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Toschi-Dias E, Montano N, Tobaldini E, Trevizan PF, Groehs RV, Antunes-Correa LM, Nobre TS, Lobo DM, Sales ARK, Ueno-Pardi LM, de Matos LDNJ, Oliveira PA, Braga AMFW, Alves MJNN, Negrão CE, Rondon MUPB. Oscillatory Pattern of Sympathetic Nerve Bursts Is Associated With Baroreflex Function in Heart Failure Patients With Reduced Ejection Fraction. Front Neurosci 2021; 15:669535. [PMID: 34531714 PMCID: PMC8439256 DOI: 10.3389/fnins.2021.669535] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 07/13/2021] [Indexed: 12/28/2022] Open
Abstract
Sympathetic hyperactivation and baroreflex dysfunction are hallmarks of heart failure with reduced ejection fraction (HFrEF). However, it is unknown whether the progressive loss of phasic activity of sympathetic nerve bursts is associated with baroreflex dysfunction in HFrEF patients. Therefore, we investigated the association between the oscillatory pattern of muscle sympathetic nerve activity (LFMSNA/HFMSNA) and the gain and coupling of the sympathetic baroreflex function in HFrEF patients. In a sample of 139 HFrEF patients, two groups were selected according to the level of LFMSNA/HFMSNA index: (1) Lower LFMSNA/HFMSNA (lower terciles, n = 46, aged 53 ± 1 y) and (2) Higher LFMSNA/HFMSNA (upper terciles, n = 47, aged 52 ± 2 y). Heart rate (ECG), arterial pressure (oscillometric method), and muscle sympathetic nerve activity (microneurography) were recorded for 10 min in patients while resting. Spectral analysis of muscle sympathetic nerve activity was conducted to assess the LFMSNA/HFMSNA, and cross-spectral analysis between diastolic arterial pressure, and muscle sympathetic nerve activity was conducted to assess the sympathetic baroreflex function. HFrEF patients with lower LFMSNA/HFMSNA had reduced left ventricular ejection fraction (26 ± 1 vs. 29 ± 1%, P = 0.03), gain (0.15 ± 0.03 vs. 0.30 ± 0.04 a.u./mmHg, P < 0.001) and coupling of sympathetic baroreflex function (0.26 ± 0.03 vs. 0.56 ± 0.04%, P < 0.001) and increased muscle sympathetic nerve activity (48 ± 2 vs. 41 ± 2 bursts/min, P < 0.01) and heart rate (71 ± 2 vs. 61 ± 2 bpm, P < 0.001) compared with HFrEF patients with higher LFMSNA/HFMSNA. Further analysis showed an association between the LFMSNA/HFMSNA with coupling of sympathetic baroreflex function (R = 0.56, P < 0.001) and left ventricular ejection fraction (R = 0.23, P = 0.02). In conclusion, there is a direct association between LFMSNA/HFMSNA and sympathetic baroreflex function and muscle sympathetic nerve activity in HFrEF patients. This finding has clinical implications, because left ventricular ejection fraction is less in the HFrEF patients with lower LFMSNA/HFMSNA.
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Affiliation(s)
- Edgar Toschi-Dias
- Instituto do Coração (InCor), Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil.,Department of Internal Medicine, Fondazione IRCSS Ca' Granda, Ospedale Maggiore Policlínico, Milan, Italy.,Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
| | - Nicola Montano
- Department of Internal Medicine, Fondazione IRCSS Ca' Granda, Ospedale Maggiore Policlínico, Milan, Italy.,Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
| | - Eleonora Tobaldini
- Department of Internal Medicine, Fondazione IRCSS Ca' Granda, Ospedale Maggiore Policlínico, Milan, Italy.,Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
| | - Patrícia F Trevizan
- Instituto do Coração (InCor), Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil
| | - Raphaela V Groehs
- Instituto do Coração (InCor), Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil
| | - Ligia M Antunes-Correa
- Instituto do Coração (InCor), Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil
| | - Thais S Nobre
- Instituto do Coração (InCor), Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil
| | - Denise M Lobo
- Instituto do Coração (InCor), Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil
| | - Allan R K Sales
- Instituto do Coração (InCor), Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil
| | - Linda M Ueno-Pardi
- Instituto do Coração (InCor), Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil
| | - Luciana D N J de Matos
- Instituto do Coração (InCor), Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil
| | - Patrícia A Oliveira
- Instituto do Coração (InCor), Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil
| | - Ana Maria F W Braga
- Instituto do Coração (InCor), Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil
| | - Maria Janieire N N Alves
- Instituto do Coração (InCor), Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil
| | - Carlos E Negrão
- Instituto do Coração (InCor), Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil.,School of Physical Education and Sport, University of São Paulo, São Paulo, Brazil
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Montano N, Furlan R, Guzzetti S, McAllen RM, Julien C. Analysis of sympathetic neural discharge in rats and humans. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2009; 367:1265-1282. [PMID: 19324708 DOI: 10.1098/rsta.2008.0285] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Neural signals convey information through two different modalities: intensity and discharge pattern. The intensity code is based on the number of action potentials per unit time, which is then easily translated into neurotransmitter release. This kind of information may be assessed simply by counting the number of spikes or bursts over a time unit. However, the discharge pattern is a further, efficient means of neural information transfer. Rhythmic patterns (i.e. oscillations) can support highly structured, temporal codes based on correlation and synchronization. It is therefore clear that applying frequency domain analysis to sympathetic activity recorded in animals and humans may provide additional information about the neural control of the circulation. Over the last century, data obtained by the analysis of sympathetic activity in experimental animals, and recently also in humans, have provided fundamental contributions to our understanding of the physiological mechanisms involved in the neural control of circulation, as well as how these are altered in cardiovascular and non-cardiovascular diseases. The aim of this paper is to address some aspects related to the recording, analysis and interpretation of sympathetic activity in rats and humans, with special emphasis on analysis in the frequency domain.
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Affiliation(s)
- Nicola Montano
- Internal Medicine II, Department of Clinical Sciences, L. Sacco Hospital, University of Milan, 20157 Milano, Italy.
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Brown DR, Cassis LA, Silcox DL, Brown LV, Randall DC. Empirical and theoretical analysis of the extremely low frequency arterial blood pressure power spectrum in unanesthetized rat. Am J Physiol Heart Circ Physiol 2006; 291:H2816-24. [PMID: 16844925 DOI: 10.1152/ajpheart.00135.2006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The slope of the log of power versus the log of frequency in the arterial blood pressure (BP) power spectrum is classically considered constant over the low-frequency range (i.e., “fractal” behavior), and is quantified by β in the relationship “1/ fβ.” In practice, the fractal range cannot extend to indefinitely low frequencies, but factor(s) that terminate this behavior, and determine β, are unclear. We present 1) data in rats ( n = 8) that reveal an extremely low frequency spectral region (0.083–1 cycle/h), where β approaches 0 (i.e., the “shoulder”); and 2) a model that 1) predicts realistic values of β within that range of the spectrum that conforms to fractal dynamics (∼1–60 cycles/h), 2) offers an explanation for the shoulder, and 3) predicts that the “successive difference” in mean BP (mBP) is an important parameter of circulatory function. We recorded BP for up to 16 days. The absolute difference between successive mBP samples at 0.1 Hz (the successive difference, or Δ) was 1.87 ± 0.21 mmHg (means ± SD). We calculated β for three frequency ranges: 1) 0.083–1; 2) 1–6; and 3) 6–60 cycles/h. The β for all three regions differed ( P < 0.01). For the two higher frequency ranges, β indicated a fractal relationship (β6–60/h = 1.27 ± 0.01; β1–6/h = 1.80 ± 0.16). Conversely, the slope of the lowest frequency region (i.e., the shoulder) was nearly flat (β0.083–1 /h = 0.32 ± 0.28). We simulated the BP time series as a random walk about 100 mmHg with ranges above and below of 10, 30, and 50 mmHg and with Δ from 0.5 to 2.5. The spectrum for the conditions mimicking actual BP time series (i.e., range, 85–115 mmHg; Δ, 2.00) resembled the observed spectra, with β in the lowest frequency range = 0.207 and fractal-like behavior in the two higher frequency ranges (β = 1.707 and 2.057). We suggest that the combined actions of mechanisms limiting the excursion of arterial BP produce the shoulder in the spectrum and that Δ contributes to determining β.
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Affiliation(s)
- David R Brown
- Center for Biomedical Engineering, University of Kentucky, Lexington, KY 40536-0298, USA
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Boustany CM, Brown DR, Randall DC, Cassis LA. AT1-receptor antagonism reverses the blood pressure elevation associated with diet-induced obesity. Am J Physiol Regul Integr Comp Physiol 2005; 289:R181-6. [PMID: 15774768 DOI: 10.1152/ajpregu.00507.2004] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Previous studies in our laboratory demonstrated that rats exhibiting obesity in response to a moderately high-fat (MHF) diet developed hypertension associated with activation of the local and systemic renin-angiotensin system. In this study, we examined the effect of the angiotensin type 1 (AT(1))-receptor antagonist, losartan, on blood pressure in obesity-prone (OP) and obesity-resistant (OR) rats fed a MHF diet. Using telemetry monitoring, we characterized the evolution of blood pressure elevations during the development of obesity. Male Sprague-Dawley rats were implanted with telemetry transducers for chronic monitoring of blood pressure, and baseline measurements were obtained. Rats were then switched to the MHF diet (32% kcal as fat) and were segregated into OP and OR groups at week 5. At week 9 on the MHF diet, OP rats exhibited significantly greater 24-h mean arterial blood pressure compared with OR rats (OP: 105 +/- 4 mmHg, OR: 96 +/- 2 mmHg; P < 0.05). Elevations in blood pressure in OP rats were manifest as an increase in systolic pressure. Administration of losartan to all rats at week 9 resulted in a reduction in blood pressure; however, losartan had the greatest effect in OP rats (percent decrease in mean arterial pressure by losartan; OP: 19 +/- 4, OR: 10 +/- 2%; P < 0.05). These results demonstrate that elevations in blood pressure occur subsequent to established obesity in rats fed a high-fat diet. Moreover, these results demonstrate the ability of losartan to reverse the blood pressure increase from diet-induced obesity, supporting a primary role for the renin-angiotensin system in obesity-associated hypertension.
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Affiliation(s)
- Carine M Boustany
- Division of Pharmaceutical Sciences, University of Kentucky, Lexington, KY 40536-0200, USA
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Randall DC, Baldridge BR, Zimmerman EE, Carroll JJ, Speakman RO, Brown DR, Taylor RF, Patwardhan A, Burgess DE. Blood pressure power within frequency range ∼0.4 Hz in rat conforms to self-similar scaling following spinal cord transection. Am J Physiol Regul Integr Comp Physiol 2005; 288:R737-41. [PMID: 15498964 DOI: 10.1152/ajpregu.00544.2003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study quantified the effect of interrupting the descending input to the sympathetic preganglionic neurons on the dynamic behavior of arterial blood pressure (BP) in the unanesthetized rat. BP was recorded for ∼4-h intervals in six rats in the neurally intact state and in the same animals after complete spinal cord transection (SCT) between T4 and T5. In the intact state, power within the frequency range of 0.35–0.45 Hz was 1.53 ± 0.38 mmHg2/Hz (mean ± SD by fast Fourier transform). One week after SCT, power within this range decreased significantly ( P < 0.05) to 0.43 ± 0.62 mmHg2/Hz. To test for self-similarity before and after SCT, we analyzed data using a wavelet (i.e., functionally, a digital bandpass filter) tuned to be maximally sensitive to fluctuations with periods of ∼2, 4, 8, 16, 32, or 64 s. In the control state, all fluctuations with periods of ≥4 s conformed to a “self-similar” (i.e., fractal) distribution. In marked contrast, the oscillations with a period of ∼2 s (i.e., ∼0.4 Hz) were significantly set apart from those at lower frequencies. One day and seven days after the complete SCT, however, the BP fluctuations at ∼0.4 Hz now also conformed to the same self-similar behavior characteristic of the lower frequencies. We conclude that 1) an intact sympathetic nervous system endows that portion of the power spectrum centered around ∼0.4 Hz with properties (e.g., a periodicity) that differ significantly from the self-similar behavior that characterizes the lower frequencies and 2) even within the relatively high frequency range at 0.4 Hz self-similarity is the “default” condition after sympathetic influences have been eliminated.
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Affiliation(s)
- David C Randall
- Department of Physiology, University of Kentucky College of Medicine, Lexington, KY 40536-0298, USA.
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Chapuis B, Vidal-Petiot E, Oréa V, Barrès C, Julien C. Linear modelling analysis of baroreflex control of arterial pressure variability in rats. J Physiol 2004; 559:639-49. [PMID: 15235092 PMCID: PMC1665118 DOI: 10.1113/jphysiol.2004.065474] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The objective of the present study was to examine whether a simple linear feedback model of arterial pressure (AP) control by the sympathetic nervous system would be able to reproduce the characteristic features of normal AP variability by using AP and renal sympathetic nerve activity (RSNA) data collected in conscious sinoaortic baroreceptor denervated (SAD) rats. As compared with baroreceptor-intact rats (n=8), SAD rats (n=10) had increased spectral power (+ 680%) of AP in the low frequency range (LF, 0.0003-0.14 Hz) and reduced power (-19%) in the mid-frequency range (MF, 0.14-0.8 Hz) containing Mayer waves. In individual SAD rats, RSNA data were translated into 'sympathetic' AP time series by using the RSNA-AP transfer function that had been previously characterized in anaesthetized rats. AP 'perturbation' time series were then calculated by subtracting 'sympathetic' from actual AP time series. Actual RSNA and AP 'perturbation' time series were introduced in a reflex loop that was closed by using the previously identified baroreflex transfer function (from baroreceptor afferent activity to RSNA). By progressively increasing the open-loop static gain, it was possible to compute virtual AP power spectra that increasingly deviated from their progenitor spectra, with spectral power decreasing in the LF range (as a result of baroreflex buffering of haemodynamic perturbations), and increasing in the MF band (as a result of increasing transients at the resonance frequency of the loop). The most accurate reproduction of actual AP and RSNA spectra observed in baroreceptor-intact rats was obtained at 20-30% of the baroreflex critical gain (open-loop static gain resulting in self-sustained oscillations at the resonance frequency). In conclusion, while the gain of the sympathetic component of the arterial baroreceptor reflex largely determines its ability to provide an efficient correction of slow haemodynamic perturbations, this is achieved at the cost of increasing transients at higher frequencies (Mayer waves). However, the system remains fundamentally stable.
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Affiliation(s)
- Bruno Chapuis
- Département de Physiologie et Pharmacologie Clinique, Faculté de Pharmacie, Université Claude Bernard Lyon 1, Lyon 69373, France
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Julien C, Chapuis B, Cheng Y, Barrès C. Dynamic interactions between arterial pressure and sympathetic nerve activity: role of arterial baroreceptors. Am J Physiol Regul Integr Comp Physiol 2003; 285:R834-41. [PMID: 12805090 DOI: 10.1152/ajpregu.00102.2003] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The role of arterial baroreceptors in controlling arterial pressure (AP) variability through changes in sympathetic nerve activity was examined in conscious rats. AP and renal sympathetic nerve activity (RSNA) were measured continuously during 1-h periods in freely behaving rats that had been subjected to sinoaortic baroreceptor denervation (SAD) or a sham operation 2 wk before study (n = 10 in each group). Fast Fourier transform analysis revealed that chronic SAD did not alter high-frequency (0.75-5 Hz) respiratory-related oscillations of mean AP (MAP) and RSNA, decreased by approximately 50% spectral power of both variables in the midfrequency band (MF, 0.27-0.74 Hz) containing the so-called Mayer waves, and induced an eightfold increase in MAP power without altering RSNA power in the low-frequency band (0.005-0.27 Hz). In both groups of rats, coherence between RSNA and MAP was maximal in the MF band and was usually weak at lower frequencies. In SAD rats, the transfer function from RSNA to MAP showed the characteristics of a second-order low-pass filter containing a fixed time delay ( approximately 0.5 s). These results indicate that arterial baroreceptors are not involved in production of respiratory-related oscillations of RSNA but play a major role in the genesis of synchronous oscillations of MAP and RSNA at the frequency of Mayer waves. The weak coupling between slow fluctuations of RSNA and MAP in sham-operated and SAD rats points to the interference of noise sources unrelated to RSNA affecting MAP and of noise sources unrelated to MAP affecting RSNA.
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Affiliation(s)
- Claude Julien
- Départmwnt de Physiologie et Pharmacie Clinique, Faculté de Pharmacie, Université Claude Bernad Lyon, Lyon, France.
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