters from afferent inputs that modulate the pattern of activity of VRG neurons.
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Affiliation(s)
- T Lonergan
- Department of Pharmacology, University of Sydney, Camperdown, New South Wales, 2006, Australia
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Viemari JC, Bévengut M, Coulon P, Hilaire G. Nasal trigeminal inputs release the A5 inhibition received by the respiratory rhythm generator of the mouse neonate. J Neurophysiol 2003; 91:746-58. [PMID: 14561692 DOI: 10.1152/jn.01153.2002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Experiments were performed on neonatal mice to analyze why, in vitro, the respiratory rhythm generator (RRG) was silent and how it could be activated. We demonstrated that in vitro the RRG in intact brain stems is silenced by a powerful inhibition arising from the pontine A5 neurons through medullary alpha(2) adrenoceptors and that in vivo nasal trigeminal inputs facilitate the RRG as nasal continuous positive airway pressure increases the breathing frequency, whereas nasal occlusion and nasal afferent anesthesia depress it. Because nasal trigeminal afferents project to the A5 nuclei, we applied single trains of negative electric shocks to the trigeminal nerve in inactive ponto-medullary preparations. They induced rhythmic phrenic bursts during the stimulation and for 2-3 min afterward, whereas repetitive trains produced on-going rhythmic activity up to the end of the experiments. Electrolytic lesion or pharmacological inactivation of the ipsilateral A5 neurons altered both the phrenic burst frequency and occurrence after the stimulation. Extracellular unitary recordings and trans-neuronal tracing experiments with the rabies virus show that the medullary lateral reticular area contains respiratory-modulated neurons, not necessary for respiratory rhythmogenesis, but that may provide an excitatory pathway from the trigeminal inputs to the RRG as their electrolytic lesion suppresses any phrenic activity induced by the trigeminal nerve stimulation. The results lead to the hypothesis that the trigeminal afferents in the mouse neonate involve at least two pathways to activate the RRG, one that may act through the medullary lateral reticular area and one that releases the A5 inhibition received by the RRG.
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Affiliation(s)
- Jean-Charles Viemari
- Centre National de la Recherche Scientifique, Université de la Méditerranée, Groupe d'Etude des Réseaux Moteurs, Biologie des Rythmes et du Développement, 13009 Marseille, France
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St-John WM, Leiter JC. High-frequency oscillations of phrenic activity in eupnea and gasping of in situ rat: influence of temperature. Am J Physiol Regul Integr Comp Physiol 2003; 285:R404-12. [PMID: 12676756 DOI: 10.1152/ajpregu.00599.2002] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We hypothesized that the in situ perfused preparation of the juvenile rat exhibits patterns of ventilatory activity comparable to eupnea and gasping in vivo. To evaluate this hypothesis, we examined high-frequency oscillations of activity of the phrenic nerve at 27-34 degrees C. The peak frequency of these high-frequency oscillations was defined from power spectral analysis. In situ, recordings were obtained in hyperoxic normocapnia, during ventilatory cycles in which the peak of integrated phrenic activity was achieved late in the burst, as in eupnea in vivo. Recordings were also obtained in hypoxic hypercapnia, when the peak of integrated phrenic activity occurred in the first half of the burst, as in gasping in vivo. In situ, peak frequencies in the power spectra were significantly higher in gasping than during eupnea. Frequencies during eupnea and gasping were progressively elevated as the temperature of the in situ preparation was increased. The shift in peak frequencies between eupnea and gasping and the temperature sensitivity of frequencies in situ were the same as in vivo. Results provide additional support for the conclusion that the in situ preparation demonstrates distinctly different patterns of automatic ventilatory activity, comparable to eupnea and gasping in vivo.
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Affiliation(s)
- Walter M St-John
- Department of Physiology, Dartmouth Medical School, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756, USA.
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Monnier A, Alheid GF, McCrimmon DR. Defining ventral medullary respiratory compartments with a glutamate receptor agonist in the rat. J Physiol 2003; 548:859-74. [PMID: 12640009 PMCID: PMC2342895 DOI: 10.1113/jphysiol.2002.038141] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2002] [Accepted: 02/24/2003] [Indexed: 11/08/2022] Open
Abstract
The regional organization of the ventral respiratory group (VRG) was examined with respect to generation of respiratory rhythm (breathing frequency) versus control of the respiratory motor pattern on individual nerves. In urethane-anaesthetized, neuromuscularly blocked and vagotomized Sprague-Dawley rats, arterial blood pressure (ABP) and respiratory motor outputs (phrenic, pharyngeal branch of the vagus, or superior laryngeal nerves) were recorded. The VRG organization was mapped systematically using injections of the excitatory amino acid DL-homocysteic acid (DLH; 5-20 mM, 2-6 nl) from single- or double-barrel pipettes at 100-200 microm intervals between the facial nucleus and the calamus scriptorius. Recording of respiratory neurons through the injection pipette ensured that the pipette was located within the VRG. At the end of each experiment, the injection pipette was used to make an electrical lesion, thereby marking the electrode position for subsequent histological reconstruction of injection sites. Four rostrocaudal regions were identified: (1) a rostral bradypnoea area, at the level of the Bötzinger complex, in which respiratory rhythm slowed and ABP increased, (2) a tachypnoea/dysrhythmia area, at the level of the preBötzinger complex, in which breathing rate either increased or became irregular, with little or no change in ABP, (3) a caudal bradypnoea area at the level of the anterior part of the rostral VRG in which ABP decreased and (4) a caudal 'no effect' region in the posterior part of the rostral VRG. The peak amplitude of phrenic nerve activity decreased with injections into all three rostral regions. Changes in respiratory rhythm were associated with opposite changes in inspiratory (TI) and expiratory (TE) durations after injections into either the Bötzinger complex or anterior rostral VRG, while both TI and TE decreased after injections into the preBötzinger complex. Effects on selected cranial nerves were similar to those on the phrenic nerve except that tonic activity was elicited on the superior larygneal nerve ipsilateral to injections in the Bötzinger complex and on the pharyngeal branch of the vagus ipsilateral to injections in the preBötzinger complex. These data reinforce the subdivision of the VRG into functionally distinct compartments and suggest that a further subdivision of the rostral VRG is warranted. They also suggest that region-specific influences, especially on the pattern of cranial motor discharge, can be used to assist the identification of recording sites within the VRG. However, the postulated clear functional separation of rhythm- versus pattern-generating regions was not supported.
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Affiliation(s)
- A Monnier
- Department of Physiology and Institute for Neuroscience, Feinberg School of Medicine, Northwestern University, 303 East Chicago Ave., Chicago, IL 60611-3008, USA
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Hayashi F, Hinrichsen CFL, McCrimmon DR. Short-term plasticity of descending synaptic input to phrenic motoneurons in rats. J Appl Physiol (1985) 2003; 94:1421-30. [PMID: 12482770 DOI: 10.1152/japplphysiol.00599.2002] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Respiratory afferent stimulation can elicit increases in respiratory motor output that outlast the period of stimulation by seconds to minutes [short-term potentiation (STP)]. This study examined the potential contribution of spinal mechanisms to STP in anesthetized, vagotomized, paralyzed rats. After C(1) spinal cord transection, stimulus trains (100 Hz, 5-60 s) of the C(1)-C(2) lateral funiculus elicited STP of phrenic nerve activity that peaked several seconds poststimulation. Intracellular recording revealed that individual phrenic motoneurons exhibited one of three different responses to stimulation: 1) depolarization that peaked several seconds poststimulation, 2) depolarization during stimulation and then exponential repolarization after stimulation, and 3) bistable behavior in which motoneurons depolarized to a new, relatively stable level that was maintained after stimulus termination. During the STP, excitatory postsynaptic potentials elicited by single-stimulus pulses were larger and longer. In conclusion, repetitive activation of the descending inputs to phrenic motoneurons causes a short-lasting depolarization of phrenic motoneurons, and augmentation of excitatory postsynaptic potentials, consistent with a contribution to STP.
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Affiliation(s)
- F Hayashi
- Department of Physiology and Institute for Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611-3008, USA
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Hilaire G, Burnet H, Ptak K, Sieweke M, Blanchi B, De Felipe C, Hunt S, Monteau R. Deletion of Tachykinin NK1 Receptor Gene in Mice does not Alter Respiratory Network Maturation but Alters Respiratory Responses to Hypoxia. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2003; 536:497-504. [PMID: 14635705 DOI: 10.1007/978-1-4419-9280-2_63] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/27/2023]
Affiliation(s)
- Gerard Hilaire
- GERM-CNRS, 280 Bd St. Marguerite, 13009 Marseille, France
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Ptak K, Burnet H, Blanchi B, Sieweke M, De Felipe C, Hunt SP, Monteau R, Hilaire G. The murine neurokinin NK1 receptor gene contributes to the adult hypoxic facilitation of ventilation. Eur J Neurosci 2002; 16:2245-52. [PMID: 12492418 DOI: 10.1046/j.1460-9568.2002.02305.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Substance P and neurokinin-1 receptors (NK1) modulate the respiratory activity and are expressed early during development. We tested the hypothesis that NK1 receptors are involved in prenatal development of the respiratory network by comparing the resting respiratory activity and the respiratory response to hypoxia of control mice and mutant mice lacking the NK1 receptor (NK1-/-). In vitro and in vivo experiments were conducted on neonatal, young and adult mice from wild-type and NK1-/- strains. In the wild strain, immunohistological, pharmacological and electrophysiological studies showed that NK1 receptors were expressed within medullary respiratory areas prior to birth and that their activation at birth modulated central respiratory activity and the membrane properties of phrenic motoneurons. Both the membrane properties of phrenic motoneurons and the respiratory activity generated in vitro by brainstem-spinal cord preparation from NK1-/- neonate mice were similar to that from the wild strain. In addition, in vivo ventilation recordings by plethysmography did not reveal interstrain differences in resting breathing parameters. The facilitation of ventilation by short-lasting hypoxia was similar in wild and NK1-/- neonates but was significantly weaker in adult NK1-/- mice. Results demonstrate that NK1 receptors do appear to be necessary for a normal respiratory response to short-lasting hypoxia in the adult. However, NK1 receptors are not obligatory for the prenatal development of the respiratory network, for the production of the rhythm, or for the regulation of breathing by short-lasting hypoxia in neonates.
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Affiliation(s)
- Krzysztof Ptak
- Physiologie Neurovégétative, UMR 6153 CNRS-INRA, Faculté des Sciences de St Jérôme, 13397 Marseille cedex 20, France
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