Dynamic characteristics of baroreflex neural and peripheral arcs are preserved in spontaneously hypertensive rats

American Journal of Physiology-Regulatory, Integrative and Comp

Shimizu

et al. 2015

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Section: Dynamic Characteristics Of A-and C-fiber Central Pathways Insupporting

confidence: 80%

Section: Dynamic Characteristics Of A-and C-fiber Central Pathways Inmentioning

confidence: 76%

Differences in the dynamic baroreflex characteristics of unmyelinated and myelinated central pathways are less evident in spontaneously hypertensive rats

Turner

American Journal of Physiology-Regulatory, Integrative and Comp

Shimizu

et al. 2015

Self Cite

“…1 Dynamic characteristics of the arterial baroreflex are also preserved in SHR. 16,17 While sino-aortic baroreceptor denervation does not affect the development of hypertension in SHR, 26 it is likely that the carotid sinus baroreflex preserved the ability to reduce AP to within a normal pressure range. The present study results might provide a rationale for the use of a carotid baroreceptor stimulator as an alternative therapy for drug-resistant hypertension.…”

Section: Baroreflex Total-loop Characteristics In Wky and Shrmentioning

confidence: 99%

Predominant Role of Neural Arc in Sympathetic Baroreflex Resetting of Spontaneously Hypertensive Rats

Sata

Shimizu

et al. 2015

Circ J

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592SATA Y et al. Circulation JournalOfficial Journal of the Japanese Circulation Society http://www. j-circ.or.jp classified as a short-term blood pressure control system, 8 carotid baroreflex activation therapy has succeeded in reducing blood pressure in patients with resistant hypertension for more than 1 year, 9 suggesting a potential role of the arterial baroreflex in the long-term regulation of blood pressure. 10 Considering the multifactorial and complex nature of hypertension, further research is needed to understand how sympathetic nerve activity (SNA) and AP are determined in hypertension. The arterial baroreflex system constitutes a key link between the autonomic nervous system and the cardiovascular system. The reflex arc of baroreflex can be divided into 2 principal arcs: the neural arc from pressure input to SNA, and the peripheral arc from SNA to AP. 11,12 Under normal physiological conditions, because the arterial baroreflex operates as a closedloop feedback control system, it is difficult to separately quantify neural and peripheral arc characteristics.The behavior of a system might be described by dynamic and static characteristics. The dynamic characteristics determine he arterial baroreflex control of arterial pressure (AP) is known to reset to a higher input pressure range in hypertension. 1 To cope with the resetting, carotid baroreflex activation is proposed as a potential treatment of drugresistant hypertension. 2,3 Involvement of both neural and cardiovascular factors has been proposed in the pathophysiology of hypertension. Previous studies have demonstrated that sympathetic outflow from the central nervous system is increased in spontaneously hypertensive rats (SHR). 4,5 Peripheral factors such as cardiac hypertrophy and increased vascular resistance are also considered responsible for high AP in SHR. 6 Abnormality in vascular function is also reported in hypertensive patients. 7 Editorial p 510Device-based neuromodulation therapy has increasingly drawn scientific interest. While the arterial baroreflex has been Background: There is ongoing controversy over whether neural or peripheral factors are the predominant cause of hypertension. The closed-loop negative feedback operation of the arterial baroreflex hampers understanding of how arterial pressure (AP) is determined through the interaction between neural and peripheral factors.

“…We and others have identified the linear dynamics of the three baroreflex arcs in the form of transfer functions (i.e., gain and phase as a function of frequency) (3)(4)(5)16). These linear models can capture the dynamic behavior of the systems to a significant extent.…”

mentioning

confidence: 99%

Nonlinear identification of the total baroreflex arc: chronic hypertension model

Moslehpour

American Journal of Physiology-Regulatory, Integrative and Comp

Sunagawa

et al. 2016

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. Its linear dynamic functioning has been shown to be preserved in spontaneously hypertensive rats (SHR). However, the system is known to exhibit nonlinear dynamic behaviors. The aim of this study was to establish nonlinear dynamic models of the total arc (and its subsystems) in hypertensive rats and to compare these models with previously published models for normotensive rats. Hypertensive rats were studied under anesthesia. The vagal and aortic depressor nerves were sectioned. The carotid sinus regions were isolated and attached to a servo-controlled piston pump. AP and sympathetic nerve activity were measured while CSP was controlled via the pump using Gaussian white noise stimulation. Second-order, nonlinear dynamics models were developed by application of nonparametric system identification to a portion of the measurements. The models of the total arc predicted AP 21-43% better (P Ͻ 0.005) than conventional linear dynamic models in response to a new portion of the CSP measurement. The linear and nonlinear terms of these validated models were compared with the corresponding terms of an analogous model for normotensive rats. The nonlinear gains for the hypertensive rats were significantly larger than those for the normotensive rats [Ϫ0.38 Ϯ 0.04 (unitless) vs. Ϫ0.22 Ϯ 0.03, P Ͻ 0.01], whereas the linear gains were similar. Hence, nonlinear dynamic functioning of the sympathetically mediated total arc may enhance baroreflex buffering of AP increases more in SHR than normotensive rats. arterial baroreflex; Gaussian white noise; system identification; nonlinear model; hypertension THE CAROTID SINUS BAROREFLEX plays a central role in maintaining arterial pressure (AP) in the face of fast-acting, exogenous disturbances and may also contribute to long-term AP regulation (7,20,21). This system responds to increases in carotid sinus pressure (CSP) by decreasing efferent sympathetic nerve activity (SNA), which, in turn, decreases AP. We refer to the aggregate, open-loop system relating CSP to AP as the total baroreflex arc, the "controller" subsystem relating CSP to SNA as the neural arc, and the "effector" subsystem relating SNA to AP as the peripheral arc.We and others have identified the linear dynamics of the three baroreflex arcs in the form of transfer functions (i.e., gain and phase as a function of frequency) (3-5, 16). These linear models can capture the dynamic behavior of the systems to a significant extent. We previously showed that the linear dynamics of the total arc are preserved in spontaneously hypertensive rats (SHR) despite resetting of mean AP (4). However, the nonlinear dynamics of this system, which have been less investigated, could possibly respond differently to the chronic hypertension model.In a recent study (9), we employed the Gaussian white noise approach for nonlinear system identification to develop a second-order, nonlinear dynamic model of the total arc in normotensive Wistar-Kyoto rats (WKY). The model predicted AP 12% better than a linear dynamic model in response to new Gaussian w...