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

Abstract

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.

Effects of tempol on baroreflex neural arc versus peripheral arc in normotensive and spontaneously hypertensive rats

“…3, C and D, Table 1), which is in agreement with our previous study (21). The two-way ANOVA did not show a significant effect of tempol on the slope or the intercept of the peripheral arc.…”

“…In the present study, the SNA value at the CSP level of 60 mmHg was assigned to 100% in individual animals. When SNA was rescaled on the basis of the pressor response to exogenous phenylephrine in our previous study (21), the response range of the neural arc became significantly greater in SHR than in WKY, and the slope of the peripheral arc did not differ between WKY and SHR. Although the rescaling of SNA affects the abscissa of the baroreflex equilibrium diagram, it does not affect the estimation of the operating-point AP because the ordinate is unchanged.…”

Nonlinear identification of the total baroreflex arc: chronic hypertension model

“…The reason for the relatively stronger nonlinearity in SHR 120 may pertain to the operating point. That is, the CSP levels for WKY and SHR 160 are in the linear regimes of their respective static sigmoidal CSP-AP relationships, while the CSP level for SHR 120 is near the nonlinear thresholding regime of its relationship (15). In this sense, comparisons between WKY and SHR 160 , as opposed to SHR 120 , may actually be more appropriate.…”

Importance of Neural Arc for Baroreflex Resetting in Hypertension

“…9 Sata et al demonstrated that the neural arc of the carotid sinus baroreflex is upregulated, indicating that central sympathetic outflow is increased in SHR. 11 In contrast, the peripheral arc, which shows the function from SNA to the vessels, does not play a major role in determining AP in SHR. It should be noted, however, that baroreflex control of renal function needs to be evaluated if these data are to be applied to hypertension, considering the long-term AP control abnormality.…”