High-cut characteristics of the baroreflex neural arc preserve baroreflex gain against pulsatile pressure

2002 ◽  
Vol 282 (3) ◽  
pp. H1149-H1156 ◽  
Author(s):  
Toru Kawada ◽  
Can Zheng ◽  
Yusuke Yanagiya ◽  
Kazunori Uemura ◽  
Tadayoshi Miyamoto ◽  
...  
Keyword(s):  
Heart Rate ◽  
Transfer Function ◽  
Sympathetic Nerve Activity ◽  
Dynamic Range ◽  
Open Loop ◽  
Loop Gain ◽  
Frequency Range ◽  
Nerve Activity ◽  
Pulsatile Pressure ◽  
Rate Frequency

A transfer function from baroreceptor pressure input to sympathetic nerve activity (SNA) shows derivative characteristics in the frequency range below 0.8 Hz in rabbits. These derivative characteristics contribute to a quick and stable arterial pressure (AP) regulation. However, if the derivative characteristics hold up to heart rate frequency, the pulsatile pressure input will yield a markedly augmented SNA signal. Such a signal would saturate the baroreflex signal transduction, thereby disabling the baroreflex regulation of AP. We hypothesized that the transfer gain at heart rate frequency would be much smaller than that predicted from extrapolating the derivative characteristics. In anesthetized rabbits ( n = 6), we estimated the neural arc transfer function in the frequency range up to 10 Hz. The transfer gain was lost at a rate of −20 dB/decade when the input frequency exceeded 0.8 Hz. A numerical simulation indicated that the high-cut characteristics above 0.8 Hz were effective to attenuate the pulsatile signal and preserve the open-loop gain when the baroreflex dynamic range was finite.

Calculation of threshold and saturation points of sigmoidal baroreflex function curves

2006 ◽  
Vol 291 (4) ◽  
pp. H2003-H2007 ◽  
Author(s):  
Lachlan M. McDowall ◽  
Roger A. L. Dampney
Keyword(s):  
Heart Rate ◽  
Sympathetic Nerve Activity ◽  
Gain Coefficient ◽  
Open Loop ◽  
Sigmoid Function ◽  
Input Output ◽  
Nerve Activity ◽  
Baroreflex Function ◽  
Range Difference ◽  
The Difference

The logistic sigmoid function curve provides an accurate description of the baroreflex input-output relationship and is the most commonly used equation for this purpose. The threshold (Thr) and saturation (Sat) values for the baroreflex are commonly defined as the values of mean arterial pressure (MAP) at which the reflexly controlled variable (e.g., heart rate or sympathetic nerve activity) is within 5% of the upper or lower plateau, respectively, of the sigmoid function. These values are referred to here as Thr5% and Sat5%. In many studies, Thr and Sat are calculated with the equations Thr = A3 − 2.0/ A2 and Sat = A3 + 2.0/ A2, where A3 is the value of MAP at the point where the reflexly controlled variable is at the midpoint of its range and A2 is the gain coefficient. Although it is commonly stated that the values of Thr and Sat calculated with these equations represent Thr5% and Sat5%, we show here that instead they are significantly greater and less than Thr5% and Sat5%, respectively. Furthermore, the operating range (difference between Thr and Sat) calculated with these equations is 32% less than the difference between Thr5% and Sat5%. We further show that the equations that provide correct values of Thr5% and Sat5% are Thr5% = A3 − 2.944/ A2 and Sat5% = A3 + 2.944/ A2. We propose that these be used as the standard equations for calculating threshold and saturation values when a logistic sigmoid function is used to model the open-loop baroreflex function curve.

Arterial baroreflex control of cardiac and renal sympathetic nerve activities is uniform in frequency domain

1991 ◽  
Vol 261 (2) ◽  
pp. R296-R300 ◽  
Author(s):  
S. Harada ◽  
S. Ando ◽  
T. Imaizumi ◽  
Y. Hirooka ◽  
K. Sunagawa ◽  
...  
Keyword(s):  
Phase Shift ◽  
Transfer Function ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Arterial Baroreflex ◽  
Frequency Range ◽  
Nerve Activity ◽  
Baroreflex Control ◽  
Renal Sympathetic Nerve ◽  
Renal Sympathetic

To investigate wideband dynamic properties of arterial baroreflex control of cardiac and renal sympathetic nerve activities, we assessed the transfer function using a "white-noise technique." In pentobarbital sodium-anesthetized cats, we simultaneously recorded, as the output, cardiac sympathetic nerve activity (CSNA) and renal sympathetic nerve activity (RSNA), while aortic pressure (AP) was randomly perturbed to impose input pressure changes with broad frequencies. We calculated the transfer function from AP to CSNA or to RSNA over the frequency range of 0.01-5 Hz through the spectral analysis of the input and output. We found that the gain, phase shift, and coherence of those transfer functions were statistically indistinguishable. The gain was rather flat below 0.05 Hz, steadily increased above 0.05 Hz, and plateaued above 0.3 Hz. The phase shift was out of phase up to 0.05 Hz and led by approximately 4 degrees above 0.05 Hz. The coherence was high (above 0.7) below 0.3 Hz and became lower above 0.3 Hz. These results suggest that arterial baroreflex control is uniform and similar between the two activities in the frequency range of 0.01-0.7 Hz.

Arterial baroreflex dynamics in normotensive and spontaneously hypertensive rats

1992 ◽  
Vol 263 (3) ◽  
pp. R524-R528 ◽  
Author(s):  
S. Harada ◽  
T. Imaizumi ◽  
S. Ando ◽  
Y. Hirooka ◽  
K. Sunagawa ◽  
...  
Keyword(s):  
Transfer Function ◽  
Sympathetic Nerve ◽  
Spontaneously Hypertensive Rats ◽  
Sympathetic Nerve Activity ◽  
Arterial Baroreflex ◽  
Frequency Range ◽  
Hypertensive Rats ◽  
Nerve Activity ◽  
Baroreflex Control ◽  
Spontaneously Hypertensive

To investigate dynamic or frequency-dependent characteristics of arterial baroreflex control of efferent sympathetic nerve activity in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY), we assessed the transfer function from aortic pressure (AP) to renal sympathetic nerve activity (RSNA) using a “white-noise technique.” In pentobarbital sodium-anesthetized rats, we recorded RSNA as the output, while AP was randomly perturbed to impose input pressure changes with broad frequencies. We calculated the transfer function from AP to RSNA over the frequency range of 0.01-5 Hz through the spectral analysis of the input and output. The results indicated that the gain, phase shift, and coherence of the transfer function for SHR and for WKY were similar and statistically indistinguishable. The gain was relatively constant below 0.05 Hz but increased steadily by fivefold as frequency increased in the frequency range of 0.05-0.8 Hz. The phase was out of phase where coherence was high. The coherence was high (greater than 0.5) in the frequency range of 0.04-0.8 and 1.00-1.03 Hz but was low in other frequencies. These results suggest that dynamic or frequency-dependent characteristics of arterial baroreflex control of RSNA were not altered in SHR as compared with WKY.

Effect of human galanin on the response of circulating catecholamines to hypoglycemia in man

1995 ◽  
Vol 133 (6) ◽  
pp. 723-728 ◽  
Author(s):  
Ettore C degli Uberti ◽  
Maria R Ambrosio ◽  
Marta Bondanelli ◽  
Giorgio Transforini ◽  
Alberto Valentini ◽  
...  
Keyword(s):  
Heart Rate ◽  
Healthy Subjects ◽  
Sympathetic Nerve Activity ◽  
Heart Rate Response ◽  
Statistical Significance ◽  
Inhibitory Effect ◽  
Amino Acid Residues ◽  
Nerve Activity ◽  
Receptor Stimulation

degli Uberti EC, Ambrosio MR, Bondanelli M, Trasforini G, Valentini A, Rossi R, Margutti A, Campo M. Effect of human galanin on the response of circulating catecholamines to hypoglycemia in man. Eur J Endocrinol 1995;133:723–8. ISSN 0804–4643 Human galanin (hGAL) is a neuropeptide with 30 amino acid residues that has been found in the peripheral and central nervous system, where it often co-exists with catecholamines. In order to clarify the possible role of hGAL in the regulation of sympathoadrenomedullary function, the effect of a 60 min infusion of hGAL (80 pmol·kg−1 · min−1) on plasma epinephrine and norepinephrine responses to insulin-induced hypoglycemia in nine healthy subjects was investigated. Human GAL administration significantly reduced both the release of basal norepinephrine and the response to insulin-induced hypoglycemia, whereas it attenuated the epinephrine response by 26%, with the hGAL-induced decrease in epinephrine release failing to achieve statistical significance. Human GAL significantly increased the heart rate in resting conditions and clearly exaggerated the heart rate response to insulin-induced hypoglycemia, whereas it had no effect on the blood pressure. We conclude that GAL receptor stimulation exerts an inhibitory effect on basal and insulin-induced hypoglycemia-stimulated release of norepinephrine. These findings provide further evidence that GAL may modulate sympathetic nerve activity in man but that it does not play an important role in the regulation of adrenal medullary function. Ettore C degli Uberti, Chair of Endocrinology, University of Ferrara, Via Savonarola 9, I-44100 Ferrara, Italy

scholarly journals The Cardiac Sympathetic Nerve Activity in the Elderly Is Attenuated in the Right Lateral Decubitus Position

2017 ◽  
Vol 3 ◽  
pp. 233372141770807 ◽  
Author(s):  
Konosuke Sasaki ◽  
Mayu Haga ◽  
Sarina Bao ◽  
Haruka Sato ◽  
Yoshikatsu Saiki ◽  
...  
Keyword(s):  
Heart Rate ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Lateral Decubitus Position ◽  
The Other ◽  
Elderly Adults ◽  
Nerve Activity ◽  
Left Lateral Decubitus Position ◽  
Lateral Decubitus ◽  
The Right

Objectives: The aim of this study was to evaluate the effect of the supine, left lateral decubitus, and right lateral decubitus positions on autonomic nervous activity in elderly adults by using spectral analysis of heart rate variability (HRV). Method: Forty-five adults aged 73.6 ± 5.7 years were enrolled. After lying in the supine position, all participants moved to the lateral decubitus positions in a random order and maintained the positions for 10 min, while electrocardiographic data were recorded to measure HRV. Results: The lowest heart rate continued for 10 min when participants were in the left lateral decubitus position compared with the other two positions ( p < .001), while the HRV indexes remained unchanged. The low-frequency HRV to high-frequency HRV ratio (LF/HF) for the right lateral decubitus position was significantly lower than that for the other positions. Discussion: The right lateral decubitus position may attenuate sympathetic nerve activity in elderly adults.

scholarly journals Disruption of phase synchronization between blood pressure and muscle sympathetic nerve activity in postural vasovagal syncope

2013 ◽  
Vol 305 (8) ◽  
pp. H1238-H1245 ◽  
Author(s):  
Christopher E. Schwartz ◽  
Elisabeth Lambert ◽  
Marvin S. Medow ◽  
Julian M. Stewart
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Phase Synchronization ◽  
Vasovagal Syncope ◽  
Muscle Sympathetic Nerve Activity ◽  
Nerve Activity ◽  
Control Subjects ◽  
Late Stages

Withdrawal of muscle sympathetic nerve activity (MSNA) may not be necessary for the precipitous fall of peripheral arterial resistance and arterial pressure (AP) during vasovagal syncope (VVS). We tested the hypothesis that the MSNA-AP baroreflex entrainment is disrupted before VVS regardless of MSNA withdrawal using the phase synchronization between blood pressure and MSNA during head-up tilt (HUT) to measure reflex coupling. We studied eight VVS subjects and eight healthy control subjects. Heart rate, AP, and MSNA were measured during supine baseline and at early, mid, late, and syncope stages of HUT. Phase synchronization indexes, measuring time-dependent differences between MSNA and AP phases, were computed. Directionality indexes, indicating the influence of AP on MSNA (neural arc) and MSNA on AP (peripheral arc), were computed. Heart rate was greater in VVS compared with control subjects during early, mid, and late stages of HUT and significantly declined at syncope ( P = 0.04). AP significantly decreased during mid, late, and syncope stages of tilt in VVS subjects only ( P = 0.001). MSNA was not significantly different between groups during HUT ( P = 0.700). However, the phase synchronization index significantly decreased during mid and late stages in VVS subjects but not in control subjects ( P < .001). In addition, the neural arc was significantly affected more than the peripheral arc before syncope. In conclusion, VVS is accompanied by a loss of the synchronous AP-MSNA relationship with or without a loss in MSNA at faint. This provides insight into the mechanisms behind the loss of vasoconstriction and drop in AP independent of MSNA at the time of vasovagal faint.

scholarly journals Heart rate variability and muscle sympathetic nerve activity response to acute stress: the effect of breathing

2010 ◽  
Vol 299 (1) ◽  
pp. R80-R91 ◽  
Author(s):  
Lindsay D. DeBeck ◽  
Stewart R. Petersen ◽  
Kelvin E. Jones ◽  
Michael K. Stickland
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Sympathetic Nerve ◽  
Spontaneous Breathing ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Cold Pressor ◽  
Isometric Handgrip ◽  
Nerve Activity ◽  
Controlled Breathing

Previous research has suggested a relationship between low-frequency power of heart rate variability (HRV; LF in normalized units, LFnu) and muscle sympathetic nerve activity (MSNA). However, investigations have not systematically controlled for breathing, which can modulate both HRV and MSNA. Accordingly, the aims of this experiment were to investigate the possibility of parallel responses in MSNA and HRV (LFnu) to selected acute stressors and the effect of controlled breathing. After data were obtained at rest, 12 healthy males (28 ± 5 yr) performed isometric handgrip exercise (30% maximal voluntary contraction) and the cold pressor test in random order, and were then exposed to hypoxia (inspired fraction of O2 = 0.105) for 7 min, during randomly assigned spontaneous and controlled breathing conditions (20 breaths/min, constant tidal volume, isocapnic). MSNA was recorded from the peroneal nerve, whereas HRV was calculated from ECG. At rest, controlled breathing did not alter MSNA but decreased LFnu ( P < 0.05 for all) relative to spontaneous breathing. MSNA increased in response to all stressors regardless of breathing. LFnu increased with exercise during both breathing conditions. During cold pressor, LFnu decreased when breathing was spontaneous, whereas in the controlled breathing condition, LFnu was unchanged from baseline. Hypoxia elicited increases in LFnu when breathing was controlled, but not during spontaneous breathing. The parallel changes observed during exercise and controlled breathing during hypoxia suggest that LFnu may be an indication of sympathetic outflow in select conditions. However, since MSNA and LFnu did not change in parallel with all stressors, a cautious approach to the use of LFnu as a marker of sympathetic activity is warranted.

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