THE ISOLATED AND ASSOCIATED EFFECTS OF AEROBIC EXERCISE AND LOW-DOSE ESTROGEN THERAPY ON BLOOD PRESSURE, SYMPATHETIC NERVE ACTIVITY AND FOREARM BLOOD FLOW IN HEALTHY POSTMENOPAUSAL WOMEN

Skin sympathetic nerve activity (SSNA) exhibits low- and high-frequency spectral components in normothermic subjects. However, spectral characteristics of SSNA in heat-stressed subjects are unknown. Because the main components of the integrated SSNA during heat stress (sudomotor/vasodilator activities) are different from those during normothermia and cooling (vasoconstrictor activity), we hypothesize that spectral characteristics of SSNA in heat-stressed subjects will be different from those in subjects subjected to normothermia or cooling. In 17 healthy subjects, SSNA, electrocardiogram, arterial blood pressure (via Finapres), respiratory activity, and skin blood flow were recorded during normothermia and heat stress. In 7 of the 17 subjects, these variables were also recorded during cooling. Spectral characteristics of integrated SSNA, R-R interval, beat-by-beat mean blood pressure, skin blood flow variability, and respiratory excursions were assessed. Heat stress and cooling significantly increased total SSNA. SSNA spectral power in the low-frequency (0.03–0.15 Hz), high-frequency (0.15–0.45 Hz), and very-high-frequency (0.45–2.5 Hz) regions was significantly elevated by heat stress and cooling. Interestingly, heat stress caused a greater relative increase of SSNA spectral power within the 0.45- to 2.5-Hz region than in the other spectral ranges; cooling did not show this effect. Differences in the SSNA spectral distribution between normothermia/cooling and heat stress may reflect different characteristics of central modulation of vasoconstrictor and sudomotor/vasodilator activities.

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Neural control of muscle blood flow during exercise

Journal of Applied Physiology ◽

10.1152/japplphysiol.00076.2004 ◽

2004 ◽

Vol 97 (2) ◽

pp. 731-738 ◽

Cited By ~ 146

Author(s):

Gail D. Thomas ◽

Steven S. Segal

Keyword(s):

Blood Pressure ◽

Skeletal Muscle ◽

Blood Flow ◽

Arterial Blood Pressure ◽

Sympathetic Nerve ◽

Neural Control ◽

Sympathetic Nerve Activity ◽

Muscle Blood Flow ◽

Nerve Activity ◽

Arterial Blood

Activation of skeletal muscle fibers by somatic nerves results in vasodilation and functional hyperemia. Sympathetic nerve activity is integral to vasoconstriction and the maintenance of arterial blood pressure. Thus the interaction between somatic and sympathetic neuroeffector pathways underlies blood flow control to skeletal muscle during exercise. Muscle blood flow increases in proportion to the intensity of activity despite concomitant increases in sympathetic neural discharge to the active muscles, indicating a reduced responsiveness to sympathetic activation. However, increased sympathetic nerve activity can restrict blood flow to active muscles to maintain arterial blood pressure. In this brief review, we highlight recent advances in our understanding of the neural control of the circulation in exercising muscle by focusing on two main topics: 1) the role of motor unit recruitment and muscle fiber activation in generating vasodilator signals and 2) the nature of interaction between sympathetic vasoconstriction and functional vasodilation that occurs throughout the resistance network. Understanding how these control systems interact to govern muscle blood flow during exercise leads to a clear set of specific aims for future research.

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Gly16 + Glu27 β2-adrenoceptor polymorphisms cause increased forearm blood flow responses to mental stress and handgrip in humans

Journal of Applied Physiology ◽

10.1152/japplphysiol.00503.2004 ◽

2005 ◽

Vol 98 (3) ◽

pp. 787-794 ◽

Cited By ~ 33

Author(s):

Ivani C. Trombetta ◽

Luciana T. Batalha ◽

Maria U. P. B. Rondon ◽

Mateus C. Laterza ◽

Eliana Frazzatto ◽

...

Keyword(s):

Blood Flow ◽

Sympathetic Nerve ◽

Mental Stress ◽

Sympathetic Nerve Activity ◽

Forearm Blood Flow ◽

Muscle Sympathetic Nerve Activity ◽

Isometric Exercise ◽

Vascular Conductance ◽

Nerve Activity ◽

Forearm Vascular Conductance

We hypothesized that the muscle vasodilatation during mental stress and exercise would vary among humans who are polymorphic at alleles 16 and 27 of the β2-adrenoceptors. From 216 preselected volunteers, we studied 64 healthy, middle-aged normotensive women selected to represent three genotypes: homozygous for the alleles Arg16 and Gln27 (Arg16/Gln27, n = 34), Gly16 and Gln27 (Gly16/Gln27, n = 20), and Gly16 and Glu27 (Gly16/Glu27, n = 10). Forearm blood flow (plethysmography) and muscle sympathetic nerve activity (microneurography) were recorded during 3-min Stroop color-word test and 3-min handgrip isometric exercise (30% maximal voluntary contraction). Baseline muscle sympathetic nerve activity, forearm vascular conductance, mean blood pressure, and heart rate were not different among groups. During mental stress, the peak forearm vascular conductance responses were greater in Gly16/Glu27 group than in Gly16/Gln27 and Arg16/Gln27 groups (1.79 ± 0.66 vs. 0.70 ± 0.11 and 0.58 ± 0.12 units, P = 0.03). Similar results were found during exercise (0.80 ± 0.25 vs. 0.28 ± 0.08 and 0.31 ± 0.08 units, P = 0.02). Further analysis in a subset of subjects showed that brachial intra-arterial propranolol infusion abolished the difference in vasodilatory response between Gly16/Glu27 ( n = 6) and Arg16/Gln27 ( n = 7) groups during mental stress (0.33 ± 0.20 vs. 0.46 ± 0.21 units, P = 0.50) and exercise (0.08 ± 0.06 vs. 0.03 ± 0.03 units, P = 0.21). Plasma epinephrine concentration in Arg16/Gln27 and Gly16/Glu27 groups was similar. In conclusion, women who are homozygous for Gly16/Glu27 of the β2-adrenoceptors have augmented muscle vasodilatory responsiveness to mental stress and exercise.

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EFFECTS OF EXERCISE ON BLOOD PRESSURE, SYMPATHETIC NERVE ACTIVITY, AND MUSCLE BLOOD FLOW RESPONSES TO HYPERINSULINEMIA IN MEN.

Medicine & Science in Sports & Exercise ◽

10.1097/00005768-199805001-01212 ◽

1998 ◽

Vol 30 (Supplement) ◽

pp. 213

Author(s):

C. L.M. Forjaz ◽

P. R. Ramires ◽

T. Tinucci ◽

K. C. Ortega ◽

H. E.H. Salom??o ◽

...

Keyword(s):

Blood Pressure ◽

Blood Flow ◽

Sympathetic Nerve ◽

Sympathetic Nerve Activity ◽

Muscle Blood Flow ◽

Nerve Activity

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Low‐dose ketamine affects blood pressure, but not muscle sympathetic nerve activity, during progressive central hypovolemia without altering tolerance

The Journal of Physiology ◽

10.1113/jp280491 ◽

2020 ◽

Vol 598 (24) ◽

pp. 5661-5672

Author(s):

Mu Huang ◽

Joseph C. Watso ◽

Gilbert Moralez ◽

Matthew N. Cramer ◽

Joseph M. Hendrix ◽

...

Keyword(s):

Blood Pressure ◽

Sympathetic Nerve ◽

Sympathetic Nerve Activity ◽

Low Dose ◽

Muscle Sympathetic Nerve Activity ◽

Nerve Activity

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Low-dose estrogen therapy does not change postexercise hypotension, sympathetic nerve activity reduction, and vasodilation in healthy postmenopausal women

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.01222.2007 ◽

2008 ◽

Vol 295 (4) ◽

pp. H1802-H1808 ◽

Cited By ~ 5

Author(s):

Bruna Oneda ◽

Claudia L. M. Forjaz ◽

Fernanda R. Bernardo ◽

Tatiana G. Araújo ◽

Josiane L. Gusmão ◽

...

Keyword(s):

Postmenopausal Women ◽

Sympathetic Nerve ◽

Sympathetic Nerve Activity ◽

Muscle Sympathetic Nerve Activity ◽

Estrogen Therapy ◽

Calculated Data ◽

Random Order ◽

Exercise Session ◽

Nerve Activity ◽

Postexercise Hypotension

The aim of this study was to determine whether estrogen therapy enhances postexercise muscle sympathetic nerve activity (MSNA) decrease and vasodilation, resulting in a greater postexercise hypotension. Eighteen postmenopausal women received oral estrogen therapy (ET; n = 9, 1 mg/day) or placebo ( n = 9) for 6 mo. They then participated in one 45-min exercise session (cycle ergometer at 50% of oxygen uptake peak) and one 45-min control session (seated rest) in random order. Blood pressure (BP, oscillometry), heart rate (HR), MSNA (microneurography), forearm blood flow (FBF, plethysmography), and forearm vascular resistance (FVR) were measured 60 min later. FVR was calculated. Data were analyzed using a two-way ANOVA. Although postexercise physiological responses were unaltered, HR was significantly lower in the ET group than in the placebo group (59 ± 2 vs. 71 ± 2 beats/min, P < 0.01). In both groups, exercise produced significant decreases in systolic BP (145 ± 3 vs. 154 ± 3 mmHg, P = 0.01), diastolic BP (71 ± 3 vs. 75 ± 2 mmHg, P = 0.04), mean BP (89 ± 2 vs. 93 ± 2 mmHg, P = 0.02), MSNA (29 ± 2 vs. 35 ± 1 bursts/min, P < 0.01), and FVR (33 ± 4 vs. 55 ± 10 units, P = 0.01), whereas it increased FBF (2.7 ± 0.4 vs. 1.6 ± 0.2 ml·min−1·100 ml−1, P = 0.02) and did not change HR (64 ± 2 vs. 65 ± 2 beats/min, P = 0.3). Although ET did not change postexercise BP, HR, MSNA, FBF, or FVR responses, it reduced absolute HR values at baseline and after exercise.

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Assessing static and dynamic sympathetic transduction using microneurography

Journal of Applied Physiology ◽

10.1152/japplphysiol.00032.2021 ◽

2021 ◽

Author(s):

Michael M. Tymko ◽

Lindsey F. Berthelsen ◽

Rachel J. Skow ◽

Andrew R. Steele ◽

Graham M. Fraser ◽

...

Keyword(s):

Blood Pressure ◽

Heart Rate ◽

Blood Flow ◽

Sympathetic Nerve ◽

Sympathetic Nerve Activity ◽

Muscle Sympathetic Nerve Activity ◽

Peripheral Resistance ◽

Analytical Techniques ◽

Nerve Activity ◽

Physiological Outcomes

The relationship between sympathetic nerve activity and the vasculature has been of great interest due to its potential role in various cardiovascular-related disease. This relationship, termed "sympathetic transduction", has been quantified using several different laboratory and analytical techniques. The most common method is to assess the association between relative changes in muscle sympathetic nerve activity, measured via microneurography, and physiological outcomes (e.g., blood pressure, total peripheral resistance, and blood flow etc.) in response to a sympathetic stressor (e.g. exercise, cold stress, orthostatic stress). This approach, however, comes with its own caveats. For instance, elevations in blood pressure and heart rate during a sympathetic stressor can have an independent impact on muscle sympathetic nerve activity. Another assessment of sympathetic transduction was developed by Wallin and Nerhed in 1982, where alterations in blood pressure and heart rate were assessed immediately following bursts of muscle sympathetic nerve activity at rest. This approach has since been characterized and further innovated by others, including the breakdown of consecutive burst sequences (e.g., singlet, doublet, triplet, and quadruplet), and burst height (quartile analysis) on specific vascular outcomes (e.g., blood pressure, blood flow, vascular resistance). The purpose of this review is to provide an overview of the literature that has assessed sympathetic transduction using microneurography and various sympathetic stressors (static sympathetic transduction) and using the same or similar approach established by Wallin and Nerhed at rest (dynamic neurovascular transduction). Herein, we discuss the overlapping literature between these two methodologies and highlight the key physiological questions that remain.

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