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González-García M, Carrillo-Franco L, Morales-Luque C, Ponce-Velasco M, Gago B, Dawid-Milner MS, López-González MV. Uncovering the neural control of laryngeal activity and subglottic pressure in anaesthetized rats: insights from mesencephalic regions. Pflugers Arch 2024; 476:1235-1247. [PMID: 38856775 PMCID: PMC11271367 DOI: 10.1007/s00424-024-02976-3] [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: 01/23/2024] [Revised: 04/15/2024] [Accepted: 05/21/2024] [Indexed: 06/11/2024]
Abstract
To assess the possible interactions between the dorsolateral periaqueductal gray matter (dlPAG) and the different domains of the nucleus ambiguus (nA), we have examined the pattern of double-staining c-Fos/FoxP2 protein immunoreactivity (c-Fos-ir/FoxP2-ir) and tyrosine hydroxylase (TH) throughout the rostrocaudal extent of nA in spontaneously breathing anaesthetised male Sprague-Dawley rats during dlPAG electrical stimulation. Activation of the dlPAG elicited a selective increase in c-Fos-ir with an ipsilateral predominance in the somatas of the loose (p < 0.05) and compact formation (p < 0.01) within the nA and confirmed the expression of FoxP2 bilaterally in all the domains within the nA. A second group of experiments was made to examine the importance of the dlPAG in modulating the laryngeal response evoked after electrical or chemical (glutamate) dlPAG stimulations. Both electrical and chemical stimulations evoked a significant decrease in laryngeal resistance (subglottal pressure) (p < 0.001) accompanied with an increase in respiratory rate together with a pressor and tachycardic response. The results of our study contribute to new data on the role of the mesencephalic neuronal circuits in the control mechanisms of subglottic pressure and laryngeal activity.
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Affiliation(s)
- M González-García
- Department of Human Physiology, Faculty of Medicine, University of Málaga, Málaga, Spain.
- Unit of Neurophysiology of the Autonomic Nervous System (CIMES), University of Málaga, Málaga, Spain.
- IBIMA Plataforma BIONAND, Málaga, Spain.
| | - L Carrillo-Franco
- Department of Human Physiology, Faculty of Medicine, University of Málaga, Málaga, Spain
- IBIMA Plataforma BIONAND, Málaga, Spain
| | - C Morales-Luque
- Department of Human Physiology, Faculty of Medicine, University of Málaga, Málaga, Spain
| | - M Ponce-Velasco
- IBIMA Plataforma BIONAND, Málaga, Spain
- Department of Cell Biology, University of Málaga, Málaga, Spain
| | - B Gago
- Department of Human Physiology, Faculty of Medicine, University of Málaga, Málaga, Spain
- IBIMA Plataforma BIONAND, Málaga, Spain
| | - M S Dawid-Milner
- Department of Human Physiology, Faculty of Medicine, University of Málaga, Málaga, Spain
- Unit of Neurophysiology of the Autonomic Nervous System (CIMES), University of Málaga, Málaga, Spain
- IBIMA Plataforma BIONAND, Málaga, Spain
| | - M V López-González
- Department of Human Physiology, Faculty of Medicine, University of Málaga, Málaga, Spain.
- Unit of Neurophysiology of the Autonomic Nervous System (CIMES), University of Málaga, Málaga, Spain.
- IBIMA Plataforma BIONAND, Málaga, Spain.
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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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González-García M, Carrillo-Franco L, Morales-Luque C, Dawid-Milner MS, López-González MV. Central Autonomic Mechanisms Involved in the Control of Laryngeal Activity and Vocalization. BIOLOGY 2024; 13:118. [PMID: 38392336 PMCID: PMC10886357 DOI: 10.3390/biology13020118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2023] [Revised: 02/07/2024] [Accepted: 02/10/2024] [Indexed: 02/24/2024]
Abstract
In humans, speech is a complex process that requires the coordinated involvement of various components of the phonatory system, which are monitored by the central nervous system. The larynx in particular plays a crucial role, as it enables the vocal folds to meet and converts the exhaled air from our lungs into audible sounds. Voice production requires precise and sustained exhalation, which generates an air pressure/flow that creates the pressure in the glottis required for voice production. Voluntary vocal production begins in the laryngeal motor cortex (LMC), a structure found in all mammals, although the specific location in the cortex varies in humans. The LMC interfaces with various structures of the central autonomic network associated with cardiorespiratory regulation to allow the perfect coordination between breathing and vocalization. The main subcortical structure involved in this relationship is the mesencephalic periaqueductal grey matter (PAG). The PAG is the perfect link to the autonomic pontomedullary structures such as the parabrachial complex (PBc), the Kölliker-Fuse nucleus (KF), the nucleus tractus solitarius (NTS), and the nucleus retroambiguus (nRA), which modulate cardiovascular autonomic function activity in the vasomotor centers and respiratory activity at the level of the generators of the laryngeal-respiratory motor patterns that are essential for vocalization. These cores of autonomic structures are not only involved in the generation and modulation of cardiorespiratory responses to various stressors but also help to shape the cardiorespiratory motor patterns that are important for vocal production. Clinical studies show increased activity in the central circuits responsible for vocalization in certain speech disorders, such as spasmodic dysphonia because of laryngeal dystonia.
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Affiliation(s)
- Marta González-García
- Department of Human Physiology, Faculty of Medicine, University of Málaga, 29010 Málaga, Spain
- Unit of Neurophysiology of the Autonomic Nervous System (CIMES), University of Málaga, 29010 Málaga, Spain
- Biomedical Research Institute of Málaga (IBIMA Plataforma BIONAND), 29010 Málaga, Spain
| | - Laura Carrillo-Franco
- Department of Human Physiology, Faculty of Medicine, University of Málaga, 29010 Málaga, Spain
- Unit of Neurophysiology of the Autonomic Nervous System (CIMES), University of Málaga, 29010 Málaga, Spain
- Biomedical Research Institute of Málaga (IBIMA Plataforma BIONAND), 29010 Málaga, Spain
| | - Carmen Morales-Luque
- Department of Human Physiology, Faculty of Medicine, University of Málaga, 29010 Málaga, Spain
| | - Marc Stefan Dawid-Milner
- Department of Human Physiology, Faculty of Medicine, University of Málaga, 29010 Málaga, Spain
- Unit of Neurophysiology of the Autonomic Nervous System (CIMES), University of Málaga, 29010 Málaga, Spain
- Biomedical Research Institute of Málaga (IBIMA Plataforma BIONAND), 29010 Málaga, Spain
| | - Manuel Víctor López-González
- Department of Human Physiology, Faculty of Medicine, University of Málaga, 29010 Málaga, Spain
- Unit of Neurophysiology of the Autonomic Nervous System (CIMES), University of Málaga, 29010 Málaga, Spain
- Biomedical Research Institute of Málaga (IBIMA Plataforma BIONAND), 29010 Málaga, Spain
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Krohn F, Novello M, van der Giessen RS, De Zeeuw CI, Pel JJM, Bosman LWJ. The integrated brain network that controls respiration. eLife 2023; 12:83654. [PMID: 36884287 PMCID: PMC9995121 DOI: 10.7554/elife.83654] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Accepted: 01/29/2023] [Indexed: 03/09/2023] Open
Abstract
Respiration is a brain function on which our lives essentially depend. Control of respiration ensures that the frequency and depth of breathing adapt continuously to metabolic needs. In addition, the respiratory control network of the brain has to organize muscular synergies that integrate ventilation with posture and body movement. Finally, respiration is coupled to cardiovascular function and emotion. Here, we argue that the brain can handle this all by integrating a brainstem central pattern generator circuit in a larger network that also comprises the cerebellum. Although currently not generally recognized as a respiratory control center, the cerebellum is well known for its coordinating and modulating role in motor behavior, as well as for its role in the autonomic nervous system. In this review, we discuss the role of brain regions involved in the control of respiration, and their anatomical and functional interactions. We discuss how sensory feedback can result in adaptation of respiration, and how these mechanisms can be compromised by various neurological and psychological disorders. Finally, we demonstrate how the respiratory pattern generators are part of a larger and integrated network of respiratory brain regions.
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Affiliation(s)
- Friedrich Krohn
- Department of Neuroscience, Erasmus MC, Rotterdam, Netherlands
| | - Manuele Novello
- Department of Neuroscience, Erasmus MC, Rotterdam, Netherlands
| | | | - Chris I De Zeeuw
- Department of Neuroscience, Erasmus MC, Rotterdam, Netherlands.,Netherlands Institute for Neuroscience, Royal Academy of Arts and Sciences, Amsterdam, Netherlands
| | - Johan J M Pel
- Department of Neuroscience, Erasmus MC, Rotterdam, Netherlands
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Kubin L. Breathing during sleep. HANDBOOK OF CLINICAL NEUROLOGY 2022; 188:179-199. [PMID: 35965026 DOI: 10.1016/b978-0-323-91534-2.00005-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The depth, rate, and regularity of breathing change following transition from wakefulness to sleep. Interactions between sleep and breathing involve direct effects of the central mechanisms that generate sleep states exerted at multiple respiratory regulatory sites, such as the central respiratory pattern generator, respiratory premotor pathways, and motoneurons that innervate the respiratory pump and upper airway muscles, as well as effects secondary to sleep-related changes in metabolism. This chapter discusses respiratory effects of sleep as they occur under physiologic conditions. Breathing and central respiratory neuronal activities during nonrapid eye movement (NREM) sleep and REM sleep are characterized in relation to activity of central wake-active and sleep-active neurons. Consideration is given to the obstructive sleep apnea syndrome because in this common disorder, state-dependent control of upper airway patency by upper airway muscles attains high significance and recurrent arousals from sleep are triggered by hypercapnic and hypoxic episodes. Selected clinical trials are discussed in which pharmacological interventions targeted transmission in noradrenergic, serotonergic, cholinergic, and other state-dependent pathways identified as mediators of ventilatory changes during sleep. Central pathways for arousals elicited by chemical stimulation of breathing are given special attention for their important role in sleep loss and fragmentation in sleep-related respiratory disorders.
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Affiliation(s)
- Leszek Kubin
- Department of Biomedical Sciences, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, United States.
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6
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Wijdicks EFM. Historical awareness of the brainstem: From a subsidiary structure to a vital center. Neurology 2020; 95:484-488. [PMID: 32934155 DOI: 10.1212/wnl.0000000000010504] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 07/15/2020] [Indexed: 11/15/2022] Open
Abstract
The historical trajectory of the discovery of the brainstem as a vital center has been rarely explored. Focusing on its tracts and neurons first, anatomists much later expanded their understanding of the brainstem with the discovery of groups of nuclear networks that affected major vital functions. Comparative anatomists (i.e., Edinger) postulated a primordial paleopallium that indirectly implied the centrality of the brainstem and a neopallidum with its differentiation and specialization up to Homo sapiens Methods that governed the discovery of the brainstem were (1) comparative anatomy, (2) embryonic growth, (3) vivisection, (4) brain dissection, and, much later, (5) microscopy and chemical feedback loops. This historical study traces how neuroscientists of the 18th and 19th century became increasingly aware of the vital functions performed by the brainstem. The anatomists of the 20th century found the ascending reticular formation, the respiratory center, and pressor centers-all automatic and vital functions. It took centuries for this realization to open the way to use the testable brainstem centers to establish the criteria for a neurologic determination of death. The ontogenetic conclusion is that the brainstem is the ancestor of the developed human brain; the physiologic conclusion is that the brainstem is a vital center and a structural support system and conduit. When afunctional, life ends.
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Affiliation(s)
- Eelco F M Wijdicks
- From the Mayo Clinic Division of Neurocritical Care and Hospital Neurology.
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Subramanian HH, Huang ZG, Silburn PA, Balnave RJ, Holstege G. The physiological motor patterns produced by neurons in the nucleus retroambiguus in the rat and their modulation by vagal, peripheral chemosensory, and nociceptive stimulation. J Comp Neurol 2017; 526:229-242. [DOI: 10.1002/cne.24318] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Accepted: 08/17/2017] [Indexed: 11/12/2022]
Affiliation(s)
- Hari H. Subramanian
- Queensland Brain Institute, Asia-Pacific Centre for Neuromodulation, The University of Queensland; Brisbane 4072 Australia
- Discipline of Biomedical Science, The University of Sydney; Lidcombe NSW 1825 Australia
| | - Zheng-Gui Huang
- Discipline of Biomedical Science, The University of Sydney; Lidcombe NSW 1825 Australia
- Department of Pharmacology; Wannan Medical College; Wuhu City Anhui Province 241002 People's Republic of China
| | - Peter A. Silburn
- Queensland Brain Institute, Asia-Pacific Centre for Neuromodulation, The University of Queensland; Brisbane 4072 Australia
| | - Ron J. Balnave
- Discipline of Biomedical Science, The University of Sydney; Lidcombe NSW 1825 Australia
| | - Gert Holstege
- The University of Queensland; Brisbane 4072 Australia
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Jones SE, Dutschmann M. Testing the hypothesis of neurodegeneracy in respiratory network function with a priori transected arterially perfused brain stem preparation of rat. J Neurophysiol 2016; 115:2593-607. [PMID: 26888109 DOI: 10.1152/jn.01073.2015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Accepted: 02/12/2016] [Indexed: 11/22/2022] Open
Abstract
Degeneracy of respiratory network function would imply that anatomically discrete aspects of the brain stem are capable of producing respiratory rhythm. To test this theory we a priori transected brain stem preparations before reperfusion and reoxygenation at 4 rostrocaudal levels: 1.5 mm caudal to obex (n = 5), at obex (n = 5), and 1.5 (n = 7) and 3 mm (n = 6) rostral to obex. The respiratory activity of these preparations was assessed via recordings of phrenic and vagal nerves and lumbar spinal expiratory motor output. Preparations with a priori transection at level of the caudal brain stem did not produce stable rhythmic respiratory bursting, even when the arterial chemoreceptors were stimulated with sodium cyanide (NaCN). Reperfusion of brain stems that preserved the pre-Bötzinger complex (pre-BötC) showed spontaneous and sustained rhythmic respiratory bursting at low phrenic nerve activity (PNA) amplitude that occurred simultaneously in all respiratory motor outputs. We refer to this rhythm as the pre-BötC burstlet-type rhythm. Conserving circuitry up to the pontomedullary junction consistently produced robust high-amplitude PNA at lower burst rates, whereas sequential motor patterning across the respiratory motor outputs remained absent. Some of the rostrally transected preparations expressed both burstlet-type and regular PNA amplitude rhythms. Further analysis showed that the burstlet-type rhythm and high-amplitude PNA had 1:2 quantal relation, with burstlets appearing to trigger high-amplitude bursts. We conclude that no degenerate rhythmogenic circuits are located in the caudal medulla oblongata and confirm the pre-BötC as the primary rhythmogenic kernel. The absence of sequential motor patterning in a priori transected preparations suggests that pontine circuits govern respiratory pattern formation.
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Affiliation(s)
- Sarah E Jones
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia
| | - Mathias Dutschmann
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia
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Dorsal and ventral aspects of the most caudal medullary reticular formation have differential roles in modulation and formation of the respiratory motor pattern in rat. Brain Struct Funct 2015; 221:4353-4368. [DOI: 10.1007/s00429-015-1165-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 11/26/2015] [Indexed: 11/24/2022]
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10
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Holstege G, Subramanian HH. Two different motor systems are needed to generate human speech. J Comp Neurol 2015; 524:1558-77. [DOI: 10.1002/cne.23898] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Revised: 09/03/2015] [Accepted: 09/03/2015] [Indexed: 11/08/2022]
Affiliation(s)
- Gert Holstege
- Asia-Pacific Centre for Neuromodulation; Queensland Brain Institute; The University of Queensland; Brisbane 4072 Australia
| | - Hari H. Subramanian
- Asia-Pacific Centre for Neuromodulation; Queensland Brain Institute; The University of Queensland; Brisbane 4072 Australia
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11
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Farmer DGS, Bautista TG, Jones SE, Stanic D, Dutschmann M. The midbrain periaqueductal grey has no role in the generation of the respiratory motor pattern, but provides command function for the modulation of respiratory activity. Respir Physiol Neurobiol 2014; 204:14-20. [PMID: 25058161 DOI: 10.1016/j.resp.2014.07.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Revised: 07/02/2014] [Accepted: 07/15/2014] [Indexed: 01/09/2023]
Abstract
It has previously been shown that stimulation of cell-columns in the periaqueductal grey (PAG) triggers site-specific cardiorespiratory effects. These are believed to facilitate changes in behaviour through coordinated changes in autonomic outflow. Here, we investigated whether PAG-evoked respiratory commands can be studied in situ using the decerebrate perfused brainstem preparation. Phrenic, vagus and abdominal iliohypogastric nerves were recorded before and after microinjection of L-glutamate (30-50 nl, 10 mM) or isoguvacine (GABA-receptor agonist, 30-50 nl, 10 mM) into the PAG. L-glutamate microinjection triggered a range of site-specific respiratory modulations (n = 17 preparations). Subsequent microinjection of isoguvacine into the same PAG sites had no effect on the baseline respiratory motor pattern or rhythm. We conclude that while the PAG has no function in respiratory pattern generation, PAG-evoked respiratory modulations can be evoked in situ in the absence of higher brain centres and while homeostatic parameters that may affect respiratory drive are held static.
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Affiliation(s)
- David G S Farmer
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Gate 11, Royal Parade, Victoria 3052, Australia
| | - Tara G Bautista
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Gate 11, Royal Parade, Victoria 3052, Australia
| | - Sarah E Jones
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Gate 11, Royal Parade, Victoria 3052, Australia
| | - Davor Stanic
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Gate 11, Royal Parade, Victoria 3052, Australia
| | - Mathias Dutschmann
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Gate 11, Royal Parade, Victoria 3052, Australia.
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12
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Neural mechanisms of female sexual behavior in the rat; comparison with male ejaculatory control. Pharmacol Biochem Behav 2014; 121:16-30. [DOI: 10.1016/j.pbb.2013.11.025] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Revised: 11/12/2013] [Accepted: 11/18/2013] [Indexed: 01/20/2023]
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13
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Subramanian HH, Holstege G. Stimulation of the midbrain periaqueductal gray modulates preinspiratory neurons in the ventrolateral medulla in the rat in vivo. J Comp Neurol 2014; 521:3083-98. [PMID: 23630049 PMCID: PMC3761193 DOI: 10.1002/cne.23334] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2012] [Revised: 03/06/2013] [Accepted: 03/13/2013] [Indexed: 12/11/2022]
Abstract
The midbrain periaqueductal gray (PAG) is involved in many basic survival behaviors that affect respiration. We hypothesized that the PAG promotes these behaviors by changing the firing of preinspiratory (pre-I) neurons in the pre-Bötzinger complex, a cell group thought to be important in generating respiratory rhythm. We tested this hypothesis by recording single unit activity of pre-Bötzinger pre-I neurons during stimulation in different parts of the PAG. Stimulation in the dorsal PAG increased the firing of pre-I neurons, resulting in tachypnea. Stimulation in the medial part of the lateral PAG converted the pre-I neurons into inspiratory phase-spanning cells, resulting in inspiratory apneusis. Stimulation in the lateral part of the lateral PAG generated an early onset of the pre-I neuronal discharge, which continued throughout the inspiratory phase, while at the same time attenuating diaphragm contraction. Stimulation in the ventral part of the lateral PAG induced tachypnea but inhibited pre-I cell firing, whereas stimulation in the ventrolateral PAG inhibited not only pre-I cells but also the diaphragm, leading to apnea. These findings show that PAG stimulation changes the activity of the pre-Bötzinger pre-I neurons. These changes are in line with the different behaviors generated by the PAG, such as the dorsal PAG generating avoidance behavior, the lateral PAG generating fight and flight, and the ventrolateral PAG generating freezing and immobility. J. Comp. Neurol. 521: 3083–3098, 2013. © 2013 Wiley Periodicals, Inc.
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Affiliation(s)
- Hari H Subramanian
- The University of Queensland Centre for Clinical Research, Herston, Queensland, 4029, Australia
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Schmidt MF, Martin Wild J. The respiratory-vocal system of songbirds: anatomy, physiology, and neural control. PROGRESS IN BRAIN RESEARCH 2014; 212:297-335. [PMID: 25194204 DOI: 10.1016/b978-0-444-63488-7.00015-x] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
This wide-ranging review presents an overview of the respiratory-vocal system in songbirds, which are the only other vertebrate group known to display a degree of respiratory control during song rivalling that of humans during speech; this despite the fact that the peripheral components of both the respiratory and vocal systems differ substantially in the two groups. We first provide a brief description of these peripheral components in songbirds (lungs, air sacs and respiratory muscles, vocal organ (syrinx), upper vocal tract) and then proceed to a review of the organization of central respiratory-related neurons in the spinal cord and brainstem, the latter having an organization fundamentally similar to that of the ventral respiratory group of mammals. The second half of the review describes the nature of the motor commands generated in a specialized "cortical" song control circuit and how these might engage brainstem respiratory networks to shape the temporal structure of song. We also discuss a bilaterally projecting "respiratory-thalamic" pathway that links the respiratory system to "cortical" song control nuclei. This necessary pathway for song originates in the brainstem's primary inspiratory center and is hypothesized to play a vital role in synchronizing song motor commands both within and across hemispheres.
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Affiliation(s)
- Marc F Schmidt
- Department of Biology and Neuroscience Program, University of Pennsylvania, Philadelphia, PA, USA.
| | - J Martin Wild
- Department of Anatomy with Radiology, School of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.
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Holstege G. The periaqueductal gray controls brainstem emotional motor systems including respiration. PROGRESS IN BRAIN RESEARCH 2014; 209:379-405. [PMID: 24746059 DOI: 10.1016/b978-0-444-63274-6.00020-5] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Respiration is a motor system essential for the survival of the individual and of the species. Because of its vital significance, studies on respiration often assume that breathing takes place independent of other motor systems. However, motor systems generating vocalization, coughing, sneezing, vomiting, as well as parturition, ejaculation, and defecation encompass abdominal pressure control, which involves changes in the respiratory pattern. The mesencephalic periaqueductal gray (PAG) controls all these motor systems. It determines the level setting of the whole body by means of its very strong projections to the ventromedial medullary tegmentum, but it also controls the cell groups that generate vocalization, coughing, sneezing, vomiting, as well as respiration. For this control, the PAG maintains very strong connections with the nucleus retroambiguus, which enables it to control abdominal and intrathoracic pressure. In this same context, the PAG also runs the pelvic organs, bladder, uterus, prostate, seminal vesicles, and the distal colon and rectum via its projections to the pelvic organ stimulating center and the pelvic floor stimulating center. These cell groups, via long descending projections, have direct control of the parasympathetic motoneurons in the sacral cord as well as of the somatic motoneurons in the nucleus of Onuf, innervating the pelvic floor. Respiration, therefore, is not a motor system that functions by itself, but is strongly regulated by the same systems that also control the other motor output systems.
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Affiliation(s)
- Gert Holstege
- UQ Centre for Clinical Research, The University of Queensland, Herston, Queensland, Australia.
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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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Abstract
Among the several topics included in respiratory studies investigators have focused on the control of breathing for a relatively few number of years, perhaps only the last 75 to 80. For a very long time, the phenomenon of respiration presented a great mystery. The Chinese had suggestions for proper breathing, and later the Egyptians sought to understand its purpose. But in the western world, the early Greeks made the more significant observations. Centuries passed before the anatomical structures pertinent to respiration were properly visualized and located. There followed efforts to understand if lung movement was necessary for life and what happened in the lung. The rise of chemistry in the 18th century eventually clarified the roles of the gases significant in respiratory behavior. More time was needed to understand what gases provoked increases in breathing and where those gases worked. At this point, control of breathing became a significant focus of respiratory investigators. Studies included identifying the structures and functions of central and peripheral chemoreceptors, and airway receptors, sources of respiratory rhythm and pattern generation, the impact of the organism's status on its breathing including environment and disease/trauma. At this same time, mid- to late-20th century, efforts to mathematicize the variables in the control of breathing appeared. So though wonderment about the mysterious phenomenon of respiration began over two millennia ago, serious physiological investigation into its control is by comparison very young.
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Affiliation(s)
- Robert S Fitzgerald
- Departments of Environmental Health Sciences Division of Physiology, of Physiology, and of Medicine, The Johns Hopkins Medical Institutions, Baltimore, Maryland, 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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Road JD, Ford TW, Kirkwood PA. Connections between expiratory bulbospinal neurons and expiratory motoneurons in thoracic and upper lumbar segments of the spinal cord. J Neurophysiol 2013; 109:1837-51. [PMID: 23324322 PMCID: PMC3628013 DOI: 10.1152/jn.01008.2012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Cross-correlation of neural discharges was used to investigate the connections between expiratory bulbospinal neurons (EBSNs) in the caudal medulla and expiratory motoneurons innervating thoracic and abdominal muscles in anesthetized cats. Peaks were seen in the cross-correlation histograms for around half of the EBSN-nerve pairs for the following: at T8, the nerve branches innervating internal intercostal muscle and external abdominal oblique muscle and a more distal branch of the internal intercostal nerve; and at L1, a nerve branch innervating internal abdominal oblique muscle and a more distal branch of the ventral ramus. Fewer peaks were seen for the L1 nerve innervating external abdominal oblique, but a paucity of presumed α-motoneuron discharges could explain the rarity of the peaks in this instance. Taking into account individual EBSN conduction times to T8 and to L1, as well as peripheral conduction times, nearly all of the peaks were interpreted as representing monosynaptic connections. Individual EBSNs showed connections at both T8 and L1, but without any discernible pattern. The overall strength of the monosynaptic connection from EBSNs at L1 was found to be very similar to that at T8, which was previously argued to be substantial and responsible for the temporal patterns of expiratory motoneuron discharges. However, we argue that other inputs are required to create the stereotyped spatial patterns of discharges in the thoracic and abdominal musculature.
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Affiliation(s)
- J D Road
- Sobell Department of Motor Neuroscience and Movement Disorders, UCL Institute of Neurology, London, United Kingdom
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Subramanian HH. Descending control of the respiratory neuronal network by the midbrain periaqueductal grey in the rat in vivo. J Physiol 2012; 591:109-22. [PMID: 23129795 DOI: 10.1113/jphysiol.2012.245217] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Emotional reactions such as vocalization take place during expiration, and thus expression of emotional behaviour requires a switch from inspiration to expiration. I investigated how the midbrain periaqueductal grey (PAG), a known behavioural modulator of breathing, influences the inspiratory-to-expiratory phase transition. Contemporary models propose that late inspiratory (late-I) and post-inspiratory (post-I) neurones found in the medulla, which are active during the inspiratory-to-expiratory phase transition are involved in converting inspiration to expiration. I examined the effect of excitatory amino acid (d,l-homocysteic acid; DLH) stimulation of the PAG on the discharge function of late-I and post-I neurones. The data show a topographical organization of DLH-induced late-I and post-I neuronal modulation within the PAG. Dorsal PAG stimulation induced tachypnoea and caused excitation of both the late-I and post-I neurones. Lateral PAG induced inspiratory prolongation and caused an excitation of late-I neurones but inhibition of post-I neurones. Ventrolateral PAG induced expiratory prolongation and caused a persistent activation of post-I neurones. As well, PAG stimulation modulated both the late-I and post-I cells for least two-three breaths even prior to the change in respiratory motor pattern. This indicates that the PAG influences the late-I and post-I cells independent of pulmonary or other sensory afferent feedback. I conclude that the PAG modulates the activity of the medullary late-I and post-I neurones, and this modulation contributes to the conversion of eupnoea into a behavioural breathing pattern.
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Affiliation(s)
- Hari H Subramanian
- The Florey Institute of Neuroscience and Mental Health, Parkville, Victoria 3010, Australia.
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Jones SE, Saad M, Lewis DI, Subramanian HH, Dutschmann M. The nucleus retroambiguus as possible site for inspiratory rhythm generation caudal to obex. Respir Physiol Neurobiol 2012; 180:305-10. [PMID: 22210466 PMCID: PMC3282833 DOI: 10.1016/j.resp.2011.12.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2011] [Revised: 12/14/2011] [Accepted: 12/14/2011] [Indexed: 11/17/2022]
Abstract
We investigated whether spinalized animals can produce inspiratory rhythm. We recorded spinal inspiratory phrenic (PNA) and cranial inspiratory hypoglossal (HNA) nerve activity in the perfused brainstem preparation of rat. Complete transverse transections were performed at 1.5 (pyramidal decussation) or 2mm (first cervical spinal segment) caudal to obex. Excitatory drive was enhanced by either extracellular potassium, hypercapnia or by stimulating arterial chemoreceptors. Caudal transections immediately eliminated descending network drive for PNA, while the cranial inspiratory HNA remained unaffected. After transection, PNA bursting remained sporadic even during enhanced excitatory drive. This implies, cervical spinal circuits lack intrinsic rhythmogenic capacity. Rostral transections also abolished PNA immediately. However, HNA also progressively lost its amplitude and rhythm. Chemoreceptor activation only triggered tonic, non-rhythmic HNA. Thus the integrity of ponto-medullary circuitry was maintained. Our results suggest that an area overlapping the caudal nucleus retroambiguus provides critical ascending input to the ponto-medullary respiratory network for inspiratory rhythm generation.
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Affiliation(s)
- Sarah E. Jones
- Institute of Membrane and Systems Biology, Garstang Building, University of Leeds, Leeds LS2 9JT
| | - Mona Saad
- Institute of Membrane and Systems Biology, Garstang Building, University of Leeds, Leeds LS2 9JT
| | - David I. Lewis
- Institute of Membrane and Systems Biology, Garstang Building, University of Leeds, Leeds LS2 9JT
| | - Hari H. Subramanian
- Florey Neurosciences Institutes, Gate 11, Royal Parade, University of Melbourne, Victoria, 3052, Australia
| | - Mathias Dutschmann
- Institute of Membrane and Systems Biology, Garstang Building, University of Leeds, Leeds LS2 9JT
- Florey Neurosciences Institutes, Gate 11, Royal Parade, University of Melbourne, Victoria, 3052, Australia
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22
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Holstege G, Huynh HK. Brain circuits for mating behavior in cats and brain activations and de-activations during sexual stimulation and ejaculation and orgasm in humans. Horm Behav 2011; 59:702-7. [PMID: 21352827 DOI: 10.1016/j.yhbeh.2011.02.008] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2011] [Accepted: 02/16/2011] [Indexed: 10/18/2022]
Abstract
In cats, there exists a descending system that controls the posture necessary for mating behavior. A key role is played by the mesencephalic periaqueductal gray (PAG), which maintains strong specific projections to the nucleus retroambiguus located laterally in the most caudal medulla. The NRA, in turn, has direct access to motoneurons in the lumbosacral cord that produce the mating posture. This pathway is slightly different in males and females, but in females its strength fluctuates strongly depending on whether or not the cat is in heat. This way the PAG determines whether or not mating can take place. Via the PAG many other regions in the limbic system as well as in the prefrontal cortex and insula can influence mating behavior. In humans, the brain also controls responses to sexual stimulation as well as ejaculation in men and orgasm in women. Neuroimaging techniques show activations and de-activations but are not able to verify whether the PAG has a similar effect as in cats. PET-scanning results revealed that there is activation in the upper brainstem and cerebellum, as well as insula in men and in the somatomotor and somatosensory cortex in women. During sexual stimulation, but especially during ejaculation and orgasm there was strong de-activation mainly on the left side in the temporal lobe and ventral prefrontal cortex. These neuroimaging results show the importance of lowering the level of alertness regarding your immediate environment (left hemisphere) to have proper sexual behavior.
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Affiliation(s)
- Gert Holstege
- University of Groningen, UMCG, Center for Uroneurology, Postbus 196, 9700 AD Groningen, The Netherlands.
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23
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24
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25
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26
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27
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Dempsey JA, Olson EB, Skatrud JB. Hormones and Neurochemicals in the Regulation of Breathing. Compr Physiol 2011. [DOI: 10.1002/cphy.cp030207] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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28
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Cough following low thoracic hemisection in the cat. Exp Neurol 2010; 222:165-70. [PMID: 20043908 DOI: 10.1016/j.expneurol.2009.12.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2009] [Revised: 12/14/2009] [Accepted: 12/17/2009] [Indexed: 01/15/2023]
Abstract
A function of the abdominal expiratory muscles is the generation of cough, a critical respiratory defense mechanism that is often disrupted following spinal cord injury. We assessed the effects of a lateral T9/10 hemisection on cough production at 4, 13 and 21 weeks post-injury in cats receiving extensive locomotor training. The magnitudes of esophageal pressure as well as of bilateral rectus abdominis electromyogram activity during cough were not significantly different from pre-injury values at all time points evaluated. The results show that despite considerable interruption of the descending pre-motor drive from the brainstem to the expiratory motoneuron pools, the cough motor system shows a significant function by 4 weeks following incomplete thoracic injury.
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Bianchi AL, Gestreau C. The brainstem respiratory network: An overview of a half century of research. Respir Physiol Neurobiol 2009; 168:4-12. [DOI: 10.1016/j.resp.2009.04.019] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2009] [Revised: 04/14/2009] [Accepted: 04/22/2009] [Indexed: 12/01/2022]
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30
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Yoshida, Katsuyuki Yatake, Yasumasa Y. Morphological Observation of Laryngeal Motoneurons by Means of Cholera Toxin B Subunit Tracing Technique. Acta Otolaryngol 2009. [DOI: 10.1080/00016489850182800-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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31
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Subramanian HH, Holstege G. The nucleus retroambiguus control of respiration. J Neurosci 2009; 29:3824-32. [PMID: 19321779 PMCID: PMC6665025 DOI: 10.1523/jneurosci.0607-09.2009] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2009] [Accepted: 02/20/2009] [Indexed: 12/13/2022] Open
Abstract
The role of the nucleus retroambiguus (NRA) in the context of respiration control has been subject of debate for considerable time. To solve this problem, we chemically (using d, l-homocysteic acid) stimulated the NRA in unanesthetized precollicularly decerebrated cats and studied the respiratory effect via simultaneous measurement of tracheal pressure and electromyograms of diaphragm, internal intercostal (IIC), cricothyroid (CT), and external oblique abdominal (EO) muscles. NRA-stimulation 0-1 mm caudal to the obex resulted in recruitment of IIC muscle and reduction in respiratory frequency. NRA-stimulation 1-3 mm caudal to the obex produced vocalization along with CT activation and slight increase in tracheal pressure, but no change in respiratory frequency. NRA-stimulation 3-5 mm caudal to the obex produced CT muscle activation and an increase in respiratory frequency, but no vocalization. NRA-stimulation 5-8 mm caudal to the obex produced EO muscle activation and reduction in respiratory frequency. A change to the inspiratory effort was never observed, regardless of which NRA part was stimulated. The results demonstrate that NRA does not control eupneic inspiration but consists of topographically separate groups of premotor interneurons each producing detailed motor actions. These motor activities have in common that they require changes to eupneic breathing. Different combination of activation of these premotor neurons determines the final outcome, e.g., vocalization, vomiting, coughing, sneezing, mating posture, or child delivery. Higher brainstem regions such as the midbrain periaqueductal gray (PAG) decides which combination of NRA neurons are excited. In simple terms, the NRA is the piano, the PAG one of the piano players.
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Affiliation(s)
- Hari H. Subramanian
- Center for Uroneurology, University of Groningen, University Medical Center Groningen, 9700 RB Groningen, The Netherlands
| | - Gert Holstege
- Center for Uroneurology, University of Groningen, University Medical Center Groningen, 9700 RB Groningen, The Netherlands
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32
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Wild JM, Kubke MF, Mooney R. Avian nucleus retroambigualis: cell types and projections to other respiratory-vocal nuclei in the brain of the zebra finch (Taeniopygia guttata). J Comp Neurol 2009; 512:768-83. [PMID: 19067354 DOI: 10.1002/cne.21932] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
In songbirds song production requires the intricate coordination of vocal and respiratory muscles under the executive influence of the telencephalon, as for speech in humans. In songbirds the site of this coordination is suspected to be the nucleus retroambigualis (RAm), because it contains premotor neurons projecting upon both vocal motoneurons and spinal motoneurons innervating expiratory muscles, and because it receives descending inputs from the telencephalic vocal control nucleus robustus archopallialis (RA). Here we used tract-tracing techniques to provide a more comprehensive account of the projections of RAm and to identify the different populations of RAm neurons. We found that RAm comprises diverse projection neuron types, including: 1) bulbospinal neurons that project, primarily contralaterally, upon expiratory motoneurons; 2) a separate group of neurons that project, primarily ipsilaterally, upon vocal motoneurons in the tracheosyringeal part of the hypoglossal nucleus (XIIts); 3) neurons that project throughout the ipsilateral and contralateral RAm; 4) another group that sends reciprocal, ascending projections to all the brainstem sources of afferents to RAm, namely, nucleus parambigualis, the ventrolateral nucleus of the rostral medulla, nucleus infra-olivarus superior, ventrolateral parabrachial nucleus, and dorsomedial nucleus of the intercollicular complex; and 5) a group of relatively large neurons that project their axons into the vagus nerve. Three morphological classes of RAm cells were identified by intracellular labeling, the dendritic arbors of which were confined to RAm, as defined by the terminal field of RA axons. Together the ascending and descending projections of RAm confirm its pivotal role in the mediation of respiratory-vocal control.
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Affiliation(s)
- J M Wild
- Department of Anatomy, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.
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Abstract
Following systemic administration, centrally acting antitussive drugs are generally assumed to act in the brainstem to inhibit cough. However, recent work in humans has raised the possibility of suprapontine sites of action for cough suppressants. For drugs that may act in the brainstem, the specific locations, types of neurones affected, and receptor specificities of the compounds represent important issues regarding their cough-suppressant actions. Two medullary areas that have received the most attention regarding the actions of antitussive drugs are the nucleus of the tractus solitarius (NTS) and the caudal ventrolateral respiratory column. Studies that have implicated these two medullary areas have employed both microinjection and in vitro recording methods to control the location of action of the antitussive drugs. Other brainstem regions contain neurones that participate in the production of cough and could represent potential sites of action of antitussive drugs. These regions include the raphe nuclei, pontine nuclei, and rostral ventrolateral medulla. Specific receptor subtypes have been associated with the suppression of cough at central sites, including 5-HT1A, opioid (mu, kappa, and delta), GABA-B, tachykinin neurokinin-1 (NK-1) and neurokinin-2, non-opioid (NOP-1), cannabinoid, dopaminergic, and sigma receptors. Aside from tachykinin NK-1 receptors in the NTS, relatively little is known regarding the receptor specificity of putative antitussive drugs in particular brainstem regions. Our understanding of the mechanisms of action of antitussive drugs would be significantly advanced by further work in this area.
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Affiliation(s)
- D C Bolser
- Department of Physiological Sciences, University of Florida, College of Veterinary Medicine, Gainesville, FL 32610-0144, USA.
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35
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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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36
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Poliacek I, Corrie LWC, Wang C, Rose MJ, Bolser DC. Microinjection of DLH into the region of the caudal ventral respiratory column in the cat: evidence for an endogenous cough-suppressant mechanism. J Appl Physiol (1985) 2006; 102:1014-21. [PMID: 17138836 PMCID: PMC1817661 DOI: 10.1152/japplphysiol.00616.2006] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The caudal ventral respiratory column (cVRC) contains premotor expiratory neurons that play an important role in cough-related expiratory activity of chest wall and abdominal muscles. Microinjection of d,l-homocysteic acid (DLH) was used to test the hypothesis that local activation of cVRC neurons can suppress the cough reflex. DLH (20-50 mM, 10-30 nl) was injected into the region of cVRC in nine anesthetized spontaneously breathing cats. Repetitive coughing was elicited by mechanical stimulation of the intrathoracic airways. Electromyograms (EMG) were recorded bilaterally from inspiratory parasternal and expiratory transversus abdominis (ABD) and unilaterally from laryngeal posterior cricoarytenoid and thyroarytenoid muscles. Unilateral microinjection of DLH (1-1.5 nmol) elicited bilateral increases in tonic and phasic respiratory ABD EMG activity, and it altered the respiratory pattern and laryngeal motor activities. However, DLH also decreased cough frequency by 51 +/- 7% compared with control (P < 0.001) and the amplitude of the contralateral (-35 +/- 3%; P < 0.001) and ipsilateral (-34 +/- 5%; P < 0.001) ABD EMGs during postinjection coughs compared with control. The cough alterations were much less pronounced after microinjection of a lower dose of DLH (0.34-0.8 nmol). No cough depression was observed after microinjections of vehicle. These results suggest that an endogenous cough suppressant neuronal network in the region of the cVRC may exist, and this network may be involved in the control of cough reflex excitability.
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Affiliation(s)
- Ivan Poliacek
- Dept. of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610-0144, USA
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37
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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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Kuipers R, Mensinga GM, Boers J, Klop EM, Holstege G. Infralimbic cortex projects to all parts of the pontine and medullary lateral tegmental field in cat. Eur J Neurosci 2006; 23:3014-24. [PMID: 16819990 DOI: 10.1111/j.1460-9568.2006.04843.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The infralimbic cortex (ILc) in cat is the ventralmost part of the anterior cingulate gyrus. The ILc, together with the amygdala, bed nucleus of the stria terminalis and lateral hypothalamus, is involved in the regulation of fear behavior. The latter three structures are thought to take part in triggering the fear response by means of their projections to the pontine and medullary lateral tegmental field (LTF). The LTF is a large region extending from the parabrachial nuclei rostrally to the spinal cord caudally. It contains almost all the premotor interneurons for the brainstem and for some upper spinal cord motoneurons innervating the muscles of face, head and throat. The question is whether ILc also projects to the LTF. Such a pathway would allow the ILc to influence the fear response by acting directly on these premotor interneurons. Anterograde tracer injections were made in the medial surface of the cortex in four cats. Only when the injection sites involved ILc were anterogradely labeled fibers observed throughout the rostrocaudal extent of the LTF. To verify whether these projections indeed originated from ILc, in two other cases retrograde tracer injections were made in the pontomedullary LTF. The results showed many retrogradely labeled neurons in ILc, but none in adjacent cortical regions. These results show that the ILc projects to the LTF in cat and can possibly modulate the fear response not only via indirect but also via direct routes to the premotor interneurons in the brainstem.
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Affiliation(s)
- Rutger Kuipers
- Department of Anatomy and Embryology, University Medical Center Groningen, University of Groningen, Antonius Deusinglaan 1, bldg 3215, PO Box 196, 9713 AV Groningen, The Netherlands.
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Lieske SP, Ramirez JM. Pattern-specific synaptic mechanisms in a multifunctional network. II. Intrinsic modulation by metabotropic glutamate receptors. J Neurophysiol 2006; 95:1334-44. [PMID: 16492945 DOI: 10.1152/jn.00506.2004] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The in vitro respiratory network contained in the transverse brain stem slice of mice simultaneously generates fast (approximately 15 min(-1)) and slow ( approximately 0.5 min(-1)) rhythmic activities corresponding to fictive eupnea ("normal" breathing) and fictive sighs. We show that these two activity patterns are differentially controlled through the modulatory actions of metabotropic glutamate receptors (mGluRs). Sighs were selectively inhibited by agonists of the group III mGluRs according to a pharmacological profile most consistent with activation of mGluR8. Sighs were also blocked by the supposedly inactive L-isomer of the widely used N-methyl-D-aspartate (NMDA) receptor antagonist 2-amino-5-phosphonopentanoic acid (L-AP5, 5 microM), an effect that was abolished in the presence of group III mGluR antagonists. Excitatory postsynaptic potentials (EPSPs) were recorded in pre-Bötzinger Complex neurons after stimulation of the contralateral ventral respiratory group (VRG); evoked EPSP amplitude was variably reduced after bath application of the group III agonist L-serine-O-phosphate (L-SOP), with an average reduction of 15%. Therefore although group III mGluRs do play a role in regulating synapse strength, this seems to be only a minor factor in the regulation of synapses made by midline-crossing axons. Intrinsic modulation of the respiratory central pattern generator by mGluRs appears to be an essential component of the multifunctionality that characterizes this network.
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Affiliation(s)
- Steven P Lieske
- Committee on Neurobiology, The University of Chicago, 1027 E. 57th St., Chicago, IL 60637-1508, USA
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Lieske SP, Ramirez JM. Pattern-Specific Synaptic Mechanisms in a Multifunctional Network. I. Effects of Alterations in Synapse Strength. J Neurophysiol 2006; 95:1323-33. [PMID: 16492944 DOI: 10.1152/jn.00505.2004] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Many neuronal networks are multifunctional, producing different patterns of activity in different circumstances, but the mechanisms responsible for this reconfiguration are in many cases unresolved. The mammalian respiratory network is an example of such a system. Normal respiratory activity (eupnea) is periodically interrupted by distinct large-amplitude inspirations known as sighs. Both rhythms originate from a single multifunctional neural network, and both are preserved in the in vitro transverse medullary slice of mice. Here we show that the generation of fictive sighs were more sensitive than eupnea to reductions of excitatory synapse strength caused by either the P/Q-type (α1A-containing) calcium channel antagonist ω-agatoxin TK or the non- N-methyl-d-aspartate (NMDA) glutamate receptor antagonist 6-cyano-7-nitroquinoxalene-2,3-dione (CNQX). In contrast, the NMDA receptor antagonist MK-801, while also inhibiting eupnea, increased the occurrence of sighs. This suggests that among the glutamatergic synapses subserving eupneic rhythmogenesis, there is a specific subset—highly sensitive to agatoxin and insensitive to NMDA receptor blockade—that is essential for sighs. Blockade of N-type calcium channels with ω-conotoxin GVIA also had pattern-specific effects: eupneic activity was not affected, but sigh frequency was increased and postsigh apnea decreased. We hypothesize that N-type (α1B) calcium channels selectively coupled to calcium-activated potassium channels contribute to the generation of the postsigh apnea.
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Affiliation(s)
- Steven P Lieske
- Committee on Neurobiology, The University of Chicago, 1027 E. 57th S., Chicago, IL 60637-1508, USA
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Boers J, Kirkwood PA, de Weerd H, Holstege G. Ultrastructural evidence for direct excitatory retroambiguus projections to cutaneous trunci and abdominal external oblique muscle motoneurons in the cat. Brain Res Bull 2006; 68:249-56. [PMID: 16377430 DOI: 10.1016/j.brainresbull.2005.08.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2005] [Revised: 08/23/2005] [Accepted: 08/23/2005] [Indexed: 11/15/2022]
Abstract
The nucleus retroambiguus (NRA) is a group of neurons, located laterally in the caudal medulla oblongata. The NRA is thought to modulate abdominal pressure in the framework of respiration, vomiting, vocalization, probably parturition, and, in all likelihood mating behavior. The NRA exerts this control through its projections to motoneurons to the nucleus ambiguus in the lateral medulla (innervating pharynx, larynx), and spinal cord (innervating cutaneous trunci, intercostal, abdominal, pelvic floor, and lower limb muscles). The nature of these NRA-motoneuronal projections is unknown. In this study we have determined the ultrastructure of the NRA-motoneuronal projections, and especially those to the abdominal external oblique and cutaneous trunci muscles. In four cats 0.1% cholera toxin subunit b was injected in the external oblique and cutaneous trunci muscles to retrogradely label their motoneurons in the spinal cord. Wheat germ agglutinin-conjugated horseradish peroxidase was injected into the NRA to anterogradely label its contralaterally descending fibers to the motoneurons of both muscles. In order to prevent anterograde labeling of ipsilaterally descending systems not originating from the NRA, a hemisection was made at the level of C2 prior to the NRA injection. The ultrastructural results indicate that the majority (60-74%) of the anterogradely labeled NRA-terminals made monosynaptic contacts with retrogradely labeled dendrites of the external oblique and the cutaneous trunci muscle motoneurons. The majority (86-95%) of the NRA terminals made asymmetric synaptic contacts and 79-84% contained round vesicles. These results demonstrate the existence of direct, presumably excitatory, projections from NRA to external oblique and cutaneous trunci muscle motoneurons.
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Affiliation(s)
- J Boers
- Department of Anatomy and Embryology, University Medical Center Groningen, University of Groningen, A. Deusinglaan 1, 9700 AD Groningen, The Netherlands
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Boers J, Ford TW, Holstege G, Kirkwood PA. Functional Heterogeneity Among Neurons in the Nucleus Retroambiguus With Lumbosacral Projections in Female Cats. J Neurophysiol 2005; 94:2617-29. [PMID: 15972831 DOI: 10.1152/jn.00370.2005] [Citation(s) in RCA: 19] [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
Nucleus retroambiguus (NRA), in the caudal medulla, projects to all spinal levels. One physiological role is abdominal pressure control, evidenced by projections to intercostal and abdominal motoneurons from expiratory bulbospinal neurons (EBSNs) within NRA. The roles of NRA projections to the lumbosacral cord are less certain, although those to limb motoneurons may relate to mating behavior and those to Onuf's nucleus (ON) to maintaining continence. To clarify this we physiologically characterized NRA projections to the lumbosacral cord. Extracellular recordings were made in NRA under anesthesia and paralysis in estrus cats. Administered CO2gave a strong respiratory drive. Antidromic unit responses were recorded to stimulation of the contralateral ventrolateral funiculus of L6, L7, or sacral segments and to microstimulation in the region of semimembranosus motor nucleus or ON. All units were found at sites showing expiratory discharges. Units that showed collisions between antidromic and spontaneous spikes (all in late expiration) were identified as EBSNs. These were common from the ventrolateral funiculus (VLF) of L6(42.5%) or L7(32.9%), but rare from the sacral VLF or the motor nuclei. Antidromic latencies revealed a subthreshold respiratory drive in some non-EBSNs. This group had lower conduction velocities than the EBSNs. The remainder, with a negligible respiratory drive, had even lower conduction velocities. A new population of NRA neurons has thus been defined. They are not active even with a strong respiratory drive, but may provide most of the synaptic input from NRA to lower lumbar and sacral segments and could subserve functions related to mating behavior.
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Affiliation(s)
- J Boers
- Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, UK
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Vanderhorst VGJM. Nucleus retroambiguus-spinal pathway in the mouse: Localization, gender differences, and effects of estrogen treatment. J Comp Neurol 2005; 488:180-200. [PMID: 15924340 DOI: 10.1002/cne.20574] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Nucleus retroambiguus (NRA)-motoneuronal projections are species-specific and serve expiration, Valsalva maneuvers, vocalization, and sexual behavior. In cat and monkey, estrogen induces sprouting of NRA-spinal axons. This pathway may thus serve as a model to study mechanisms through which estrogen induces neuronal plasticity. In this study, NRA-spinal projections are described in adult mice by using anterograde and retrograde tracing techniques, with attention to gender, strain (CD-1 and C57BL/6), and estrogen-induced changes (in ovariectomized females). Labeled NRA-spinal neurons at the level of the decussation of the corticospinal tract were most numerous after tracer injections into the thoracic and upper lumbar cord. They were medium-sized and had axons that descended through the contralateral cord. A group of small neurons was labeled in the NRA immediately rostral to the decussation of the corticospinal tract after cervical and thoracic, but not after lumbar injections. This group projected mainly via an ipsilateral pathway. The main projections from the caudal NRA involved motoneurons in the thoracic and upper-lumbar cord that supply abdominal wall and cremaster muscles. Pelvic floor motoneurons did not receive substantial input. NRA-spinal projections, especially those involving the upper lumbar cord, were sexually dimorphic, being more extensive in males than in females. Moreover, they were more distinct in estrogen-treated females than in control females. Strain differences were not observed. The unique features of the caudal NRA-spinal pathway in the mouse are discussed in the framework of possible functions of this system, such as mating behavior and related social behaviors, parturition, thermoregulation, and control of balance.
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Affiliation(s)
- Veronique G J M Vanderhorst
- Department of Pathology and Laboratory Medicine, University of Groningen, NL-9700 RB Groningen, The Netherlands.
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Affiliation(s)
- John E Remmers
- Department of Medicine, Heritage Medical Research Building, University of Calgary, 3330 Hospital Drive NW, Room 293, Calgary, Alberta T2N 4N1, Canada.
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Kubke MF, Yazaki-Sugiyama Y, Mooney R, Wild JM. Physiology of neuronal subtypes in the respiratory-vocal integration nucleus retroamigualis of the male zebra finch. J Neurophysiol 2005; 94:2379-90. [PMID: 15928060 DOI: 10.1152/jn.00257.2005] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Learned vocalizations, such as bird song, require intricate coordination of vocal and respiratory muscles. Although the neural basis for this coordination remains poorly understood, it likely includes direct synaptic interactions between respiratory premotor neurons and vocal motor neurons. In birds, as in mammals, the medullary nucleus retroambigualis (RAm) receives synaptic input from higher level respiratory and vocal control centers and projects to a variety of targets. In birds, these include vocal motor neurons in the tracheosyringeal part of the hypoglossal motor nucleus (XIIts), other respiratory premotor neurons, and expiratory motor neurons in the spinal cord. Although various cell types in RAm are distinct in their anatomical projections, their electrophysiological properties remain unknown. Furthermore, although prior studies have shown that RAm provides both excitatory and inhibitory input onto XIIts motor neurons, the identity of the cells in RAm providing either of these inputs remains to be established. To characterize the different RAm neuron types electrophysiologically, we used intracellular recordings in a zebra finch brain stem slice preparation. Based on numerous differences in intrinsic electrophysiological properties and a principal components analysis, we identified two distinct RAm neuron types (types I and II). Antidromic stimulation methods and intracellular staining revealed that type II neurons, but not type I neurons, provide bilateral synaptic input to XIIts. Paired intracellular recordings in RAm and XIIts further indicated that type II neurons with a hyperpolarization-dependent bursting phenotype are a potential source of inhibitory input to XIIts motor neurons. These results indicate that electrically distinct cell types exist in RAm, affording physiological heterogeneity that may play an important role in respiratory-vocal signaling.
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Affiliation(s)
- M F Kubke
- Division of Anatomy, Faculty of Medical and Health Sciences, University of Auckland, New Zealand.
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Fong J, Sandhu G, Ellaway P, Davey N, Strutton P, Murphy K, Guz A. What do we know about how humans cough? Pulm Pharmacol Ther 2005; 17:431-4. [PMID: 15564087 DOI: 10.1016/j.pupt.2004.09.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2004] [Accepted: 09/13/2004] [Indexed: 11/21/2022]
Abstract
We review the evidence that activation of the cerebral cortex can lead to movements of the vocal folds and possibly to cough. Electrical stimulation of the motor cortex can cause movements of the vocal folds and vocalizatioin, but cough has not been reported. The motor pathways are via the nucleus ambiguous and possibly the nucleus retroambuigualis in the brainstem. In humans, activation of the cerebral cortex by transcranial magnetic stimulation can cause motor potentials in the intrinsic laryngeal muscles and corresponding surface potentials. The relationships between the cortical sensation related to cough, the voluntary control of cough and the involvement of reflex pathways remain to be clarified.
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Affiliation(s)
- J Fong
- ENT Department, Charing Cross Hospital, London, UK
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Hayakawa T, Takanaga A, Tanaka K, Maeda S, Seki M. Ultrastructure of the rostral ventral respiratory group neurons in the ventrolateral medulla of the rat. Brain Res 2004; 1027:94-102. [PMID: 15494161 DOI: 10.1016/j.brainres.2004.08.059] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/19/2004] [Indexed: 02/02/2023]
Abstract
The neurons in the ventrolateral medulla that project to the spinal cord are called the rostral ventral respiratory group (rVRG) because they activate spinal respiratory motor neurons. We retrogradely labeled rVRG neurons with Fluoro-Gold (FG) injections into the fourth cervical spinal cord segment to determine their distribution. The rostral half of the rVRG was located in the area ventral to the semicompact formation of the nucleus ambiguus (AmS). A cluster of the neurons moved dorsally and intermingled with the palatopharyngeal motor neurons at the caudal end of the AmS. The caudal half of the rVRG was located in the area including the loose formation of the nucleus ambiguus caudal to the AmS. We also labeled the rVRG neurons retrogradely with wheat germ agglutinin-horseradish peroxidase (WGA-HRP) to determine their ultrastructural characteristics. The neurons of the rVRG were medium to large (38.1 x 22.1 microm), oval or ellipsoid in shape, and had a dark cytoplasm containing numerous free ribosomes, rough endoplasmic reticulum (rER), mitochondria, Golgi apparatuses, lipofuscin granules and a round nucleus with an invaginated nuclear membrane. The average number of axosomatic terminals in a profile was 33.2. The number of axosomatic terminals containing round vesicles and making asymmetric synaptic contacts (Gray's type I) was almost equal to those containing pleomorphic vesicles and making symmetric synaptic contacts (Gray's type II). The axodendritic terminals were large (1.55 microm), and about 60% of them were Gray's type I. The rVRG neurons have ultrastructural characteristics, which are different from the palatopharyngeal motor neurons or the prorpiobulbar neurons.
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Affiliation(s)
- Tetsu Hayakawa
- Department of Anatomy, Hyogo College of Medicine, Mukogawa, Nishinomiya, Hyogo 663-8501, Japan.
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Ambalavanar R, Tanaka Y, Selbie WS, Ludlow CL. Neuronal activation in the medulla oblongata during selective elicitation of the laryngeal adductor response. J Neurophysiol 2004; 92:2920-32. [PMID: 15212423 PMCID: PMC2376830 DOI: 10.1152/jn.00064.2004] [Citation(s) in RCA: 32] [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
Swallow and cough are complex motor patterns elicited by rapid and intense electrical stimulation of the internal branch of the superior laryngeal nerve (ISLN). The laryngeal adductor response (LAR) includes only a laryngeal response, is elicited by single stimuli to the ISLN, and is thought to represent the brain stem pathway involved in laryngospasm. To identify which regions in the medulla are activated during elicitation of the LAR alone, single electrical stimuli were presented once every 2 s to the ISLN. Two groups of five cats each were studied; an experimental group with unilateral ISLN stimulation at 0.5 Hz and a surgical control group. Three additional cats were studied to evaluate whether other oral, pharyngeal, or respiratory muscles were activated during ISLN stimulation eliciting LAR. We quantified < or = 22 sections for each of 14 structures in the medulla to determine if regions had increased Fos-like immunoreactive neurons in the experimental group. Significant increases (P < 0.0033) occurred with unilateral ISLN stimulation in the interstitial subnucleus, the ventrolateral subnucleus, the commissural subnucleus of the nucleus tractus solitarius, the lateral tegmental field of the reticular formation, the area postrema, and the nucleus ambiguus. Neither the dorsal motor nucleus of the vagus, usually active for swallow, nor the nucleus retroambiguus, retrofacial nucleus, and the lateral reticular nucleus, usually active for cough, were active with elicitation of the laryngeal adductor response alone. The results demonstrate that the laryngeal adductor pathway is contained within the broader pathways for cough and swallow in the medulla.
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Affiliation(s)
- Ranjinidevi Ambalavanar
- Laryngeal and Speech Section, National Institute of Neurological Disorders and Strokes, Bethesda, MD 20892-1416, USA
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Gerrits PO, Mouton LJ, de Weerd H, Georgiadis JR, Krukerink M, Holstege G. Ultrastructural evidence for a direct excitatory pathway from the nucleus retroambiguus to lateral longissimus and quadratus lumborum motoneurons in the female golden hamster. J Comp Neurol 2004; 480:352-63. [PMID: 15558782 DOI: 10.1002/cne.20366] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
During mating, the female golden hamster displays a stereotyped specific receptive posture, characterized by lordosis of the back, elevation of the tail, and extension of the legs. Muscles involved in this posture are thought to be iliopsoas, cutaneus trunci, lateral longissimus (LL), and quadratus lumborum (QL). Lesion studies in rats suggest that mating behavior is controlled by the mesencephalic periaqueductal gray (PAG). The PAG does not project directly to the motoneurons innervating the muscles involved in mating, but is thought to make use of the nucleus retroambiguus (NRA) as relay. The NRA is located ventrolaterally in the most caudal medulla, and projects directly to iliopsoas and cutaneus trunci motoneuronal cell groups. The question is whether this is also true for LL and QL muscles. Retrograde HRP tracing experiments revealed that LL and QL motoneurons are located medially in the ventral horn of the T12-L6 and T13-L4 segments, respectively. A subsequent ultrastructural study combined wheatgerm agglutinin-conjugated horseradish peroxidase injections in the NRA with cholera-toxin B-subunit injections in LL and QL muscles. The results revealed monosynaptic contacts between anterogradely labeled NRA-fiber terminals with retrogradely labeled dendrites of both LL and QL motoneurons. Almost all these terminals had asymmetrical synapses and contained spherical vesicles, suggesting an excitatory function of this NRA-motoneuronal pathway. These results correspond with the hypothesis that in hamster the PAG-NRA-motoneuronal projection not only involves motoneurons of iliopsoas and cutaneus trunci but also of LL and QL.
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Affiliation(s)
- Peter O Gerrits
- Department of Anatomy and Embryology, Faculty of Medical Sciences, University of Groningen, Ant. Deusinglaan 1, 9700 AD Groningen, The Netherlands.
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Kirkwood PA, Ford TW. Do respiratory neurons control female receptive behavior: a suggested role for a medullary central pattern generator? PROGRESS IN BRAIN RESEARCH 2004; 143:105-14. [PMID: 14653155 DOI: 10.1016/s0079-6123(03)43010-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Nucleus retroambiguus (NRA) consists of a column of neurons in the caudal medulla with crossed descending axons that terminate in almost all spinal segments. Many of these neurons transmit the drive for expiratory movements to the spinal cord. The same neurons are also known to participate, however, in other motor acts, such as vomiting and abdominal straining, for which it appears that the medullary circuits controlling the respiratory pattern are reconfigured. Plasticity in projections from the NRA to hindlimb motor nuclei provides evidence that some of these projections are involved in yet another motor act, female receptive behavior. Here, we present the hypothesis that the medullary circuits are also reconfigured to act as a central pattern generator for this behavior. In addition, we suggest that during estrus, plasticity is shown not only in spinal cord connections, but also in a selected membrane property of hindlimb motoneurons.
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Affiliation(s)
- Peter A Kirkwood
- Sobell Department for Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK.
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