Increased muscle sympathetic nerve activity and impaired baroreflex control in isolated REM-sleep behavior disorder

Smoking is a risk factor for cardiovascular diseases. Prior reports showed a transient increase in blood pressure (BP) following a spontaneous burst of muscle sympathetic nerve activity (MSNA). We hypothesized that this pressor response would be accentuated in smokers. Using signal-averaging techniques, we examined the BP (Finometer) response to MSNA in 18 otherwise healthy smokers and 42 healthy nonsmokers during resting conditions. The sensitivities of baroreflex control of MSNA and heart rate were also assessed. The mean resting MSNA, heart rate, and mean arterial pressure (MAP) were higher in smokers than nonsmokers. The MAP increase following a burst of MSNA was significantly greater in smokers than nonsmokers (Δ3.4 ± 0.3 vs. Δ1.6 ± 0.1 mmHg, P < 0.001). The baroreflex sensitivity (BRS) of burst incidence, burst area, or total activity was not different between the two groups. However, cardiac BRS was lower in smokers than nonsmokers (14.6 ± 1.7 vs. 24.6 ± 1.5 ms/mmHg, P < 0.001). Moreover, the MAP increase following a burst was negatively correlated with the cardiac BRS. These observations suggest that habitual smoking in otherwise healthy individuals raises the MAP increase following spontaneous MSNA and that the attenuated cardiac BRS in the smokers was a contributing factor. We speculate that the accentuated pressor increase in response to spontaneous MSNA may contribute to the elevated resting BP in the smokers.

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Whole body heat stress attenuates baroreflex control of muscle sympathetic nerve activity during postexercise muscle ischemia

Journal of Applied Physiology ◽

10.1152/japplphysiol.00135.2008 ◽

2009 ◽

Vol 106 (4) ◽

pp. 1125-1131 ◽

Cited By ~ 9

Author(s):

Jian Cui ◽

Manabu Shibasaki ◽

Scott L. Davis ◽

David A. Low ◽

David M. Keller ◽

...

Keyword(s):

Heart Rate ◽

Heat Stress ◽

Sympathetic Nerve ◽

Sympathetic Nerve Activity ◽

Muscle Sympathetic Nerve Activity ◽

Whole Body ◽

Nerve Activity ◽

Baroreflex Control ◽

Whole Body Heat Stress ◽

Body Heat

Both whole body heat stress and stimulation of muscle metabolic receptors activate muscle sympathetic nerve activity (MSNA) through nonbaroreflex pathways. In addition to stimulating muscle metaboreceptors, exercise has the potential to increase internal temperature. Although we and others report that passive whole body heating does not alter the gain of the arterial baroreflex, it is unknown whether increased body temperature, often accompanying exercise, affects baroreflex function when muscle metaboreceptors are stimulated. This project tested the hypothesis that whole body heating alters the gain of baroreflex control of muscle sympathetic nerve activity (MSNA) and heart rate during muscle metaboreceptor stimulation engaged via postexercise muscle ischemia (PEMI). MSNA, blood pressure (BP, Finometer), and heart rate were recorded from 11 healthy volunteers. The volunteers performed isometric handgrip exercise until fatigue, followed by 2.5 min of PEMI. During PEMI, BP was acutely reduced and then raised pharmacologically using the modified Oxford technique. This protocol was repeated two to three times when volunteers were normothermic, and again during heat stress (increase core temperature ∼ 0.7°C) conditions. The slope of the relationship between MSNA and BP during PEMI was less negative (i.e., decreased baroreflex gain) during whole body heating when compared with the normothermic condition (−4.34 ± 0.40 to −3.57 ± 0.31 units·beat−1·mmHg−1, respectively; P = 0.015). The gain of baroreflex control of heart rate during PEMI was also decreased during whole body heating ( P < 0.001). These findings indicate that whole body heat stress reduces baroreflex control of MSNA and heart rate during muscle metaboreceptor stimulation.

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F14 Two different methods to evaluate baroreflex control of muscle sympathetic nerve activity

American Journal of Hypertension ◽

10.1016/s0895-7061(97)89299-0 ◽

1997 ◽

Vol 10 (4) ◽

pp. 176A

Author(s):

T TINUCCI

Keyword(s):

Sympathetic Nerve ◽

Sympathetic Nerve Activity ◽

Muscle Sympathetic Nerve Activity ◽

Nerve Activity ◽

Baroreflex Control

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Baroreflex control of muscle sympathetic nerve activity in postural orthostatic tachycardia syndrome

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.01243.2004 ◽

2005 ◽

Vol 289 (3) ◽

pp. H1226-H1233 ◽

Cited By ~ 37

Author(s):

N. Muenter Swift ◽

N. Charkoudian ◽

R. M. Dotson ◽

G. A. Suarez ◽

P. A. Low

Keyword(s):

Sympathetic Nerve ◽

Sympathetic Nerve Activity ◽

Valsalva Maneuver ◽

Muscle Sympathetic Nerve Activity ◽

Vasoactive Drug ◽

Postural Orthostatic Tachycardia Syndrome ◽

Nerve Activity ◽

Baroreflex Control ◽

Control Subjects ◽

Healthy Control

Postural orthostatic tachycardia syndrome (POTS) is characterized by excessive tachycardia during orthostasis. To test the hypothesis that patients with POTS have decreased sympathetic neural responses to baroreflex stimuli, we measured heart rate (HR) and muscle sympathetic nerve activity (MSNA) responses to three baroreflex stimuli including vasoactive drug boluses (modified Oxford technique), Valsalva maneuver, and head-up tilt (HUT) in POTS patients and healthy control subjects. The MSNA response to the Valsalva maneuver was significantly greater in the POTS group (controls, 26 ± 7 vs. POTS, 48 ± 6% of baseline MSNA/mmHg; P = 0.03). POTS patients also had an exaggerated MSNA response to 30° HUT (controls, 123 ± 24 vs. POTS, 208 ± 30% of baseline MSNA; P = 0.03) and tended to have an exaggerated response to 45° HUT (controls, 137 ± 27 vs. POTS, 248 ± 58% of baseline MSNA; P = 0.10). Sympathetic baroreflex sensitivity calculated during administration of the vasoactive drug boluses also tended to be greater in the POTS patients; however, this did not reach statistical significance ( P = 0.15). Baseline MSNA values during supine rest were not different between the groups (controls, 23 ± 4 vs. POTS, 16 ± 5 bursts/100 heartbeats; P = 0.30); however, resting HR was significantly higher in the POTS group (controls, 58 ± 3 vs. POTS, 82 ± 4 beats/min; P = 0.0001). Our results suggest that POTS patients have exaggerated MSNA responses to baroreflex challenges compared with healthy control subjects, although resting supine MSNA values did not differ between the groups.

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Dynamic and static baroreflex control of muscle sympathetic nerve activity (SNA) parallels that of renal and cardiac SNA during physiological change in pressure

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00642.2005 ◽

2005 ◽

Vol 289 (6) ◽

pp. H2641-H2648 ◽

Cited By ~ 16

Author(s):

Atsunori Kamiya ◽

Toru Kawada ◽

Kenta Yamamoto ◽

Daisaku Michikami ◽

Hideto Ariumi ◽

...

Keyword(s):

Sympathetic Nerve ◽

Sympathetic Nerve Activity ◽

Muscle Sympathetic Nerve Activity ◽

Rapid Change ◽

Pressure Change ◽

Systemic Circulation ◽

Open Loop ◽

Operating Pressure ◽

Nerve Activity ◽

Baroreflex Control

Despite accumulated knowledge on human baroreflex control of muscle sympathetic nerve activity (SNA), whether baroreflex control of muscle SNA parallels that of other SNAs, in particular renal and cardiac SNAs, remains unclear. Using urethane and α-chloralose-anesthetized, vagotomized and aortic-denervated rabbits ( n = 10), we recorded muscle SNA from tibial nerve by microneurography, simultaneously with renal and cardiac SNAs by wire electrode. To produce a baroreflex open-loop condition, we isolated the carotid sinuses from systemic circulation and altered the intracarotid sinus pressure (CSP) according to a binary white noise sequence of operating pressure ± 20 mmHg (for investigating dynamic characteristics of baroreflex) or in stepwise 20-mmHg increments from 40 to 160 mmHg (for investigating static characteristics of baroreflex). Dynamic high-pass characteristics of baroreflex control of muscle SNA, assessed by the increasing slope of transfer gain, showed that more rapid change of arterial pressure resulted in greater response of muscle SNA to pressure change and that these characteristics were similar to cardiac SNA but greater than renal SNA. However, numerical simulation based on the transfer function shows that the differences in dynamic baroreflex control at various organs result in detectable differences among SNAs only when CSP changes at unphysiologically high rates (i.e., 5 mmHg/s). On the other hand, static reverse-sigmoid characteristics of baroreflex control of muscle SNA agreed well with those of renal or cardiac SNAs. In conclusion, dynamic-linear and static-nonlinear baroreflex control of muscle SNA is similar to that of renal and cardiac SNAs under physiological pressure change.

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