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Abbariki F, Roy M, Labrecque L, Drapeau A, Imhoff S, Smirl JD, Brassard P. Influence of high-intensity interval training to exhaustion on the directional sensitivity of the cerebral pressure-flow relationship in young endurance-trained men. Physiol Rep 2022; 10:e15384. [PMID: 35822439 PMCID: PMC9277516 DOI: 10.14814/phy2.15384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 06/23/2022] [Indexed: 06/15/2023] Open
Abstract
We previously reported subtle dynamic cerebral autoregulation (dCA) alterations following 6 weeks of high-intensity interval training (HIIT) to exhaustion using transfer function analysis (TFA) on forced mean arterial pressure (MAP) oscillations in young endurance-trained men. However, accumulating evidence suggests the cerebrovasculature better buffers cerebral blood flow changes when MAP acutely increases compared to when MAP acutely decreases. Whether HIIT affects the directional sensitivity of the cerebral pressure-flow relationship in these athletes is unknown. In 18 endurance-trained men (age: 27 ± 6 years, VO2 max: 55.5 ± 4.7 ml·kg-1 ·min-1 ), we evaluated the impact of 6 weeks of HIIT to exhaustion on dCA directionality using induced MAP oscillations during 5-min 0.05 and 0.10 Hz repeated squat-stands. We calculated time-adjusted changes in middle cerebral artery mean blood velocity (MCAv) per change in MAP (ΔMCAvT /ΔMAPT ) for each squat transition. Then, we compared averaged ΔMCAvT /ΔMAPT during MAP increases and decreases. Before HIIT, ΔMCAvT /ΔMAPT was comparable between MAP increases and decreases during 0.05 Hz repeated squat-stands (p = 0.518). During 0.10 Hz repeated squat-stands, ΔMCAvT /ΔMAPT was lower during MAP increases versus decreases (0.87 ± 0.17 vs. 0.99 ± 0.23 cm·s-1 ·mmHg-1 , p = 0.030). Following HIIT, ΔMCAvT /ΔMAPT was superior during MAP increases over decreases during 0.05 Hz repeated squat-stands (0.97 ± 0.38 vs. 0.77 ± 0.35 cm·s-1 ·mmHg-1 , p = 0.002). During 0.10 Hz repeated squat-stands, dCA directional sensitivity disappeared (p = 0.359). These results suggest the potential for HIIT to influence the directional sensitivity of the cerebral pressure-flow relationship in young endurance-trained men.
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Affiliation(s)
- Faezeh Abbariki
- Department of Kinesiology, Faculty of MedicineUniversité LavalQuébec CityQuébecCanada
- Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de QuébecQuébec CityQuébecCanada
| | - Marc‐Antoine Roy
- Department of Kinesiology, Faculty of MedicineUniversité LavalQuébec CityQuébecCanada
- Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de QuébecQuébec CityQuébecCanada
| | - Lawrence Labrecque
- Department of Kinesiology, Faculty of MedicineUniversité LavalQuébec CityQuébecCanada
- Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de QuébecQuébec CityQuébecCanada
| | - Audrey Drapeau
- Department of Kinesiology, Faculty of MedicineUniversité LavalQuébec CityQuébecCanada
- Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de QuébecQuébec CityQuébecCanada
| | - Sarah Imhoff
- Department of Kinesiology, Faculty of MedicineUniversité LavalQuébec CityQuébecCanada
- Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de QuébecQuébec CityQuébecCanada
| | - Jonathan D. Smirl
- Cerebrovascular Concussion Laboratory, Faculty of KinesiologyUniversity of CalgaryCalgaryAlbertaCanada
- Sport Injury Prevention Research Centre, Faculty of KinesiologyUniversity of CalgaryCalgaryAlbertaCanada
- Human Performance Laboratory, Faculty of KinesiologyUniversity of CalgaryCalgaryAlbertaCanada
- Hotchkiss Brain InstituteUniversity of CalgaryCalgaryAlbertaCanada
- Integrated Concussion Research ProgramUniversity of CalgaryCalgaryAlbertaCanada
- Alberta Children's Hospital Research InstituteUniversity of CalgaryCalgaryAlbertaCanada
- Libin Cardiovascular Institute of AlbertaUniversity of CalgaryAlbertaCanada
- Concussion Research Laboratory, Faculty of Health and Exercise ScienceUniversity of British ColumbiaKelownaBritish ColumbiaCanada
| | - Patrice Brassard
- Department of Kinesiology, Faculty of MedicineUniversité LavalQuébec CityQuébecCanada
- Research Center of the Institut Universitaire de Cardiologie et de Pneumologie de QuébecQuébec CityQuébecCanada
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Tomoto T, Repshas J, Zhang R, Tarumi T. Midlife aerobic exercise and dynamic cerebral autoregulation: associations with baroreflex sensitivity and central arterial stiffness. J Appl Physiol (1985) 2021; 131:1599-1612. [PMID: 34647828 PMCID: PMC8616602 DOI: 10.1152/japplphysiol.00243.2021] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 10/04/2021] [Accepted: 10/11/2021] [Indexed: 12/20/2022] Open
Abstract
Midlife aerobic exercise may significantly impact age-related changes in the cerebro- and cardiovascular regulations. This study investigated the associations of midlife aerobic exercise with dynamic cerebral autoregulation (dCA), cardiovagal baroreflex sensitivity (BRS), and central arterial stiffness. Twenty middle-aged athletes (MA) who had aerobic training for >10 yr were compared with 20 young (YS) and 20 middle-aged sedentary (MS) adults. Beat-to-beat cerebral blood flow velocity, blood pressure (BP), and heart rate were measured at rest and during forced BP oscillations induced by repeated sit-stand maneuvers at 0.05 Hz. Transfer function analysis was used to calculate dCA and BRS parameters. Carotid distensibility was measured by ultrasonography. MA had the highest peak oxygen uptake (V̇o2peak) among all groups. During forced BP oscillations, MS showed lower BRS gain than YS, but this age-related reduction was absent in MA. Conversely, dCA was similar among all groups. At rest, BRS and dCA gains at low frequency (∼0.1 Hz) were higher in the MA than in MS and YS groups. Carotid distensibility was similar between MA and YS groups, but it was lower in the MS. Across all subjects, V̇o2peak was positively associated with BRS gains at rest and during forced BP oscillations (r = 0.257∼0.382, P = 0.003∼0.050) and carotid distensibility (r = 0.428∼0.490, P = 0.001). Furthermore, dCA gain at rest and carotid distensibility were positively correlated with BRS gain at rest in YS and MA groups (all P < 0.05). These findings suggest that midlife aerobic exercise improves central arterial elasticity and BRS, which may contribute to cerebral blood flow (CBF) regulation through dCA.NEW & NOTEWORTHY Middle-aged athletes (MA) showed intact dynamic cerebral autoregulation (dCA) during sit-stand maneuvers when compared with young (YS) and middle-aged sedentary (MS) adults. Conversely, MA showed the significant attenuation of age-related carotid distensibility and baroreflex sensitivity (BRS) impairments. In MA and YS groups, BRS was positively associated with dCA gain at rest and carotid distensibility. Our findings suggest that midlife aerobic exercise improves BRS by reducing central arterial stiffness, which contributes to CBF regulation through dCA.
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Affiliation(s)
- Tsubasa Tomoto
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
- Department of Neurology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Justin Repshas
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
| | - Rong Zhang
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
- Department of Neurology, University of Texas Southwestern Medical Center, Dallas, Texas
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Takashi Tarumi
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
- Department of Neurology, University of Texas Southwestern Medical Center, Dallas, Texas
- Human Informatics and Interaction Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
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Shibata S, Hirabuki K, Hata N, Suzuki R, Suda T, Uechi T, Hirasawa A. Pivotal Role of Heart for Orthostasis: Left Ventricular Untwisting Mechanics and Physical Fitness. Exerc Sport Sci Rev 2021; 49:88-98. [PMID: 33720910 DOI: 10.1249/jes.0000000000000247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Augmentation of left ventricular (LV) untwisting due to central hypovolemia is likely to be a compensatory mechanism for maintaining stroke volume, which is reduced by a decrease in cardiac filling during orthostatic stress. Orthostatic intolerance observed in both high and low fitness levels may be explained by the impaired response of LV untwisting due to central hypovolemia.
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Affiliation(s)
| | | | | | - Rina Suzuki
- Emergency Department, Kyorin University Hospital
| | - Tomoya Suda
- Emergency Department, Kyorin University Hospital
| | | | - Ai Hirasawa
- Department of Health and Welfare, Faculty of Health Sciences, Kyorin University, Tokyo, Japan
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Acute hypotension attenuates brachial flow-mediated dilation in young healthy men. Eur J Appl Physiol 2019; 120:161-169. [PMID: 31701274 DOI: 10.1007/s00421-019-04260-0] [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: 07/19/2019] [Accepted: 11/01/2019] [Indexed: 12/11/2022]
Abstract
PURPOSE This study aimed to test our hypothesis that acute hypotension attenuates brachial flow-mediated dilation (FMD) as an index of endothelial function in healthy humans. METHODS Twelve healthy men (21.8 ± 1.6 years, body mass index; 22.2 ± 1.6 kg/m2) participated in this study. Brachial FMD was measured in three trials: standardized FMD protocol (control trial), abrupt decrease in blood pressure (BP) via thigh cuff inflation-deflation (hypotension trial) and decrease in shear rate (SR) via a shortened forearm occlusion time (SR reduction trial). Brachial diameter and blood velocity were measured using Duplex ultrasound. RESULTS Mean arterial pressure during reactive hyperaemia showed a marked decrease in the hypotension trial (- 23.7 ± 6.0 mmHg), but not in the control and SR reduction trials. SR area under the curve was attenuated in the SR reduction trial (P < 0.001), but not in the control and hypotension trials (P = 0.316). Consequently, FMD was attenuated in the hypotension and SR reduction trials compared with that in the control trial (P = 0.003 and P = 0.043, respectively), and was attenuated to a greater extent in the hypotension trial compared with the SR reduction trial (P = 0.006; control, 6.9 ± 3.5%; hypotension, 3.5 ± 1.7%; SR reduction, 5.0 ± 2.2%). After adjusting FMD using SR, FMD remained attenuated in the hypotension trial (P = 0.014), but not in the SR reduction trial. CONCLUSION Our findings indicate that arterial pressure as well as sympathetic nervous system activation could be an important determinant of FMD. Blunted FMD of peripheral arteries may be a rational response to restore BP and/or prevent further reduction of BP following acute hypotension in healthy humans.
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Ogoh S, Tarumi T. Cerebral blood flow regulation and cognitive function: a role of arterial baroreflex function. J Physiol Sci 2019; 69:813-823. [PMID: 31444691 PMCID: PMC10717347 DOI: 10.1007/s12576-019-00704-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Accepted: 08/13/2019] [Indexed: 10/26/2022]
Abstract
A strict adequate perfusion pressure via arterial baroreflex for the delivery of oxygen to the tissues of the body is well established; however, the importance of baroreflex for cerebral blood flow (CBF) is unclear. On the other hand, there is convincing evidence for arterial baroreflex function playing an important role in maintaining brain homeostasis, e.g., cerebral metabolism, cerebral hemodynamics, and cognitive function. For example, mild cognitive impairment attenuates the sensitivity of baroreflex, and Alzheimer's disease further decreases it. These clinical findings suggest that CBF and cerebral function are affected by systemic blood pressure regulation via the arterial baroreflex. However, dysfunction of arterial baroreflex is likely to affect CBF regulation as well as the underlying neuronal function, but identifying how this is achieved is arduous since neurological diseases affect systemic as well as cerebral circulation independently. Recent insights into the influence of blood pressure regulation via the arterial baroreflex on cerebral function and blood flow regulation may help elucidate this important question. This review summarizes some update findings regarding direct (autonomic regulation) and indirect (systemic blood pressure regulation) contributions of the arterial baroreflex to the maintenance of cerebral vasculature regulation.
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Affiliation(s)
- Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, 2100 Kujirai, Kawagoe, Saitama, 350-8585, Japan.
| | - Takashi Tarumi
- Human Informatics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
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Gibbons TD, Zuj KA, Prince CN, Kingston DC, Peterson SD, Hughson RL. Haemodynamic and cerebrovascular effects of intermittent lower-leg compression as countermeasure to orthostatic stress. Exp Physiol 2019; 104:1790-1800. [PMID: 31578774 DOI: 10.1113/ep088077] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Accepted: 09/30/2019] [Indexed: 02/04/2023]
Abstract
NEW FINDINGS What is the central question of this study? Does smartly timed intermittent compression of the lower legs alter cerebral blood velocity and oxygenation during acute orthostatic challenges? What is the main finding and its importance? Intermittent compression timed to the local diastolic phase increased the blood flux through the legs and heart after two different orthostatic stress tests. Cerebral blood velocity improved during the first minute of recovery, and indices of cerebral tissue oxygenation remained elevated for 2 min. These results provide promise for the use of lower-leg active compression as a therapeutic tool for individuals vulnerable to initial orthostatic hypotension and orthostatic stress. ABSTRACT Intermittent compression of the lower legs provides the possibility of improving orthostatic tolerance by actively promoting venous return and improving central haemodynamics. We tested the hypothesis that intermittent compression of 65 mmHg timed to occur only within the local diastolic phase of each cardiac cycle would attenuate the decrease in blood pressure and improve cerebral haemodynamics during the first minute of recovery from two different orthostatic stress tests. Fourteen subjects (seven female) performed four squat-to-stand transitions and four repeats of standing bilateral thigh-cuff occlusion and release (TCR), with intermittent compression of the lower legs applied in half of the trials. Blood flow in the superficial femoral artery, mean arterial pressure, Doppler ultrasound cardiac output, total peripheral resistance, middle cerebral artery blood velocity (MCAv) and cerebral tissue saturation index (TSI%) were monitored. With both orthostatic stress tests, there was a significant compression × time interaction for superficial femoral artery flow (P < 0.001). The hypotensive state was attenuated with intermittent compression despite decreased total peripheral resistance (squat-to-stand, compression × time interaction, P < 0.001; TCR, compression × time interaction, P = 0.002) as a consequence of elevated cardiac output in both tests (P < 0.001). Intermittent compression also increased MCAv (P = 0.001) and TSI% (P < 0.001) during the squat-to-stand transition and during TCR (MCAv and TSI%, compression × time interaction, P < 0.001). Intermittent compression of the lower legs during quiet standing after an active orthostatic challenge augmented local, central and cerebral haemodynamics, providing potential as a therapeutic tool for individuals vulnerable to orthostatic stress.
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Affiliation(s)
- Travis D Gibbons
- Faculty of Applied Health Sciences, University of Waterloo, Waterloo, ON, Canada
| | - Kathryn A Zuj
- Faculty of Applied Health Sciences, University of Waterloo, Waterloo, ON, Canada
| | - Chekema N Prince
- Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, Canada
| | - David C Kingston
- Faculty of Applied Health Sciences, University of Waterloo, Waterloo, ON, Canada
| | - Sean D Peterson
- Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, Canada
| | - Richard L Hughson
- Schlegel-University of Waterloo Research Institute for Aging, Faculty of Applied Health Sciences, Waterloo, ON, Canada
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Gibbons TD, Zuj KA, Peterson SD, Hughson RL. Comparison of pulse contour, aortic Doppler ultrasound and bioelectrical impedance estimates of stroke volume during rapid changes in blood pressure. Exp Physiol 2019; 104:368-378. [PMID: 30582758 DOI: 10.1113/ep087240] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Accepted: 12/18/2018] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Pulse contour analysis of the finger arterial pressure by Windkessel modelling is commonly used to estimate stroke volume continuously. But is it valid during dynamic changes in blood pressure? What is the main finding and its importance? Second-by-second analysis revealed that pulse contour analysis underestimated stroke volume by up to 25% after standing from a squat, and 16% after standing thigh-cuff release, when compared with aortic Doppler ultrasound estimates. These results reveal that pulse contour analysis of stroke volume should be interpreted with caution during rapid changes in physiological state. ABSTRACT Dynamic measurements of stroke volume (SV) and cardiac output provide an index of central haemodynamics during transitional states, such as postural changes and onset of exercise. The most widely used method to assess dynamic fluctuations in SV is the Modelflow method, which uses the arterial blood pressure waveform along with age- and sex-specific aortic properties to compute beat-to-beat estimates of aortic flow. Modelflow has been validated against more direct methods in steady-state conditions, but not during dynamic changes in physiological state, such as active orthostatic stress testing. In the present study, we compared the dynamic SV responses from Modelflow (SVMF ), aortic Doppler ultrasound (SVU/S ) and bioelectrical impedance analysis (SVBIA ) during two different orthostatic stress tests, a squat-to-stand (S-S) transition and a standing bilateral thigh-cuff release (TCR), in 15 adults (six females). Second-by-second analysis revealed that when compared with estimates of SV by aortic Doppler ultrasound, Modelflow underestimated SV by up to 25% from 3 to 11 s after standing from the squat position and by up to 16% from 3 to 7 s after TCR (P < 0.05). The SVMF and SVBIA were similar during the first minute of the S-S transition, but were different 3 s after TCR and at intermittent time points between 34 and 44 s (P < 0.05). These findings indicate that the physiological conditions elicited by orthostatic stress testing violate some of the inherent assumptions of Modelflow and challenge models used to interpret bioelectrical impedance responses, resulting in an underestimation in SV during rapid changes in physiological state.
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Affiliation(s)
- Travis D Gibbons
- Faculty of Applied Health Sciences, University of Waterloo, Waterloo, ON, Canada
| | - Kathryn A Zuj
- Faculty of Applied Health Sciences, University of Waterloo, Waterloo, ON, Canada
| | - Sean D Peterson
- Department of Mechanical and Mechatronic Engineering, University of Waterloo, Waterloo, ON, Canada
| | - Richard L Hughson
- Faculty of Applied Health Sciences, University of Waterloo, Waterloo, ON, Canada.,Schlegel-University of Waterloo Research Institute for Aging, Waterloo, ON, Canada
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Mueller PJ, Clifford PS, Crandall CG, Smith SA, Fadel PJ. Integration of Central and Peripheral Regulation of the Circulation during Exercise: Acute and Chronic Adaptations. Compr Physiol 2017; 8:103-151. [DOI: 10.1002/cphy.c160040] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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9
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What is important for aging-induced arterial stiffening, autonomic dysfunction, vascular characteristics or both? Hypertens Res 2017; 40:434-435. [DOI: 10.1038/hr.2017.8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Gkaliagkousi E, Gavriilaki E, Douma S. Effects of acute and chronic exercise in patients with essential hypertension: benefits and risks. Am J Hypertens 2015; 28:429-39. [PMID: 25362114 DOI: 10.1093/ajh/hpu203] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The importance of regular physical activity in essential hypertension has been extensively investigated over the last decades and has emerged as a major modifiable factor contributing to optimal blood pressure control. Aerobic exercise exerts its beneficial effects on the cardiovascular system by promoting traditional cardiovascular risk factor regulation, as well as by favorably regulating sympathetic nervous system (SNS) activity, molecular effects, cardiac, and vascular function. Benefits of resistance exercise need further validation. On the other hand, acute exercise is now an established trigger of acute cardiac events. A number of possible pathophysiological links have been proposed, including SNS, vascular function, coagulation, fibrinolysis, and platelet function. In order to fully interpret this knowledge into clinical practice, we need to better understand the role of exercise intensity and duration in this pathophysiological cascade and in special populations. Further studies in hypertensive patients are also warranted in order to clarify the possibly favorable effect of antihypertensive treatment on exercise-induced effects.
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Affiliation(s)
- Eugenia Gkaliagkousi
- 2nd Propedeutic Department of Internal Medicine, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Eleni Gavriilaki
- 3rd Department of Internal Medicine, Papageorgiou Hospital, Aristotle University of Thessaloniki, Thessaloniki, Greece.
| | - Stella Douma
- 3rd Department of Internal Medicine, Papageorgiou Hospital, Aristotle University of Thessaloniki, Thessaloniki, Greece
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Hobika G, Porhomayon J, Kocz R, Matson B, Paladino M. Prolonged Hypotension Following Innominate and Left Common Carotid Artery Bypass. J Cardiothorac Vasc Anesth 2015; 30:154-7. [PMID: 25813224 DOI: 10.1053/j.jvca.2014.12.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Indexed: 11/11/2022]
Affiliation(s)
- Geoffrey Hobika
- Department of Anesthesiology, VA Western New York Healthcare System, State University of New York at Buffalo School of Medicine and Biomedical Sciences, Buffalo, NY
| | - Jahan Porhomayon
- Department of Anesthesiology, VA Western New York Healthcare System, State University of New York at Buffalo School of Medicine and Biomedical Sciences, Buffalo, NY.
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Peçanha T, Vianna JM, Sousa ÉDD, Panza PS, Lima JRPD, Reis VM. Influência do grupamento muscular na recuperação da frequência cardíaca após o exercício resistido. REV BRAS MED ESPORTE 2013. [DOI: 10.1590/s1517-86922013000400010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
INTRODUÇÃO: O exercício resistido (ER) é um tipo de exercício amplamente praticado, sendo recomendado para a manutenção ou aprimoramento da força e massa musculares e utilizado com fins estéticos e de saúde. Apesar disto, pouco se sabe sobre o impacto deste tipo de exercício sobre o controle autonômico cardíaco, tampouco da influência do grupamento muscular nesta resposta. OBJETIVO: Verificar a influência do grupamento muscular utilizado durante o ER, na recuperação da frequência cardíaca (REC-FC) pós-exercício. MÉTODOS: Participaram deste estudo 14 indivíduos do sexo masculino (27,4 ± 6,1 anos; 79,4 ± 10,4 kg; 1,77 ± 0,1 m; 10,5 ± 4,6 %G) experientes na prática de ER. O protocolo experimental constou da realização de teste e reteste de 1RM nos exercícios supino horizontal e meio agachamento para determinação da força dinâmica máxima e execução do número máximo de repetições a 80% de 1RM com avaliação da REC-FC durante um minuto pós-exercício. RESULTADOS: Os resultados encontrados indicam menor REC-FC nos 10, 20, 30 e 40 segundos após o exercício meio agachamento em comparação ao supino horizontal. CONCLUSÃO: Os achados confirmam a influência do grupamento muscular na resposta autonômica cardíaca pós-esforço, no ER.
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Ichikawa D, Miyazawa T, Horiuchi M, Kitama T, Fisher JP, Ogoh S. Relationship between aerobic endurance training and dynamic cerebral blood flow regulation in humans. Scand J Med Sci Sports 2013; 23:e320-9. [DOI: 10.1111/sms.12082] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/04/2013] [Indexed: 11/28/2022]
Affiliation(s)
| | - T. Miyazawa
- Research Institute of Industrial Technology; Toyo University; Kawagoe-Shi; Saitama; Japan
| | - M. Horiuchi
- Research Institute of Industrial Technology; Toyo University; Kawagoe-Shi; Saitama; Japan
| | | | - J. P. Fisher
- School of Sport and Exercise Sciences; University of Birmingham; Birmingham; UK
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14
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Miki K, Yoshimoto M. Reprint of "Sympathetic nerve activity during sleep, exercise, and mental stress". Auton Neurosci 2013; 175:70-5. [DOI: 10.1016/j.autneu.2013.04.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Revised: 12/18/2012] [Accepted: 12/26/2012] [Indexed: 10/27/2022]
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15
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Sympathetic nerve activity during sleep, exercise, and mental stress. Auton Neurosci 2013; 174:15-20. [DOI: 10.1016/j.autneu.2012.12.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Revised: 12/18/2012] [Accepted: 12/26/2012] [Indexed: 11/18/2022]
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16
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Mueller PJ, Mischel NA. Selective enhancement of glutamate-mediated pressor responses after GABA(A) receptor blockade in the RVLM of sedentary versus spontaneous wheel running rats. Front Physiol 2012; 3:447. [PMID: 23189062 PMCID: PMC3505845 DOI: 10.3389/fphys.2012.00447] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Accepted: 11/07/2012] [Indexed: 11/26/2022] Open
Abstract
Overactivity of the sympathetic nervous system (SNS) is a hallmark of many cardiovascular diseases. It is also well-known that physical inactivity independently contributes to cardiovascular diseases, likely in part via increased SNS activity. Recent work from our laboratory has demonstrated increased SNS responses in sedentary animals following either direct activation or disinhibition of the rostral ventrolateral medulla (RVLM), an integral cardiovascular brainstem region. These data led us to hypothesize that the interaction between excitation and inhibition of the RVLM is altered in sedentary versus physically active animals. To test this hypothesis, we recorded mean arterial pressure (MAP) and lumbar sympathetic nerve activity (LSNA) in Inactin anesthetized rats that were housed for 8-12 weeks with or without access to a running wheel. Pressor responses to direct activation of the RVLM with glutamate were similar between groups under intact conditions. However, blockade of γ-aminobutyric acid (GABA)(A) receptors with bicuculline selectively enhanced pressor responses to glutamate in sedentary animals. Interestingly, LSNA responses to glutamate were not enhanced in sedentary versus active animals in the presence or absence of tonic GABAergic tone. These results suggest that sedentary compared to active conditions enhance GABAergic inhibition of glutamate-sensitive neurons in the RVLM that are involved in blood pressure regulation, and by mechanisms that do not involve LSNA. We also speculate that regular physical activity has differential effects on SNS activity to specific vascular beds and may reduce the risk of developing cardiovascular diseases via changes occurring in the RVLM.
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Affiliation(s)
- Patrick J. Mueller
- Department of Physiology, Wayne State University School of MedicineDetroit, MI, USA
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Stern JE, Sonner PM, Son SJ, Silva FCP, Jackson K, Michelini LC. Exercise training normalizes an increased neuronal excitability of NTS-projecting neurons of the hypothalamic paraventricular nucleus in hypertensive rats. J Neurophysiol 2012; 107:2912-21. [PMID: 22357793 DOI: 10.1152/jn.00884.2011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Elevated sympathetic outflow and altered autonomic reflexes, including impaired baroreflex function, are common findings observed in hypertensive disorders. Although a growing body of evidence supports a contribution of preautonomic neurons in the hypothalamic paraventricular nucleus (PVN) to altered autonomic control during hypertension, the precise underlying mechanisms remain unknown. Here, we aimed to determine whether the intrinsic excitability and repetitive firing properties of preautonomic PVN neurons that innervate the nucleus tractus solitarii (PVN-NTS neurons) were altered in spontaneously hypertensive rats (SHR). Moreover, given that exercise training is known to improve and/or correct autonomic deficits in hypertensive conditions, we evaluated whether exercise is an efficient behavioral approach to correct altered neuronal excitability in hypertensive rats. Patch-clamp recordings were obtained from retrogradely labeled PVN-NTS neurons in hypothalamic slices obtained from sedentary (S) and trained (T) Wistar-Kyoto (WKY) and SHR rats. Our results indicate an increased excitability of PVN-NTS neurons in SHR-S rats, reflected by an enhanced input-output function in response to depolarizing stimuli, a hyperpolarizing shift in Na(+) spike threshold, and smaller hyperpolarizing afterpotentials. Importantly, we found exercise training in SHR rats to restore all these parameters back to those levels observed in WKY-S rats. In several cases, exercise evoked opposing effects in WKY-S rats compared with SHR-S rats, suggesting that exercise effects on PVN-NTS neurons are state dependent. Taken together, our results suggest that elevated preautonomic PVN-NTS neuronal excitability may contribute to altered autonomic control in SHR rats and that exercise training efficiently corrects these abnormalities.
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Affiliation(s)
- Javier E Stern
- Dept. of Physiology, Georgia Health Sciences Univ., Augusta, GA 30912, USA.
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Sugawara J, Willie CK, Miyazawa T, Komine H, Ainsle PN, Ogoh S. Effects of transient change in carotid arterial stiffness on arterial baroreflex during mild orthostatic stimulation. Artery Res 2012. [DOI: 10.1016/j.artres.2012.05.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Miyazawa T, Horiuchi M, Ichikawa D, Sato K, Tanaka N, Bailey DM, Ogoh S. Kinetics of exercise-induced neural activation; interpretive dilemma of altered cerebral perfusion. Exp Physiol 2011; 97:219-27. [PMID: 22041980 DOI: 10.1113/expphysiol.2011.061978] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Neural activation decreases cerebral deoxyhaemoglobin (HHb(C)) and increases oxyhaemoglobin concentration (O(2)Hb(C)). In contrast, patients who present with restricted cerebral blood flow, such as those suffering from cerebral ischaemia or Alzheimer's disease, and during the course of ageing the converse occurs, in that HHb(C) increases and O(2)Hb(C) decreases during neural activation. In the present study, we examined the interpretive implications of altered exercise-induced cerebral blood flow for cortical oxygenation in healthy subjects. Both O(2)Hb(C) and HHb(C) (prefrontal cortex) were determined in 11 healthy men using near-infrared spectroscopy (NIRS). Middle cerebral artery mean blood velocity (MCA V(mean)) was determined via transcranial Doppler ultrasonography. Measurements were performed during contralateral hand-grip exercise during suprasystolic bilateral thigh-cuff occlusion (Cuff+) and within 2 s of cuff release (Cuff-) for the acute manipulation of cerebral perfusion. During Cuff+, both MCA V(mean) and O(2)Hb(C) increased during exercise, whereas HHb(C) decreased. In contrast, the opposite occurred during the Cuff- manipulation. These findings highlight the inverse relationship between cerebral blood flow and cerebral oxygenation as determined by NIRS, which has interpretive implications for the kinetics underlying exercise-induced neural activation.
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Affiliation(s)
- Taiki Miyazawa
- Department of Biomedical Engineering, Toyo University, 2100 Kujirai, Kawagoe-shi, Saitama 350-8585, Japan
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Kim A, Deo SH, Vianna LC, Balanos GM, Hartwich D, Fisher JP, Fadel PJ. Sex differences in carotid baroreflex control of arterial blood pressure in humans: relative contribution of cardiac output and total vascular conductance. Am J Physiol Heart Circ Physiol 2011; 301:H2454-65. [PMID: 21963834 DOI: 10.1152/ajpheart.00772.2011] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It is presently unknown whether there are sex differences in the magnitude of blood pressure (BP) responses to baroreceptor perturbation or if the relative contribution of cardiac output (CO) and total vascular conductance (TVC) to baroreflex-mediated changes in BP differs in young women and men. Since sympathetic vasoconstrictor tone is attenuated in women, we hypothesized that carotid baroreflex-mediated BP responses would be attenuated in women by virtue of a blunted vascular response (i.e., an attenuated TVC response). BP, heart rate (HR), and stroke volume were continuously recorded during the application of 5-s pulses of neck pressure (NP; carotid hypotension) and neck suction (NS; carotid hypertension) ranging from +40 to -80 Torr in women (n = 20, 21 ± 0.5 yr) and men (n = 20, 21 ± 0.4 yr). CO and TVC were calculated on a beat-to-beat basis. Women demonstrated greater depressor responses to NS (e.g., -60 Torr, -17 ± 1%baseline in women vs. -11 ± 1%baseline in men, P < 0.05), which were driven by augmented decreases in HR that, in turn, contributed to larger reductions in CO (-60 Torr, -15 ± 2%baseline in women vs. -6 ± 2%baseline in men, P < 0.05). In contrast, pressor responses to NP were similar in women and men (e.g., +40 Torr, +14 ± 2%baseline in women vs. +10 ± 1%baseline in men, P > 0.05), with TVC being the primary mediating factor in both groups. Our findings indicate that sex differences in the baroreflex control of BP are evident during carotid hypertension but not carotid hypotension. Furthermore, in contrast to our hypothesis, young women exhibited greater BP responses to carotid hypertension by virtue of a greater cardiac responsiveness.
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Affiliation(s)
- Areum Kim
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, 65212, USA
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21
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Lind-Holst M, Cotter JD, Helge JW, Boushel R, Augustesen H, Van Lieshout JJ, Pott FC. Cerebral autoregulation dynamics in endurance-trained individuals. J Appl Physiol (1985) 2011; 110:1327-33. [DOI: 10.1152/japplphysiol.01497.2010] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Aerobic fitness may be associated with reduced orthostatic tolerance. To investigate whether trained individuals have less effective regulation of cerebral vascular resistance, we studied the middle cerebral artery (MCA) mean blood velocity ( Vmean) response to a sudden drop in mean arterial pressure (MAP) after 2.5 min of leg ischemia in endurance athletes and untrained subjects (maximal O2 uptake: 69 ± 7 vs. 42 ± 5 ml O2·min−1·kg−1; n = 9 for both, means ± SE). After cuff release when seated, endurance athletes had larger drops in MAP (94 ± 6 to 62 ± 5 mmHg, −39%, vs. 99 ± 5 to 73 ± 4 mmHg, −26%) and MCA Vmean (53 ± 3 to 37 ± 2 cm/s, −30%, vs. 58 ± 3 to 43 ± 2 cm/s, −25%). The athletes also had a slower recovery to baseline of both MAP (25 ± 2 vs. 16 ± 1 s, P < 0.01) and MCA Vmean (15 ± 1 vs. 11 ± 1 s, P < 0.05). The onset of autoregulation, determined by the time point of increase in the cerebrovascular conductance index (CVCi = MCA Vmean/MAP) appeared later in the athletes (3.9 ± 0.4 vs. 2.7 ± 0.4s, P = 0.01). Spectral analysis revealed a normal MAP-to-MCA Vmean phase in both groups but ∼40% higher normalized MAP to MCA Vmean low-frequency transfer function gain in the trained subjects. No significant differences were detected in the rates of recovery of MAP and MCA Vmean and the rate of CVCi regulation (18 ± 4 vs. 24 ± 7%/s, P = 0.2). In highly trained endurance athletes, a drop in blood pressure after the release of resting leg ischemia was more pronounced than in untrained subjects and was associated with parallel changes in indexes of cerebral blood flow. Once initiated, the autoregulatory response was similar between the groups. A delayed onset of autoregulation with a larger normalized transfer gain conforms with a less effective dampening of MAP oscillations, indicating that athletes may be more prone to instances of symptomatic cerebral hypoperfusion when MAP declines.
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Affiliation(s)
- Mikkel Lind-Holst
- Bispebjerg Hospital Research Unit for Anaesthesia and Intensive Care, University of Copenhagen, Copenhagen, Denmark
| | - James D. Cotter
- School of Physical Education, University of Otago, Dunedin, New Zealand
| | - Jørn W. Helge
- Copenhagen Muscle Research Centre, Department of Biomedical Science, Faculty of Health Science, University of Copenhagen, Copenhagen, Denmark
| | - Robert Boushel
- Copenhagen Muscle Research Centre, Department of Biomedical Science, Faculty of Health Science, University of Copenhagen, Copenhagen, Denmark
| | - Helene Augustesen
- Bispebjerg Hospital Research Unit for Anaesthesia and Intensive Care, University of Copenhagen, Copenhagen, Denmark
| | - Johannes J. Van Lieshout
- Special Medical Care, Department of Internal Medicine, and
- Laboratory for Clinical Cardiovascular Physiology, AMC Center for Heart Failure, University of Amsterdam, Amsterdam, The Netherlands
| | - Frank C. Pott
- Bispebjerg Hospital Research Unit for Anaesthesia and Intensive Care, University of Copenhagen, Copenhagen, Denmark
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Willie CK, Colino FL, Bailey DM, Tzeng YC, Binsted G, Jones LW, Haykowsky MJ, Bellapart J, Ogoh S, Smith KJ, Smirl JD, Day TA, Lucas SJ, Eller LK, Ainslie PN. Utility of transcranial Doppler ultrasound for the integrative assessment of cerebrovascular function. J Neurosci Methods 2011; 196:221-37. [PMID: 21276818 DOI: 10.1016/j.jneumeth.2011.01.011] [Citation(s) in RCA: 397] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2010] [Revised: 01/05/2011] [Accepted: 01/06/2011] [Indexed: 01/05/2023]
Abstract
There is considerable utility in the use of transcranial Doppler ultrasound (TCD) to assess cerebrovascular function. The brain is unique in its high energy and oxygen demand but limited capacity for energy storage that necessitates an effective means of regional blood delivery. The relative low cost, ease-of-use, non-invasiveness, and excellent temporal resolution of TCD make it an ideal tool for the examination of cerebrovascular function in both research and clinical settings. TCD is an efficient tool to access blood velocities within the cerebral vessels, cerebral autoregulation, cerebrovascular reactivity to CO(2), and neurovascular coupling, in both physiological states and in pathological conditions such as stroke and head trauma. In this review, we provide: (1) an overview of TCD methodology with respect to other techniques; (2) a methodological synopsis of the cerebrovascular exam using TCD; (3) an overview of the physiological mechanisms involved in regulation of the cerebral blood flow; (4) the utility of TCD for assessment of cerebrovascular pathology; and (5) recommendations for the assessment of four critical and complimentary aspects of cerebrovascular function: intra-cranial blood flow velocity, cerebral autoregulation, cerebral reactivity, and neurovascular coupling. The integration of these regulatory mechanisms from an integrated systems perspective is discussed, and future research directions are explored.
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Affiliation(s)
- C K Willie
- Department of Human Kinetics, Faculty of Health and Social Development, University of British Columbia Okanagan, 3333 University Way, Kelowna, BC, Canada V1V 1V7.
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Ogoh S, Tzeng YC, Lucas SJE, Galvin SD, Ainslie PN. Influence of baroreflex-mediated tachycardia on the regulation of dynamic cerebral perfusion during acute hypotension in humans. J Physiol 2009; 588:365-71. [PMID: 19933752 DOI: 10.1113/jphysiol.2009.180844] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The effect of acute arterial baroreflex dysfunction on cerebral autoregulation (CA) in otherwise healthy humans is unknown. We identified dynamic CA with and without arterial baroreflex-mediated tachycardia and consequent changes in cardiac output during acute hypotension whilst continuously monitoring changes in middle cerebral artery mean blood velocity (MCA V(mean)). Acute hypotension was induced in nine healthy subjects (mean +/- s.d.; 26 +/- 3 years) by releasing bilateral thigh cuffs after 6 min of supra-systolic resting ischaemia. Hypotension was induced before and after sympathetic blockade (beta-1 receptors), and combined sympathetic-cholinergic blockade. That sequential bolus injections of sodium nitroprusside (50 microg), followed 60 s later by phenylephrine hydrochloride (50 microg), elicited < 5 beats min(-1) change in heart rate was verified to confirm that full cardiac autonomic blockade was achieved. Thigh cuff release elicited a transient drop in mean arterial pressure and resultant tachycardia. This tachycardic response was diminished in full cardiac blockade (vs. control, P = 0.029; vs. beta-1 adrenergic blockade, P = 0.031). Dynamic CA was also attenuated in the full blockade condition compared to both control (P = 0.028) and beta-1 adrenergic blockade conditions (P = 0.015), and was related with the attenuated tachycardia response (P = 0.015). These data indicate an important role of the cardiac baroreflex in dynamic CA.
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Affiliation(s)
- Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, Kawagoe-shi, Saitama, Japan.
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Sympatho-vagal responses in patients with sleep and typical vasovagal syncope. Clin Sci (Lond) 2009; 117:345-53. [PMID: 19281451 DOI: 10.1042/cs20080497] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Sleep syncope is a recently described form of vasovagal syncope that interrupts sleep. The pathophysiology of this condition is uncertain but a ‘central’ non-baroreflex-mediated trigger has been suggested. In the present study, we tested the hypothesis that patients with sleep syncope have abnormal sympatho-vagal responses to non-baroreflex, but normal responses to baroreflex stimuli. We collected historical data from SS patients (patients with vasovagal syncope with sleep syncope; n=16) and NSS patients (patients with vasovagal syncope without sleep syncope; n=35), including demography, and triggers and symptoms during syncope. MBP (mean blood pressure), HR (heart rate) and MSNA (muscle sympathetic nerve activity) in SS patients were compared with NSS patients and matched controls (n=16) during HG (handgrip), CPTs (cold pressor tests), HUT (head-up tilting) and tilt-induced pre-syncope. Patients and controls were of similar age and gender distribution [SS patients, age 46.0±4 years (69% female); NSS patients, 47.3±4 years (63% female); controls, 43.7±5 years (69% female)]. Compared with NSS patients, SS patients reported more fainting episodes: (i) triggered by phobias (75 compared with 37%; P=0.001); (ii) while in the horizontal position (44 compared with 6%; P=0.001); and (iii) associated with abdominal symptoms (69 compared with 9%; P=0.001). Compared with controls, the MBP response to HG was attenuated in SS patients (P=0.016), and MSNA (burst frequency and incidence) responses to CPT were attenuated in both syncope groups (SS, P=0.011 and 0.003 respectively; NSS, P=0.021 and 0.049 respectively). MSNA responses to HUT did not differ. For both non-baroreflex and baroreflex responses, there were no differences in any of the MSNA indices between the syncope groups. Patients with vasovagal syncope, with or without sleep syncope, have very similar sympatho-vagal responses to both non-baroreflex and baroreflex stimuli. This is consistent with sleep syncope being a subform of vasovagal syncope. Attenuation of sympathetic responses to non-baroreflex pathways may be important in the mechanism of vasovagal syncope.
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Ogoh S, Brothers RM, Eubank WL, Raven PB. Autonomic neural control of the cerebral vasculature: acute hypotension. Stroke 2008; 39:1979-87. [PMID: 18451346 DOI: 10.1161/strokeaha.107.510008] [Citation(s) in RCA: 140] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE The effect of antihypertensive drugs on autonomic neural control of the cerebral circulation remains unclear. This study was designed to compare middle cerebral artery mean blood velocity responses to acute hypotension with and without alpha(1)-adrenoreceptor blockade (Prazosin) in young, healthy humans. METHODS Acute hypotension was induced nonpharmacologically in 6 healthy subjects (mean+/-SE; 28+/-2 years) by releasing bilateral thigh cuffs after 9 minutes of suprasystolic resting ischemia before and after an oral dose of Prazosin (1 mg/20 kg body weight). RESULTS Prazosin had no effect on thigh cuff release-induced reductions in mean arterial pressure and middle cerebral artery mean blood velocity. However, Prazosin attenuated the amount of peripheral vasoconstriction through the arterial baroreflex as evidenced by a slower return of mean arterial pressure to baseline (P=0.03). Immediately after cuff release, cerebral vascular conductance index increased through cerebral autoregulation and returned to resting values as a result of an increased perfusion pressure mediated through arterial baroreflex mechanisms. The rate of regulation, an index of cerebral autoregulation, was attenuated with Prazosin (control versus Prazosin; rate of regulation=0.204+/-0.020 versus 0.006+/-0.053/s, P=0.037). In addition, as mean arterial pressure was returning to resting values, the rate of change in cerebral vascular conductance index was decreased with Prazosin (0.005+/-0.006/s) compared with control (0.025+/-0.005/s; P=0.010). CONCLUSIONS These data suggest that during recovery from acute hypotension, decreases in cerebral vascular conductance index were mediated by increases in arterial blood pressure and sympathetically mediated cerebral vasoconstriction.
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Affiliation(s)
- Shigehiko Ogoh
- Department of Integrative Physiology, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107, USA.
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Mueller PJ. Exercise training and sympathetic nervous system activity: evidence for physical activity dependent neural plasticity. Clin Exp Pharmacol Physiol 2007; 34:377-84. [PMID: 17324153 DOI: 10.1111/j.1440-1681.2007.04590.x] [Citation(s) in RCA: 139] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
1. It has been generally accepted that regular physical activity is associated with beneficial effects on the cardiovascular system. In fact, the idea that exercise maintains cardiovascular health is evident by the direct links between a sedentary lifestyle and the risk of cardiovascular and other disease states. 2. Cardiovascular diseases, such as hypertension and heart failure, are often associated with sympathetic nervous system (SNS) overactivity. Conversely, exercise has been shown to reduce hypertension and decrease elevated SNS activity. In addition, there is evidence that exercise may reduce resting blood pressure and sympathetic outflow in normal individuals. 3. Although somewhat controversial in humans, evidence from animal studies also indicates that exercise training reduces baroreflex-mediated and other forms of sympathoexcitation in normal individuals. Collectively, these data are consistent with the hypothesis that physical activity may decrease, and physical inactivity may increase, the incidence of cardiovascular disease via alterations in SNS activity. Despite the important clinical implications of this possibility, the mechanisms by which exercise alters control of SNS activity remain to be fully elucidated. 4. Recent evidence suggests that central nervous system (CNS) plasticity occurs under a variety of conditions, including varying levels of physical activity. The purpose of the present brief review is to provide evidence that changes within the CNS contribute importantly to altered regulation of the SNS observed following exercise training. The primary hypothesis is that physical activity versus inactivity produces plasticity within neural networks that regulate SNS activity. This hypothesis is supported by published and preliminary data that suggest that exercise training may reduce sympathoexcitation by reducing activation of neurons within cardiovascular regions of the brain. These mechanisms are likely to be important in disease states of sympathetic overactivity and in normal healthy individuals whose risk of cardiovascular disease is reduced by leading an active versus sedentary lifestyle.
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Affiliation(s)
- Patrick J Mueller
- Dalton Cardiovascular Research Center and Department of Biomedical Sciences, University of Missouri-Columbia, Columbia, MO, USA.
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Pellinger TK, Halliwill JR. Effect of propranolol on sympathetically mediated leg vasoconstriction in humans. J Physiol 2007; 583:797-809. [PMID: 17627989 PMCID: PMC2277027 DOI: 10.1113/jphysiol.2007.137422] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Sympatho-excitatory manoeuvres are used to study vascular responsiveness in humans, but it is unclear if circulating adrenaline attenuates peripheral vasoconstriction during these manoeuvres. We hypothesized that vasoconstrictor responses to three manoeuvres (neck pressure, unilateral thigh-cuff release and isometric handgrip) would be greater after the administration of the beta-adrenergic blocker propranolol. Seven men and six women underwent these manoeuvres while beat-by-beat arterial pressure (finger photoplethysmography), femoral mean blood velocity (Doppler ultrasound) and femoral artery diameter (edge-detection software) were measured. Femoral vascular conductance was calculated as flow/pressure. Propranolol had no effect on baseline femoral vascular conductance (P > 0.05). As a result of neck pressure, femoral vascular conductance was reduced 23.9 +/- 3.5% before vs. 33.2 +/- 3.2% after infusion of propranolol (P = 0.033). After thigh-cuff release, femoral vascular conductance declined 50.2 +/- 5.8% before vs. 57.4 +/- 9.6% after propranolol infusion (P = 0.496). During handgrip, femoral vascular conductance was reduced 47.2 +/- 9.6% before vs. 55.2 +/- 9.2% after propranolol administration (P = 0.447). After handgrip, women had a greater rise in conductance than men (women: 153 +/- 16.2%; men: 36.4 +/- 10.6%; P < 0.001), which was blunted by 54.8% by propranolol (P < 0.001 vs. control), but unaffected by propranolol in men (P = 0.355 vs. control). The finding that beta-adrenergic receptor-mediated vasodilatation minimally affects vascular responses to these sympatho-excitatory manoeuvres reinforces their utility in the investigation of sympathetic vascular regulation in humans. Interestingly, post-handgrip hyperaemia is greater in women than men and is, in part, beta-adrenergic receptor mediated.
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Affiliation(s)
- Thomas K Pellinger
- Department of Human Physiology, University of Oregon, Eugene, OR 97403-1240, USA
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Mueller PJ. Exercise training attenuates increases in lumbar sympathetic nerve activity produced by stimulation of the rostral ventrolateral medulla. J Appl Physiol (1985) 2006; 102:803-13. [PMID: 17053106 DOI: 10.1152/japplphysiol.00498.2006] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Exercise training (ExTr) has been associated with blunted activation of the sympathetic nervous system in several animal models and in some human studies. Although these data are consistent with the hypothesis that ExTr reduces the incidence of cardiovascular diseases via reduced sympathoexcitation, the mechanisms are unknown. The rostral ventrolateral medulla (RVLM) is important in control of sympathetic nervous system activity in both physiological and pathophysiological states. The purpose of the present study was to test the hypothesis that ExTr results in reduced sympathoexcitation mediated at the level of the RVLM. Male Sprague-Dawley rats were treadmill trained or remained sedentary for 8-10 wk. RVLM microinjections were performed under Inactin anesthesia while mean arterial pressure, heart rate, and lumbar sympathetic nerve activity (LSNA) were recorded. Bilateral microinjections of the GABA(A) antagonist bicuculline (5 mM, 90 nl) into the RVLM increased LSNA in sedentary animals (169 +/- 33%), which was blunted in ExTr animals (100 +/- 22%, P < 0.05). Activation of the RVLM with unilateral microinjections of glutamate (10 mM, 30 nl) increased LSNA in sedentary animals (76 +/- 13%), which was also attenuated by training (26 +/- 2%, P < 0.05). Bilateral microinjections of the ionotropic glutamate receptor antagonist kynurenate (40 mM, 90 nl) produced small increases in mean arterial pressure and LSNA that were similar between groups. Results suggest that ExTr may reduce increases in LSNA due to reduced activation of the RVLM. Conversely, we speculate that the relatively enhanced activation of LSNA in sedentary animals may be related to the increased incidence of cardiovascular disease associated with a sedentary lifestyle.
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Affiliation(s)
- Patrick J Mueller
- Dalton Cardiovascular Research Center and Dept. of Biomedical Sciences, University of Missouri-Columbia, 65211-3300, USA.
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Diaz T, Taylor JA. Probing the arterial baroreflex: is there a ‘spontaneous’ baroreflex? Clin Auton Res 2006; 16:256-61. [PMID: 16732466 DOI: 10.1007/s10286-006-0352-5] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2006] [Accepted: 03/30/2006] [Indexed: 12/21/2022]
Abstract
The arterial baroreflex is important for beat-to-beat arterial pressure control and its sensitivity has predictive value for clinical outcomes in a myriad of cardiovascular conditions. Given this, researchers have sought approaches for baroreflex assessment that are not invasive and easily obtained. These techniques have exploited the beat-by-beat parallel changes in arterial pressure and heart period to produce estimates that have been termed 'spontaneous' baroreflex indices. The two most commonly used analyses--frequency domain or spectral analyses and sequence analysis have been evaluated in both animals and humans. The animal data suggests an important baroreflex role in linking spontaneous heart period and pressure variabilities, but do not resolve the extent to which these fluctuations reflect baroreflex gain. The human data suggest a high correlation between spontaneous indices and pharmacologically derived baroreflex gain, but also indicate a poor correspondence between them. This may be due to the fact that short-term fluctuations in RR interval are not intimately and always linked to those in pressure via the baroreflex and thus simple observation of arterial pressure and heart period alone may not reveal the extent of arterial baroreflex involvement. If baroreflex function is to be assessed with the fewest and safest assumptions, the input to the system should be driven externally to create large and apparent responses. Nonetheless, spontaneous baroreflex indices may have predictive power; although it remains unknown whether spontaneous indices provide predictive power beyond that provided by heart rate variability indices alone.
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Affiliation(s)
- Tulio Diaz
- Cardiovascular Research Laboratory, Harvard Medical School, Spaulding Rehabiliation Hospital, Boston, MA 02114, USA
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Guo H, Tierney N, Schaller F, Raven PB, Smith SA, Shi X. Cerebral autoregulation is preserved during orthostatic stress superimposed with systemic hypotension. J Appl Physiol (1985) 2006; 100:1785-92. [PMID: 16424075 DOI: 10.1152/japplphysiol.00690.2005] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We sought to determine whether cerebral autoregulation (CA) is compromised during orthostatic stress superimposed with systemic hypotension. Transient systemic hypotension was produced by deflation of thigh cuffs previously inflated to suprasystolic pressure, combined with or without lower body negative pressure (LBNP). Cardiac output (CO) decreased from a baseline of 5.0+/-0.5 l/min by -8.3+/-1.7, -19.2+/-2.0, and -30.6+/-3.4% during LBNP of -15, -30, and -50 Torr, respectively. Mean arterial pressure (MAP) was maintained during LBNP, despite decreases in systolic and pulse pressures. Middle cerebral arterial blood flow velocity (VMCA) decreased significantly from a baseline of 64+/-3 to 58+/-4 cm/s (-9.7+/-2.4%) at -50 Torr of LBNP. The reduction in VMCA was associated with a decrease in regional cerebral O2 saturation. However, the percent decrease in VMCA was markedly less than that of CO. This suggests that the magnitude of the change in VMCA (an index of cerebral blood flow) is less than would be predicted, given the decrease in CO. Transient systemic hypotension decreased MAP by -21+/-2, -24+/-2, -28+/-3, and -26+/-3% at rest and during LBNP of -15, -30, and -50 Torr, respectively. Likewise, this acute hypotension resulted in decreases in VMCA of -20+/-2, -21+/-2, -24+/-25, and -19+/-2% and regional cerebral O2 saturation of -5+/-1, -6+/-1, -6+/-1, and -7+/-2% at rest and during LBNP of -15, -30, and -50 Torr, respectively. Complete recovery of VMCA to baseline values following transient hypotension (ranging from 5 to 8 s) occurred significantly earlier compared with MAP (from 10 to 12 s). No subjects experienced syncope during acute hypotension. We conclude that CA is preserved during LBNP, superimposed with transient systemic hypotension, despite the decrease in VMCA associated with sustained central hypovolemia in normal healthy individuals. This preserved CA is vital for the prevention of orthostatic syncope.
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Affiliation(s)
- Hong Guo
- Department of Integrative Physiology, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107, USA
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Mueller PJ, Hasser EM. Putative role of the NTS in alterations in neural control of the circulation following exercise training in rats. Am J Physiol Regul Integr Comp Physiol 2005; 290:R383-92. [PMID: 16179489 DOI: 10.1152/ajpregu.00455.2005] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Exercise training (ExTr) has been associated with alterations in neural control of the circulation, including effects on arterial baroreflex function. The nucleus tractus solitarius (NTS) is the primary termination site of cardiovascular afferents and critical in the regulation of baroreflex-mediated changes in heart rate (HR) and sympathetic nervous system outflow. The purpose of the present study was to determine whether ExTr is associated with alterations in neurotransmitter regulation of neurons involved in control of cardiovascular function at the level of the NTS. We hypothesized that ExTr would increase glutamatergic and reduce GABAergic transmission in the NTS and that, collectively, these changes would result in a greater overall sympathoinhibitory drive from the NTS in ExTr animals. To test these hypotheses, male Sprague-Dawley rats were treadmill trained or maintained under sedentary conditions for 8-10 wk. NTS microinjections were performed in Inactin-anesthetized animals instrumented to record mean arterial pressure (MAP), HR, and lumbar sympathetic nerve activity (LSNA). Generalized activation of the NTS with unilateral microinjections of glutamate (1-10 mM, 30 nl) produced dose-dependent decreases in MAP, HR, and LSNA that were unaffected by ExTr. Bilateral inhibition of NTS with the GABAA agonist muscimol (1 mM, 90 nl) produced increases in MAP and LSNA that were blunted by ExTr. In contrast, pressor and sympathoexcitatory responses to bilateral microinjections of the ionotropic glutamate receptor antagonist, kynurenate (40 mM, 90 nl), were similar between groups. Bradycardic responses to bilateral microinjections of the GABAA antagonist bicuculline (0.1 mM, 90 nl) were attenuated by ExTr. These data indicate that alterations in neurotransmission at the level of the NTS contribute importantly to regulation of HR and LSNA in ExTr animals. In addition to alterations at NTS, these experiments suggest indirectly that changes in other cardiovascular nuclei contribute to the observed alterations in neural control of the circulation following ExTr.
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Affiliation(s)
- Patrick J Mueller
- Dalton Cardiovascular Research Center, University of Missouri-Columbia, MO 65211-3300, USA.
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Alvarez GE, Halliwill JR, Ballard TP, Beske SD, Davy KP. Sympathetic neural regulation in endurance-trained humans: fitness vs. fatness. J Appl Physiol (1985) 2005; 98:498-502. [PMID: 15489260 DOI: 10.1152/japplphysiol.01020.2004] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We tested the hypothesis that muscle sympathetic nerve activity (MSNA) would be higher in endurance-trained (ET) compared with sedentary (Sed) men with similar levels of total body and abdominal adiposity. We further hypothesized that sympathetic baroreflex gain would be augmented in ET compared with Sed men independent of the level of adiposity. To address this, we measured MSNA (via microneurography), sympathetic and vagal baroreflex responses (the modified Oxford technique), body composition (dual-energy X-ray absorptiometry), and waist circumference (Gulick tape) in Sed ( n = 22) and ET men ( n = 8). The ET men were also compared with a subgroup of Sed men ( n = 6) with similar levels of total body and abdominal adiposity. Basal MSNA was greater in the ET compared with Sed men with similar levels of total body and abdominal adiposity (28 ± 2.0 vs. 21 ± 2.0 bursts/min; P < 0.05) but similar to the larger group of Sed men ( n = 22) with higher total body and abdominal adiposity (vs. 26 ± 3 bursts/min; P > 0.05). In contrast to our hypothesis, sympathetic baroreflex gain was lower in the ET compared with Sed men (−6.4 ± 0.8 vs. −8.4 ± 0.4 arbitrary integrative units·beat−1·mmHg−1; P < 0.05) regardless of the level of adiposity. Taken together, the results of the present study suggest that MSNA is higher in ET compared with Sed men with similar levels of total body and abdominal adiposity. In addition, sympathetic baroreflex gain is lower in ET compared with Sed men. That sympathetic baroreflex gain was lower in ET compared with Sed men regardless of the level of adiposity suggests an influence of the ET state per se.
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Affiliation(s)
- Guy E Alvarez
- Human Integrative Physiology Laboratory, Department of Human Nutrition, Foods, and Exercise, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA
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33
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Okano H, Ohkubo C. Effects of neck exposure to 5.5 mT static magnetic field on pharmacologically modulated blood pressure in conscious rabbits. Bioelectromagnetics 2005; 26:469-80. [PMID: 16108042 DOI: 10.1002/bem.20115] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Static magnetic fields (SMF) in the millitesla (mT) range have been reported to modulate microcirculatory hemodynamics and/or blood pressure (BP) under pharmacologically modified state in mammals. This study was designed to investigate the acute effects of local application of a SMF to neck or pelvic region under pharmacologically modulated BP; norepinephrine (NE)-induced hypertension as well as an L-type voltage-gated Ca(2+) channel blocker, nicardipine (NIC)-induced hypotension in conscious rabbits. Magnetic flux densities were up to 5.5 mT and the spatial magnetic gradient peaked in neck (carotid sinus baroreceptor) region at the level of approximately 0.06 mT/mm. The duration of exposure was 30 min (including 10 min of pretreatment) and the effects on BP were investigated up to 100 min postexposure. Baroreflex sensitivity (BRS) was estimated from invasive recordings of systolic BP and pulse interval. Neck exposure to 5.5 mT significantly attenuated the pharmacologically induced vasoconstriction or vasodilation, and subsequently suppressed the increase or decrease in BP compared with sham exposure. In contrast, pelvic exposure to 5.5 mT did not significantly antagonized NE-elevated BP or NIC-reduced BP. The neck exposure to 5.5 mT has a biphasic and restorative effect on vascular tone and BP acting to normalize the tone and BP. The neck exposure to 5.5 mT caused a significant increase in BRS in NE-elevated BP compared with sham exposure. The buffering effects of the SMF on increased hemodynamic variability under NE-induced high vascular tone and NIC-induced low vascular tone might be, in part, dependent on baroreflex pathways, which could modulate NE-mediated response in conjunction with Ca(2+) dynamics.
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Affiliation(s)
- Hideyuki Okano
- Department of Environmental Health, National Institute of Public Health, Saitama, Japan.
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Okano H, Ohkubo C. Exposure to a moderate intensity static magnetic field enhances the hypotensive effect of a calcium channel blocker in spontaneously hypertensive rats. Bioelectromagnetics 2005; 26:611-23. [PMID: 16189831 DOI: 10.1002/bem.20144] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We investigated the combined effects of a moderate intensity static magnetic field (SMF) and an L-type voltage-gated Ca(2+) channel blocker, nicardipine in stroke-resistant spontaneously hypertensive rats during the development of hypertension. Five-week-old male rats were exposed to SMF intensity up to 180 mT (B(max)) with a peak spatial gradient of 133 mT/mm for 14 weeks. Four experimental groups of 14 animals each were examined: (1) sham exposure with intraperitoneal (ip) saline injection (control); (2) SMF exposure with ip saline injection (SMF); (3) sham exposure with ip nicardipine injection (NIC); (4) SMF exposure with ip nicardipine injection (SMF + NIC). A disc-shaped permanent magnet or a dummy magnet was implanted in the vicinity adjacent to the left carotid sinus baroreceptor region in the neck of each rat. Nicardipine (2 mg/kg ip) was administered three times a week for 14 weeks, and then 15 min after each injection, arterial blood pressure (BP), heart rate (HR), baroreflex sensitivity (BRS), skin blood flow (SBF), skin blood velocity (SBV), plasma nitric oxide (NO) metabolites (NO(x) = NO(2) (-) + NO(3) (-)), plasma catecholamine levels and behavioral parameters of a functional observational battery were monitored. The action of nicardipine significantly decreased BP, and increased HR, SBF, SBV, plasma epinephrine and norepinephrine in the NIC group compared with the control respective age-matched group without changing plasma NO(x) levels. Neck exposure to SMF alone for 5-8 weeks significantly suppressed or retarded the development of hypertension together with increased BRS in SMF group. Furthermore, the exposure to SMF for 1-8 weeks significantly promoted the nicardipine-induced BP decrease in the SMF + NIC group compared with the respective NIC group. Moreover, the SMF induced a significant increase in plasma NO(x) in the nicardipine-induced hypotension. There were no significant differences in any of the physiological or behavioral parameters measured between the SMF + NIC and the NIC groups, nor between the SMF and the control groups. These results suggest that the SMF may enhance nicardipine-induced hypotension by more effectively antagonizing the Ca(2+) influx through the Ca(2+) channels compared with the NIC treatment alone. Furthermore, the enhanced antihypertensive effects of the SMF on the nicardipine-treated group appear to be partially related to the increased NO(x). Theoretical considerations suggest that the applied SMF (B(max) 40 mT, 0 Hz) can be converted into a changing magnetic field (B(max) 30-40 mT, 5.7-6.5 Hz or 7.5-8.3 Hz) in the baroreceptor region by means of the carotid artery pulsation. Therefore, we propose that the moderate intensity changing magnetic field, i.e., the magnetic field modulated by the pulse rate, may influence the activity of baroreceptor and baroreflex function.
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Affiliation(s)
- Hideyuki Okano
- Department of Environmental Health, National Institute of Public Health, Saitama, Japan.
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O'Leary DD, Shoemaker JK, Edwards MR, Hughson RL. Spontaneous beat-by-beat fluctuations of total peripheral and cerebrovascular resistance in response to tilt. Am J Physiol Regul Integr Comp Physiol 2004; 287:R670-9. [PMID: 15117726 DOI: 10.1152/ajpregu.00408.2003] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Beat-by-beat estimates of total peripheral resistance (TPR) can be obtained from continuous measurements of cardiac output by using Doppler ultrasound and noninvasive mean arterial blood pressure (MAP). We employed transfer function analysis to study the heart rate (HR) and vascular response to spontaneous changes in blood pressure from the relationships of systolic blood pressure (SBP) to HR (SBP→HR), MAP to total peripheral resistance (TPR) and cerebrovascular resistance index (CVRi) (MAP→TPR and MAP→CVRi), as well as stroke volume (SV) to TPR in nine healthy subjects in supine and 45° head-up tilt positions. The gain of the SBP→HR transfer function was reduced with tilt in both the low- (0.03–0.15 Hz) and high-frequency (0.15–0.35 Hz) regions. In contrast, MAP→TPR transfer function gain was not affected by head-up tilt, but it did increase from low- to high-frequency regions. The phase relationships between MAP→TPR were unaffected by head-up tilt, but, consistent with an autoregulatory system, changes in MAP were followed by directionally similar changes in TPR, just as observed for the MAP→CVRi. The SV→TPR had high coherence with a constant phase of 150–160°. Together, these data that showed changes in MAP preceded changes in TPR, as well as a possible link between SV and TPR, are consistent with complex interactions between the vascular component of the arterial and cardiopulmonary baroreflexes and intrinsic properties such as the myogenic response of the resistance arteries.
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Affiliation(s)
- Deborah D O'Leary
- Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
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Hamner JW, Cohen MA, Mukai S, Lipsitz LA, Taylor JA. Spectral indices of human cerebral blood flow control: responses to augmented blood pressure oscillations. J Physiol 2004; 559:965-73. [PMID: 15254153 PMCID: PMC1665190 DOI: 10.1113/jphysiol.2004.066969] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
We set out to fully examine the frequency domain relationship between arterial pressure and cerebral blood flow. Oscillatory lower body negative pressure (OLBNP) was used to create consistent blood pressure oscillations of varying frequency and amplitude to rigorously test for a frequency- and/or amplitude-dependent relationship between arterial pressure and cerebral flow. We also examined the predictions from OLBNP data for the cerebral flow response to the stepwise drop in pressure subsequent to deflation of ischaemic thigh cuffs. We measured spectral powers, cross-spectral coherence, and transfer function gains and phases in arterial pressure and cerebral flow during three amplitudes (0, 20, and 40 mmHg) and three frequencies (0.10, 0.05, and 0.03 Hz) of OLBNP in nine healthy young volunteers. Pressure fluctuations were directly related to OLBNP amplitude and inversely to OLBNP frequency. Although cerebral flow oscillations were increased, they did not demonstrate the same frequency dependence seen in pressure oscillations. The overall pattern of the pressure-flow relation was of decreasing coherence and gain and increasing phase with decreasing frequency, characteristic of a high-pass filter. Coherence between pressure and flow was increased at all frequencies by OLBNP, but was still significantly lower at frequencies below 0.07 Hz despite the augmented pressure input. In addition, predictions of thigh cuff data from spectral estimates were extremely inconsistent and highly variable, suggesting that cerebral autoregulation is a frequency-dependent mechanism that may not be fully characterized by linear methods.
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Affiliation(s)
- J W Hamner
- Laboratory for Cardiovascular Research, Research and Training Institute, Hebrew Rehabilitation Center for Aged, Boston, MA 02131, USA
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Nagura S, Sakagami T, Kakiichi A, Yoshimoto M, Miki K. Acute shifts in baroreflex control of renal sympathetic nerve activity induced by REM sleep and grooming in rats. J Physiol 2004; 558:975-83. [PMID: 15194739 PMCID: PMC1665029 DOI: 10.1113/jphysiol.2004.064527] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The present study aimed to determine the impact of REM sleep and grooming on the baroreflex stimulus-response curve for renal sympathetic nerve activity (RSNA). At least 3 days before study, Wistar female rats (n= 12) were chronically implanted with catheters to measure systemic arterial pressure (P(a)) and to intravenously infuse vasoactive drugs. In addition, electrodes were placed for measurements of RSNA, electroencephalogram, trapezius electromyogram and electrocardiogram. The baroreflex curve for RSNA was determined by changing P(a) using rapid intravenous infusions of phenylephrine and nitroprusside and then fitted to an inverse sigmoid function curve. REM sleep induced a vertical suppression of the P(a)-RSNA baroreflex curve, which was characterized by significant decreases in the maximum response (by 72.0%, P < 0.05) and the maximum gain (by 4.02% mmHg(-1), P < 0.05) compared with NREM sleep level. Grooming shifted the P(a)-RSNA baroreflex curve upward and to the right, which was associated with increases in the maximum response (by 45.2%, P < 0.05), the minimum response (by 20.7%, P < 0.05) and the pressure at the centering point (by 11.1 mmHg, P < 0.05). These data suggest that the P(a)-RSNA baroreflex curve was shifted acutely and differently in a state-dependent manner during natural sleep and wake cycle in rats.
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Affiliation(s)
- Satsuki Nagura
- Department of Environmental Health, Life Science and Human Technology, Nara Women's University, Kita-Uoya Nishimachi, Nara 630-8506, Japan
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Ogoh S, Volianitis S, Nissen P, Wray DW, Secher NH, Raven PB. Carotid baroreflex responsiveness to head-up tilt-induced central hypovolaemia: effect of aerobic fitness. J Physiol 2003; 551:601-8. [PMID: 12813144 PMCID: PMC2343210 DOI: 10.1113/jphysiol.2003.046029] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
This investigation examined the interaction between carotid baroreflex (CBR) responsiveness during head-up tilt (HUT)-induced central hypovolaemia and aerobic fitness. Seven average fit (AF) individuals, with a mean maximal oxygen uptake (VO2max) of 49 +/- 1 (ml O2) kg-1 min-1, and seven high fit (HF) individuals, with a VO2max of 61 +/- 1 (ml O2) kg-1 min-1, voluntarily participated in the investigation. After 10-15 min supine, each subject was exposed to nine levels of progressively increasing HUT by 10 deg increments from -20 deg to +60 deg. During the final 3 min of each stage of HUT, the CBR responsiveness was measured using a rapid pulse (500 ms) train of neck pressure (NP) and neck suction (NS) ranging from +40 to -80 Torr. The maximal gain of the carotid-HR (Gmax-HR) and carotid-MAP (Gmax-MAP) baroreflex function curves was identified as measures of CBR responsiveness. During HUT-induced decreases in thoracic admittance, an index of central blood volume (CBV), the Gmax-HR and Gmax-MAP of the AF subjects increased more than the Gmax-HR and Gmax-MAP of the HF subjects (P < 0.05). The data demonstrate that the increase in the CBR responsiveness during a tilt-induced progressive unloading of the cardiopulmonary baroreceptors was attenuated in endurance-trained subjects. These findings provide an explanation for the predisposition to orthostatic hypotension and intolerance in well-trained athletes.
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Affiliation(s)
- Shigehiko Ogoh
- Department of Integrative Physiology, University of North Texas Health Science Center at Fort Worth, TX 76107, USA.
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Affiliation(s)
- Johannes J van Lieshout
- Department of Internal Medicine, F7-205, Cardiovascular Research Institute, Academic Medical Centre, University of Amsterdam, PO BOX 22700, 1100 DE Amsterdam, The Netherlands.
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Yamazaki F, Sone R. Skin vascular response in the hand during sinusoidal exercise in physically trained subjects. Eur J Appl Physiol 2003; 90:159-64. [PMID: 14504948 DOI: 10.1007/s00421-003-0864-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/11/2003] [Indexed: 11/27/2022]
Abstract
The effect of physical training on the cutaneous vascular response during transient exercise load is unclear. We determined the phase response and amplitude response of cutaneous vascular conductance (CVC) in the hand during sinusoidal exercise in endurance exercise-trained and untrained subjects. Subjects exercised on a cycle ergometer with a sinusoidal load for 32 min. The load variation ranged from 10% [23 (1) W in the trained group, 19 (1) W in the untrained group] to 60% [137 (4) W, 114 (6) W] of peak O(2) uptake, and five different time periods (1, 2, 4, 8, and 16 min) were selected. Skin blood flow in the dorsal hand and palm were monitored by laser-Doppler flowmetry. CVC was evaluated from the ratio of blood flow to mean arterial pressure. During sinusoidal exercise, the amplitude of CVC was smaller in the dorsal hand than palm for shorter periods (1, 2, and 4 min) ( P<0.05). The phase lag of CVC was smaller in the dorsal hand than palm for longer periods (8 and 16 min) ( P<0.05). The amplitude response did not differ significantly between the two groups. The phase lag of CVC in the dorsal hand ( P<0.05) and palm ( P=0.06) was larger in the trained group than untrained group. These findings suggest that glabrous and nonglabrous skin vascular responses in the hand differ during transient exercise load, and physically trained subjects show a slower vascular response in the two skin areas to exercise stimulation than do untrained subjects.
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Affiliation(s)
- Fumio Yamazaki
- Department of Clinical Pathophysiology, School of Health Sciences, Univ. of Occupational and Environmental Health (UOEH), 1-1 Iseigaoka, Yahatanishi-ku, 807-8555 Kitakyushu, Japan.
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Miki K, Yoshimoto M, Tanimizu M. Acute shifts of baroreflex control of renal sympathetic nerve activity induced by treadmill exercise in rats. J Physiol 2003; 548:313-22. [PMID: 12562953 PMCID: PMC2342807 DOI: 10.1113/jphysiol.2002.033050] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The present study aimed to investigate whether there was a resetting of the baroreflex control of renal sympathetic nerve activity (RSNA) and heart rate (HR) during exercise. Wistar female rats (n = 11) were chronically implanted with catheters for the measurement of systemic arterial (Pa) and central venous pressures and with electrodes for measurement of RSNA and electrocardiogram (ECG) at least 3 days before study. The baroreflex curve for RSNA was determined by changing Pa using rapid intravenous infusions of phenylephrine and nitroprusside. The baroreflex response curves for RSNA and HR were characterized by an inverse sigmoid function curve from which the response range, gain, centering point and minimum response were estimated. Exercise shifted the Pa-RSNA baroreflex curve upward and to the right and was associated with increases in response range of 122 +/- 44 % (P < 0.05), maximum response of 173 +/- 40 % (P < 0.05), maximum gain of 149 +/- 66 % (P < 0.05) and midpoint pressure of 15 +/- 5 mmHg (P < 0.05) compared with the pre-exercise level. After cessation of exercise, the Pa-RSNA baroreflex curve was suppressed vertically with a significant decrease in maximum response of 57 +/- 14 % (P < 0.05) compared with the pre-exercise level. These data suggest that the right-upward shift of baroreflex control of sympathetic nerve activity may play a critical role in raising and stabilizing Pa during exercise. The suppression of the baroreflex control of sympathetic nerve activity may partly explain the post-exercise inhibition of sympathetic nerve activity and contribute to the post-exercise hypotension.
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Affiliation(s)
- Kenju Miki
- Department of Environmental Health, Life Science and Human Technology, Nara Women's University, Kita-Uoya Nishimachi, Nara, 630-8506, Japan.
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Fadel PJ, Stromstad M, Wray DW, Smith SA, Raven PB, Secher NH. New insights into differential baroreflex control of heart rate in humans. Am J Physiol Heart Circ Physiol 2003; 284:H735-43. [PMID: 12388288 DOI: 10.1152/ajpheart.00246.2002] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Recent data indicate that bilateral carotid sinus denervation in patients results in a chronic impairment in the rapid reflex control of blood pressure during orthostasis. These findings are inconsistent with previous human experimental investigations indicating a minimal role for the carotid baroreceptor-cardiac reflex in blood pressure control. Therefore, we reexamined arterial baroreflex [carotid (CBR) and aortic baroreflex (ABR)] control of heart rate (HR) using newly developed methodologies. In 10 healthy men, 27 +/- 1 yr old, an abrupt decrease in mean arterial pressure (MAP) was induced nonpharmacologically by releasing a unilateral arterial thigh cuff (300 Torr) after 9 min of resting leg ischemia under two conditions: 1) ABR and CBR deactivation (control) and 2) ABR deactivation. Under control conditions, cuff release decreased MAP by 13 +/- 1 mmHg, whereas HR increased 11 +/- 2 beats/min. During ABR deactivation, neck suction was gradually applied to maintain carotid sinus transmural pressure during the initial 20 s after cuff release (suction). This attenuated the increase in HR (6 +/- 1 beats/min) and caused a greater decrease in MAP (18 +/- 2 mmHg, P < 0.05). Furthermore, estimated cardiac baroreflex responsiveness (DeltaHR/DeltaMAP) was significantly reduced during suction compared with control conditions. These findings suggest that the carotid baroreceptors contribute more importantly to the reflex control of HR than previously reported in healthy individuals.
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Affiliation(s)
- P J Fadel
- Department of Integrative Physiology and Cardiovascular Research Institute, University of North Texas Health Science Center, Fort Worth 76107, USA.
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