1
|
Analysis of phase interactions between heart rate variability, respiration and peripheral microhemodynamics oscillations of upper and lower extremities in human. Biomed Signal Process Control 2022. [DOI: 10.1016/j.bspc.2021.103091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
2
|
Klassen SA, Joyner MJ, Baker SE. The impact of ageing and sex on sympathetic neurocirculatory regulation. Semin Cell Dev Biol 2021; 116:72-81. [PMID: 33468420 PMCID: PMC8282778 DOI: 10.1016/j.semcdb.2021.01.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Revised: 12/30/2020] [Accepted: 01/04/2021] [Indexed: 02/07/2023]
Abstract
The sympathetic nervous system represents a critical mechanism for homoeostatic blood pressure regulation in humans. This review focuses on age-related alterations in neurocirculatory regulation in men and women by highlighting human studies that examined the relationship between muscle sympathetic nerve activity (MSNA) acquired by microneurography and circulatory variables (e.g., blood pressure, vascular resistance). We frame this review with epidemiological evidence highlighting sex-specific patterns in age-related blood pressure increases in developed nations. Indeed, young women exhibit lower blood pressure than men, but women demonstrate larger blood pressure increases with age, such that by about age 60 years, blood pressure is greater in women. Sympathetic neurocirculatory mechanisms contribute to sex differences in blood pressure rises with age. Muscle sympathetic nerve activity increases with age in both sexes, but women demonstrate greater age-related increases. The circulatory adjustments imposed by MSNA - referred to as neurovascular transduction or autonomic (sympathetic) support of blood pressure - differ in men and women. For example, whereas young men demonstrate a positive relationship between resting MSNA and vascular resistance, this relationship is absent in young women due to beta-2 adrenergic vasodilation, which offsets alpha-adrenergic vasoconstriction. However, post-menopausal women demonstrate a positive relationship between MSNA and vascular resistance due to a decline in beta-2 adrenergic vasodilatory mechanisms. Emerging data suggest that greater aerobic fitness appears to modulate neurocirculatory regulation, at least in young, healthy men and women. This review also highlights recent advances in microneurographic recordings of sympathetic action potential discharge, which may nuance our understanding of age-related alterations in sympathetic neurocirculatory regulation in humans.
Collapse
Affiliation(s)
- Stephen A Klassen
- Human and Integrative Physiology and Clinical Pharmacology Laboratory, Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, USA
| | - Michael J Joyner
- Human and Integrative Physiology and Clinical Pharmacology Laboratory, Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, USA
| | - Sarah E Baker
- Human and Integrative Physiology and Clinical Pharmacology Laboratory, Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, USA.
| |
Collapse
|
3
|
Yoshida K, Nishidate I. Phase Velocity of Facial Blood Volume Oscillation at a Frequency of 0.1 Hz. Front Physiol 2021; 12:627354. [PMID: 33584350 PMCID: PMC7876320 DOI: 10.3389/fphys.2021.627354] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 01/04/2021] [Indexed: 11/13/2022] Open
Abstract
Facial blood flow, which typically exhibits distinctive oscillation at a frequency of around 0.1 Hz, has been extensively studied. Although this oscillation may include important information about blood flow regulation, its origin remains unknown. The spatial phase distribution of the oscillation is thus desirable. Therefore, we visualized facial blood volume oscillation at a frequency of around 0.1 Hz using a digital camera imaging method with an improved approximation equation, which enabled precise analysis over a large area. We observed a slow spatial movement of the 0.1-Hz oscillation. The oscillation phase was not synchronized, but instead moved slowly. The phase velocity varies with person, measurement location, and time. An average phase velocity of 3.8 mm/s was obtained for several subjects. The results are consistent with previous studies; however, the conventional explanation that the blood flow at a certain point oscillates independently of adjacent areas should be corrected. If the primary origin of the movement is myogenic activity, the movement may ascend along a blood vessel toward the upstream. Otherwise, the oscillation and its propagation can be considered to be related to Mayer waves. By determining the mechanism, some questions regarding Mayer waves can be answered. The direction of the wave (upstream or downstream) provides important information.
Collapse
Affiliation(s)
| | - Izumi Nishidate
- Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Tokyo, Japan
| |
Collapse
|
4
|
Moir ME, Klassen SA, Zamir M, Shoemaker JK. Rapid changes in vascular compliance contribute to cerebrovascular adjustments during transient reductions in blood pressure in young, healthy adults. J Appl Physiol (1985) 2020; 129:27-35. [PMID: 32463732 DOI: 10.1152/japplphysiol.00272.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Characterization of dynamic cerebral autoregulation has focused primarily on adjustments in cerebrovascular resistance in response to blood pressure (BP) alterations. However, the role of vascular compliance in dynamic autoregulatory processes remains elusive. The present study examined changes in cerebrovascular compliance and resistance during standing-induced transient BP reductions in nine young, healthy adults (3 women). Brachial artery BP (Finometer) and middle cerebral artery blood velocity (BV; Multigon) waveforms were collected. Beginning 20 beats before standing and continuing 40 beats after standing, individual BP and BV waveforms of every second heartbeat were extracted and input into a four-element modified Windkessel model to calculate indexes of cerebrovascular resistance (Ri) and compliance (Ci). Standing elicited a transient reduction in mean BP of 20 ± 9 mmHg. In all participants, a large increase in Ci (165 ± 84%; P < 0.001 vs. seated baseline) occurred 2 ± 2 beats following standing. Reductions in Ri occurred 11 ± 3 beats after standing (Ci vs. Ri delay: P < 0.001). The increase in Ci contributed to maintained systolic BV before the decrease in Ri. The present results demonstrate rapid, large but transient increases in Ci that precede reductions in Ri, in response to standing-induced reductions in BP. Therefore, Ci represents a discreet component of cerebrovascular responses during acute decreases in BP and, consequently, dynamic autoregulation.NEW & NOTEWORTHY Historically, dynamic cerebral autoregulation has been characterized by adjustments in cerebrovascular resistance following systematic changes in blood pressure. However, with the use of Windkessel modeling approaches, this study revealed rapid and large increases in cerebrovascular compliance that preceded reductions in cerebrovascular resistance following standing-induced blood pressure reductions. Importantly, the rapid cerebrovascular compliance response contributed to preservation of systolic blood velocity during the transient hypotensive phase. These results broaden our understanding of dynamic cerebral autoregulation.
Collapse
Affiliation(s)
- M Erin Moir
- School of Kinesiology, University of Western Ontario, London, Ontario, Canada
| | - Stephen A Klassen
- School of Kinesiology, University of Western Ontario, London, Ontario, Canada
| | - Mair Zamir
- Department of Applied Mathematics, University of Western Ontario, London, Ontario, Canada.,Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada
| | - J Kevin Shoemaker
- School of Kinesiology, University of Western Ontario, London, Ontario, Canada.,Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada
| |
Collapse
|
5
|
Anderson GK, Sprick JD, Park FS, Rosenberg AJ, Rickards CA. Responses of cerebral blood velocity and tissue oxygenation to low-frequency oscillations during simulated haemorrhagic stress in humans. Exp Physiol 2019; 104:1190-1201. [PMID: 31090115 PMCID: PMC11022286 DOI: 10.1113/ep087358] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Accepted: 05/14/2019] [Indexed: 04/19/2024]
Abstract
NEW FINDINGS What is the central question of this study? Do low-frequency oscillations in arterial pressure and cerebral blood velocity protect cerebral blood velocity and oxygenation during central hypovolaemia? What is the main finding and its importance? Low-frequency oscillations in arterial pressure and cerebral blood velocity attenuate reductions in cerebral oxygen saturation but do not protect absolute cerebral blood velocity during central hypovolaemia. This finding indicates the potential importance of haemodynamic oscillations in maintaining cerebral oxygenation and therefore viability of tissues during challenges to cerebral blood flow and oxygen delivery. ABSTRACT Tolerance to both real and simulated haemorrhage varies between individuals. Exaggerated low-frequency (∼0.1 Hz) oscillations in mean arterial pressure and brain blood flow [indexed via middle cerebral artery velocity (MCAv)] have been associated with improved tolerance to reduced central blood volume. The mechanism for this association has not been explored. We hypothesized that inducing low-frequency oscillations in arterial pressure and cerebral blood velocity would attenuate reductions in cerebral blood velocity and oxygenation during simulated haemorrhage. Fourteen subjects (11 men and three women) were exposed to oscillatory (0.1 and 0.05 Hz) and non-oscillatory (0 Hz) lower-body negative pressure profiles with an average chamber pressure of -60 mmHg (randomized and counterbalanced order). Measurements included arterial pressure and stroke volume via finger photoplethysmography, MCAv via transcranial Doppler ultrasound, and cerebral oxygenation of the frontal lobe via near-infrared spectroscopy. Tolerance was higher during the two oscillatory profiles compared with the 0 Hz profile (0.05 Hz, P = 0.04; 0.1 Hz, P = 0.09), accompanied by attenuated reductions in stroke volume (P < 0.001) and cerebral oxygenation of the frontal lobe (P ≤ 0.02). No differences were observed between profiles for reductions in mean arterial pressure (P = 0.17) and MCAv (P = 0.30). In partial support of our hypothesis, cerebral oxygenation, but not cerebral blood velocity, was protected during the oscillatory profiles. Interestingly, more subjects tolerated the oscillatory profiles compared with the static 0 Hz profile, despite similar arterial pressure responses. These findings emphasize the potential importance of haemodynamic oscillations in maintaining perfusion and oxygenation of cerebral tissues during haemorrhagic stress.
Collapse
Affiliation(s)
- Garen K. Anderson
- Cerebral & Cardiovascular Physiology Laboratory, Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Justin D. Sprick
- Cerebral & Cardiovascular Physiology Laboratory, Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA
- Division of Renal Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, GA, USA
| | - Flora S. Park
- Cerebral & Cardiovascular Physiology Laboratory, Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Alexander J. Rosenberg
- Cerebral & Cardiovascular Physiology Laboratory, Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Caroline A. Rickards
- Cerebral & Cardiovascular Physiology Laboratory, Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA
| |
Collapse
|
6
|
Shoemaker JK, Klassen SA, Badrov MB, Fadel PJ. Fifty years of microneurography: learning the language of the peripheral sympathetic nervous system in humans. J Neurophysiol 2018; 119:1731-1744. [PMID: 29412776 DOI: 10.1152/jn.00841.2017] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
As a primary component of homeostasis, the sympathetic nervous system enables rapid adjustments to stress through its ability to communicate messages among organs and cause targeted and graded end organ responses. Key in this communication model is the pattern of neural signals emanating from the central to peripheral components of the sympathetic nervous system. But what is the communication strategy employed in peripheral sympathetic nerve activity (SNA)? Can we develop and interpret the system of coding in SNA that improves our understanding of the neural control of the circulation? In 1968, Hagbarth and Vallbo (Hagbarth KE, Vallbo AB. Acta Physiol Scand 74: 96-108, 1968) reported the first use of microneurographic methods to record sympathetic discharges in peripheral nerves of conscious humans, allowing quantification of SNA at rest and sympathetic responsiveness to physiological stressors in health and disease. This technique also has enabled a growing investigation into the coding patterns within, and cardiovascular outcomes associated with, postganglionic SNA. This review outlines how results obtained by microneurographic means have improved our understanding of SNA outflow patterns at the action potential level, focusing on SNA directed toward skeletal muscle in conscious humans.
Collapse
Affiliation(s)
- J Kevin Shoemaker
- School of Kinesiology, University of Western Ontario , London, Ontario , Canada
| | - Stephen A Klassen
- School of Kinesiology, University of Western Ontario , London, Ontario , Canada
| | - Mark B Badrov
- School of Kinesiology, University of Western Ontario , London, Ontario , Canada
| | - Paul J Fadel
- Department of Kinesiology, University of Texas at Arlington , Arlington, Texas
| |
Collapse
|
7
|
Rimehaug AE, Hoff IE, Høiseth LØ, Hisdal J, Aadahl P, Kirkeby-Garstad I. Cardiac power parameters during hypovolemia, induced by the lower body negative pressure technique, in healthy volunteers. BMC Anesthesiol 2016; 16:31. [PMID: 27364749 PMCID: PMC4929737 DOI: 10.1186/s12871-016-0195-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2015] [Accepted: 05/13/2016] [Indexed: 02/02/2023] Open
Abstract
Background Changes in cardiac power parameters incorporate changes in both aortic flow and blood pressure. We hypothesized that dynamic and non-dynamic cardiac power parameters would track hypovolemia better than equivalent flow- and pressure parameters, both during spontaneous breathing and non-invasive positive pressure ventilation (NPPV). Methods Fourteen healthy volunteers underwent lower body negative pressure (LBNP) of 0, −20, −40, −60 and −80 mmHg to simulate hypovolemia, both during spontaneous breathing and during NPPV. We recorded aortic flow using suprasternal ultrasound Doppler and blood pressure using Finometer, and calculated dynamic and non-dynamic parameters of cardiac power, flow and blood pressure. These were assessed on their association with LBNP-levels. Results Respiratory variation in peak aortic flow was the dynamic parameter most affected during spontaneous breathing increasing 103 % (p < 0.001) from baseline to LBNP −80 mmHg. Respiratory variation in pulse pressure was the most affected dynamic parameter during NPPV, increasing 119 % (p < 0.001) from baseline to LBNP −80 mmHg. The cardiac power integral was the most affected non-dynamic parameter falling 59 % (p < 0.001) from baseline to LBNP −80 mmHg during spontaneous breathing, and 68 % (p < 0.001) during NPPV. Conclusions Dynamic cardiac power parameters were not better than dynamic flow- and pressure parameters at tracking hypovolemia, seemingly due to previously unknown variation in peripheral vascular resistance matching respiratory changes in hemodynamics. Of non-dynamic parameters, the power parameters track hypovolemia slightly better than equivalent flow parameters, and far better than equivalent pressure parameters.
Collapse
Affiliation(s)
- Audun Eskeland Rimehaug
- Department of Anesthesiology and Intensive care, St Olav Trondheim University Hospital, Trondheim, Norway. .,Department of Circulation and Medical Imaging, NTNU, Norwegian University of Science and Technology, Trondheim, Norway. .,Circulation research group Trondheim (CIRCUT), Trondheim, Norway.
| | - Ingrid Elise Hoff
- Norwegian Air Ambulance Foundation, Drøbak, Norway.,Department of Anesthesiology, Oslo University Hospital, Oslo, Norway
| | - Lars Øivind Høiseth
- Department of Anesthesiology, Oslo University Hospital, Oslo, Norway.,Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Jonny Hisdal
- Department of Vascular Medicine, Oslo University Hospital, Oslo, Norway
| | - Petter Aadahl
- Department of Anesthesiology and Intensive care, St Olav Trondheim University Hospital, Trondheim, Norway.,Department of Circulation and Medical Imaging, NTNU, Norwegian University of Science and Technology, Trondheim, Norway.,Circulation research group Trondheim (CIRCUT), Trondheim, Norway
| | - Idar Kirkeby-Garstad
- Department of Anesthesiology and Intensive care, St Olav Trondheim University Hospital, Trondheim, Norway.,Department of Circulation and Medical Imaging, NTNU, Norwegian University of Science and Technology, Trondheim, Norway.,Circulation research group Trondheim (CIRCUT), Trondheim, Norway
| |
Collapse
|
8
|
Tankanag AV, Grinevich AA, Kirilina TV, Krasnikov GV, Piskunova GM, Chemeris NK. Wavelet phase coherence analysis of the skin blood flow oscillations in human. Microvasc Res 2014; 95:53-9. [DOI: 10.1016/j.mvr.2014.07.003] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Revised: 07/04/2014] [Accepted: 07/05/2014] [Indexed: 11/25/2022]
|
9
|
Delgado E, Marques-Neves C, Rocha I, Sales-Luís J, Silva-Carvalho L. Myogenic oscillations in rabbit ocular vasculature are very low frequency. Ophthalmic Res 2013; 50:123-8. [PMID: 23899812 DOI: 10.1159/000351629] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Accepted: 03/03/2013] [Indexed: 11/19/2022]
Abstract
BACKGROUND/AIMS In a previously described model of isolated rabbit eye, we detected myogenic intrinsic vascular tone of unknown origin in the ophthalmic artery. In order to better understand the origin of these low frequency oscillations, we analyzed their spectral characteristics using fast Fourier. METHODS Hybrid New Zealand rabbits of either sex (n = 24) were used; they were divided into 2 groups according to age. The spectral characteristics of the myogenic behaviour of the rabbit external ophthalmic artery were analyzed using the fast Fourier algorithm. RESULTS The frequency of the oscillations of the myogenic activity seen in the rabbit external ophthalmic artery varied between 0.033 and 0.066 Hz (mean 0.045 ± 0.012 Hz), all in the region of very low frequency (VLF) oscillations (VLF <0.07 Hz for the rabbit). The frequency of spontaneous oscillations was higher in younger animals. CONCLUSION Fast Fourier analysis proved to be an adequate mathematical tool to analyze the myogenic tone oscillations, which were all in the range of VLF in the model we used. These results indicate that myogenic vascular function of ocular blood flow is composed of VLF oscillations, and they provide a new explanation for the origin of VLF in arterial spectra. They also suggest that the ocular local myogenic vascular function observed is more efficient in younger animals.
Collapse
Affiliation(s)
- E Delgado
- Departamento de Clínica, Centro de Investigação Interdisciplinar em Sanidade Animal, Faculty of Veterinary Medicine, Lisbon Technical University, Lisbon, Portugal.
| | | | | | | | | |
Collapse
|
10
|
Mateus J, Hargens AR. Bone hemodynamic responses to changes in external pressure. Bone 2013; 52:604-10. [PMID: 23168293 DOI: 10.1016/j.bone.2012.11.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2012] [Revised: 10/15/2012] [Accepted: 11/13/2012] [Indexed: 11/19/2022]
Abstract
Adequate blood supply and circulation to the bones is required to maintain a healthy skeleton. Inadequate blood perfusion is associated with numerous bone pathologies and a decrease in bone mineral density, yet bone hemodynamics remains poorly understood. This study aims to 1) quantify bone hemodynamic responses to changes in external pressure, and 2) identify the predominant mechanisms regulating bone hemodynamic responses to pressure changes. Photoplethysmography was used to measure bone and skin perfusion in response to changes in external pressure. Single-limb pressure chamber experiments were performed over a pressure range of -50 to +50mmHg. Bone perfusion is decreased at all negative pressures, and larger decrements in perfusion are observed at the more extreme pressure differences. At positive pressures we observed an initial increase in perfusion followed by activation of intramuscular pressure receptors at +30mmHg, which overrides the initial response and results in decreased perfusion at the highest positive pressure levels. The myogenic effect is observed and is shown to be the predominant control mechanism in bone over a wide range of pressure exposures. Greater understanding of these hemodynamic mechanisms may be important in developing new drugs and therapies to treat various bone disorders.
Collapse
Affiliation(s)
- Jaime Mateus
- Massachusetts Institute of Technology, Man-Vehicle Laboratory, Department of Aeronautics and Astronautics, 77 Massachusetts Avenue, Room 37-219, Cambridge, MA 02139, USA.
| | | |
Collapse
|
11
|
Kiviniemi AM, Frances MF, Rachinsky M, Craen R, Petrella RJ, Huikuri HV, Tulppo MP, Shoemaker JK. Non-alpha-adrenergic effects on systemic vascular conductance during lower-body negative pressure, static exercise and muscle metaboreflex activation. Acta Physiol (Oxf) 2012; 206:51-61. [PMID: 22591110 DOI: 10.1111/j.1748-1716.2012.02447.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Revised: 02/27/2012] [Accepted: 04/16/2012] [Indexed: 11/28/2022]
Abstract
AIM This study tested the hypothesis that non-α-adrenergic mechanisms contribute to systemic vascular conductance (SVC) in a reflex-specific manner during the sympathoexcitatory manoeuvres. METHODS Twelve healthy subjects underwent lower-body negative pressure (LBNP, -40 mmHg) as well as static handgrip exercise (HG, 20% of maximal force) followed by post-exercise forearm circulatory occlusion (PECO, 5 min each) with and without α-adrenergic blockade induced by phentolamine (PHE). Aortic blood flow, finger blood pressure and superficial femoral artery blood flow were measured to calculate cardiac output, SVC and leg vascular conductance (LVC) during the last minute of each intervention. RESULTS Mean arterial pressure (MAP) decreased more during LBNP with PHE compared with saline (-7 ± 7 vs. -2 ± 5%, P = 0.016). PHE did not alter the MAP response to HG (+20 ± 12 and +24 ± 16%, respectively, for PHE and saline) but decreased the change in MAP during PECO (+12 ± 7 vs. +21 ± 14%, P = 0.005). The decrease in SVC and LVC with LBNP did not differ between saline and PHE trials (-13 ± 10 vs. -17 ± 10%, respectively, for SVC, P = 0.379). In contrast, the SVC response to HG increased from -9 ± 12 with saline to + 5 ± 15% with PHE (P = 0.002) and from -16 ± 15 with saline to +1 ± 16% with PHE during PECO (P = 0.003). LVC responses to HG or PECO were not different from saline with PHE. CONCLUSIONS Non-α-adrenergic vasoconstriction was present during LBNP. The systemic vasoconstriction during static exercise and isolated muscle metaboreflex activation, in the absence of leg vasoconstriction, was explained by an α-adrenergic mechanism. Therefore, non-α-adrenergic vasoconstriction is more emphasized during baroreflex, but not metaboreflex-mediated sympathetic activation.
Collapse
Affiliation(s)
| | - M. F. Frances
- School of Kinesiology; The University of Western Ontario; London; ON; Canada
| | - M. Rachinsky
- Department of Anesthesia and Perioperative Medicine; The University of Western Ontario; London; ON; Canada
| | - R. Craen
- Department of Anesthesia and Perioperative Medicine; The University of Western Ontario; London; ON; Canada
| | - R. J. Petrella
- School of Kinesiology; The University of Western Ontario; London; ON; Canada
| | - H. V. Huikuri
- Institute of Clinical Medicine; The University of Oulu; Oulu; Finland
| | | | - J. K. Shoemaker
- School of Kinesiology; The University of Western Ontario; London; ON; Canada
| |
Collapse
|
12
|
Yang H, Cooke WH, Reed KS, Carter JR. Sex differences in hemodynamic and sympathetic neural firing patterns during orthostatic challenge in humans. J Appl Physiol (1985) 2012; 112:1744-51. [DOI: 10.1152/japplphysiol.01407.2011] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Recent evidence suggests that young men and women may have different strategies for regulating arterial blood pressure, and the purpose of the present study was to determine if sex differences exist in diastolic arterial pressure (DAP) and muscle sympathetic nerve activity (MSNA) relations during simulated orthostatic stress. We hypothesized that young men would demonstrate stronger DAP-MSNA coherence and a greater percentage of “consecutive integrated bursts” during orthostatic stress. Fourteen men and 14 women (age 23 ± 1 yr) were examined at rest and during progressive lower body negative pressure (LBNP; −5 to −40 mmHg). Progressive LBNP did not alter mean arterial pressure (MAP) in either sex. Heart rate increased and stroke volume decreased to a greater extent during LBNP in women (interactions, P < 0.05). DAP-MSNA coherence was strong (i.e., r ≥ 0.5) at rest and increased throughout all LBNP stages in men. In contrast, DAP-MSNA coherence was lower in women, and responses to progressive LBNP were attenuated compared with men (time × sex, P = 0.029). Men demonstrated a higher percentage of consecutive bursts during all stages of LBNP (sex, P < 0.05), although the percentage of consecutive bursts increased similarly during progressive LBNP between sexes. In conclusion, men and women demonstrate different firing patterns of integrated MSNA during LBNP that appear to be related to differences in DAP oscillatory patterns. Men tend to have more consecutive bursts, which likely contribute to a stronger DAP-MSNA coherence. These findings may help explain why young women are more prone to orthostatic intolerance.
Collapse
Affiliation(s)
- Huan Yang
- Department of Kinesiology and Integrated Physiology, Michigan Technological University, Houghton, Michigan; and
| | - William H. Cooke
- Department of Health and Kinesiology, University of Texas at San Antonio, San Antonio, Texas
| | - Kristen S. Reed
- Department of Kinesiology and Integrated Physiology, Michigan Technological University, Houghton, Michigan; and
| | - Jason R. Carter
- Department of Kinesiology and Integrated Physiology, Michigan Technological University, Houghton, Michigan; and
| |
Collapse
|
13
|
Kiviniemi AM, Frances MF, Tiinanen S, Craen R, Rachinsky M, Petrella RJ, Seppänen T, Huikuri HV, Tulppo MP, Shoemaker JK. α-Adrenergic effects on low-frequency oscillations in blood pressure and R-R intervals during sympathetic activation. Exp Physiol 2011; 96:718-35. [PMID: 21602293 DOI: 10.1113/expphysiol.2011.058768] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The present study was designed to address the contribution of α-adrenergic modulation to the genesis of low-frequency (LF; 0.04-0.15 Hz) oscillations in R-R interval (RRi), blood pressure (BP) and muscle sympathetic nerve activity (MSNA) during different sympathetic stimuli. Blood pressure and RRi were measured continuously in 12 healthy subjects during 5 min periods each of lower body negative pressure (LBNP; -40 mmHg), static handgrip exercise (HG; 20% of maximal force) and postexercise forearm circulatory occlusion (PECO) with and without α-adrenergic blockade by phentolamine. Muscle sympathetic nerve activity was recorded in five subjects during LBNP and in six subjects during HG and PECO. Low-frequency powers and median frequencies of BP, RRi and MSNA were calculated from power spectra. Low-frequency power during LBNP was lower with phentolamine versus without for both BP and RRi oscillations (1.6 ± 0.6 versus 1.2 ± 0.7 ln mmHg(2), P = 0.049; and 6.9 ± 0.8 versus 5.4 ± 0.9 ln ms(2), P = 0.001, respectively). In contrast, the LBNP with phentolamine increased the power of high-frequency oscillations (0.15-0.4 Hz) in BP and MSNA (P < 0.01 for both), which was not observed during saline infusion. Phentolamine also blunted the increases in the LBNP-induced increase in frequency of LF oscillations in BP and RRi. Phentolamine decreased the LF power of RRi during HG (P = 0.015) but induced no other changes in LF powers or frequencies during HG. Phentolamine resulted in decreased frequency of LF oscillations in RRi (P = 0.004) during PECO, and a similar tendency was observed in BP and MSNA. The power of LF oscillation in MSNA did not change during any intervention. We conclude that α-adrenergic modulation contributes to LF oscillations in BP and RRi during baroreceptor unloading (LBNP) but not during static exercise. Also, α-adrenergic modulation partly explains the shift to a higher frequency of LF oscillations during baroreceptor unloading and muscle metaboreflex activation.
Collapse
Affiliation(s)
- Antti M Kiviniemi
- Department of Exercise and Medical Physiology, Verve Research, Oulu, Finland.
| | | | | | | | | | | | | | | | | | | |
Collapse
|