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McCarthy B, Datta S, Sesa-Ashton G, Wong R, Henderson LA, Dawood T, Macefield VG. Non-additive effects of electrical stimulation of the dorsolateral prefrontal cortex and the vestibular system on muscle sympathetic nerve activity in humans. Exp Brain Res 2024:10.1007/s00221-024-06852-5. [PMID: 38822824 DOI: 10.1007/s00221-024-06852-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Accepted: 05/11/2024] [Indexed: 06/03/2024]
Abstract
Sinusoidal galvanic vestibular stimulation (sGVS) induces robust modulation of muscle sympathetic nerve activity (MSNA) alongside perceptions of side-to-side movement, sometimes with an accompanying feeling of nausea. We recently showed that transcranial alternating current stimulation (tACS) of the dorsolateral prefrontal cortex (dlPFC) also modulates MSNA, but does not generate any perceptions. Here, we tested the hypothesis that when the two stimuli are given concurrently, the modulation of MSNA would be additive. MSNA was recorded from 11 awake participants via a tungsten microelectrode inserted percutaneously into the right common peroneal nerve at the fibular head. Sinusoidal stimuli (± 2 mA, 0.08 Hz, 100 cycles) were applied in randomised order as follows: (i) tACS of the dlPFC at electroencephalogram (EEG) site F4 and referenced to the nasion; (ii) bilateral sGVS applied to the vestibular apparatuses via the mastoid processes; and (iii) tACS and sGVS together. Previously obtained data from 12 participants supplemented the data for stimulation protocols (i) and (ii). Cross-correlation analysis revealed that each stimulation protocol caused significant modulation of MSNA (modulation index (paired data): 35.2 ± 19.4% for sGVS; 27.8 ± 15.2% for tACS), but there were no additive effects when tACS and sGVS were delivered concurrently (32.1 ± 18.5%). This implies that the vestibulosympathetic reflexes are attenuated with concurrent dlPFC stimulation. These results suggest that the dlPFC is capable of blocking the processing of vestibular inputs through the brainstem and, hence, the generation of vestibulosympathetic reflexes.
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Affiliation(s)
- Brendan McCarthy
- Baker Heart and Diabetes Institute, Melbourne, VIC, Australia
- Baker Department of Cardiometabolic Health, The University of Melbourne, Melbourne, VIC, Australia
| | - Sudipta Datta
- Baker Heart and Diabetes Institute, Melbourne, VIC, Australia
- Baker Department of Cardiometabolic Health, The University of Melbourne, Melbourne, VIC, Australia
| | | | - Rebecca Wong
- Baker Heart and Diabetes Institute, Melbourne, VIC, Australia
- Baker Department of Cardiometabolic Health, The University of Melbourne, Melbourne, VIC, Australia
| | - Luke A Henderson
- School of Medical Sciences (Neuroscience), Brain and Mind Centre, The University of Sydney, Camperdown, NSW, Australia
| | - Tye Dawood
- Baker Heart and Diabetes Institute, Melbourne, VIC, Australia
- Baker Department of Cardiometabolic Health, The University of Melbourne, Melbourne, VIC, Australia
| | - Vaughan G Macefield
- Baker Heart and Diabetes Institute, Melbourne, VIC, Australia.
- Baker Department of Cardiometabolic Health, The University of Melbourne, Melbourne, VIC, Australia.
- Department of Neuroscience, School of Translational Medicine, Monash University, The Alfred Centre, 99 Commercial Road, Melbourne, VIC, 3004, Australia.
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D'Alesio G, Stumpp LI, Sciarrone P, Navari A, Gentile F, Borrelli C, Ballanti S, Degl'Innocenti E, Carrasco A, Costa AC, Andrade A, Mannini A, Macefield VG, Emdin M, Passino C, Mazzoni A, Giannoni A, Oddo CM. An open computational toolbox to analyze multi- and single-unit sympathetic nerve activity in microneurography. BIOPHYSICS REVIEWS 2024; 5:021401. [PMID: 38895135 PMCID: PMC11184970 DOI: 10.1063/5.0202385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/04/2024] [Accepted: 05/08/2024] [Indexed: 06/21/2024]
Abstract
Microelectrode recordings from human peripheral and cranial nerves provide a means to study both afferent and efferent axonal signals at different levels of detail, from multi- to single-unit activity. Their analysis can lead to advancements both in diagnostic and in the understanding of the genesis of neural disorders. However, most of the existing computational toolboxes for the analysis of microneurographic recordings are limited in scope or not open-source. Additionally, conventional burst-based metrics are not suited to analyze pathological conditions and are highly sensitive to distance of the microelectrode tip from the active axons. To address these challenges, we developed an open-source toolbox that offers advanced analysis capabilities for studying neuronal reflexes and physiological responses to peripheral nerve activity. Our toolbox leverages the observation of temporal sequences of action potentials within inherently cyclic signals, introducing innovative methods and indices to enhance analysis accuracy. Importantly, we have designed our computational toolbox to be accessible to novices in biomedical signal processing. This may include researchers and professionals in healthcare domains, such as clinical medicine, life sciences, and related fields. By prioritizing user-friendliness, our software application serves as a valuable resource for the scientific community, allowing to extract advanced metrics of neural activity in short time and evaluate their impact on other physiological variables in a consistent and standardized manner, with the final aim to widen the use of microneurography among researchers and clinicians.
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Affiliation(s)
- Giacomo D'Alesio
- The BioRobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy
| | | | | | - Alessandro Navari
- Cardiovascular Medicine Department, Fondazione Toscana Gabriele Monasterio, Pisa, Italy
| | | | - Chiara Borrelli
- Medical Research Center, University of Iowa, Iowa City, Iowa, USA
| | - Sara Ballanti
- The BioRobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy
| | | | | | | | - Alexandre Andrade
- Instituto de Biofísica e Engenharia Biomédica, Faculdade de Ciências da Universidade de Lisboa, Lisbon, Portugal
| | - Andrea Mannini
- Artificial Intelligence for Rehabilitation Laboratory, Fondazione Don Carlo Gnocchi IRCCS, Florence, Italy
| | | | | | | | - Alberto Mazzoni
- The BioRobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy
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Sesa-Ashton G, Macefield VG. Sympathetic vascular transduction and baroreflex sensitivity in the context of severe COPD. Clin Auton Res 2024; 34:219-222. [PMID: 38044409 DOI: 10.1007/s10286-023-01003-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Accepted: 11/13/2023] [Indexed: 12/05/2023]
Affiliation(s)
- Gianni Sesa-Ashton
- Human Neurotransmitters Laboratory, Baker Heart and Diabetes Institute, Melbourne, VIC, 3004, Australia
| | - Vaughan G Macefield
- Department of Neuroscience, Central Clinical School, Monash University, Level 6, 75 Commercial Road, Melbourne, VIC, 3004, Australia.
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Sympathetic System in Wound Healing: Multistage Control in Normal and Diabetic Skin. Int J Mol Sci 2023; 24:ijms24032045. [PMID: 36768369 PMCID: PMC9916402 DOI: 10.3390/ijms24032045] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 01/14/2023] [Accepted: 01/18/2023] [Indexed: 01/22/2023] Open
Abstract
In this review, we discuss sympathetic regulation in normal and diabetic wound healing. Experimental denervation studies have confirmed that sympathetic nerve endings in skin have an important and complex role in wound healing. Vasoconstrictor neurons secrete norepinephrine (NE) and neuropeptide Y (NPY). Both mediators decrease blood flow and interact with inflammatory cells and keratinocytes. NE acts in an ambiguous way depending on receptor type. Beta2-adrenoceptors could be activated near sympathetic endings; they suppress inflammation and re-epithelialization. Alpha1- and alpha2-adrenoceptors induce inflammation and activate keratinocytes. Sudomotor neurons secrete acetylcholine (ACh) and vasoactive intestinal peptide (VIP). Both induce vasodilatation, angiogenesis, inflammation, keratinocytes proliferation and migration. In healthy skin, all effects are important for successful healing. In treatment of diabetic ulcers, mediator balance could be shifted in different ways. Beta2-adrenoceptors blockade and nicotinic ACh receptors activation are the most promising directions in treatment of diabetic ulcers with neuropathy, but they require further research.
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5
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Suresh S, Everett TH, Shi R, Duerstock BS. Automatic Detection and Characterization of Autonomic Dysreflexia Using Multi-Modal Non-Invasive Sensing and Neural Networks. Neurotrauma Rep 2022; 3:501-510. [DOI: 10.1089/neur.2022.0041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Shruthi Suresh
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, USA
| | - Thomas H. Everett
- Krannert Cardiovascular Research Center, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Riyi Shi
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, USA
- Center for Paralysis Research, West Lafayette, Indiana, USA
- Department of Basic Medical Sciences, West Lafayette, Indiana, USA
| | - Bradley S. Duerstock
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, USA
- Center for Paralysis Research, West Lafayette, Indiana, USA
- School of Industrial Engineering, West Lafayette, Indiana, USA
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Hansen AB, Amin SB, Hofstätter F, Mugele H, Simpson LL, Gasho C, Dawkins TG, Tymko MM, Ainslie PN, Villafuerte FC, Hearon CM, Lawley JS, Moralez G. Global Reach 2018: sympathetic neural and hemodynamic responses to submaximal exercise in Andeans with and without chronic mountain sickness. Am J Physiol Heart Circ Physiol 2022; 322:H844-H856. [PMID: 35333117 PMCID: PMC9018046 DOI: 10.1152/ajpheart.00555.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 03/14/2022] [Accepted: 03/14/2022] [Indexed: 11/22/2022]
Abstract
Andeans with chronic mountain sickness (CMS) and polycythemia have similar maximal oxygen uptakes to healthy Andeans. Therefore, this study aimed to explore potential adaptations in convective oxygen transport, with a specific focus on sympathetically mediated vasoconstriction of nonactive skeletal muscle. In Andeans with (CMS+, n = 7) and without (CMS-, n = 9) CMS, we measured components of convective oxygen delivery, hemodynamic (arterial blood pressure via intra-arterial catheter), and autonomic responses [muscle sympathetic nerve activity (MSNA)] at rest and during steady-state submaximal cycling exercise [30% and 60% peak power output (PPO) for 5 min each]. Cycling caused similar increases in heart rate, cardiac output, and oxygen delivery at both workloads between both Andean groups. However, at 60% PPO, CMS+ had a blunted reduction in Δtotal peripheral resistance (CMS-, -10.7 ± 3.8 vs. CMS+, -4.9 ± 4.1 mmHg·L-1·min-1; P = 0.012; d = 1.5) that coincided with a greater Δforearm vasoconstriction (CMS-, -0.2 ± 0.6 vs. CMS+, 1.5 ± 1.3 mmHg·mL-1·min-1; P = 0.008; d = 1.7) and a rise in Δdiastolic blood pressure (CMS-, 14.2 ± 7.2 vs. CMS+, 21.6 ± 4.2 mmHg; P = 0.023; d = 1.2) compared with CMS-. Interestingly, although MSNA burst frequency did not change at 30% or 60% of PPO in either group, at 60% Δburst incidence was attenuated in CMS+ (P = 0.028; d = 1.4). These findings indicate that in Andeans with polycythemia, light intensity exercise elicited similar cardiovascular and autonomic responses compared with CMS-. Furthermore, convective oxygen delivery is maintained during moderate-intensity exercise despite higher peripheral resistance. In addition, the elevated peripheral resistance during exercise was not mediated by greater sympathetic neural outflow, thus other neural and/or nonneural factors are perhaps involved.NEW & NOTEWORTHY During submaximal exercise, convective oxygen transport is maintained in Andeans suffering from polycythemia. Light intensity exercise elicited similar cardiovascular and autonomic responses compared with healthy Andeans. However, during moderate-intensity exercise, we observed a blunted reduction in total peripheral resistance, which cannot be ascribed to an exaggerated increase in muscle sympathetic nerve activity, indicating possible contributions from other neural and/or nonneural mechanisms.
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Affiliation(s)
- Alexander B Hansen
- Division of Performance, Physiology and Prevention, Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Sachin B Amin
- Division of Performance, Physiology and Prevention, Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Florian Hofstätter
- Division of Performance, Physiology and Prevention, Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Hendrik Mugele
- Division of Performance, Physiology and Prevention, Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Lydia L Simpson
- Division of Performance, Physiology and Prevention, Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Christopher Gasho
- Division of Pulmonary and Critical Care, Department of Medicine, University of Loma Linda, Loma Linda, California
| | - Tony G Dawkins
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Michael M Tymko
- Physical Activity and Diabetes Laboratory, Faculty of Kinesiology and Recreation, University of Alberta, Edmonton, Alberta, Canada
- Centre of Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Philip N Ainslie
- Centre of Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Francisco C Villafuerte
- Laboratorio de Fisiología Comparada/Fisiología del Transporte de Oxígeno Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Christopher M Hearon
- Department of Applied Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas
| | - Justin S Lawley
- Division of Performance, Physiology and Prevention, Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Gilbert Moralez
- Department of Applied Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
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Clyburn C, Andresen MC, Ingram SL, Habecker BA. Untangling Peripheral Sympathetic Neurocircuits. Front Cardiovasc Med 2022; 9:842656. [PMID: 35224065 PMCID: PMC8866570 DOI: 10.3389/fcvm.2022.842656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Accepted: 01/19/2022] [Indexed: 11/13/2022] Open
Abstract
The sympathetic nervous system plays a critical role in regulating many autonomic functions, including cardiac rhythm. The postganglionic neurons in the sympathetic chain ganglia are essential components that relay sympathetic signals to target tissues and disruption of their activity leads to poor health outcomes. Despite this importance, the neurocircuitry within sympathetic ganglia is poorly understood. Canonically, postganglionic sympathetic neurons are thought to simply be activated by monosynaptic inputs from preganglionic cholinergic neurons of the intermediolateral cell columns of the spinal cord. Early electrophysiological studies of sympathetic ganglia where the peripheral nerve trunks were electrically stimulated identified excitatory cholinergic synaptic events in addition to retrograde action potentials, leading some to speculate that excitatory collateral projections are present. However, this seemed unlikely since sympathetic postganglionic neurons were known to synthesize and release norepinephrine and expression of dual neurochemical phenotypes had not been well recognized. In vitro studies clearly established the capacity of cultured sympathetic neurons to express and release acetylcholine and norepinephrine throughout development and even in pathophysiological conditions. Given this insight, we believe that the canonical view of ganglionic transmission needs to be reevaluated and may provide a mechanistic understanding of autonomic imbalance in disease. Further studies likely will require genetic models manipulating neurochemical phenotypes within sympathetic ganglia to resolve the function of cholinergic collateral projections between postganglionic neurons. In this perspective article, we will discuss the evidence for collateral projections in sympathetic ganglia, determine if current laboratory techniques could address these questions, and discuss potential obstacles and caveats.
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Affiliation(s)
- Courtney Clyburn
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, United States
| | - Michael C. Andresen
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, United States
| | - Susan L. Ingram
- Department of Neurological Surgery, Oregon Health and Science University, Portland, OR, United States
| | - Beth A. Habecker
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, United States
- *Correspondence: Beth A. Habecker
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Stute NL, Stickford JL, Province VM, Augenreich MA, Ratchford SM, Stickford ASL. COVID-19 is getting on our nerves: sympathetic neural activity and haemodynamics in young adults recovering from SARS-CoV-2. J Physiol 2021; 599:4269-4285. [PMID: 34174086 PMCID: PMC8447023 DOI: 10.1113/jp281888#support-information-section] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Accepted: 06/16/2021] [Indexed: 11/10/2023] Open
Abstract
KEY POINTS The impact of SARS-CoV-2 infection on autonomic and cardiovascular function in otherwise healthy individuals is unknown. For the first time it is shown that young adults recovering from SARS-CoV-2 have elevated resting sympathetic activity, but similar heart rate and blood pressure, compared with control subjects. Survivors of SARS-CoV-2 also exhibit similar sympathetic nerve activity and haemodynamics, but decreased pain perception, during a cold pressor test compared with healthy controls. Further, these individuals display higher sympathetic nerve activity throughout an orthostatic challenge, as well as an exaggerated heart rate response to orthostasis. If similar autonomic dysregulation, like that found here in young individuals, is present in older adults following SARS-CoV-2 infection, there may be substantial adverse implications for cardiovascular health. ABSTRACT The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can elicit systemic adverse physiological effects. However, the impact of SARS-CoV-2 on autonomic and cardiovascular function in otherwise healthy individuals remains unclear. Young adults who tested positive for SARS-CoV-2 (COV+; n = 16, 8 F) visited the laboratory 35 ± 16 days following diagnosis. Muscle sympathetic nerve activity (MSNA), systolic (SBP) and diastolic (DBP) blood pressure, and heart rate (HR) were measured in participants at rest and during a 2 min cold pressor test (CPT) and 5 min each at 30° and 60° head-up tilt (HUT). Data were compared with age-matched healthy controls (CON; n = 14, 9 F). COV+ participants (18.2 ± 6.6 bursts min-1 ) had higher resting MSNA burst frequency compared with CON (12.7 ± 3.4 bursts min-1 ) (P = 0.020), as well as higher MSNA burst incidence and total activity. Resting HR, SBP and DBP were not different. During CPT, there were no differences in MSNA, HR, SBP or DBP between groups. COV+ participants reported less pain during the CPT compared with CON (5.7 ± 1.8 vs. 7.2 ± 1.9 a.u., P = 0.036). MSNA was higher in COV+ compared with CON during HUT. There was a group-by-position interaction in MSNA burst incidence, as well as HR, in response to HUT. These results indicate resting sympathetic activity, but not HR or BP, may be elevated following SARS-CoV-2 infection. Further, cardiovascular and perceptual responses to physiological stress may be altered, including both exaggerated (orthostasis) and suppressed (pain perception) responses, compared with healthy young adults.
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Affiliation(s)
- Nina L. Stute
- Department of Health & Exercise ScienceAppalachian State UniversityBooneNCUSA
| | | | - Valesha M. Province
- Department of Health & Exercise ScienceAppalachian State UniversityBooneNCUSA
| | - Marc A. Augenreich
- Department of Health & Exercise ScienceAppalachian State UniversityBooneNCUSA
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Valensi P. Autonomic nervous system activity changes in patients with hypertension and overweight: role and therapeutic implications. Cardiovasc Diabetol 2021; 20:170. [PMID: 34412646 PMCID: PMC8375121 DOI: 10.1186/s12933-021-01356-w] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 07/27/2021] [Indexed: 12/12/2022] Open
Abstract
The incidence and prevalence of hypertension is increasing worldwide, with approximately 1.13 billion of people currently affected by the disease, often in association with other diseases such as diabetes mellitus, chronic kidney disease, dyslipidemia/hypercholesterolemia, and obesity. The autonomic nervous system has been implicated in the pathophysiology of hypertension, and treatments targeting the sympathetic nervous system (SNS), a key component of the autonomic nervous system, have been developed; however, current recommendations provide little guidance on their use. This review discusses the etiology of hypertension, and more specifically the role of the SNS in the pathophysiology of hypertension and its associated disorders. In addition, the effects of current antihypertensive management strategies, including pharmacotherapies, on the SNS are examined, with a focus on imidazoline receptor agonists.
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Affiliation(s)
- Paul Valensi
- Unit of Endocrinology, Diabetology and Nutrition, Jean Verdier Hospital, CINFO, CRNH-IdF, AP-HP, Paris Nord University, Avenue du 14 Juillet, 93140, Bondy, France.
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Hansen AB, Moralez G, Amin SB, Simspon LL, Hofstaetter F, Anholm JD, Gasho C, Stembridge M, Dawkins TG, Tymko MM, Ainslie PN, Villafuerte F, Romero SA, Hearon CM, Lawley JS. Global REACH 2018: the adaptive phenotype to life with chronic mountain sickness and polycythaemia. J Physiol 2021; 599:4021-4044. [PMID: 34245004 DOI: 10.1113/jp281730] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Accepted: 06/18/2021] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Humans suffering from polycythaemia undergo multiple circulatory adaptations including changes in blood rheology and structural and functional vascular adaptations to maintain normal blood pressure and vascular shear stresses, despite high blood viscosity. During exercise, several circulatory adaptations are observed, especially involving adrenergic and non-adrenergic mechanisms within non-active and active skeletal muscle to maintain exercise capacity, which is not observed in animal models. Despite profound circulatory stress, i.e. polycythaemia, several adaptations can occur to maintain exercise capacity, therefore making early identification of the disease difficult without overt symptomology. Pharmacological treatment of the background heightened sympathetic activity may impair the adaptive sympathetic response needed to match local oxygen delivery to active skeletal muscle oxygen demand and therefore inadvertently impair exercise capacity. ABSTRACT Excessive haematocrit and blood viscosity can increase blood pressure, cardiac work and reduce aerobic capacity. However, past clinical investigations have demonstrated that certain human high-altitude populations suffering from excessive erythrocytosis, Andeans with chronic mountain sickness, appear to have phenotypically adapted to life with polycythaemia, as their exercise capacity is comparable to healthy Andeans and even with sea-level inhabitants residing at high altitude. By studying this unique population, which has adapted through natural selection, this study aimed to describe how humans can adapt to life with polycythaemia. Experimental studies included Andeans with (n = 19) and without (n = 17) chronic mountain sickness, documenting exercise capacity and characterizing the transport of oxygen through blood rheology, including haemoglobin mass, blood and plasma volume and blood viscosity, cardiac output, blood pressure and changes in total and local vascular resistances through pharmacological dissection of α-adrenergic signalling pathways within non-active and active skeletal muscle. At rest, Andeans with chronic mountain sickness had a substantial plasma volume contraction, which alongside a higher red blood cell volume, caused an increase in blood viscosity yet similar total blood volume. Moreover, both morphological and functional alterations in the periphery normalized vascular shear stress and blood pressure despite high sympathetic nerve activity. During exercise, blood pressure, cardiac work and global oxygen delivery increased similar to healthy Andeans but were sustained by modifications in both non-active and active skeletal muscle vascular function. These findings highlight widespread physiological adaptations that can occur in response to polycythaemia, which allow the maintenance of exercise capacity.
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Affiliation(s)
- Alexander B Hansen
- Department of Sport Science, Division of Performance Physiology and Prevention, University of Innsbruck, Innsbruck, Austria
| | - Gilbert Moralez
- Department of Applied Clinical Research, University of Southwestern Medical Center, Dallas, Texas, USA
| | - Sachin B Amin
- Department of Sport Science, Division of Performance Physiology and Prevention, University of Innsbruck, Innsbruck, Austria
| | - Lydia L Simspon
- Department of Sport Science, Division of Performance Physiology and Prevention, University of Innsbruck, Innsbruck, Austria
| | - Florian Hofstaetter
- Department of Sport Science, Division of Performance Physiology and Prevention, University of Innsbruck, Innsbruck, Austria
| | - James D Anholm
- Department of Medicine, Division of Pulmonary and Critical Care, Loma Linda University, Loma Linda, California, USA
| | - Christopher Gasho
- Department of Medicine, Division of Pulmonary and Critical Care, Loma Linda University, Loma Linda, California, USA
| | - Mike Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | - Tony G Dawkins
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | - Michael M Tymko
- Physical Activity and Diabetes Laboratory, Faculty of Kinesiology, Sport and Recreation, University of Alberta, Edmonton, Alberta, Canada.,Centre of Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada
| | - Philip N Ainslie
- Centre of Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada
| | - Francisco Villafuerte
- Laboratorio de Fisiología Comparada/Fisiología del Transporte de Oxígeno, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Steven A Romero
- University of North Texas Health Science Center, Fort Worth, Texas, USA
| | - Christopher M Hearon
- Department of Applied Clinical Research, University of Southwestern Medical Center, Dallas, Texas, USA.,Institute of Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas, USA
| | - Justin S Lawley
- Department of Sport Science, Division of Performance Physiology and Prevention, University of Innsbruck, Innsbruck, Austria
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11
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Stute NL, Stickford JL, Province VM, Augenreich MA, Ratchford SM, Stickford ASL. COVID-19 is getting on our nerves: sympathetic neural activity and haemodynamics in young adults recovering from SARS-CoV-2. J Physiol 2021; 599:4269-4285. [PMID: 34174086 PMCID: PMC8447023 DOI: 10.1113/jp281888] [Citation(s) in RCA: 50] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Accepted: 06/16/2021] [Indexed: 12/19/2022] Open
Abstract
Key points The impact of SARS‐CoV‐2 infection on autonomic and cardiovascular function in otherwise healthy individuals is unknown. For the first time it is shown that young adults recovering from SARS‐CoV‐2 have elevated resting sympathetic activity, but similar heart rate and blood pressure, compared with control subjects. Survivors of SARS‐CoV‐2 also exhibit similar sympathetic nerve activity and haemodynamics, but decreased pain perception, during a cold pressor test compared with healthy controls. Further, these individuals display higher sympathetic nerve activity throughout an orthostatic challenge, as well as an exaggerated heart rate response to orthostasis. If similar autonomic dysregulation, like that found here in young individuals, is present in older adults following SARS‐CoV‐2 infection, there may be substantial adverse implications for cardiovascular health.
Abstract The novel severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) can elicit systemic adverse physiological effects. However, the impact of SARS‐CoV‐2 on autonomic and cardiovascular function in otherwise healthy individuals remains unclear. Young adults who tested positive for SARS‐CoV‐2 (COV+; n = 16, 8 F) visited the laboratory 35 ± 16 days following diagnosis. Muscle sympathetic nerve activity (MSNA), systolic (SBP) and diastolic (DBP) blood pressure, and heart rate (HR) were measured in participants at rest and during a 2 min cold pressor test (CPT) and 5 min each at 30° and 60° head‐up tilt (HUT). Data were compared with age‐matched healthy controls (CON; n = 14, 9 F). COV+ participants (18.2 ± 6.6 bursts min−1) had higher resting MSNA burst frequency compared with CON (12.7 ± 3.4 bursts min−1) (P = 0.020), as well as higher MSNA burst incidence and total activity. Resting HR, SBP and DBP were not different. During CPT, there were no differences in MSNA, HR, SBP or DBP between groups. COV+ participants reported less pain during the CPT compared with CON (5.7 ± 1.8 vs. 7.2 ± 1.9 a.u., P = 0.036). MSNA was higher in COV+ compared with CON during HUT. There was a group‐by‐position interaction in MSNA burst incidence, as well as HR, in response to HUT. These results indicate resting sympathetic activity, but not HR or BP, may be elevated following SARS‐CoV‐2 infection. Further, cardiovascular and perceptual responses to physiological stress may be altered, including both exaggerated (orthostasis) and suppressed (pain perception) responses, compared with healthy young adults. The impact of SARS‐CoV‐2 infection on autonomic and cardiovascular function in otherwise healthy individuals is unknown. For the first time it is shown that young adults recovering from SARS‐CoV‐2 have elevated resting sympathetic activity, but similar heart rate and blood pressure, compared with control subjects. Survivors of SARS‐CoV‐2 also exhibit similar sympathetic nerve activity and haemodynamics, but decreased pain perception, during a cold pressor test compared with healthy controls. Further, these individuals display higher sympathetic nerve activity throughout an orthostatic challenge, as well as an exaggerated heart rate response to orthostasis. If similar autonomic dysregulation, like that found here in young individuals, is present in older adults following SARS‐CoV‐2 infection, there may be substantial adverse implications for cardiovascular health.
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Affiliation(s)
- Nina L Stute
- Department of Health & Exercise Science, Appalachian State University, Boone, NC, USA
| | - Jonathon L Stickford
- Department of Health & Exercise Science, Appalachian State University, Boone, NC, USA
| | - Valesha M Province
- Department of Health & Exercise Science, Appalachian State University, Boone, NC, USA
| | - Marc A Augenreich
- Department of Health & Exercise Science, Appalachian State University, Boone, NC, USA
| | - Stephen M Ratchford
- Department of Health & Exercise Science, Appalachian State University, Boone, NC, USA
| | - Abigail S L Stickford
- Department of Health & Exercise Science, Appalachian State University, Boone, NC, USA
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12
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Miura K, Kashima H, Namura S, Morimoto M, Endo MY, Oue A, Fukuba Y. Effects of cooling or warming of the distal upper limb on skin vascular conductance and brachial artery shear profiles during cycling exercise. Res Sports Med 2021; 30:308-324. [PMID: 33472421 DOI: 10.1080/15438627.2021.1872573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
The relative influence of skin vascular conductance in glabrous (G; palm) and non-glabrous (NG; dorsal and forearm) regions to upstream brachial artery-shear stress (BA-SS) profile are unknown. This study aimed to elucidate the effects of G and/or NG skin vascular conductance (VC), which were modulated by warming or cooling manipulation, on BA-shear rate (SR, an estimate of SS) during cycling exercise. Seven healthy subjects performed 60-min exercise. Between 20 and 50 min of the exercise, the NG+G or G skin region were warmed to 42°C or cooled to 15°C using a water bath. Throughout the protocol, diameter and blood velocity in BA and skin VCs in forearm and palm were measured. All measurements showed that a steady-state response was reached after 20 min of exercise. Subsequently, during cooling manipulation, forearm VC was significantly decreased, and the concomitant BA-SR profile was revealed (primarily characterized by decreased antegrade SR and increased retrograde SR) in the NG+G. Such changes were not observed in G alone. During warming manipulation, forearm VC and mean BA-SR significantly increased only in the NG+G. In conclusion, vascular response in NG skin possibly plays a major role in the modulation of BA-SS profile during cycling exercise.
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Affiliation(s)
- Kohei Miura
- Department of Exercise Science and Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, Japan.,Department of Health and Nutrition, Faculty of Health Sciences, University of Hiroshima Shudo, Hiroshima, Japan
| | - Hideaki Kashima
- Department of Exercise Science and Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, Japan
| | - Saki Namura
- Department of Exercise Science and Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, Japan
| | - Marina Morimoto
- Department of Exercise Science and Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, Japan
| | - Masako Y Endo
- Department of Exercise Science and Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, Japan
| | - Anna Oue
- Faculty of Food and Nutritional Sciences, Toyo University, Gunma, Japan
| | - Yoshiyuki Fukuba
- Department of Exercise Science and Physiology, School of Health Sciences, Prefectural University of Hiroshima, Hiroshima, Japan
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13
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Ottaviani MM, Wright L, Dawood T, Macefield VG. In vivo recordings from the human vagus nerve using ultrasound-guided microneurography. J Physiol 2020; 598:3569-3576. [PMID: 32538473 DOI: 10.1113/jp280077] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Accepted: 06/05/2020] [Indexed: 12/22/2022] Open
Abstract
KEY POINTS The vagus nerve is the largest cranial nerve and innervates many structures in the neck, thorax and abdomen. Although single-unit recordings from the vagus nerve have been performed in experimental animals for several decades, no recordings have ever been made from the human vagus nerve. The vagus nerve is routinely stimulated clinically, yet we know little of its physiology in humans. We describe the methodology and provide preliminary results of the first intraneural single-unit recordings from the cervical vagus in awake humans, using tungsten microelectrodes inserted into the nerve through ultrasound guidance. ABSTRACT Intraneural microelectrodes have been used extensively to record from single somatosensory axons supplying muscle, tendons, joints and skin, as well as to record from postganglionic sympathetic axons supplying muscle and skin, in accessible peripheral nerves in awake humans. However, the vagus nerve has never been targeted, probably because of its close proximity to the carotid artery and jugular vein in the neck. Here, we report the first unitary recordings from the human cervical vagus nerve, obtained using ultrasound-guided insertion of tungsten microelectrodes into fascicles of the nerve. We identified tonically-active neurones in which firing rates were inversely related to heart rate (and directly related to the cardiac interval), which we classified as putative preganglionic parasympathetic axons directed to the sinoatrial node of the heart. We also recorded from tonically-active presumed sensory axons from the airways and presumed motor axons to the larynx. This new methodology opens exciting new opportunities for studying the physiology of the human vagus nerve in health and disease.
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Affiliation(s)
| | - Leah Wright
- Baker Heart and Diabetes Institute, Melbourne, VIC, Australia
| | - Tye Dawood
- Baker Heart and Diabetes Institute, Melbourne, VIC, Australia
| | - Vaughan G Macefield
- Baker Heart and Diabetes Institute, Melbourne, VIC, Australia.,Department of Physiology, University of Melbourne, Melbourne, VIC, Australia
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14
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Yoo JK, Badrov MB, Huang M, Bain RA, Dorn RP, Anderson EH, Wiblin JL, Suris A, Shoemaker JK, Fu Q. Abnormal sympathetic neural recruitment patterns and hemodynamic responses to cold pressor test in women with posttraumatic stress disorder. Am J Physiol Heart Circ Physiol 2020; 318:H1198-H1207. [DOI: 10.1152/ajpheart.00684.2019] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The novel findings of the present study are that women with posttraumatic stress disorder (PTSD) have an augmented pressor response to the sympathoexcitatory stimulus of a cold pressor test (CPT) compared with healthy control subjects. Although integrated muscle sympathetic nerve activity burst responses were not significantly different between groups, total sympathetic action potential discharge in response to the CPT was markedly elevated in women with PTSD exhibiting increased firing of low-threshold axons as well as the recruitment of latent subpopulations of larger-sized axons that are otherwise silent at baseline. Aberrant autonomic circulatory control in response to sympathoexcitatory stimulus may in part explain the propensity toward developing hypertension and cardiovascular disease in this population.
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Affiliation(s)
- Jeung-Ki Yoo
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
- Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - Mark B. Badrov
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
- Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - Mu Huang
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
- Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - Ryan A. Bain
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
| | - Raymond P. Dorn
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
| | - Elizabeth H. Anderson
- Department of Psychiatry, The University of Texas Southwestern Medical Center, Dallas, Texas
- Department of Veterans Affairs North Texas Health Care System, Dallas, Texas
| | - Jessica L. Wiblin
- Department of Psychiatry, The University of Texas Southwestern Medical Center, Dallas, Texas
- Department of Veterans Affairs North Texas Health Care System, Dallas, Texas
| | - Alina Suris
- Department of Psychiatry, The University of Texas Southwestern Medical Center, Dallas, Texas
- Department of Veterans Affairs North Texas Health Care System, Dallas, Texas
| | - J. Kevin Shoemaker
- School of Kinesiology, University of Western Ontario, London, Ontario, Canada
| | - Qi Fu
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
- Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, Texas
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15
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Ang R, Marina N. Low-Frequency Oscillations in Cardiac Sympathetic Neuronal Activity. Front Physiol 2020; 11:236. [PMID: 32256390 PMCID: PMC7093552 DOI: 10.3389/fphys.2020.00236] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 03/02/2020] [Indexed: 12/25/2022] Open
Abstract
Sudden cardiac death caused by ventricular arrhythmias is among the leading causes of mortality, with approximately half of all deaths attributed to heart disease worldwide. Periodic repolarization dynamics (PRD) is a novel marker of repolarization instability and strong predictor of death in patients post-myocardial infarction that is believed to occur in association with low-frequency oscillations in sympathetic nerve activity. However, this hypothesis is based on associations of PRD with indices of sympathetic activity that are not directly linked to cardiac function, such as muscle vasoconstrictor activity and the variability of cardiovascular autospectra. In this review article, we critically evaluate existing scientific evidence obtained primarily in experimental animal models, with the aim of identifying the neuronal networks responsible for the generation of low-frequency sympathetic rhythms along the neurocardiac axis. We discuss the functional significance of rhythmic sympathetic activity on neurotransmission efficacy and explore its role in the pathogenesis of ventricular repolarization instability. Most importantly, we discuss important gaps in our knowledge that require further investigation in order to confirm the hypothesis that low frequency cardiac sympathetic oscillations play a causative role in the generation of PRD.
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Affiliation(s)
- Richard Ang
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
| | - Nephtali Marina
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom.,Division of Medicine, University College London, London, United Kingdom
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16
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Incognito AV, Samora M, Shepherd AD, Cartafina RA, Guimarães GMN, Daher M, Millar PJ, Vianna LC. Arterial baroreflex regulation of muscle sympathetic single-unit activity in men: influence of resting blood pressure. Am J Physiol Heart Circ Physiol 2020; 318:H937-H946. [DOI: 10.1152/ajpheart.00700.2019] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The arterial baroreflex has dominant control over multiunit muscle sympathetic nerve activity (MSNA) burst occurrence, but whether this extends to all single units or is influenced by resting blood pressure status is unclear. In 22 men (32 ± 8 yr), we assessed 68 MSNA single units during sequential bolus injections of nitroprusside and phenylephrine (modified Oxford). Sympathetic baroreflex sensitivity (sBRS) was quantified as the weighted negative linear regression slope between diastolic blood pressure (DBP) and single-unit spike firing probability and multiple spike firing. Strong negative linear relationships ( r ≥ −0.50) between DBP and spike firing probability were observed in 63/68 (93%) single units (−2.27 ± 1.27%·cardiac cycle−1·mmHg−1 [operating range, 18 ± 8 mmHg]). In contrast, only 45/68 (66%) single units had strong DBP-multiple spike firing relationships (−0.13 ± 0.18 spikes·cardiac cycle−1·mmHg−1 [operating range, 14 ± 7 mmHg]). Participants with higher resting DBP (65 ± 3 vs. 77 ± 3 mmHg, P < 0.001) had similar spike firing probability sBRS (low vs. high, −2.08 ± 1.08 vs. −2.46 ± 1.42%·cardiac cycle−1·mmHg−1, P = 0.33), but a smaller sBRS operating range (20 ± 6 vs. 16 ± 9 mmHg, P = 0.01; 86 ± 24 vs. 52 ± 25% of total range, P < 0.001) and a higher proportion of single units without arterial baroreflex control outside this range [6/31 (19%) vs. 21/32 (66%), P < 0.001]. Participants with higher resting DBP also had fewer single units with arterial baroreflex control of multiple spike firing (79 vs. 53%, P = 0.04). The majority of MSNA single units demonstrate strong arterial baroreflex control over spike firing probability during pharmacological manipulation of blood pressure. Changes in single-unit sBRS operating range and control of multiple spike firing may represent altered sympathetic recruitment patterns associated with the early development of hypertension. NEW & NOTEWORTHY Muscle sympathetic single units can be differentially controlled during stress. In contrast, we demonstrate that 93% of single units maintain strong arterial baroreflex control during pharmacological manipulation of blood pressure. Interestingly, the operating range and proportion of single units that lose arterial baroreflex control outside of this range are influenced by resting blood pressure levels. Altered single unit, but not multiunit, arterial baroreflex control may represent changes in sympathetic recruitment patterns in early stage development of hypertension.
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Affiliation(s)
- Anthony V. Incognito
- Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
- NeuroV̇ASQ̇-Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Brasília, Brazil
| | - Milena Samora
- NeuroV̇ASQ̇-Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Brasília, Brazil
| | - Andrew D. Shepherd
- Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Roberta A. Cartafina
- NeuroV̇ASQ̇-Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Brasília, Brazil
| | | | - Mauricio Daher
- NeuroV̇ASQ̇-Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Brasília, Brazil
| | - Philip J. Millar
- Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Lauro C. Vianna
- NeuroV̇ASQ̇-Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Brasília, Brazil
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17
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Cutaneous warmth, but not touch, increases muscle sympathetic nerve activity during a muscle fatigue hand-grip task. Exp Brain Res 2020; 238:1035-1042. [PMID: 32198543 PMCID: PMC7181540 DOI: 10.1007/s00221-020-05779-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 03/10/2020] [Indexed: 12/05/2022]
Abstract
In homeostasis, somatosensory C fibre afferents are hypothesised to mediate input to the brain about interactions with external stimuli and sympathetic efference provides the output that regulates bodily functions. We aimed to test this hypothesis and whether different types of innocuous somatosensory input have differential effects. Healthy volunteers performed a muscle fatigue (hand-grip) task to exhaustion, which produces increased muscle sympathetic nerve activity (MSNA), as measured through microneurography. Participants completed the muscle fatigue task without concurrent cutaneous sensory stimulation (control) or we applied skin warming (heat pack) as a C fibre stimulation, slow brush stroking as C and Aβ fibre stimulation, or vibration as Aβ fibre stimulation, to the participant’s forearm. We also measured heart rate, the duration of the hand-grip task, and ratings of pain at the end of the task. Concurrent skin warming showed increased MSNA compared to the other conditions. Tactile stimuli (brushing, vibration) were not significantly different to the control (no intervention) condition. Warming increased the pain from the muscle contraction, whereas the tactile stimuli did not. We interpret the effect of warming on MSNA as providing relevant afferent information during muscle contraction, which needed to be counteracted via vasoconstriction to maintain homeostasis. Brushing and vibration were less homeostatically relevant stimuli for the muscle contraction and hence had no significant effect. The findings add sensory specificity to our current understanding of homeostatic regulation through somatosensory afferent and sympathetic efferent pathways.
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18
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Macefield VG, Henderson LA. Identifying Increases in Activity of the Human RVLM Through MSNA-Coupled fMRI. Front Neurosci 2020; 13:1369. [PMID: 32038124 PMCID: PMC6985468 DOI: 10.3389/fnins.2019.01369] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2019] [Accepted: 12/04/2019] [Indexed: 11/13/2022] Open
Abstract
AIM We initially developed concurrent recording of muscle sympathetic nerve activity (MSNA) and functional magnetic resonance imaging (fMRI) of the brain to functionally identify the human homolog of the rostral ventrolateral medulla (RVLM). Here we summarize the cortical and subcortical connections to the RVLM, as identified using MSNA-coupled fMRI. METHODS MSNA was recorded via tungsten microelectrodes inserted into the peroneal nerve. Gradient echo, echo-planar fMRI was performed at 3T (Philips Achieva). 200 volumes (46 axial slices (TR = 8 s, TE = 4 s, flip angle = 90°, raw voxel size = 1.5 × 1.5 × 2.75 mm) were collected in a 4 s-ON, 4 s-OFF sparse sampling protocol and MSNA measured in each 1 s epoch in the 4-s period between scans. Blood oxygen level dependent (BOLD) signal intensity was measured in the corresponding 1 s epoch 4 s later to account for peripheral neural conduction and central neurovascular coupling delays. RESULTS BOLD signal intensity was positively related to bursts of MSNA in the RVLM, dorsomedial hypothalamus (DMH), ventromedial hypothalamus (VMH), insula, dorsolateral prefrontal cortex (dlPFC), posterior cingulate cortex (PCC), and precuneus, and negatively related in the caudal ventrolateral medulla (CVLM), nucleus tractus solitarius (NTS), and the midbrain periaqueductal gray (PAG). During physiological increases in MSNA (tonic muscle pain), MSNA-coupled BOLD signal intensity was greater in RVLM, NTS, PAG, DMH, dlPFC, medial prefrontal cortex (mPFC), precuneus, and anterior cingulate cortex (ACC) than at rest. During pathophysiological increases in MSNA [obstructive sleep apnoea (OSA)] signal intensity was also higher in dlPFC, mPFC, ACC, and precuneus than in controls. Conversely, signal intensity was lower in RVLM in OSA than in controls, which we interpret as reflecting a withdrawal of active inhibition of the RVLM. CONCLUSION These results suggest that multiple cortical and subcortical areas are functionally coupled to the RVLM, which in turn is functionally coupled to the generation of spontaneous bursts of MSNA and their augmentation during physiological and pathophysiological increase in vasoconstrictor drive.
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Affiliation(s)
- Vaughan G. Macefield
- Human Autonomic Neurophysiology Laboratory, School of Medicine, Baker Heart and Diabetes Institute, Melbourne, VIC, Australia
- Department of Physiology, School of Biomedical Sciences, The University of Melbourne, Melbourne, VIC, Australia
| | - Luke A. Henderson
- Discipline of Anatomy and Histology, School of Medical Sciences, The University of Sydney, Sydney, NSW, Australia
- Brain and Mind Centre, The University of Sydney, Sydney, NSW, Australia
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19
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Goldberger JJ, Arora R, Buckley U, Shivkumar K. Autonomic Nervous System Dysfunction: JACC Focus Seminar. J Am Coll Cardiol 2020; 73:1189-1206. [PMID: 30871703 DOI: 10.1016/j.jacc.2018.12.064] [Citation(s) in RCA: 124] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 12/21/2018] [Accepted: 12/30/2018] [Indexed: 12/20/2022]
Abstract
Autonomic nervous system control of the heart is a dynamic process in both health and disease. A multilevel neural network is responsible for control of chronotropy, lusitropy, dromotropy, and inotropy. Intrinsic autonomic dysfunction arises from diseases that directly affect the autonomic nerves, such as diabetes mellitus and the syndromes of primary autonomic failure. Extrinsic autonomic dysfunction reflects the changes in autonomic function that are secondarily induced by cardiac or other disease. An array of tests interrogate various aspects of cardiac autonomic control in either resting conditions or with physiological perturbations from resting conditions. The prognostic significance of these assessments have been well established. Clinical usefulness has not been established, and the precise mechanistic link to mortality is less well established. Further efforts are required to develop optimal approaches to delineate cardiac autonomic dysfunction and its adverse effects to develop tools that can be used to guide clinical decision-making.
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Affiliation(s)
- Jeffrey J Goldberger
- Cardiovascular Division, Department of Medicine, University of Miami Miller School of Medicine, Miami, Florida.
| | - Rishi Arora
- Feinberg Cardiovascular Research Institute, Division of Cardiology, Department of Medicine, Northwestern University-Feinberg School of Medicine, Chicago, Illinois
| | - Una Buckley
- Cardiac Arrhythmia Center and Neurocardiology Research Center of Excellence, University of California-Los Angeles Los Angeles, California
| | - Kalyanam Shivkumar
- Cardiac Arrhythmia Center and Neurocardiology Research Center of Excellence, University of California-Los Angeles Los Angeles, California
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20
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Yoo JK, Badrov MB, Parker RS, Anderson EH, Wiblin JL, North CS, Suris A, Fu Q. Early onset neurocirculatory response to static handgrip is associated with greater blood pressure variability in women with posttraumatic stress disorder. Am J Physiol Heart Circ Physiol 2020; 318:H49-H58. [PMID: 31756119 DOI: 10.1152/ajpheart.00490.2019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Posttraumatic stress disorder (PTSD) is a psychiatric illness that is more prevalent in women, and accumulating evidence suggests a link between PTSD and future development of cardiovascular disease. The underlying mechanisms are unclear, but augmented sympathetic reactivity to daily stressors may be involved. We measured muscle sympathetic nerve activity (MSNA), blood pressure (BP), and heart rate responses in 14 women with PTSD and 14 healthy women (controls) during static handgrip (SHG) exercise to fatigue at 40% of maximal voluntary contraction (MVC). Two minutes of postexercise circulatory arrest (PECA) was followed immediately after SHG to fatigue. MVC and the time to fatigue during SHG did not differ between groups (both P > 0.05). At the first 30 s of SHG, women with PTSD showed augmented sympathetic neural [mean ± SD, ∆MSNA burst frequency (BF): 5 ± 4 vs. 2 ± 3 bursts/30 s, P = 0.02 and ∆MSNA total activity (TA): 82 ± 58 vs. 25 ± 38 arbitrary units/30 s, P = 0.004] and pressor (∆systolic BP: 10 ± 5 vs. 4 ± 3 mmHg, P = 0.003) responses compared with controls. However, MSNA and BP responses at fatigue and during PECA were not different between groups. More interestingly, the augmented initial neural and pressor responses to SHG were associated with greater awake systolic BP variability during ambulation in women with PTSD (MSNA BF: r = 0.55, MSNA TA: r = 0.62, and SBP: r = 0.69, all P < 0.05). These results suggest that early onset exercise pressor response in women with PTSD may be attributed to enhanced mechano- rather than metaboreflexes, which might contribute to the mechanisms underlying the link between PTSD and cardiovascular risk.NEW & NOTEWORTHY The novel findings of the current study are that women with posttraumatic stress disorder (PTSD) exhibited augmented sympathetic neural and pressor responses at the first 30 s of submaximal isometric muscle contraction. More interestingly, exaggerated neurocirculatory responses at the onset of muscle contraction were associated with greater ambulatory awake systolic blood pressure fluctuations in women with PTSD. Our findings expand the knowledge on the physiological mechanisms that perhaps contribute to increased risk of cardiovascular disease in such a population.
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Affiliation(s)
- Jeung-Ki Yoo
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Texas.,Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - Mark B Badrov
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Texas.,Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - Rosemary S Parker
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Texas
| | - Elizabeth H Anderson
- Psychiatry, The University of Texas Southwestern Medical Center, Dallas, Texas.,Veterans Affairs North Texas Health Care System, Dallas, Texas
| | - Jessica L Wiblin
- Psychiatry, The University of Texas Southwestern Medical Center, Dallas, Texas.,Veterans Affairs North Texas Health Care System, Dallas, Texas
| | - Carol S North
- Psychiatry, The University of Texas Southwestern Medical Center, Dallas, Texas.,Metrocare Services, Dallas, Texas
| | - Alina Suris
- Psychiatry, The University of Texas Southwestern Medical Center, Dallas, Texas.,Veterans Affairs North Texas Health Care System, Dallas, Texas
| | - Qi Fu
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Texas.,Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, Texas
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21
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Lai S, Mangiulli M, Perrotta AM, Di Lazzaro Giraldi G, Testorio M, Rosato E, Cianci R, Gigante A. Reduction in Heart Rate Variability in Autosomal Dominant Polycystic Kidney Disease. Kidney Blood Press Res 2019; 44:1142-1148. [PMID: 31550720 DOI: 10.1159/000502419] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Accepted: 07/30/2019] [Indexed: 11/19/2022] Open
Abstract
INTRODUCTION Cardiovascular disease is one of the main causes of morbidity and mortality in patients with autosomal dominant polycystic kidney disease (ADPKD). Autonomic dysfunction is associated with an increased risk for all cardiovascular events in the general population and can be evaluated with heart rate variability (HRV). OBJECTIVE To evaluate HRV in ADPKD patients with mild hypertension versus hypertensive patients with organ damage and healthy controls (HC). MATERIALS AND METHODS We have enrolled 65 patients: 21 ADPKD patients (10 males), 20 patients with hypertension (14 males), and 24 HC (10 males). Biochemical analysis, clinical evaluation, anthropometric data, intima-media thickness, 24-h ECG Holter recording, and echocardiography were investigated at the time of enrollment. RESULTS No significant differences in HRV parameters were found between ADPKD with mild hypertension and hypertensive patients with organ damage. The median of HRV variables in time domain as SDNN (global autonomic activity) was significantly lower in ADPKD and hypertensive patients than HC (p < 0.05). In the frequency domain analysis, low frequency (LF), which mainly reflects the sympathetic component, showed higher values in ADPKD and hypertensive patients than HC during the night (p < 0.01). During the night, the sympathovagal balance, LF/high frequency (HF), showed higher values in ADPKD and hypertensive patients than HC (p < 0.0001). Conversely, LF day was lower in ADPKD and hypertensive patients than HC (p < 0.01). HF, which mainly reflects the parasympathetic component, was lower in ADPKD and hypertensive patients during the night than HC (p < 0.0001). CONCLUSIONS HRV reduction is present in ADPKD patients with mild hypertension in the absence of organ damage. The evaluation of sympathovagal balance can provide novel information on the cardiovascular risk in ADPKD patients in addition to classical risk factors.
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Affiliation(s)
- Silvia Lai
- Nephrology Unit, Department of Translational and Precision Medicine, Sapienza University of Rome, Rome, Italy,
| | - Marco Mangiulli
- Nephrology Unit, Department of Translational and Precision Medicine, Sapienza University of Rome, Rome, Italy
| | - Adolfo M Perrotta
- Nephrology Unit, Department of Translational and Precision Medicine, Sapienza University of Rome, Rome, Italy
| | | | - Massimo Testorio
- Nephrology Unit, Department of Gynecologic-Obstetrical Sciences and Urological Sciences, Sapienza University of Rome, Rome, Italy
| | - Edoardo Rosato
- Department of Translational and Precision Medicine, Sapienza University of Rome, Rome, Italy
| | - Rosario Cianci
- Nephrology Unit, Department of Translational and Precision Medicine, Sapienza University of Rome, Rome, Italy
| | - Antonietta Gigante
- Department of Translational and Precision Medicine, Sapienza University of Rome, Rome, Italy
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22
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Grimaldi D, Goldstein MR, Carter JR. Insomnia and cardiovascular autonomic control. Auton Neurosci 2019; 220:102551. [DOI: 10.1016/j.autneu.2019.05.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 05/10/2019] [Accepted: 05/15/2019] [Indexed: 01/13/2023]
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Sales ARK, Negrão MV, Testa L, Ferreira-Santos L, Groehs RVR, Carvalho B, Toschi-Dias E, Rocha NG, Laurindo FRM, Debbas V, Rondon MUPB, Mano MS, Hajjar LA, Hoff PMG, Filho RK, Negrão CE. Chemotherapy acutely impairs neurovascular and hemodynamic responses in women with breast cancer. Am J Physiol Heart Circ Physiol 2019; 317:H1-H12. [DOI: 10.1152/ajpheart.00756.2018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The purpose of the present study was to test the hypothesis that doxorubicin (DX) and cyclophosphamide (CY) adjuvant chemotherapy (CHT) acutely impairs neurovascular and hemodynamic responses in women with breast cancer. Sixteen women (age: 47.0 ± 2.0 yr; body mass index: 24.2 ± 1.5 kg/m) with stage II-III breast cancer and indication for adjuvant CHT underwent two experimental sessions, saline (SL) and CHT. In the CHT session, DX (60 mg/m2) and CY (600 mg/m2) were administered over 45 min. In the SL session, a matching SL volume was infused in 45 min. Muscle sympathetic nerve activity (MSNA) from peroneal nerve (microneurography), calf blood flow (CBF; plethysmography) and calf vascular conductance (CVC), heart rate (HR; electrocardiography), and beat-to-beat blood pressure (BP; finger plethysmography) were measured at rest before, during, and after each session. Venous blood samples (5 ml) were collected before and after both sessions for assessment of circulating endothelial microparticles (EMPs; flow cytometry), a surrogate marker for endothelial damage. MSNA and BP responses were increased ( P < 0.001), whereas CBF and CVC responses were decreased ( P < 0.001), during and after CHT session when compared with SL session. Interestingly, the vascular alterations were also observed at the molecular level through an increased EMP response to CHT ( P = 0.03, CHT vs. SL session). No difference in HR response was observed ( P > 0.05). Adjuvant CHT with DX and CY in patients treated for breast cancer increases sympathetic nerve activity and circulating EMP levels and, in addition, reduces muscle vascular conductance and elevates systemic BP. These responses may be early signs of CHT-induced cardiovascular alterations and may represent potential targets for preventive interventions. NEW & NOTEWORTHY It is known that chemotherapy regimens increase the risk of cardiovascular events in patients treated for cancer. Here, we identified that a single cycle of adjuvant chemotherapy with doxorubicin and cyclophosphamide in women treated for breast cancer dramatically increases sympathetic nerve activity and circulating endothelial microparticle levels, reduces the muscle vascular conductance, and elevates systemic blood pressure.
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Affiliation(s)
| | - Marcelo Vailati Negrão
- Cancer Institute of the State of São Paulo, University of São Paulo Medical School, São Paulo, Brazil
- Department of Thoracic/Head and Neck Medical Oncology, The University of Texas, MD Anderson Cancer Center, Houston, Texas
| | - Laura Testa
- Cancer Institute of the State of São Paulo, University of São Paulo Medical School, São Paulo, Brazil
| | | | | | - Bruna Carvalho
- Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil
| | - Edgar Toschi-Dias
- Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil
| | - Natalia Galito Rocha
- Department of Physiology and Pharmacology, Fluminense Federal University, Niteroi, Brazil
| | | | - Victor Debbas
- Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil
| | | | - Max Sena Mano
- Cancer Institute of the State of São Paulo, University of São Paulo Medical School, São Paulo, Brazil
| | - Ludhmila Abrahao Hajjar
- Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil
- Cancer Institute of the State of São Paulo, University of São Paulo Medical School, São Paulo, Brazil
| | - Paulo Marcelo Gehm Hoff
- Cancer Institute of the State of São Paulo, University of São Paulo Medical School, São Paulo, Brazil
| | - Roberto Kalil Filho
- Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil
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24
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Carter JR, Grimaldi D, Fonkoue IT, Medalie L, Mokhlesi B, Cauter EV. Assessment of sympathetic neural activity in chronic insomnia: evidence for elevated cardiovascular risk. Sleep 2019. [PMID: 29522186 DOI: 10.1093/sleep/zsy048] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Study Objectives Chronic insomnia affects up to 15 per cent of adults. Recent cross-sectional and prospective epidemiological studies report an association between insomnia and hypertension, including incident hypertension, yet mechanisms underlying the association remain unknown. We hypothesized that participants with chronic insomnia would have elevated sympathetic neural outflow, blunted baroreflex sensitivity, and augmented sympathetic neural and cardiovascular reactivity to stress when compared with good-sleeper controls. Methods Twelve participants with chronic insomnia (11 women, 1 man) and 12 controls (8 women, 4 men) underwent one night of laboratory polysomnography, two weeks of at-home wrist actigraphy, and one night of controlled laboratory sleep prior to a comprehensive morning autonomic function test. The autonomic function test consisted of simultaneous recordings of muscle sympathetic nerve activity (MSNA; microneurography), beat-to-beat blood pressure (finger plethysmography), and heart rate (electrocardiogram) during a 10 min supine baseline and a 2 min cold pressor test. Results Baseline blood pressure, heart rate, and MSNA were not different between groups, but sympathetic baroreflex sensitivity was significantly blunted in participants with insomnia (-2.1 ± 1.0 vs. -4.3 ± 1.3 bursts/100 heartbeats/mm Hg; p < 0.001). During the cold pressor test, systolic arterial pressure reactivity (Δ21 ± 11 vs. Δ14 ± 8 mm Hg; time × group = 0.04) and total MSNA reactivity (Δ127%, 54%-208% vs. Δ52%, 30%-81%; time × group = 0.02) were augmented in chronic insomnia. Conclusions Participants with chronic insomnia demonstrated impaired sympathetic baroreflex function and augmented neural cardiovascular responsiveness to stress, when compared with controls. These findings support growing evidence of cardiovascular risk and physiological hyperarousal in chronic insomnia. Clinical Trial Registration NCT02048878. https://clinicaltrials.gov/ct2/show/NCT02048878.
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Affiliation(s)
- Jason R Carter
- Sleep, Metabolism and Health Center, The University of Chicago, Chicago, IL.,Department of Kinesiology and Integrative Physiology, Michigan Technological University, Houghton, MI
| | - Daniela Grimaldi
- Sleep, Metabolism and Health Center, The University of Chicago, Chicago, IL.,Department of Neurology, Center for Circadian and Sleep Medicine, Northwestern University, Chicago, IL
| | - Ida T Fonkoue
- Department of Kinesiology and Integrative Physiology, Michigan Technological University, Houghton, MI
| | - Lisa Medalie
- Sleep, Metabolism and Health Center, The University of Chicago, Chicago, IL.,Section of Pulmonary and Critical Care, Sleep Disorders Center, The University of Chicago, Chicago, IL
| | - Babak Mokhlesi
- Sleep, Metabolism and Health Center, The University of Chicago, Chicago, IL.,Section of Pulmonary and Critical Care, Sleep Disorders Center, The University of Chicago, Chicago, IL
| | - Eve Van Cauter
- Sleep, Metabolism and Health Center, The University of Chicago, Chicago, IL.,Section of Endocrinology, Diabetes and Metabolism, The University of Chicago, Chicago, IL
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25
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Carter JR. Microneurography and sympathetic nerve activity: a decade-by-decade journey across 50 years. J Neurophysiol 2019; 121:1183-1194. [PMID: 30673363 DOI: 10.1152/jn.00570.2018] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The technique of microneurography has advanced the field of neuroscience for the past 50 years. While there have been a number of reviews on microneurography, this paper takes an objective approach to exploring the impact of microneurography studies. Briefly, Web of Science (Thomson Reuters) was used to identify the highest citation articles over the past 50 years, and key findings are presented in a decade-by-decade highlight. This includes the establishment of microneurography in the 1960s, the acceleration of the technique by Gunnar Wallin in the 1970s, the international collaborations of the 1980s and 1990s, and finally the highest impact studies from 2000 to present. This journey through 50 years of microneurographic research related to peripheral sympathetic nerve activity includes a historical context for several of the laboratory interventions commonly used today (e.g., cold pressor test, mental stress, lower body negative pressure, isometric handgrip, etc.) and how these interventions and experimental approaches have advanced our knowledge of cardiovascular, cardiometabolic, and other human diseases and conditions.
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Affiliation(s)
- Jason R Carter
- Department of Kinesiology and Integrative Physiology, Michigan Technological University , Houghton, Michigan
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26
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Strauss M, Smith W, Wei W, Fedorova OV, Schutte AE. Autonomic activity and its relationship with the endogenous cardiotonic steroid marinobufagenin: the African-PREDICT study. Nutr Neurosci 2019; 23:849-859. [PMID: 30614779 DOI: 10.1080/1028415x.2018.1564985] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Aim: Marinobufagenin (MBG), a cardiotonic steroid and a natriuretic hormone, is elevated in response to high salt diet consumption. In animal models salt intake stimulates adrenocortical MBG secretion via increased angiotensin II, sympathetic activity and aldosterone. No evidence in humans exists to suggest the involvement of the angiotensinergic-sympatho-excitatory pathway in MBG production. We investigated whether MBG is related to indices of autonomic activity in men and women. Methods: This cross-sectional study included 680 black and white, men and women from the African-PREDICT study (aged 20-30 years). Continuous 24 hr ECG recordings were used to obtain low and high frequency (LF, HF) heart rate variability (HRV). We measured 24 hr urinary MBG excretion and serum aldosterone. Results: We found a positive association of MBG excretion with estimated salt intake (P < 0.001) and aldosterone (P < 0.001) in women and men. In women only, a positive relationship was evident between MBG excretion and LF HRV in multivariate adjusted regression analyses (Adj. R 2 = 0.33; β = 0.11; P = 0.030). In men, MBG excretion associated positively with HF HRV in similar regression analyses (R 2 = 0.36; β = 0.12; P = 0.034). Sex-specific results were corroborated only in blacks, namely, a positive association of MBG excretion with LF HRV in black women (R 2 = 0.38; β = 0.13; P = 0.036), and negative association with HF HRV in black men (R 2 = 0.40; β = 0.18; P = 0.045). No relationships were evident in white women (P = 0.58) or men (P = 0.27). Conclusion: Our findings in this human cohort support suggested mechanisms whereby MBG is elevated as a result of increased salt intake, including autonomic activity, previously demonstrated in Dahl salt-sensitive hypertension.
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Affiliation(s)
- Michél Strauss
- Hypertension in Africa Research Team (HART), North-West University, Potchefstroom, South Africa
| | - Wayne Smith
- Hypertension in Africa Research Team (HART), North-West University, Potchefstroom, South Africa.,MRC Research Unit: Hypertension and Cardiovascular Disease, North-West University, Potchefstroom, South Africa
| | - Wen Wei
- Laboratory of Cardiovascular Science, National Institute on Aging, NIH, Baltimore, MD, USA
| | - Olga V Fedorova
- Laboratory of Cardiovascular Science, National Institute on Aging, NIH, Baltimore, MD, USA
| | - Aletta E Schutte
- Hypertension in Africa Research Team (HART), North-West University, Potchefstroom, South Africa.,MRC Research Unit: Hypertension and Cardiovascular Disease, North-West University, Potchefstroom, South Africa
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27
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Fealey RD. Thermoregulation in neuropathies. HANDBOOK OF CLINICAL NEUROLOGY 2018; 157:777-787. [PMID: 30459040 DOI: 10.1016/b978-0-444-64074-1.00048-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2023]
Abstract
Peripheral neuropathy affecting autonomic and small sensory fibers can cause abnormalities of both autonomic and behavioral thermoregulation. Quantitative autonomic and sensory neurophysiologic tests and quantification of the linear density of intraepidermal nerve fibers potentially can stratify those at risk of impaired thermoregulation during cold and heat challenges. New data relating to thermoregulatory sweating impairment in neuropathy are presented in this chapter. Of 516 neuropathy patients analyzed, 345 were found to have thermoregulatory sweat test (TST) abnormalities with a mean percentage of anterior body surface anhidrosis (TST%) of 12% and a significant reduction in total body sweat rate, although the rate of core temperature rise with heating (slope) was not significantly different from that of patients with a normal TST. However a subset of abnormal TST patients having 25% or greater TST% showed a significantly more rapid rise in core temperature (lower slope) than age- and sex-matched neuropathy patients with a normal TST. Etiologies of neuropathy in this more severe group included diabetes, erythromelalgia, immune-mediated autonomic neuropathy, primary systemic amyloidosis, and neuropathy associated with postganglionic-autonomic degenerative disorders.
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Affiliation(s)
- Robert D Fealey
- Department of Neurology, Mayo Clinic, Rochester, MN, United States.
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28
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Kobuch S, Fazalbhoy A, Brown R, Macefield VG, Henderson LA. Muscle sympathetic nerve activity-coupled changes in brain activity during sustained muscle pain. Brain Behav 2018; 8:e00888. [PMID: 29541532 PMCID: PMC5840447 DOI: 10.1002/brb3.888] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
INTRODUCTION Long-lasting experimental muscle pain elicits divergent muscle sympathetic responses, with some individuals exhibiting a persistent increase in muscle sympathetic nerve activity (MSNA), and others a decrease. These divergent responses are thought to result from sustained functional changes in specific brain regions that modulate the cardiovascular responses to pain. AIM The aim of this study was to investigate brain regions that are functionally coupled to the generation of an MSNA burst at rest and to determine their behavior during tonic muscle pain. METHODS Functional magnetic resonance imaging of the brain was performed concurrently with microelectrode recording of MSNA from the common peroneal nerve during a 40 min infusion of hypertonic saline into the ipsilateral tibialis anterior muscle of 37 healthy human subjects. RESULTS At rest, blood oxygen level-dependent signal intensity coupled to bursts of MSNA increased in the rostral ventrolateral medulla, insula, dorsolateral prefrontal cortex, posterior cingulate cortex, and precuneus and decreased in the region of the midbrain periaqueductal gray. During pain, MSNA-coupled signal intensity was greater in the region of the nucleus tractus solitarius, midbrain periaqueductal gray, dorsolateral prefrontal, medial prefrontal, and anterior cingulate cortices, than at rest. Conversely, MSNA-coupled signal intensity decreased during pain in parts of the prefrontal cortex. CONCLUSIONS These results suggest that multiple brain regions are recruited in a burst-to-burst manner, and the magnitude of these signal changes is correlated to the overall change in MSNA amplitude during tonic muscle pain.
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Affiliation(s)
- Sophie Kobuch
- School of Medicine Western Sydney University Sydney NSW Australia
| | - Azharuddin Fazalbhoy
- Neuroscience Research Australia Sydney NSW Australia.,School of Health Sciences RMIT University Melbourne Vic Australia
| | - Rachael Brown
- School of Medicine Western Sydney University Sydney NSW Australia.,Neuroscience Research Australia Sydney NSW Australia
| | - Vaughan G Macefield
- School of Medicine Western Sydney University Sydney NSW Australia.,Neuroscience Research Australia Sydney NSW Australia.,College of Medicine Mohammed Bin Rashid University of Medicine & Health Sciences Dubai UAE
| | - Luke A Henderson
- Department of Anatomy and Histology University of Sydney Sydney NSW Australia
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29
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Macefield VG, Wallin BG. Physiological and pathophysiological firing properties of single postganglionic sympathetic neurons in humans. J Neurophysiol 2017; 119:944-956. [PMID: 29142091 DOI: 10.1152/jn.00004.2017] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
It has long been known from microneurographic recordings in human subjects that the activity of postganglionic sympathetic axons occurs as spontaneous bursts, with muscle sympathetic nerve activity (MSNA) exhibiting strong cardiac rhythmicity via the baroreflex and skin sympathetic nerve activity showing much weaker cardiac modulation. Here we review the firing properties of single sympathetic neurons, obtained using highly selective microelectrodes. Individual vasoconstrictor neurons supplying muscle or skin, or sudomotor neurons supplying sweat glands, always discharge with a low firing probability (~30%) and at very low frequencies (~0.5 Hz). Moreover, they usually fire only once per cardiac interval but can fire greater than four times within a burst. Modeling has shown that this pattern can best be explained by individual neurons being driven by, on average, two preganglionic inputs. Unitary recordings of muscle vasoconstrictor neurons have been made in several pathophysiological states, including heart failure, hypertension, obstructive sleep apnea, bronchiectasis, chronic obstructive pulmonary disease, depression, and panic disorder. The augmented MSNA in each of these diseases features an increase in firing probability and discharge frequency of individual muscle vasoconstrictor neurons above that seen in healthy subjects, yet firing rates rarely exceed 1 Hz. However, unlike patients with heart failure, all patients with respiratory disease or panic disorder, and patients with hyperhidrosis, exhibited an increase in multiple within-burst firing, which emphasizes the different modes by which the sympathetic nervous system grades its output in pathophysiological states of high sympathetic nerve activity.
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Affiliation(s)
- Vaughan G Macefield
- School of Medicine, Western Sydney University , Sydney , Australia.,Neuroscience Research Australia, Sydney , Australia.,Baker Heart and Diabetes Institute , Melbourne , Australia
| | - B Gunnar Wallin
- Department of Clinical Neurophysiology, Institute of Neuroscience and Physiology, Sahlgren Academy at University of Gothenburg , Gothenburg , Sweden
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30
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A review of human neuroimaging investigations involved with central autonomic regulation of baroreflex-mediated cardiovascular control. Auton Neurosci 2017; 207:10-21. [DOI: 10.1016/j.autneu.2017.05.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 03/10/2017] [Accepted: 05/13/2017] [Indexed: 12/30/2022]
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31
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Greaney JL, Kenney WL. Measuring and quantifying skin sympathetic nervous system activity in humans. J Neurophysiol 2017; 118:2181-2193. [PMID: 28701539 DOI: 10.1152/jn.00283.2017] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Revised: 07/10/2017] [Accepted: 07/10/2017] [Indexed: 01/23/2023] Open
Abstract
Development of the technique of microneurography has substantially increased our understanding of the function of the sympathetic nervous system (SNS) in health and in disease. The ability to directly record signals from peripheral autonomic nerves in conscious humans allows for qualitative and quantitative characterization of SNS responses to specific stimuli and over time. Furthermore, distinct neural outflow to muscle (MSNA) and skin (SSNA) can be delineated. However, there are limitations and caveats to the use of microneurography, measurement criteria, and signal analysis and interpretation. MSNA recordings have a longer history and are considered relatively more straightforward from a measurement and analysis perspective. This brief review provides an overview of the development of the technique as used to measure SSNA. The focus is on the utility of measuring sympathetic activity directed to the skin, the unique issues related to analyzing and quantifying multiunit SSNA, and the challenges related to its interpretation.
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Affiliation(s)
- Jody L Greaney
- Noll Laboratory, Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
| | - W Larry Kenney
- Noll Laboratory, Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania
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32
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Hart EC, Head GA, Carter JR, Wallin BG, May CN, Hamza SM, Hall JE, Charkoudian N, Osborn JW. Recording sympathetic nerve activity in conscious humans and other mammals: guidelines and the road to standardization. Am J Physiol Heart Circ Physiol 2017; 312:H1031-H1051. [PMID: 28364017 DOI: 10.1152/ajpheart.00703.2016] [Citation(s) in RCA: 103] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 03/06/2017] [Accepted: 03/06/2017] [Indexed: 01/03/2023]
Abstract
Over the past several decades, studies of the sympathetic nervous system in humans, sheep, rabbits, rats, and mice have substantially increased mechanistic understanding of cardiovascular function and dysfunction. Recently, interest in sympathetic neural mechanisms contributing to blood pressure control has grown, in part because of the development of devices or surgical procedures that treat hypertension by manipulating sympathetic outflow. Studies in animal models have provided important insights into physiological and pathophysiological mechanisms that are not accessible in human studies. Across species and among laboratories, various approaches have been developed to record, quantify, analyze, and interpret sympathetic nerve activity (SNA). In general, SNA demonstrates "bursting" behavior, where groups of action potentials are synchronized and linked to the cardiac cycle via the arterial baroreflex. In humans, it is common to quantify SNA as bursts per minute or bursts per 100 heart beats. This type of quantification can be done in other species but is only commonly reported in sheep, which have heart rates similar to humans. In rabbits, rats, and mice, SNA is often recorded relative to a maximal level elicited in the laboratory to control for differences in electrode position among animals or on different study days. SNA in humans can also be presented as total activity, where normalization to the largest burst is a common approach. The goal of the present paper is to put together a summary of "best practices" in several of the most common experimental models and to discuss opportunities and challenges relative to the optimal measurement of SNA across species.Listen to this article's corresponding podcast at https://ajpheart.podbean.com/e/guidelines-for-measuring-sympathetic-nerve-activity/.
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Affiliation(s)
- Emma C Hart
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom;
| | - Geoffrey A Head
- Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia
| | | | | | - Clive N May
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | | | - John E Hall
- Department of Physiology and Biophysics, Mississippi Center for Obesity Research, University of Mississippi Medical Center, Jackson, Mississippi
| | - Nisha Charkoudian
- United States Army Research Institute of Environmental Medicine, Natick, Massachusetts; and
| | - John W Osborn
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, Minneapolis, Minnesota
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33
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Chen DLT, Brown R, Liess C, Poljak A, Xu A, Zhang J, Trenell M, Jenkins A, Chisholm D, Samocha-Bonet D, Macefield VG, Greenfield JR. Muscle Sympathetic Nerve Activity Is Associated with Liver Insulin Sensitivity in Obese Non-Diabetic Men. Front Physiol 2017; 8:101. [PMID: 28293196 PMCID: PMC5328983 DOI: 10.3389/fphys.2017.00101] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2016] [Accepted: 02/07/2017] [Indexed: 12/14/2022] Open
Abstract
Introduction: Muscle sympathetic nerve activity (MSNA) may play a role in insulin resistance in obesity. However, the direction and nature of the relationship between MSNA and insulin resistance in obesity remain unclear. We hypothesized that resting MSNA would correlate inversely with both muscle and liver insulin sensitivity and that it would be higher in insulin-resistant vs. insulin-sensitive subjects. Materials and methods: Forty-five non-diabetic obese subjects were studied. As no significant relationships were found in women, the data presented in on 22 men aged 48 ± 12 years. Two-step (15 and 80 mU/m2/min) hyperinsulinaemic-euglycaemic clamps were performed using deuterated glucose to determine liver and muscle insulin sensitivity. Clinical and metabolic parameters were assessed. MSNA was measured via a microelectrode inserted percutaneously into the common peroneal nerve. Results: MSNA burst frequency correlated inversely with liver insulin sensitivity (r = −0.53, P = 0.02) and positively with the hepatokines C-reactive protein (CRP) and fibroblast growth factor (FGF)-19 (r = 0.57, P = 0.006, and r = −0.47, P = 0.03, respectively). MSNA burst frequency was lower in Liversen compared to Liverres (27 ± 5 vs. 38 ± 2 bursts per minute; P = 0.03). Muscle insulin sensitivity was unrelated to MSNA. Discussion: Sympathetic neural activation is related to liver insulin sensitivity and circulating hepatokines CRP and FGF-19 in non-diabetic obese men. These results suggest a potential hepato-endocrine-autonomic axis. Future studies are needed to clarify the influence of MSNA on liver insulin sensitivity in men.
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Affiliation(s)
- Daniel L T Chen
- Diabetes and Metabolism Division, Garvan Institute of Medical Research Sydney, NSW, Australia
| | - Rachael Brown
- School of Medicine, University of Western SydneySydney, NSW, Australia; Neuroscience Research AustraliaSydney, NSW, Australia
| | - Carsten Liess
- Philips Healthcare Luebeckertordamm, Hamburg, Germany
| | - Anne Poljak
- Bioanalytical Mass Spectrometry Facility, UNSW SydneySydney, NSW, Australia; School of Medical Sciences, UNSW SydneySydney, NSW, Australia
| | - Aimin Xu
- State Key Laboratory of Pharmaceutical Biotechnology, University of Hong Kong Hong Kong, Hong Kong
| | - Jialiang Zhang
- State Key Laboratory of Pharmaceutical Biotechnology, University of Hong Kong Hong Kong, Hong Kong
| | | | - Arthur Jenkins
- Diabetes and Metabolism Division, Garvan Institute of Medical ResearchSydney, NSW, Australia; School of Health Science, University of WollongongWollongong, NSW, Australia
| | - Donald Chisholm
- Diabetes and Metabolism Division, Garvan Institute of Medical Research Sydney, NSW, Australia
| | - Dorit Samocha-Bonet
- Diabetes and Metabolism Division, Garvan Institute of Medical ResearchSydney, NSW, Australia; School of Medical Sciences, UNSW SydneySydney, NSW, Australia
| | - Vaughan G Macefield
- School of Medicine, University of Western SydneySydney, NSW, Australia; Neuroscience Research AustraliaSydney, NSW, Australia
| | - Jerry R Greenfield
- Diabetes and Metabolism Division, Garvan Institute of Medical ResearchSydney, NSW, Australia; Department of Endocrinology and Diabetes Center, St. Vincent's HospitalSydney, NSW, Australia
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34
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Briant LJB, Charkoudian N, Hart EC. Sympathetic regulation of blood pressure in normotension and hypertension: when sex matters. Exp Physiol 2016; 101:219-29. [PMID: 26682826 DOI: 10.1113/ep085368] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 12/14/2015] [Indexed: 12/21/2022]
Abstract
NEW FINDINGS What is the topic of this review? Hypertension is a major problem in Western society. Risk of hypertension increases with age, especially in women, who have lower risk compared with men until menopause. This review outlines the sex differences in the sympathetic control of blood pressure and how these mechanisms change with age. What advances does it highlight? It has recently been recognized that men and women regulate blood pressure by different physiological mechanisms. This is important for both the understanding and the clinical management of individual patients with hypertension. This review summarizes recent advances in understanding how the regulation of blood pressure in hypertension by the sympathetic nervous system differs between men and women. The sympathetic nervous system has a central role in the regulation of arterial blood pressure (BP) and in the development of hypertension in humans. Recent evidence points to differences between the sexes in the integrative mechanisms by which BP is controlled, suggesting that the development of hypertension may follow distinct pathways in women compared with men. An important aspect of sympathetic control of BP is its substantial interindividual variability. In healthy young men, the variability in sympathetic nerve activity (SNA) is balanced by variability in cardiac output and vascular adrenergic responses, such that BP remains similar, and normal, across a severalfold range of resting SNA values. In young women, variability in resting SNA is similar to that seen in men, but the 'balancing' mechanisms are strikingly different; women exhibit greater β-adrenergic vasodilatation compared with men, which minimizes the pressor effects of a given level of SNA. Ageing is associated with increased SNA and a loss of the balancing factors seen in younger people, leading to an increased risk of hypertension in older people. Loss of oestrogen with menopause in women appears to be linked mechanistically with the decrease in β-adrenergic vasodilatation and the increased risk of hypertension in older women. Other important factors contributing to hypertension via sympathetic mechanisms are obesity and arterial stiffening, both of which increase with ageing. We conclude with a discussion of important areas in which more work is needed to understand and manage appropriately the sex-specific mechanisms in the development and maintenance of hypertension.
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Affiliation(s)
- L J B Briant
- Clinical Research and Imaging Centre, Cardionomics Group, University of Bristol, Bristol, UK
| | - N Charkoudian
- US Army Research Institute of Environmental Medicine, Natick, MA, USA
| | - E C Hart
- Clinical Research and Imaging Centre, Cardionomics Group, University of Bristol, Bristol, UK
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Macefield VG, Henderson LA. "Real-time" imaging of cortical and subcortical sites of cardiovascular control: concurrent recordings of sympathetic nerve activity and fMRI in awake subjects. J Neurophysiol 2016; 116:1199-207. [PMID: 27334958 PMCID: PMC5018056 DOI: 10.1152/jn.00783.2015] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 06/03/2016] [Indexed: 11/22/2022] Open
Abstract
We review our approach to functionally identifying cortical and subcortical areas involved in the generation of spontaneous fluctuations in sympathetic outflow to muscle or skin. We record muscle sympathetic nerve activity (MSNA) or skin sympathetic nerve activity (SSNA), via a tungsten microelectrode inserted percutaneously into the common peroneal nerve, at the same time as performing functional magnetic resonance imaging (fMRI) of the brain. By taking advantage of the neurovascular coupling delay associated with BOLD (blood oxygen level dependent) fMRI, and the delay associated with conduction of a burst of sympathetic impulses to the peripheral recording site, we can identify structures in which BOLD signal intensity covaries with MSNA or SSNA. Using this approach, we found MSNA-coupled increases in BOLD signal intensity in the mid-insula and dorsomedial hypothalamus on the left side, and in dorsolateral prefrontal cortex, posterior cingulate cortex, precuneus, ventromedial hypothalamus and rostral ventrolateral medulla on both sides. Conversely, spontaneous bursts of SSNA were positively correlated with BOLD signal intensity in the ventromedial thalamus and posterior insula on the left side, and in the anterior insula, orbitofrontal cortex and frontal cortex on the right side, and in the mid-cingulate cortex and precuneus on both sides. Inverse relationships were observed between MSNA and BOLD signal intensity in the right ventral insula, nucleus tractus solitarius and caudal ventrolateral medulla, and between SSNA and signal intensity in the left orbitofrontal cortex. These results emphasize the contributions of cortical regions of the brain to sympathetic outflow in awake human subjects, and the extensive interactions between cortical and subcortical regions in the ongoing regulation of sympathetic nerve activity to muscle and skin in awake human subjects.
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Affiliation(s)
- Vaughan G Macefield
- School of Medicine, Western Sydney University, Sydney, New South Wales, Australia; Neuroscience Research Australia, Sydney, New South Wales, Australia; and
| | - Luke A Henderson
- Department of Anatomy & Histology, University of Sydney, Sydney, New South Wales, Australia
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Sympathetic neural and cardiovascular responses during static handgrip exercise in women with a history of hypertensive pregnancy. Clin Auton Res 2016; 26:395-405. [PMID: 27506589 DOI: 10.1007/s10286-016-0372-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Accepted: 07/26/2016] [Indexed: 02/07/2023]
Abstract
PURPOSE Women with a history of hypertensive pregnancy are at greater risk for future cardiovascular events; however, the mechanisms for this increased risk are unknown. Evidence suggests that an exercise stimulus unmasks latent hypertensive tendencies, identifying individuals at the greatest risk for developing cardiovascular disease. The current study examined the hypothesis that women with a hypertensive pregnancy history exhibit an augmented exercise pressor response. METHODS Normotensive women with a history of healthy pregnancy (CON; n = 9) and hypertensive pregnancy (HP+; n = 12) were studied during the mid-luteal phase of the menstrual cycle. Heart rate (HR), systolic and diastolic blood pressure (SBP, DBP), and muscle sympathetic nerve activity (MSNA) were measured during a cold pressor test (CPT), and, following a sufficient period of recovery, during static handgrip to fatigue (SHG) and post-exercise circulatory arrest (PECA). RESULTS The BP, HR, and MSNA responses to the CPT were similar between groups. The SBP response to SHG and PECA was similar between groups, but DBP and HR were significantly greater in HP+ women (both p < 0.05). MSNA burst frequency, but not burst incidence or total activity, tended to be elevated in HP+ women during the stressor (peak Δ from baseline 31 ± 13 vs. 23 ± 13 bursts/min; p for group = 0.06). CONCLUSION Despite no clinical signs of cardiovascular disease or hypertension, women with a history of hypertensive pregnancy display an enhanced cardiovascular reactivity to an exercise stimulus compared to women with a healthy pregnancy history. This response may be indicative of impaired cardiovascular control that precedes the clinical manifestation of hypertension or cardiovascular events.
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Deuchars SA, Lall VK. Sympathetic preganglionic neurons: properties and inputs. Compr Physiol 2016; 5:829-69. [PMID: 25880515 DOI: 10.1002/cphy.c140020] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The sympathetic nervous system comprises one half of the autonomic nervous system and participates in maintaining homeostasis and enabling organisms to respond in an appropriate manner to perturbations in their environment, either internal or external. The sympathetic preganglionic neurons (SPNs) lie within the spinal cord and their axons traverse the ventral horn to exit in ventral roots where they form synapses onto postganglionic neurons. Thus, these neurons are the last point at which the central nervous system can exert an effect to enable changes in sympathetic outflow. This review considers the degree of complexity of sympathetic control occurring at the level of the spinal cord. The morphology and targets of SPNs illustrate the diversity within this group, as do their diverse intrinsic properties which reveal some functional significance of these properties. SPNs show high degrees of coupled activity, mediated through gap junctions, that enables rapid and coordinated responses; these gap junctions contribute to the rhythmic activity so critical to sympathetic outflow. The main inputs onto SPNs are considered; these comprise afferent, descending, and interneuronal influences that themselves enable functionally appropriate changes in SPN activity. The complexity of inputs is further demonstrated by the plethora of receptors that mediate the different responses in SPNs; their origins and effects are plentiful and diverse. Together these different inputs and the intrinsic and coupled activity of SPNs result in the rhythmic nature of sympathetic outflow from the spinal cord, which has a variety of frequencies that can be altered in different conditions.
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Affiliation(s)
- Susan A Deuchars
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
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White DW, Shoemaker JK, Raven PB. Methods and considerations for the analysis and standardization of assessing muscle sympathetic nerve activity in humans. Auton Neurosci 2015; 193:12-21. [PMID: 26299824 DOI: 10.1016/j.autneu.2015.08.004] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 08/01/2015] [Accepted: 08/03/2015] [Indexed: 01/20/2023]
Abstract
The technique of microneurography and the assessment of muscle sympathetic nerve activity (MSNA) are used in laboratories throughout the world. The variables used to describe MSNA, and the criteria by which these variables are quantified from the integrated neurogram, vary among studies and laboratories and, therefore, can become confusing to those starting to learn the technique. Therefore, the purpose of this educational review is to discuss guidelines and standards for the assessment of sympathetic nervous activity through the collection and analysis of MSNA. This review will reiterate common practices in the collection of MSNA, but will also introduce considerations for the evaluation and physiological inference using MSNA.
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Affiliation(s)
- Daniel W White
- The Department of Kinesiology & Nutrition, University of Illinois at Chicago, Chicago, IL, USA.
| | - J Kevin Shoemaker
- The School of Kinesiology, University of Western Ontario, London, ON, Canada
| | - Peter B Raven
- Department of Integrative Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA
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Briant LJB, Paton JFR, Pickering AE, Champneys AR. Modelling the vascular response to sympathetic postganglionic nerve activity. J Theor Biol 2015; 371:102-16. [PMID: 25698230 PMCID: PMC4386929 DOI: 10.1016/j.jtbi.2015.01.037] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 01/22/2015] [Accepted: 01/27/2015] [Indexed: 11/17/2022]
Abstract
This paper explores the influence of burst properties of the sympathetic nervous system on arterial contractility. Specifically, a mathematical model is constructed of the pathway from action potential generation in a sympathetic postganglionic neurone to contraction of an arterial smooth muscle cell. The differential equation model is a synthesis of models of the individual physiological processes, and is shown to be consistent with physiological data. The model is found to be unresponsive to tonic (regular) stimulation at typical frequencies recorded in sympathetic efferents. However, when stimulated at the same average frequency, but with repetitive respiratory-modulated burst patterns, it produces marked contractions. Moreover, the contractile force produced is found to be highly dependent on the number of spikes in each burst. In particular, when the model is driven by preganglionic spike trains recorded from wild-type and spontaneously hypertensive rats (which have increased spiking during each burst) the contractile force was found to be 10-fold greater in the hypertensive case. An explanation is provided in terms of the summative increased release of noradrenaline. Furthermore, the results suggest the marked effect that hypertensive spike trains had on smooth muscle cell tone can provide a significant contribution to the pathology of hypertension. We model the sympathetic-driven contraction of a vascular smooth muscle cell. The cell is unresponsive to tonic stimulation at typical sympathetic frequencies. We quantify the force produced by the cell in response to sympathetic bursting. The response of the cell is strongly dependent on burst amplitude and duration. Recordings from hypertensive animals produce significant contractile forces.
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Affiliation(s)
- Linford J B Briant
- School of Physiology & Pharmacology, Medical Sciences Building, University Walk, University of Bristol, Bristol BS8 1TD, UK; Department of Engineering Mathematics, Merchant Venturers Building, Woodland Road, University of Bristol, Bristol BS8 1UB, UK
| | - Julian F R Paton
- School of Physiology & Pharmacology, Medical Sciences Building, University Walk, University of Bristol, Bristol BS8 1TD, UK
| | - Anthony E Pickering
- School of Physiology & Pharmacology, Medical Sciences Building, University Walk, University of Bristol, Bristol BS8 1TD, UK; Department of Anaesthesia, University Hospitals Bristol, Bristol BS2 8HW, UK
| | - Alan R Champneys
- Department of Engineering Mathematics, Merchant Venturers Building, Woodland Road, University of Bristol, Bristol BS8 1UB, UK.
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Armaganijan L, Staico R, Moreira D, Amodeo C, Borelli F, Sousa M, Sousa A, Abizaid A. Effects of Renal Sympathetic Denervation in Renal Artery Diameter Evaluated By Quantitative Angiography. ACTA ACUST UNITED AC 2014. [DOI: 10.1590/0104-1843000000027] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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