Intravenous Angiotensin II Does Not Affect Dynamic Baroreflex Characteristics of the Neural or Peripheral Arc

Kashihara, Koji; Takahashi, Yukina; Chatani, Kaori; Kawada, Toru; Zheng, Can; Li, Meihua; Sugimachi, Masaru; Sunagawa, Kenji

doi:10.2170/jjphysiol.53.135

Cited by 8 publications

(8 citation statements)

References 36 publications

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“…Reflex responses in SNA, AP and HR were not attenuated in the presence of ANG II. Dashed boxes indicate the step cycles used for the statistical analysis unaltered, which agreed with a previous study from our laboratory in which intravenous ANG II at 100 ng kg -1 min -1 did not change the dynamic gain of the neural arc in anesthetized rabbits [23]. In contrast, Sanderford and Bishop demonstrated that ANG II at 10 or 20 ng kg -1 min -1 significantly reduced the maximum renal SNA and attenuated the range of baroreflex control of renal SNA in conscious rabbits [9,24].…”

Section: Effects Of Ang II On Open-loop Baroreflex Control Of Snasupporting

confidence: 88%

High levels of circulating angiotensin II shift the open-loop baroreflex control of splanchnic sympathetic nerve activity, heart rate and arterial pressure in anesthetized rats

Kawada

Kamiya

et al. 2009

J Physiol Sci

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Although an acute arterial pressure (AP) elevation induced by intravenous angiotensin II (ANG II) does not inhibit sympathetic nerve activity (SNA) compared to an equivalent AP elevation induced by phenylephrine, there are conflicting reports as to how circulating ANG II affects the baroreflex control of SNA. Because most studies have estimated the baroreflex function under closed-loop conditions, differences in the rate of input pressure change and the magnitude of pulsatility may have biased the estimation results. We examined the effects of intravenous ANG II (10 microg kg(-1) h(-1)) on the open-loop system characteristics of the carotid sinus baroreflex in anesthetized and vagotomized rats. Carotid sinus pressure (CSP) was raised from 60 to 180 mmHg in increments of 20 mmHg every minute, and steady-state responses in systemic AP, splanchnic SNA and heart rate (HR) were analyzed using a four-parameter logistic function. ANG II significantly increased the minimum values of AP (67.6 +/- 4.6 vs. 101.4 +/- 10.9 mmHg, P < 0.01), SNA (33.3 +/- 5.4 vs. 56.5 +/- 11.5%, P < 0.05) and HR (391.1 +/- 13.7 vs. 417.4 +/- 11.5 beats/min, P < 0.01). ANG II, however, did not attenuate the response range for AP (56.2 +/- 7.2 vs. 49.7 +/- 6.2 mmHg), SNA (69.6 +/- 5.7 vs. 78.9 +/- 9.1%) or HR (41.7 +/- 5.1 vs. 51.2 +/- 3.8 beats/min). The maximum gain was not affected for AP (1.57 +/- 0.28 vs. 1.20 +/- 0.25), SNA (1.94 +/- 0.34 vs. 2.04 +/- 0.42%/mmHg) or HR (1.11 +/- 0.12 vs. 1.28 +/- 0.19 beats min(-1) mmHg(-1)). It is concluded that high levels of circulating ANG II did not attenuate the response range of open-loop carotid sinus baroreflex control for AP, SNA or HR in anesthetized and vagotomized rats.

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Section: Effects Of Ang II On Open-loop Baroreflex Control Of Snasupporting

confidence: 88%

High levels of circulating angiotensin II shift the open-loop baroreflex control of splanchnic sympathetic nerve activity, heart rate and arterial pressure in anesthetized rats

Kawada

Kamiya

et al. 2009

J Physiol Sci

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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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“…The closed-loop operating AP (Table 3) provides a rationale for the selection of the mean input pressure of CSP. When CSP was perturbed around the operating-point pressure, however, mean SNA and AP usually decreased (10). The phenomenon may be related to the input pulsatility and the effect of input amplitude (3,17,35).…”

Section: Discussionmentioning

confidence: 97%

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

Kawada

Shimizu

Kamiya

et al. 2011

American Journal of Physiology-Regulatory, Integrative and Comp

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Although baroreceptors are known to reset to operate in a higher pressure range in spontaneously hypertensive rats (SHR), the total profile of dynamic arterial pressure (AP) regulation remains to be clarified. We estimated open-loop transfer functions of the carotid sinus baroreflex in SHR and Wistar Kyoto (WKY) rats. Mean input pressures were set at 120 (WKY120 and SHR120) and 160 mmHg (SHR160). The neural arc transfer function from carotid sinus pressure to efferent splanchnic sympathetic nerve activity (SNA) revealed derivative characteristics in both WKY and SHR. The slope of dynamic gain (in decibels per decade) between 0.1 and 1 Hz was not different between WKY120 (10.1 ± 1.0) and SHR120 (10.4 ± 1.1) but was significantly greater in SHR160 (13.2 ± 0.8, P < 0.05 with Bonferroni correction) than in SHR120. The peripheral arc transfer function from SNA to AP showed low-pass characteristics. The slope of dynamic gain (in decibels per decade) did not differ between WKY120 (−34.0 ± 1.2) and SHR120 (−31.4 ± 1.0) or between SHR120 and SHR160 (−32.8 ± 1.3). The total baroreflex showed low-pass characteristics and the dynamic gain at 0.01 Hz did not differ between WKY120 (0.91 ± 0.08) and SHR120 (0.84 ± 0.13) or between SHR120 and SHR160 (0.83 ± 0.11). In both WKY and SHR, the declining slope of dynamic gain was significantly gentler for the total baroreflex than for the peripheral arc, suggesting improved dynamic AP response in the total baroreflex. In conclusion, the dynamic characteristics of AP regulation by the carotid sinus baroreflex were well preserved in SHR despite significantly higher mean AP.

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Intravenous Angiotensin II Does Not Affect Dynamic Baroreflex Characteristics of the Neural or Peripheral Arc

Cited by 8 publications

References 36 publications

High levels of circulating angiotensin II shift the open-loop baroreflex control of splanchnic sympathetic nerve activity, heart rate and arterial pressure in anesthetized rats

High levels of circulating angiotensin II shift the open-loop baroreflex control of splanchnic sympathetic nerve activity, heart rate and arterial pressure in anesthetized rats

Bezold-Jarisch reflex attenuates dynamic gain of baroreflex neural arc

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

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