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Moe AAK, Bautista TG, Trewella MW, Korim WS, Yao ST, Behrens R, Driessen AK, McGovern AE, Mazzone SB. Investigation of vagal sensory neurons in mice using optical vagal stimulation and tracheal neuroanatomy. iScience 2024; 27:109182. [PMID: 38414860 PMCID: PMC10897902 DOI: 10.1016/j.isci.2024.109182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Revised: 12/28/2023] [Accepted: 02/06/2024] [Indexed: 02/29/2024] Open
Abstract
In rats and guinea pigs, sensory innervation of the airways is derived largely from the vagus nerve, with the extrapulmonary airways innervated by Wnt1+ jugular neurons and the intrapulmonary airways and lungs by Phox2b+ nodose neurons; however, our knowledge of airway innervation in mice is limited. We used genetically targeted expression of enhanced yellow fluorescent protein-channelrhodopsin-2 (EYFP-ChR2) in Wnt1+ or Phox2b+ tissues to characterize jugular and nodose-mediated physiological responses and airway innervation in mice. With optical stimulation, Phox2b+ vagal fibers modulated cardiorespiratory function in a frequency-dependent manner while right Wnt1+ vagal fibers induced a small increase in respiratory rate. Mouse tracheae contained sparse Phox2b-EYFP fibers but dense networks of Wnt1-EYFP fibers. Retrograde tracing from the airways showed limited tracheal innervation by the jugular sensory neurons, distinct from other species. These differences in physiology and vagal sensory distribution have important implications when using mice for studying airway neurobiology.
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Affiliation(s)
- Aung Aung Kywe Moe
- Department of Anatomy and Physiology, School of Biomedical Sciences, The University of Melbourne, Parkville, VIC 3010, Australia
- Department of Medical Imaging and Radiation Sciences, School of Primary and Allied Health Care, Monash University, Clayton Campus, Clayton, VIC 3800, Australia
| | - Tara G Bautista
- Department of Anatomy and Physiology, School of Biomedical Sciences, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Matthew W Trewella
- Department of Anatomy and Physiology, School of Biomedical Sciences, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Willian S Korim
- Department of Anatomy and Physiology, School of Biomedical Sciences, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Song T Yao
- Department of Anatomy and Physiology, School of Biomedical Sciences, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Robert Behrens
- Department of Anatomy and Physiology, School of Biomedical Sciences, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Alexandria K Driessen
- Department of Anatomy and Physiology, School of Biomedical Sciences, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Alice E McGovern
- Department of Anatomy and Physiology, School of Biomedical Sciences, The University of Melbourne, Parkville, VIC 3010, Australia
| | - Stuart B Mazzone
- Department of Anatomy and Physiology, School of Biomedical Sciences, The University of Melbourne, Parkville, VIC 3010, Australia
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Elsaafien K, Sloan JM, Evans RG, Cochrane AD, Marino B, McCall PR, Hood SG, Yao ST, Korim WS, Bailey SR, Jufar AH, Peiris RM, Bellomo R, Miles LF, May CN, Lankadeva YR. Associations Between Systemic and Cerebral Inflammation in an Ovine Model of Cardiopulmonary Bypass. Anesth Analg 2023; 136:802-813. [PMID: 36928157 DOI: 10.1213/ane.0000000000006379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
BACKGROUND Intraoperative inflammation may contribute to postoperative neurocognitive disorders after cardiac surgery requiring cardiopulmonary bypass (CPB). However, the relative contributions of general anesthesia (GA), surgical site injury, and CPB are unclear. METHODS In adult female sheep, we investigated (1) the temporal profile of proinflammatory and anti-inflammatory cytokines and (2) the extent of microglia activation across major cerebral cortical regions during GA and surgical trauma with and without CPB (N = 5/group). Sheep were studied while conscious, during GA and surgical trauma, with and without CPB. RESULTS Plasma tumor necrosis factor-alpha (mean [95% confidence intervals], 3.7 [2.5-4.9] vs 1.6 [0.8-2.3] ng/mL; P = .0004) and interleukin-6 levels (4.4 [3.0-5.8] vs 1.6 [0.8-2.3] ng/mL; P = .029) were significantly higher at 1.5 hours, with a further increase in interleukin-6 at 3 hours (7.0 [3.7-10.3] vs 1.8 [1.1-2.6] ng/mL; P < .0001) in animals undergoing CPB compared with those that did not. Although cerebral oxygen saturation was preserved throughout CPB, there was pronounced neuroinflammation as characterized by greater microglia circularity within the frontal cortex of sheep that underwent CPB compared with those that did not (0.34 [0.32-0.37] vs 0.30 [0.29-0.32]; P = .029). Moreover, microglia had fewer branches within the parietal (7.7 [6.5-8.9] vs 10.9 [9.4-12.5]; P = .001) and temporal (7.8 [7.2-8.3] vs 9.9 [8.2-11.7]; P = .020) cortices in sheep that underwent CPB compared with those that did not. CONCLUSIONS CPB enhanced the release of proinflammatory cytokines beyond that initiated by GA and surgical trauma. This systemic inflammation was associated with microglial activation across 3 major cerebral cortical regions, with a phagocytic microglia phenotype within the frontal cortex, and an inflammatory microglia phenotype within the parietal and temporal cortices. These data provide direct histopathological evidence of CPB-induced neuroinflammation in a large animal model and provide further mechanistic data on how CPB-induced cerebral inflammation might drive postoperative neurocognitive disorders in humans.
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Affiliation(s)
- Khalid Elsaafien
- From the Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health
- Cardiovascular Neuroscience Laboratory, Department of Anatomy and Physiology, University of Melbourne, Melbourne, Victoria, Australia
- Centre for Integrative Cardiovascular and Metabolic Diseases, Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, Florida
| | - Jasmine M Sloan
- From the Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health
- Cardiovascular Neuroscience Laboratory, Department of Anatomy and Physiology, University of Melbourne, Melbourne, Victoria, Australia
| | - Roger G Evans
- From the Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health
- Cardiovascular Disease Program, Biomedicine Discovery Institute and Department of Physiology, Monash University, Melbourne, Victoria, Australia
| | - Andrew D Cochrane
- Department of Cardiothoracic Surgery, Monash Health, and Department of Surgery (School of Clinical Sciences at Monash Health), Monash University, Melbourne, Victoria, Australia
| | - Bruno Marino
- Cellsaving and Perfusion Resources, Melbourne, Victoria, Australia
| | - Peter R McCall
- Department of Anaesthesia, Austin Health, Heidelberg, Victoria, Australia
- Department of Critical Care, Melbourne Medical School, Melbourne, Victoria, Australiaand
| | - Sally G Hood
- From the Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health
| | - Song T Yao
- Cardiovascular Neuroscience Laboratory, Department of Anatomy and Physiology, University of Melbourne, Melbourne, Victoria, Australia
| | - Willian S Korim
- Cardiovascular Neuroscience Laboratory, Department of Anatomy and Physiology, University of Melbourne, Melbourne, Victoria, Australia
| | - Simon R Bailey
- Faculty of Veterinary Science, University of Melbourne, Melbourne, Victoria, Australia
| | - Alemayehu H Jufar
- From the Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health
- Cardiovascular Disease Program, Biomedicine Discovery Institute and Department of Physiology, Monash University, Melbourne, Victoria, Australia
| | - Rachel M Peiris
- From the Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health
| | - Rinaldo Bellomo
- Department of Critical Care, Melbourne Medical School, Melbourne, Victoria, Australiaand
| | - Lachlan F Miles
- From the Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health
- Department of Anaesthesia, Austin Health, Heidelberg, Victoria, Australia
- Department of Critical Care, Melbourne Medical School, Melbourne, Victoria, Australiaand
| | - Clive N May
- From the Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health
- Department of Critical Care, Melbourne Medical School, Melbourne, Victoria, Australiaand
| | - Yugeesh R Lankadeva
- From the Pre-Clinical Critical Care Unit, Florey Institute of Neuroscience and Mental Health
- Department of Critical Care, Melbourne Medical School, Melbourne, Victoria, Australiaand
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Booth LC, Yao ST, Korsak A, Farmer DGS, Hood SG, McCormick D, Boesley Q, Connelly AA, McDougall SJ, Korim WS, Guild SJ, Mastitskaya S, Le P, Teschemacher AG, Kasparov S, Ackland GL, Malpas SC, McAllen RM, Allen AM, May CN, Gourine AV. Selective optogenetic stimulation of efferent fibers in the vagus nerve of a large mammal. Brain Stimul 2020; 14:88-96. [PMID: 33217609 PMCID: PMC7836098 DOI: 10.1016/j.brs.2020.11.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Revised: 10/26/2020] [Accepted: 11/11/2020] [Indexed: 12/26/2022] Open
Abstract
Background Electrical stimulation applied to individual organs, peripheral nerves, or specific brain regions has been used to treat a range of medical conditions. In cardiovascular disease, autonomic dysfunction contributes to the disease progression and electrical stimulation of the vagus nerve has been pursued as a treatment for the purpose of restoring the autonomic balance. However, this approach lacks selectivity in activating function- and organ-specific vagal fibers and, despite promising results of many preclinical studies, has so far failed to translate into a clinical treatment of cardiovascular disease. Objective Here we report a successful application of optogenetics for selective stimulation of vagal efferent activity in a large animal model (sheep). Methods and results Twelve weeks after viral transduction of a subset of vagal motoneurons, strong axonal membrane expression of the excitatory light-sensitive ion channel ChIEF was achieved in the efferent projections innervating thoracic organs and reaching beyond the level of the diaphragm. Blue laser or LED light (>10 mW mm−2; 1 ms pulses) applied to the cervical vagus triggered precisely timed, strong bursts of efferent activity with evoked action potentials propagating at speeds of ∼6 m s−1. Conclusions These findings demonstrate that in species with a large, multi-fascicled vagus nerve, it is possible to stimulate a specific sub-population of efferent fibers using light at a site remote from the vector delivery, marking an important step towards eventual clinical use of optogenetic technology for autonomic neuromodulation. Described is a method of selective efferent vagus nerve stimulation using light. Vagal preganglionic neurons are targeted to express light-sensitive channels. Specific efferent VNS by light delivery to the cervical vagus is achieved in a large animal model. Demonstrates feasibility of using optogenetic technology for autonomic neuromodulation.
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Affiliation(s)
- Lindsea C Booth
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia
| | - Song T Yao
- Florey Department of Neuroscience and Mental Health, MDHS, University of Melbourne, Melbourne, Australia
| | - Alla Korsak
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - David G S Farmer
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia; Department of Physiology, The University of Melbourne, Melbourne, Australia
| | - Sally G Hood
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia
| | - Daniel McCormick
- Department of Physiology and Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Quinn Boesley
- Department of Physiology and Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Angela A Connelly
- Department of Physiology, The University of Melbourne, Melbourne, Australia
| | - Stuart J McDougall
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia
| | - Willian S Korim
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia
| | - Sarah-Jane Guild
- Department of Physiology and Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Svetlana Mastitskaya
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Phuong Le
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia
| | - Anja G Teschemacher
- Physiology, Neuroscience and Pharmacology, University of Bristol, Bristol, UK
| | - Sergey Kasparov
- Physiology, Neuroscience and Pharmacology, University of Bristol, Bristol, UK; Baltic Federal University, Kaliningrad, Russian Federation
| | - Gareth L Ackland
- Translational Medicine and Therapeutics, William Harvey Research Institute, Queen Mary University of London, London, UK
| | - Simon C Malpas
- Department of Physiology and Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Robin M McAllen
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia
| | - Andrew M Allen
- Department of Physiology, The University of Melbourne, Melbourne, Australia
| | - Clive N May
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia.
| | - Alexander V Gourine
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK.
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Elsaafien K, Korim WS, Setiadi A, May CN, Yao ST. Chemoattraction and Recruitment of Activated Immune Cells, Central Autonomic Control, and Blood Pressure Regulation. Front Physiol 2019; 10:984. [PMID: 31427987 PMCID: PMC6688384 DOI: 10.3389/fphys.2019.00984] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 07/15/2019] [Indexed: 12/16/2022] Open
Abstract
Inflammatory mediators play a critical role in the regulation of sympathetic outflow to cardiovascular organs in hypertension. Emerging evidence highlights the involvement of immune cells in the regulation of blood pressure. However, it is still unclear how these immune cells are activated and recruited to key autonomic brain regions to regulate sympathetic outflow to cardiovascular organs. Chemokines such as C-C motif chemokine ligand 2 (CCL2), and pro-inflammatory cytokines such as tumor necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1β), are upregulated both peripherally and centrally in hypertension. More specifically, they are upregulated in key autonomic brain regions that control sympathetic activity and blood pressure such as the paraventricular nucleus of the hypothalamus and the rostral ventrolateral medulla. Furthermore, this upregulation of inflammatory mediators is associated with the infiltration of immune cells to these brain areas. Thus, expression of pro-inflammatory chemokines and cytokines is a potential mechanism promoting invasion of immune cells into key autonomic brain regions. In pathophysiological conditions, this can result in abnormal activation of brain circuits that control sympathetic nerve activity to cardiovascular organs and ultimately in increases in blood pressure. In this review, we discuss emerging evidence that helps explain how immune cells are chemoattracted to autonomic nuclei and contribute to changes in sympathetic outflow and blood pressure.
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Affiliation(s)
- Khalid Elsaafien
- Discovery Science, Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
| | - Willian S. Korim
- Discovery Science, Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
| | - Anthony Setiadi
- Discovery Science, Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
| | - Clive N. May
- Discovery Science, Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
| | - Song T. Yao
- Discovery Science, Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
- Florey Department of Neuroscience and Mental Health, The University of Melbourne, Parkville, VIC, Australia
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Decataldo F, Cramer T, Martelli D, Gualandi I, Korim WS, Yao ST, Tessarolo M, Murgia M, Scavetta E, Amici R, Fraboni B. Stretchable Low Impedance Electrodes for Bioelectronic Recording from Small Peripheral Nerves. Sci Rep 2019; 9:10598. [PMID: 31332219 PMCID: PMC6646361 DOI: 10.1038/s41598-019-46967-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Accepted: 07/03/2019] [Indexed: 12/24/2022] Open
Abstract
Monitoring of bioelectric signals in peripheral sympathetic nerves of small animal models is crucial to gain understanding of how the autonomic nervous system controls specific body functions related to disease states. Advances in minimally-invasive electrodes for such recordings in chronic conditions rely on electrode materials that show low-impedance ionic/electronic interfaces and elastic mechanical properties compliant with the soft and fragile nerve strands. Here we report a highly stretchable low-impedance electrode realized by microcracked gold films as metallic conductors covered with stretchable conducting polymer composite to facilitate ion-to-electron exchange. The conducting polymer composite based on poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) obtains its adhesive, low-impedance properties by controlling thickness, plasticizer content and deposition conditions. Atomic Force Microscopy measurements under strain show that the optimized conducting polymer coating is compliant with the micro-crack mechanics of the underlying Au-layer, necessary to absorb the tensile deformation when the electrodes are stretched. We demonstrate functionality of the stretchable electrodes by performing high quality recordings of renal sympathetic nerve activity under chronic conditions in rats.
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Affiliation(s)
| | - Tobias Cramer
- Department of Physics and Astronomy, University of Bologna, Bologna, Italy.
| | - Davide Martelli
- Department of Biomedical and Neuromotor Sciences - Physiology, University of Bologna, Bologna, Italy
| | - Isacco Gualandi
- Department of Industrial Chemistry, University of Bologna, Bologna, Italy
| | - Willian S Korim
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia
| | - Song T Yao
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia
| | - Marta Tessarolo
- Department of Physics and Astronomy, University of Bologna, Bologna, Italy
| | - Mauro Murgia
- Instituto per lo Studio dei Materiali Nanostrutturati (ISMN), Centro Nazionale delle Ricerche (CNR), Via Gobetti 101, 40129, Bologna, Italy
| | - Erika Scavetta
- Department of Industrial Chemistry, University of Bologna, Bologna, Italy
| | - Roberto Amici
- Department of Biomedical and Neuromotor Sciences - Physiology, University of Bologna, Bologna, Italy
| | - Beatrice Fraboni
- Department of Physics and Astronomy, University of Bologna, Bologna, Italy
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Korim WS, Elsaafien K, Basser J, Setiadi A, May CN, Yao ST. In Renovascular Hypertension, TNF‐α Type‐1 Receptors in the Area Postrema Mediate Increases in Cardiac and Renal Sympathetic Nerve Activity and Blood Pressure. FASEB J 2019. [DOI: 10.1096/fasebj.2019.33.1_supplement.565.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Willian S Korim
- Florey Institute of Neuroscience and Mental HealthMelbourneAustralia
| | - Khalid Elsaafien
- Florey Institute of Neuroscience and Mental HealthMelbourneAustralia
| | - Jeremy Basser
- Florey Institute of Neuroscience and Mental HealthMelbourneAustralia
| | - Anthony Setiadi
- Florey Institute of Neuroscience and Mental HealthMelbourneAustralia
| | - Clive N May
- Florey Institute of Neuroscience and Mental HealthMelbourneAustralia
| | - Song T Yao
- Florey Institute of Neuroscience and Mental HealthMelbourneAustralia
- Florey Department of Neuroscience and Mental HealthUniversity of MelbourneMelbourneAustralia
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Gao H, Korim WS, Yao ST, Heesch CM, Derbenev AV. Glycinergic neurotransmission in the rostral ventrolateral medulla controls the time course of baroreflex-mediated sympathoinhibition. J Physiol 2018; 597:283-301. [PMID: 30312491 DOI: 10.1113/jp276467] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Accepted: 10/11/2018] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS To maintain appropriate blood flow to various tissues of the body under a variety of physiological states, autonomic nervous system reflexes regulate regional sympathetic nerve activity and arterial blood pressure. Our data obtained in anaesthetized rats revealed that glycine released in the rostral ventrolateral medulla (RVLM) plays a critical role in maintaining arterial baroreflex sympathoinhibition. Manipulation of brainstem nuclei with known inputs to the RVLM (nucleus tractus solitarius and caudal VLM) unmasked tonic glycinergic inhibition in the RVLM. Whole-cell, patch clamp recordings demonstrate that both GABA and glycine inhibit RVLM neurons. Potentiation of neurotransmitter release from the active synaptic inputs in the RVLM produced saturation of GABAergic inhibition and emergence of glycinergic inhibition. Our data suggest that GABA controls threshold excitability, wherreas glycine increases the strength of inhibition under conditions of increased synaptic activity within the RVLM. ABSTRACT The arterial baroreflex is a rapid negative-feedback system that compensates changes in blood pressure by adjusting the output of presympathetic neurons in the rostral ventrolateral medulla (RVLM). GABAergic projections from the caudal VLM (CVLM) provide a primary inhibitory input to presympathetic RVLM neurons. Although glycine-dependent regulation of RVLM neurons has been proposed, its role in determining RVLM excitability is ill-defined. The present study aimed to determine the physiological role of glycinergic neurotransmission in baroreflex function, identify the mechanisms for glycine release, and evaluate co-inhibition of RVLM neurons by GABA and glycine. Microinjection of the glycine receptor antagonist strychnine (4 mm, 100 nL) into the RVLM decreased the duration of baroreflex-mediated inhibition of renal sympathetic nerve activity (control = 12 ± 1 min; RVLM-strychnine = 5.1 ± 1 min), suggesting that RVLM glycine plays a critical role in regulating the time course of sympathoinhibition. Blockade of output from the nucleus tractus solitarius and/or disinhibition of the CVLM unmasked tonic glycinergic inhibition of the RVLM. To evaluate cellular mechanisms, RVLM neurons were retrogradely labelled (prior injection of pseudorabies virus PRV-152) and whole-cell, patch clamp recordings were obtained in brainstem slices. Under steady-state conditions GABAergic inhibition of RVLM neurons predominated and glycine contributed less than 25% of the overall inhibition. By contrast, stimulation of synaptic inputs in the RVLM decreased GABAergic inhibition to 53%; and increased glycinergic inhibition to 47%. Thus, under conditions of increased synaptic activity in the RVLM, glycinergic inhibition is recruited to strengthen sympathoinhibition.
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Affiliation(s)
- Hong Gao
- Department of Physiology, School of Medicine, Tulane University, New Orleans, LA, USA
| | - Willian S Korim
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, VIC, Australia
| | - Song T Yao
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, VIC, Australia
| | - Cheryl M Heesch
- Department of Biomedical Sciences, Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA
| | - Andrei V Derbenev
- Department of Physiology, School of Medicine, Tulane University, New Orleans, LA, USA.,Brain Institute, Tulane University, New Orleans, LA, USA
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Korim WS, Elsaafien K, Basser JR, Setiadi A, May CN, Yao ST. In renovascular hypertension, TNF-α type-1 receptors in the area postrema mediate increases in cardiac and renal sympathetic nerve activity and blood pressure. Cardiovasc Res 2018; 115:1092-1101. [DOI: 10.1093/cvr/cvy268] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Revised: 10/02/2018] [Accepted: 10/24/2018] [Indexed: 12/16/2022] Open
Affiliation(s)
- Willian S Korim
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, VIC, Australia
- Wade Institute of Entrepreneurship, University of Melbourne, Parkville, VIC, Australia
| | - Khalid Elsaafien
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, VIC, Australia
| | - Jeremy R Basser
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, VIC, Australia
| | - Anthony Setiadi
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, VIC, Australia
| | - Clive N May
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, VIC, Australia
| | - Song T Yao
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, VIC, Australia
- Florey Department of Neuroscience and Mental Health, University of Melbourne, Parkville, VIC, Australia
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Hong G, Korim WS, Yao ST, Heesch CM, Derbenev AV. NOVEL ROLE OF GLYCINE IN CONTROL OF SYMPATHETIC OUTFLOW. FASEB J 2018. [DOI: 10.1096/fasebj.2018.32.1_supplement.595.4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | - Willian S. Korim
- Florey Institute of Neuroscience and Mental HealthUniversity of MelbourneMelbourneAustralia
| | - Song T. Yao
- Florey Institute of Neuroscience and Mental HealthUniversity of MelbourneMelbourneAustralia
| | - Cheryl M. Heesch
- Department of Biomedical SciencesUniversity of MissouriColumbiaMO
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Setiadi A, Korim WS, Elsaafien K, Yao ST. The role of the blood-brain barrier in hypertension. Exp Physiol 2017; 103:337-342. [PMID: 28986948 DOI: 10.1113/ep086434] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2017] [Accepted: 10/05/2017] [Indexed: 12/22/2022]
Abstract
NEW FINDINGS What is the topic of this review? This review highlights the importance of the blood-brain barrier in the context of diseases involving autonomic dysfunction, such as hypertension and heart failure. What advances does it highlight? It highlights the potential role of pro-inflammatory cytokines, leucocytes and angiotensin II in disrupting the blood-brain barrier in cardiovascular diseases. Advances are highlighted in our understanding of neurovascular unit cells, astrocytes and microglia, with a specific emphasis on their pathogenic roles within the brain. The blood-brain barrier (BBB) is a crucial barrier that provides both metabolic and physical protection to an immune-privileged CNS. The BBB has been shown to be disrupted in hypertension. This review addresses the importance of the BBB in maintaining homeostasis in the context of diseases related to autonomic dysfunction, such as hypertension. We highlight the potentially important roles of the immune system and neurovascular unit in the maintenance of the BBB, whereby dysregulation may lead to autonomic dysfunction in diseases such as heart failure and hypertension. Circulating leucocytes and factors such as angiotensin II and pro-inflammatory cytokines are thought ultimately to downregulate endothelial tight junction proteins that are a crucial component of the BBB. The specific mechanisms underlying BBB disruption and their role in contributing to autonomic dysfunction are not yet fully understood but are a growing area of interest. A greater understanding of these systems and advances in our knowledge of the molecular mechanisms causing BBB disruption will allow for the development of future therapeutic interventions in the treatment of autonomic imbalance associated with diseases such as heart failure and hypertension.
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Affiliation(s)
- Anthony Setiadi
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia
| | - Willian S Korim
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia
| | - Khalid Elsaafien
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia
| | - Song T Yao
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia.,Florey Department of Neuroscience and Mental Health, University of Melbourne, Victoria, Australia
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Sabetghadam A, Korim WS, Verberne AJM. Perifornical hypothalamic pathway to the adrenal gland: Role for glutamatergic transmission in the glucose counter-regulatory response. Auton Neurosci 2017; 203:67-73. [PMID: 28173996 DOI: 10.1016/j.autneu.2017.02.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 01/31/2017] [Accepted: 02/01/2017] [Indexed: 01/06/2023]
Abstract
Adrenaline is an important counter-regulatory hormone that helps restore glucose homeostasis during hypoglycaemia. However, the neurocircuitry that connects the brain glucose sensors and the adrenal sympathetic outflow to the chromaffin cells is poorly understood. We used electrical microstimulation of the perifornical hypothalamus (PeH) and the rostral ventrolateral medulla (RVLM) combined with adrenal sympathetic nerve activity (ASNA) recording to examine the relationship between the RVLM, the PeH and ASNA. In urethane-anaesthetised male Sprague-Dawley rats, intermittent single pulse electrical stimulation of the rostroventrolateral medulla (RVLM) elicited an evoked ASNA response that consisted of early (60±3ms) and late peaks (135±4ms) of preganglionic and postganglionic activity. In contrast, RVLM stimulation evoked responses in lumbar sympathetic nerve activity that were almost entirely postganglionic. PeH stimulation also produced an evoked excitatory response consisting of both preganglionic and postganglionic excitatory peaks in ASNA. Both peaks in ASNA following RVLM stimulation were reduced by intrathecal kynurenic acid (KYN) injection. In addition, the ASNA response to systemic neuroglucoprivation induced by 2-deoxy-d-glucose was abolished by bilateral microinjection of KYN into the RVLM. This suggests that a glutamatergic pathway from the perifornical hypothalamus (PeH) relays in the RVLM to activate the adrenal SPN and so modulate ASNA. The main findings of this study are that (i) adrenal premotor neurons in the RVLM may be, at least in part, glutamatergic and (ii) that the input to these neurons that is activated during neuroglucoprivation is also glutamatergic.
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Affiliation(s)
- A Sabetghadam
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - W S Korim
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - A J M Verberne
- University of Melbourne, Clinical Pharmacology and Therapeutics Unit, Department of Medicine, Austin Health, Heidelberg, Victoria 3084, Australia.
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Verberne AJM, Korim WS, Sabetghadam A, Llewellyn-Smith IJ. Adrenaline: insights into its metabolic roles in hypoglycaemia and diabetes. Br J Pharmacol 2016; 173:1425-37. [PMID: 26896587 DOI: 10.1111/bph.13458] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 01/20/2016] [Accepted: 02/11/2016] [Indexed: 01/05/2023] Open
Abstract
Adrenaline is a hormone that has profound actions on the cardiovascular system and is also a mediator of the fight-or-flight response. Adrenaline is now increasingly recognized as an important metabolic hormone that helps mobilize energy stores in the form of glucose and free fatty acids in preparation for physical activity or for recovery from hypoglycaemia. Recovery from hypoglycaemia is termed counter-regulation and involves the suppression of endogenous insulin secretion, activation of glucagon secretion from pancreatic α-cells and activation of adrenaline secretion. Secretion of adrenaline is controlled by presympathetic neurons in the rostroventrolateral medulla, which are, in turn, under the control of central and/or peripheral glucose-sensing neurons. Adrenaline is particularly important for counter-regulation in individuals with type 1 (insulin-dependent) diabetes because these patients do not produce endogenous insulin and also lose their ability to secrete glucagon soon after diagnosis. Type 1 diabetic patients are therefore critically dependent on adrenaline for restoration of normoglycaemia and attenuation or loss of this response in the hypoglycaemia unawareness condition can have serious, sometimes fatal, consequences. Understanding the neural control of hypoglycaemia-induced adrenaline secretion is likely to identify new therapeutic targets for treating this potentially life-threatening condition.
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Affiliation(s)
- A J M Verberne
- Clinical Pharmacology and Therapeutics Unit, Department of Medicine, Austin Health, University of Melbourne, Heidelberg, VIC, Australia
| | - W S Korim
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, VIC, Australia
| | - A Sabetghadam
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, VIC, Australia
| | - I J Llewellyn-Smith
- Cardiovascular Medicine and Human Physiology, Flinders University, Bedford Park, SA, Australia
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Korim WS, Llewellyn-Smith IJ, Verberne AJM. Activation of Medulla-Projecting Perifornical Neurons Modulates the Adrenal Sympathetic Response to Hypoglycemia: Involvement of Orexin Type 2 (OX2-R) Receptors. Endocrinology 2016; 157:810-9. [PMID: 26653571 DOI: 10.1210/en.2015-1712] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Iatrogenic hypoglycemia in response to insulin treatment is commonly experienced by patients with type 1 diabetes and can be life threatening. The body releases epinephrine in an attempt to counterregulate hypoglycemia, but the neural mechanisms underlying this phenomenon remain to be elucidated. Orexin neurons in the perifornical hypothalamus (PeH) project to the rostral ventrolateral medulla (RVLM) and are likely to be involved in epinephrine secretion during hypoglycemia. In anesthetized rats, we report that hypoglycemia increases the sympathetic preganglionic discharge to the adrenal gland by activating PeH orexin neurons that project to the RVLM (PeH-RVLM). Electrophysiological characterization shows that the majority of identified PeH-RVLM neurons, including a subpopulation of orexin neurons, are activated in response to hypoglycemia or glucoprivation. Furthermore, the excitatory input from the PeH is mediated by orexin type 2 receptors in the RVLM. These results suggest that activation of orexin PeH-RVLM neurons and orexin type 2 receptors in the RVLM facilitates epinephrine release by increasing sympathetic drive to adrenal chromaffin cells during hypoglycemia.
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Affiliation(s)
- Willian S Korim
- Clinical Pharmacology and Therapeutics Unit (W.S.K., A.J.M.V.), Department of Medicine Austin Health, University of Melbourne, Heidelberg, Victoria 3084, Australia; Florey Institute of Neuroscience and Mental Health (W.S.K.), University of Melbourne, Parkville, Victoria 3052, Australia; and Cardiovascular Medicine (I.J.L.-S.), Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University, Bedford Park, South Australia 5042, Australia
| | - Ida J Llewellyn-Smith
- Clinical Pharmacology and Therapeutics Unit (W.S.K., A.J.M.V.), Department of Medicine Austin Health, University of Melbourne, Heidelberg, Victoria 3084, Australia; Florey Institute of Neuroscience and Mental Health (W.S.K.), University of Melbourne, Parkville, Victoria 3052, Australia; and Cardiovascular Medicine (I.J.L.-S.), Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University, Bedford Park, South Australia 5042, Australia
| | - Anthony J M Verberne
- Clinical Pharmacology and Therapeutics Unit (W.S.K., A.J.M.V.), Department of Medicine Austin Health, University of Melbourne, Heidelberg, Victoria 3084, Australia; Florey Institute of Neuroscience and Mental Health (W.S.K.), University of Melbourne, Parkville, Victoria 3052, Australia; and Cardiovascular Medicine (I.J.L.-S.), Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University, Bedford Park, South Australia 5042, Australia
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Korim WS, Bou Farah L, McMullan S, Verberne AJM. Orexinergic activation of medullary premotor neurons modulates the adrenal sympathoexcitation to hypothalamic glucoprivation. Diabetes 2014; 63:1895-906. [PMID: 24550189 DOI: 10.2337/db13-1073] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Glucoprivation activates neurons in the perifornical hypothalamus (PeH) and in the rostral ventrolateral medulla (RVLM), which results in the release of adrenaline. The current study aimed to establish 1) whether neuroglucoprivation in the PeH or in the RVLM elicits adrenaline release in vivo and 2) whether direct activation by glucoprivation or orexin release in the RVLM modulates the adrenaline release. Neuroglucoprivation in the PeH or RVLM was elicited by microinjections of 2-deoxy-D-glucose or 5-thio-D-glucose in anesthetized, euglycemic rats. Firstly, inhibition of neurons in the PeH abolished the increase in adrenal sympathetic nerve activity (ASNA) to systemic glucoprivation. Secondly, glucoprivation of neurons in the PeH increased ASNA. Thirdly, in vivo or in vitro glucoprivation did not affect the activity of RVLM adrenal premotor neurons. Finally, blockade of orexin receptors in the RVLM abolished the increase in ASNA to neuroglucoprivation in the PeH. The evoked changes in ASNA were directly correlated to levels of plasma metanephrine but not to normetanephrine. These findings suggest that orexin release modulates the activation of adrenal presympathetic neurons in the RVLM.
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Affiliation(s)
- Willian S Korim
- Clinical Pharmacology and Therapeutics Unit, Department of Medicine, Austin Health, University of Melbourne, Heidelberg, Victoria, Australia
| | - Lama Bou Farah
- Australian School of Advanced Medicine, Macquarie University, Sydney, New South Wales, Australia
| | - Simon McMullan
- Australian School of Advanced Medicine, Macquarie University, Sydney, New South Wales, Australia
| | - Anthony J M Verberne
- Clinical Pharmacology and Therapeutics Unit, Department of Medicine, Austin Health, University of Melbourne, Heidelberg, Victoria, Australia
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Verberne AJM, Sabetghadam A, Korim WS. Neural pathways that control the glucose counterregulatory response. Front Neurosci 2014; 8:38. [PMID: 24616659 PMCID: PMC3935387 DOI: 10.3389/fnins.2014.00038] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Accepted: 02/10/2014] [Indexed: 02/02/2023] Open
Abstract
Glucose is an essential metabolic substrate for all bodily tissues. The brain depends particularly on a constant supply of glucose to satisfy its energy demands. Fortunately, a complex physiological system has evolved to keep blood glucose at a constant level. The consequences of poor glucose homeostasis are well-known: hyperglycemia associated with uncontrolled diabetes can lead to cardiovascular disease, neuropathy and nephropathy, while hypoglycemia can lead to convulsions, loss of consciousness, coma, and even death. The glucose counterregulatory response involves detection of declining plasma glucose levels and secretion of several hormones including glucagon, adrenaline, cortisol, and growth hormone (GH) to orchestrate the recovery from hypoglycemia. Low blood glucose leads to a low brain glucose level that is detected by glucose-sensing neurons located in several brain regions such as the ventromedial hypothalamus, the perifornical region of the lateral hypothalamus, the arcuate nucleus (ARC), and in several hindbrain regions. This review will describe the importance of the glucose counterregulatory system and what is known of the neurocircuitry that underpins it.
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Affiliation(s)
- Anthony J M Verberne
- Clinical Pharmacology and Therapeutics Unit, Department of Medicine, Austin Health Heidelberg, The University of Melbourne Melbourne, VIC, Australia
| | - Azadeh Sabetghadam
- Clinical Pharmacology and Therapeutics Unit, Department of Medicine, Austin Health Heidelberg, The University of Melbourne Melbourne, VIC, Australia
| | - Willian S Korim
- Clinical Pharmacology and Therapeutics Unit, Department of Medicine, Austin Health Heidelberg, The University of Melbourne Melbourne, VIC, Australia
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Verberne TJ, Korim WS. Glucoprivation of hypothalamic neurons elicits the counter‐regulatory response in rats. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.1120.4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Korim WS, Egwuenu E, Fong AY, McMullan S, Cravo SL, Pilowsky PM. Noxious somatic stimuli diminish respiratory-sympathetic coupling by selective resetting of the respiratory rhythm in anaesthetized rats. Exp Physiol 2012; 97:1093-104. [PMID: 22581750 DOI: 10.1113/expphysiol.2012.066365] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Noxious somatic stimulation evokes respiratory and autonomic responses. The mechanisms underlying the responses and the manner in which they are co-ordinated are still unclear. The effects of activation of somatic nociceptive fibres on lumbar sympathetic nerve activity at slow (2-10 Hz) and fast frequency bands (100-1000 Hz) and the effects on respiratory-sympathetic coupling are unknown. In anaesthetized, artificially ventilated Sprague-Dawley rats under neuromuscular blockade, ensemble averaging of sympathetic activity following high-intensity single-pulse stimulation of the sciatic nerve revealed two peaks (~140 and ~250 ms) that were present at similar latencies whether or not slow or fast band filtering was used. Additionally, in the slow band of both lumbar and splanchnic sympathetic nerve activity, a third peak with a very slow latency (~650 ms) was apparent. In the respiratory system, activation of the sciatic nerve decreased the expiratory period when the stimulus occurred during the first half of expiration, but increased the expiratory period if the stimulus was delivered in the second half of the expiratory phase. The phase shifting of the respiratory cycle also impaired the respiratory-sympathetic coupling in both splanchnic and lumbar sympathetic nerve activity in the subsequent respiratory cycle. The findings suggest that noxious somatosympathetic responses reduce the co-ordination between respiration and perfusion by resetting the respiratory pattern generator.
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Affiliation(s)
- Willian S Korim
- Australian School of Advanced Medicine, Macquarie University, Sydney, NSW, Australia
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Burke PGR, Neale J, Korim WS, McMullan S, Goodchild AK. Patterning of somatosympathetic reflexes reveals nonuniform organization of presympathetic drive from C1 and non-C1 RVLM neurons. Am J Physiol Regul Integr Comp Physiol 2011; 301:R1112-22. [PMID: 21795636 DOI: 10.1152/ajpregu.00131.2011] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
To determine the organization of presympathetic vasomotor drive by phenotypic populations of rostral ventrolateral medulla (RVLM) neurons, we examined the somatosympathetic reflex (SSR) evoked in four sympathetic nerves together with selective lesions of RVLM presympathetic neurons. Urethane-anesthetized (1.3 g/kg ip), paralyzed, vagotomized and artificially ventilated Sprague-Dawley rats (n = 41) were used. First, we determined the afferent inputs activated by sciatic nerve (SN) stimulation at graded stimulus intensities (50 sweeps at 0.5-1 Hz, 1-80 V). Second, we recorded sympathetic nerve responses (cervical, renal, splanchnic, and lumbar) to intensities of SN stimulation that activated A-fiber afferents (low) or both A- and C-fiber afferents (high). Third, with low-intensity SN stimulation, we examined the cervical SSR following RVLM microinjection of somatostatin, and we determined the splanchnic SSR in rats in which presympathetic C1 neurons were lesioned following intraspinal injections of anti-dopamine-β-hydroxylase-saporin (anti-DβH-SAP). Low-intensity SN stimulation activated A-fiber afferents and evoked biphasic responses in the renal, splanchnic, and lumbar nerves and a single peak in the cervical nerve. Depletion of presympathetic C1 neurons (59 ± 4% tyrosine hydroxylase immunoreactivity profiles lesioned) eliminated peak 2 of the splanchnic SSR and attenuated peak 1, suggesting that only RVLM neurons with fast axonal conduction were spared. RVLM injections of somatostatin abolished the single early peak of cervical SSR confirming that RVLM neurons with fast axonal conduction were inhibited by somatostatin. It is concluded that unmyelinated RVLM presympathetic neurons, presumed to be all C1, innervate splanchnic, renal, and lumbar but not cervical sympathetic outflows, whereas myelinated C1 and non-C1 RVLM neurons innervate all sympathetic outflows examined. These findings suggest that multiple levels of neural control of vasomotor tone exist; myelinated populations may set baseline tone, while unmyelinated neurons may be recruited to provide actions at specific vascular beds in response to distinct stressors.
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Affiliation(s)
- Peter G R Burke
- Australian School of Advanced Medicine, Macquarie University, Sydney, Australia
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