Summation of dynamic transfer characteristics of left  and right carotid sinus baroreflexes in rabbits

Kawada, Toru; Sato, Takayuki; Shishido, Toshiaki; Inagaki, Masumi; Tatewaki, Teiji; Yanagiya, Yusuke; Sugimachi, Masaru; Sunagawa, Kenji

doi:10.1152/ajpheart.1999.277.3.h857

Cited by 14 publications

(22 citation statements)

References 7 publications

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“…Previously the transfer function between arterial baroreceptors and blood pressure has been determined (7). Interestingly the gain and phase responses showed similar trends to those calculated here.…”

Section: Discussionsupporting

confidence: 83%

Dynamic relationship between sympathetic nerve activity and renal blood flow: a frequency domain approach

Guild

Austin

Navakatikyan

et al. 2001

American Journal of Physiology-Regulatory, Integrative and Comp

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Guild, Sarah-Jane, Paul C. Austin, Michael Navakatikyan, John V. Ringwood, and Simon C. Malpas. Dynamic relationship between sympathetic nerve activity and renal blood flow: a frequency domain approach. Am J Physiol Regulatory Integrative Comp Physiol 281: R206-R212, 2001.-Blood pressure displays an oscillation at 0.1 Hz in humans that is well established to be due to oscillations in sympathetic nerve activity (SNA). However, the mechanisms that control the strength or frequency of this oscillation are poorly understood. The aim of the present study was to define the dynamic relationship between SNA and the vasculature. The sympathetic nerves to the kidney were electrically stimulated in six pentobarbital-sodium anesthetized rabbits, and the renal blood flow response was recorded. A pseudo-random binary sequence (PRBS) was applied to the renal nerves, which contains equal spectral power at frequencies in the range of interest (Ͻ1 Hz). Transfer function analysis revealed a complex system composed of low-pass filter characteristics but also with regions of constant gain. A model was developed that accounted for this relationship composed of a 2 zero/4 pole transfer function. Although the position of the poles and zeros varied among animals, the model structure was consistent. We also found the time delay between the stimulus and the RBF responses to be consistent among animals (mean 672 Ϯ 22 ms). We propose that the identification of the precise relationship between SNA and renal blood flow (RBF) is a fundamental and necessary step toward understanding the interaction between SNA and other physiological mediators of RBF. modeling; pseudo-random binary sequence SYMPATHETIC NERVE ACTIVITY (SNA) has been proposed to play an important role in the regulation of renal blood flow (RBF) (12). Whereas much previous research has focused on how the mean level of SNA regulates the mean level of RBF in response to a range of afferent stimuli (10), there has been little consideration given to fact that SNA is a signal made up of multiple frequency bands, ranging from 10 to 0.1 Hz (9). Surprisingly little is known about how these frequency components impact on the renal vasculature. Mathematical models have been developed to describe the effect blood pressure has on RBF (4-6). These models have proven useful in understanding the dynamics of autoregulation and tubuloglomerular feedback; however, there is a paucity of information on the dynamics of the neural control of RBF. Information on how the various frequencies in SNA regulate RBF is likely to be valuable in understanding the origin of oscillations present in blood pressure (2) and in predicting how diseases or therapeutic treatments that alter SNA could affect the control of RBF and potentially blood pressure.Previous work by our lab has determined that the renal vasculature appears only able to follow frequencies in SNA below 0.7 Hz, with frequencies above this level producing steady vascular tone (11). The corresponding frequency response characteristics suggested that a ...

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Section: Discussionsupporting

confidence: 83%

Dynamic relationship between sympathetic nerve activity and renal blood flow: a frequency domain approach

Guild

Austin

Navakatikyan

et al. 2001

American Journal of Physiology-Regulatory, Integrative and Comp

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“…Second, because the vagi were kept intact, low-pressure baroreflexes from the cardiopulmonary region could interact with the arterial baroreflex, affecting estimation of carotid sinus baroreflex transfer functions. However, the transfer functions estimated in the present study were qualitatively similar to those estimated under vagotomized conditions in previous studies (8)(9)(10). We speculate that changes in RSNA, AP, and HR were mainly attributable to CSP input.…”

Section: Limitationssupporting

confidence: 89%

“…Mean AP (and therefore mean CSP) in the steady state was treated as the operating pressure (P op). To assess the dynamic characteristics of the carotid sinus baroreflex, we randomly assigned CSP to either high (P op ϩ 20 mmHg) or low (Pop Ϫ 20 mmHg) pressure every 500 ms, according to a binary white noise sequence (8)(9)(10). The power spectral density of CSP was reasonably constant up to 1 Hz.…”

Section: Protocolsmentioning

confidence: 99%

Bezold-Jarisch reflex attenuates dynamic gain of baroreflex neural arc

Kashihara

Kawada²,

Yanagiya³

et al. 2003

American Journal of Physiology-Heart and Circulatory Physiology

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risch reflex attenuates dynamic gain of baroreflex neural arc. Am J Physiol Heart Circ Physiol 285: H833-H840, 2003. First published April 24, 2003 10.1152/ajpheart.01082. 2002-Although acute myocardial ischemia or infarction may induce the Bezold-Jarisch (BJ) reflex through the activation of serotonin receptors on vagal afferent nerves, the mechanism by which the BJ reflex modulates the dynamic characteristics of arterial pressure (AP) regulation is unknown. The purpose of this study was to examine the effects of the BJ reflex induced by intravenous phenylbiguanide (PBG) on the dynamic characteristics of the arterial baroreflex. In seven anesthetized rabbits, we perturbed intracarotid sinus pressure (CSP) according to a white noise sequence while renal sympathetic nerve activity (RSNA), AP, and heart rate (HR) were recorded. We estimated the transfer function from CSP to RSNA (neural arc) and from RSNA to AP (peripheral arc) before and after 10 min of intravenous administration of PBG (100 g ⅐ kg Ϫ1 ⅐ min Ϫ1 ). The intravenous PBG decreased mean AP from 84.5 Ϯ 4.0 to 68.2 Ϯ 4.7 mmHg (P Ͻ 0.01), mean RSNA to 76.2 Ϯ 7.0% (P Ͻ 0.05), and mean HR from 301.6 Ϯ 7.7 to 288.4 Ϯ 9.0 beats/min (P Ͻ 0.01). The intravenous PBG significantly decreased neural arc dynamic gain at 0.01 Hz (1.06 Ϯ 0.08 vs. 0.59 Ϯ 0.17, P Ͻ 0.05), whereas it did not affect that of the peripheral arc (1.20 Ϯ 0.12 vs. 1.18 Ϯ 0.41). In six different rabbits without intravenous PBG, the neural arc transfer function did not change between two experimental runs with intervening interval of 10 min, excluding the possibility that the cumulative effects of anesthetics had altered the neural arc transfer function. In conclusion, excessive activation of the BJ reflex during acute myocardial ischemia may exert an adverse effect on AP regulation, not only by sympathetic suppression, but also by attenuating baroreflex dynamic gain. renal sympathetic nerve activity; transfer function; systems analysis; rabbits; carotid sinus baroreflex THE CIRCULATORY SYSTEM has several mechanoreceptors and chemoreceptors in a variety of regions. The cardiopulmonary region is rich in such receptors. The most vagal afferent fibers from the cardiopulmonary receptors to the vasomotor center are classified as C fibers.Activation of the cardiopulmonary chemosensitive vagal afferent fibers reduces arterial pressure (AP), heart rate (HR), and cardiac output (31). These responses, mediated by 5-hydroxytryptamine (5-HT 3 ) serotonergic receptors on the cardiopulmonary vagal afferent fibers, are known as the Bezold-Jarisch (BJ) reflex (2, 7, 32). Although its physiological importance remains debatable, the BJ reflex could play a significant role in developing pathological responses associated with acute myocardial ischemia (19,20,24). Elucidating the effects of the BJ reflex on the circulatory regulation would be useful for better understanding the pathophysiology of ischemic heart diseases (16, 27). The BJ reflex can be induced chemically with pharmacological agents such as 5-HT and ...

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“…In the open-loop identification protocol of the rapid pacing group, we perturbed CSP according to a binary white noise signal [5,[8][9][10][11][12] with a switching interval of 700 ms. The mean CSP (89.2Ϯ17.1 mmHg) and peak-to-peak amplitude of CSP perturbation (45.1Ϯ 10.8) were adjusted to the range of AOP response during a preliminary application of the intermittent rapid pacing.…”

Section: Methodsmentioning

confidence: 99%

Closed-Loop Identification of Carotid Sinus Baroreflex Transfer Characteristics Using Electrical Stimulation.

Kawada

Sato²,

Inagaki³

et al. 2000

JJP

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Summation of dynamic transfer characteristics of left and right carotid sinus baroreflexes in rabbits

Cited by 14 publications

References 7 publications

Dynamic relationship between sympathetic nerve activity and renal blood flow: a frequency domain approach

Dynamic relationship between sympathetic nerve activity and renal blood flow: a frequency domain approach

Bezold-Jarisch reflex attenuates dynamic gain of baroreflex neural arc

Closed-Loop Identification of Carotid Sinus Baroreflex Transfer Characteristics Using Electrical Stimulation.

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