Muscle metaboreflex modulates the arterial baroreflex dynamic effects on peripheral vascular conductance in humans

Ichinose, Masashi; Nishiyasu, Takeshi

doi:10.1152/ajpheart.00673.2004

Cited by 27 publications

(32 citation statements)

References 33 publications

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“…Indeed, this association suggests that MSNA and the magnitude of the ensuing sympathetic vascular transduction importantly contribute to the support of resting BP. In agreement, a nearly identical time line has been found for increases in MSNA and subsequent alterations in vascular tone and BP during carotid baroreceptor perturbation (13,22). Importantly, we also found that cardiac cycles without MSNA bursts (nonbursts) are followed by a subsequent increase in LVC and decrease in BP.…”

Section: Discussionsupporting

confidence: 90%

Spontaneous bursts of muscle sympathetic nerve activity decrease leg vascular conductance in resting humans

Fairfax

Padilla

Vianna

et al. 2013

American Journal of Physiology-Heart and Circulatory Physiology

118

123

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Fairfax ST, Padilla J, Vianna LC, Davis MJ, Fadel PJ. Spontaneous bursts of muscle sympathetic nerve activity decrease leg vascular conductance in resting humans. Am J Physiol Heart Circ Physiol 304: H759 -H766, 2013. First published January 4, 2013 doi:10.1152/ajpheart.00842.2012.-Previous studies in humans attempting to assess sympathetic vascular transduction have related large reflex-mediated increases in muscle sympathetic nerve activity (MSNA) to associated changes in limb vascular resistance. However, such procedures do not provide insight into the ability of MSNA to dynamically control vascular tone on a beat-by-beat basis. Thus we examined the influence of spontaneous MSNA bursts on leg vascular conductance (LVC) and how variations in MSNA burst pattern (single vs. multiple bursts) and burst size may affect the magnitude of the LVC response. In 11 young men, arterial blood pressure, common femoral artery blood flow, and MSNA were continuously recorded during 20 min of supine rest. Signal averaging was used to characterize percent changes in LVC for 15 cardiac cycles following heartbeats associated with and without MSNA bursts. LVC significantly decreased following MSNA bursts, reaching a nadir during the 6th cardiac cycle (single bursts, Ϫ2.9 Ϯ 1.1%; and multiple bursts, Ϫ11.0 Ϯ 1.4%; both, P Ͻ 0.001). Individual MSNA burst amplitudes and the total amplitude of consecutive bursts were related to the magnitude of peak decreases in LVC. In contrast, cardiac cycles without MSNA bursts were associated with a significant increase in LVC (ϩ3.1 Ϯ 0.5%; P Ͻ 0.001). Total vascular conductance decreased in parallel with LVC also reaching a nadir around the peak rise in arterial blood pressure following an MSNA burst. Collectively, these data are the first to assess beat-by-beat sympathetic vascular transduction in resting humans, demonstrating robust and dynamic decreases in LVC following MSNA bursts, an effect that was absent for cardiac cycles without MSNA bursts.MSNA; sympathetic vascular transduction; vascular responsiveness; blood pressure; femoral blood flow THE GENERATION AND REGULATION of central sympathetic outflow has been a primary focus of autonomic cardiovascular research for decades (5, 10). However, the ability of the peripheral vasculature to respond to changes in sympathetic activity has received less attention. Indeed, for sympathetic nerve impulses to influence vascular tone, there must be successful release of neurotransmitter(s) into the synaptic cleft (2), abundant receptor binding (35), and widespread signal transduction within vascular smooth muscle (34) to result in a vasomotor response (29). Although this paradigm is widely accepted (3,12,26), limited data are available in humans. Furthermore, previous studies attempting to demonstrate sympathetic vascular transduction in humans have related large reflex-mediated increases in muscle sympathetic nerve activity (MSNA) to associated changes in vascular resistance (6,17,23). While such procedures reveal that elevated MSNA increases vascular...

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Section: Discussionsupporting

confidence: 90%

Spontaneous bursts of muscle sympathetic nerve activity decrease leg vascular conductance in resting humans

Fairfax

Padilla

Vianna

et al. 2013

American Journal of Physiology-Heart and Circulatory Physiology

118

123

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“…CO and LBF were measured using Doppler ultrasound as previously described in detail (22,23,43). Briefly, a Doppler ultrasound system (HDI 3500, Philips) equipped with a hand-held transducer probe (model D2 CW) with an operating frequency of 2 MHz was used to measure aortic blood velocity in the suprasternal notch.…”

Section: Subjectsmentioning

confidence: 99%

Individual differences in cardiac and vascular components of the pressor response to isometric handgrip exercise in humans

Watanabe

Ichinose

Tahara

et al. 2014

American Journal of Physiology-Heart and Circulatory Physiology

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Watanabe K, Ichinose M, Tahara R, Nishiyasu T. Individual differences in cardiac and vascular components of the pressor response to isometric handgrip exercise in humans. Am J Physiol Heart Circ Physiol 306: H251-H260, 2014. First published November 8, 2013 doi:10.1152/ajpheart.00699.2013.-We tested the hypotheses that, in humans, changes in cardiac output (CO) and total peripheral vascular resistance (TPR) occurring in response to isometric handgrip exercise vary considerably among individuals and that those individual differences are related to differences in muscle metaboreflex and arterial baroreflex function. Thirty-nine healthy subjects performed a 1-min isometric handgrip exercise at 50% of maximal voluntary contraction. This was followed by a 4-min postexercise muscle ischemia (PEMI) period to selectively maintain activation of the muscle metaboreflex. All subjects showed increases in arterial pressure during exercise. Interindividual coefficients of variation (CVs) for the changes in CO and TPR between rest and exercise periods (CO: 95.1% and TPR: 87.8%) were more than twofold greater than CVs for changes in mean arterial pressure (39.7%). There was a negative correlation between CO and TPR responses during exercise (r ϭ Ϫ0.751, P Ͻ 0.01), but these CO and TPR responses correlated positively with the corresponding responses during PEMI (r ϭ 0.568 and 0.512, respectively, P Ͻ 0.01). The CO response during exercise did not correlate with PEMI-induced changes in an index of cardiac parasympathetic tone and cardiac baroreflex sensitivity. These findings demonstrate that the changes in CO and TPR that occur in response to isometric handgrip exercise vary considerably among individuals and that the two responses have an inverse relationship. They also suggest that individual differences in components of the pressor response are attributable in part to variations in muscle metaboreflex-mediated cardioaccelerator and vasoconstrictor responses. cardiac output; peripheral vascular resistance; muscle metaboreflex; arterial baroreflex DURING ISOMETRIC EXERCISE, arterial blood pressure, heart rate (HR), and sympathetic nerve activity all increase in association with increases in the intensity and duration of the exercise. This pressor response is governed mainly by neural mechanisms: central command (52) as well as a feedback system operating via afferent input from exercising skeletal muscle receptors (muscle metaboreflex and mechanoreflex) (40,41,51) and from arterial and cardiopulmonary baroreceptors (arterial and cardiopulmonary baroreflexes) (51, 52). While the increase in arterial pressure during isometric exercise is a well-established response, the responses of the components mediating the pressor response, cardiac output (CO) and total peripheral vascular resistance (TPR), remain controversial. In fact, previous studies have shown that, during isometric handgrip exercise in healthy humans, the pressor response occurs via an increase in CO (16,32,[34][35][36]57), an increase in TPR (6, 17), or both of those...

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“…The box pressure was measured using a pressure transducer mounted on the box. We measured exercising LBF using Doppler ultrasound, as previously described (20,48). Briefly, a Doppler ultrasound system (HDI 5000; ATL Ultrasound, Bothell, WA) equipped with a hand-held transducer probe (model L12-5) with an operating frequency of 6 MHz was utilized to simultaneously measure two-dimensional common femoral artery diameter and mean blood velocity (MBV).…”

Section: Methodsmentioning

confidence: 99%

“…The crosssectional area of the femoral artery (CSA) was estimated using a representative Dm as CSA ϭ (Dm/10/2) 2 ·. MBV was continuously estimated using a computer program developed with the aid of LabVIEW (version 6.0; National Instruments), as described in detail elsewhere (20). Our system collects MBV at 100 Hz together with the analog signals representing the ECG, blood pressure waveform, and box pressure.…”

Section: Methodsmentioning

confidence: 99%

Increasing blood flow to exercising muscle attenuates systemic cardiovascular responses during dynamic exercise in humans

Ichinose

Ichinose-Kuwahara

Kondo

et al. 2015

American Journal of Physiology-Regulatory, Integrative and Comp

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Reducing blood flow to working muscles during dynamic exercise causes metabolites to accumulate within the active muscles and evokes systemic pressor responses. Whether a similar cardiovascular response is elicited with normal blood flow to exercising muscles during dynamic exercise remains unknown, however. To address that issue, we tested whether cardiovascular responses are affected by increases in blood flow to active muscles. Thirteen healthy subjects performed dynamic plantarflexion exercise for 12 min at 20%, 40%, and 60% of peak workload (EX20, EX40, and EX60) with their lower thigh enclosed in a negative pressure box. Under control conditions, the box pressure was the same as the ambient air pressure. Under negative pressure conditions, beginning 3 min after the start of the exercise, the box pressure was decreased by 20, 45, and then 70 mmHg in stepwise fashion with 3-min step durations. During EX20, the negative pressure had no effect on blood flow or the cardiovascular responses measured. However, application of negative pressure increased blood flow to the exercising leg during EX40 and EX60. This increase in blood flow had no significant effect on systemic cardiovascular responses during EX40, but it markedly attenuated the pressor responses otherwise seen during EX60. These results demonstrate that during mild exercise, normal blood flow to exercising muscle is not a factor eliciting cardiovascular responses, whereas it elicits an important pressor effect during moderate exercise. This suggests blood flow to exercising muscle is a major determinant of cardiovascular responses during dynamic exercise at higher than moderate intensity. integrated circulatory regulation; neural cardiovascular regulation; muscle metaboreflex DURING DYNAMIC EXERCISE, INCREASED skeletal muscle blood flow is essential to ensure an appropriate supply of O 2 to the active muscles and to remove the metabolic byproducts and generated heat. This exercise-induced skeletal muscle hyperemia is thought to be initially elicited by local mechanical and metabolic factors and to be modulated by neural cardiovascular regulatory mechanisms (8,41). Neural mechanisms also act to increase cardiac output (CO) and to redistribute blood flow from inactive regions to support the increase in skeletal muscle flow. This neural cardiovascular regulation is thought to be mediated by central command (41), as well as by feedback transmitted via afferent nerves (group III and IV fibers), innervating the working skeletal muscles, which are sensitive to mechanical (the so-called muscle mechanoreflex) and metabolic changes (the so-called muscle metaboreflex) (26,33,34,37,42), and are modulated via the arterial and cardiopulmonary baroreflexes (23,41,42).Reducing the blood flow to working muscles during dynamic exercise causes accumulation of metabolites within the active muscles and evokes muscle metaboreflex-mediated increases in sympathetic nerve activity, heart rate (HR), and systemic blood pressure (1,5,12,19,29,30,35,42). In addition, the reduced b...

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Muscle metaboreflex modulates the arterial baroreflex dynamic effects on peripheral vascular conductance in humans

Cited by 27 publications

References 33 publications

Spontaneous bursts of muscle sympathetic nerve activity decrease leg vascular conductance in resting humans

Spontaneous bursts of muscle sympathetic nerve activity decrease leg vascular conductance in resting humans

Individual differences in cardiac and vascular components of the pressor response to isometric handgrip exercise in humans

Increasing blood flow to exercising muscle attenuates systemic cardiovascular responses during dynamic exercise in humans

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