Upright Tilt Resets Dynamic Transfer Function of Baroreflex Neural Arc to Minify the Pressure Disturbance in Total Baroreflex Control

Kamiya, Atsunori; Kawada, Toru; Yamamoto, Keizô; Mizuno, Masaki; Shimizu, Shuji; Sugimachi, Masaru

doi:10.2170/physiolsci.rp004308

Cited by 7 publications

(11 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Once the open-loop dynamic and static characteristics of a system are both identified, closed-loop system responses can be simulated [14][15][16]. To compare closed-loop behavior of the carotid sinus baroreflex between control and CHF conditions, step inputs ranging from -10 to -60 mmHg were applied as exogenous disturbances, and resulting AP responses were simulated.…”

Section: Simulation Studymentioning

confidence: 99%

See 1 more Smart Citation

Open-loop dynamic and static characteristics of the carotid sinus baroreflex in rats with chronic heart failure after myocardial infarction

Kawada

Kamiya

et al. 2010

J Physiol Sci

Self Cite

View full text Add to dashboard Cite

We estimated open-loop dynamic characteristics of the carotid sinus baroreflex in normal control rats and chronic heart failure (CHF) rats after myocardial infarction. First, the neural arc transfer function from carotid sinus pressure to splanchnic sympathetic nerve activity (SNA) and its corresponding step response were examined. Although the steady-state response was attenuated in CHF, the negative peak response and the time to peak did not change significantly, suggesting preserved neural arc dynamic characteristics. Next, the peripheral arc transfer function from SNA to arterial pressure (AP) and its corresponding step response were examined. The steady-state response and the initial slope were reduced in CHF, suggesting impaired end-organ responses. In a simulation study based on the dynamic and static characteristics, the percent recovery of AP was reduced progressively as the size of disturbance increased in CHF, suggesting that a reserve for AP buffering is lost in CHF despite relatively maintained baseline AP.

show abstract

Section: Simulation Studymentioning

confidence: 99%

“…5a [14][15][16]. We used impulse responses derived from the group-averaged neural and peripheral arc transfer functions (H N and H P ) to calculate dynamic responses of the carotid sinus baroreflex.…”

Section: Simulation Studymentioning

confidence: 99%

Open-loop dynamic and static characteristics of the carotid sinus baroreflex in rats with chronic heart failure after myocardial infarction

Kawada

Kamiya

et al. 2010

J Physiol Sci

Self Cite

View full text Add to dashboard Cite

show abstract

“…1996; Kawada et al . 2002; Kamiya et al . 2005 b , 2008 a ), whether the functions predict time‐series output dynamics, which would confirm the accuracy of system identification of transfer function, remains to be elucidated.…”

Section: Discussionmentioning

confidence: 99%

Closed‐loop spontaneous baroreflex transfer function is inappropriate for system identification of neural arc but partly accurate for peripheral arc: predictability analysis

Kamiya

Kawada

Shimizu

et al. 2011

The Journal of Physiology

Self Cite

View full text Add to dashboard Cite

Non-technical summaryThe arterial baroreflex is a closed-loop, negative feedback control system that senses baroreceptor pressure and controls systemic arterial pressure (AP) to attenuate perturbations in AP. The total arc of the baroreflex consists of two subsystems: the neural (baroreceptor pressure input to sympathetic nerve activity (SNA)) and peripheral (SNA input to AP) arcs. We show that although the spontaneous baroreflex transfer function obtained by closed-loop analysis has been believed to represent the neural arc function, it is inappropriate for system identification of the neural arc but is essentially appropriate for the peripheral arc under resting condition, when compared with open-loop transfer functions that have good predictabilities of time-series output dynamics from input signals. Our results indicate that in the spontaneous baroreflex system under closed-loop conditions, the peripheral arc (feedforward) function predominates over the neural arc (feedback) function, probably because of the SNA component that is independent of the baroreceptor pressure input.Abstract Although the dynamic characteristics of the baroreflex system have been described by baroreflex transfer functions obtained from open-loop analysis, the predictability of time-series output dynamics from input signals, which should confirm the accuracy of system identification, remains to be elucidated. Moreover, despite theoretical concerns over closed-loop system identification, the accuracy and the predictability of the closed-loop spontaneous baroreflex transfer function have not been evaluated compared with the open-loop transfer function. Using urethane and α-chloralose anaesthetized, vagotomized and aortic-denervated rabbits (n = 10), we identified open-loop baroreflex transfer functions by recording renal sympathetic nerve activity (SNA) while varying the vascularly isolated intracarotid sinus pressure (CSP) according to a binary random (white-noise) sequence (operating pressure ± 20 mmHg), and using a simplified equation to calculate closed-loop-spontaneous baroreflex transfer function while matching CSP with systemic arterial pressure (AP). Our results showed that the open-loop baroreflex transfer functions for the neural and peripheral arcs predicted the time-series SNA and AP outputs from measured CSP and SNA inputs, with r 2 of 0.8 ± 0.1 and 0.8 ± 0.1, respectively. In contrast, the closed-loop-spontaneous baroreflex transfer function for the neural arc was markedly different from the open-loop transfer function (enhanced gain increase and a phase lead), and did not predict the time-series SNA dynamics (r 2 ; 0.1 ± 0.1). However, the closed-loop-spontaneous baroreflex transfer function of the peripheral arc partially matched the open-loop transfer function in gain and phase functions, and had limited but reasonable predictability of the time-series AP dynamics (r 2 , 0.7 ± 0.1). A numerical simulation suggested that a noise predominantly in the neural arc under resting conditions might be a possible mechanism respo...

show abstract

“…Because the main frequency components of the arterial pulse waves were HR-frequency waves (4 -5 Hz in urethane-anesthetized rabbits) and their harmonics, the ANG II-induced changes in phasic unit activities and RSNA that were observed in the present experiments only reflect the action of ANG II on dynamic baroreflex characteristics at these frequencies. On the other hand, system-analysis studies on sympathetic baroreflex control in rabbits (26,27) demonstrate that baroreceptor signals in a frequency range of ϳ0.8 Hz are most effectively transferred to peripheral sympathetic outflow. Therefore, the action of ANG II on baroreflex responses of RVLM neurons in this frequency range would be more significant in the phasic control of sympathetic outflow, which remains to be determined in future studies.…”

Section: Discussionmentioning

confidence: 99%

ANG II modulates both slow and rapid baroreflex responses of barosensitive bulbospinal neurons in the rabbit rostral ventrolateral medulla

Saigusa

2014

American Journal of Physiology-Regulatory, Integrative and Comp

View full text Add to dashboard Cite

Saigusa T, Arita J. ANG II modulates both slow and rapid baroreflex responses of barosensitive bulbospinal neurons in the rabbit rostral ventrolateral medulla. Am J Physiol Regul Integr Comp Physiol 306: R538 -R551, 2014. First published February 12, 2014 doi:10.1152/ajpregu.00285.2013.-This study investigated the effects of ANG II on slow and rapid baroreflex responses of barosensitive bulbospinal neurons in the rostral ventrolateral medulla (RVLM) in urethane-anesthetized rabbits to determine whether the sympathetic baroreflex modulation induced by application of ANG II into the RVLM can be explained by the total action of ANG II on individual RVLM neurons. In response to pharmacologically induced slow ramp changes in mean arterial pressure (MAP), individual RVLM neurons exhibited a unit activity-MAP relationship that was fitted by a straight line with upper and lower plateaus. Iontophoretically applied ANG II raised the upper plateau without changing the slope, and, thereby, increased the working range of the baroreflex response. An asymmetric sigmoid curve that was determined by averaging individual unit activity-MAP relationship lines became more symmetric with ANG II application. The characteristics of the average curves, both before and during ANG II application, were consistent with the renal sympathetic nerve activity-MAP relationship curves obtained under the same experimental conditions. ANG II also affected rapid baroreflex responses of RVLM neurons that were induced by cardiac beats, as application of ANG II predominantly raised the average unit activities in the downstroke phase of arterial pulse waves. The present study provides a possible explanation for the ANG II-induced sympathetic baroreflex modulation based on the action of ANG II on barosensitive bulbospinal RVLM neurons. Our results also suggest that ANG II changes both static and dynamic characteristics of baroreflex responses of RVLM neurons. angiotensin II; baroreflex; sympathetic nervous system; single-unit recording; medulla oblongata THE ROSTRAL VENTROLATERAL medulla (RVLM) contains a group of neurons that project directly to the sympathetic preganglionic neurons in the spinal cord (8,16,20,38) and that provide an essential source of the sympathetic nerve activity (SNA) to maintain mean arterial pressure (MAP) within normal levels (14,21,43,53). A substantial portion of the bulbospinal neurons in the RVLM receive inhibitory inputs driven by arterial baroreceptor inputs, and, thus, display phasic activities that are synchronized to the cardiac cycle (8,28,55). Since blockade of inhibitory neurotransmission in the RVLM largely interferes with sympathetic baroreflex responses (7), the barosensitive bulbospinal neurons in the RVLM are believed to be a key component of the sympathetic baroreflex mechanism.ANG II is one of the peptides that have been identified in nerve terminals within the RVLM (13). Although the origins of the ANG II-containing axon tracts have not been fully identified, several supramedullary regions, such as the late...

show abstract

Upright Tilt Resets Dynamic Transfer Function of Baroreflex Neural Arc to Minify the Pressure Disturbance in Total Baroreflex Control

Cited by 7 publications

References 21 publications

Open-loop dynamic and static characteristics of the carotid sinus baroreflex in rats with chronic heart failure after myocardial infarction

Open-loop dynamic and static characteristics of the carotid sinus baroreflex in rats with chronic heart failure after myocardial infarction

Closed‐loop spontaneous baroreflex transfer function is inappropriate for system identification of neural arc but partly accurate for peripheral arc: predictability analysis

ANG II modulates both slow and rapid baroreflex responses of barosensitive bulbospinal neurons in the rabbit rostral ventrolateral medulla

Contact Info

Product

Resources

About