Open-loop static and dynamic characteristics of the arterial baroreflex system in rabbits and rats

Mukkamala

Sugimachi

2019

ABE

Self Cite

The arterial barore ex system is an important negative feedback system that controls arterial pressure (AP) within a normal range during daily activities. We have analyzed this system in anesthetized animals. Several issues need to be considered: the presence of physiological and measurement noises that interfere with the system identi cation, the closed-loop nature of the arterial barore ex system, the existence of parallel feedback systems that may modify the system responses, and the presence of nonlinear responses. We opened the negative feedback loop by surgically isolating the carotid sinus baroreceptor regions from the systemic circulation. We eliminated the effects from parallel feedback systems by sectioning the aortic depressor and vagal nerves. We used a white noise approach to estimate the system characteristics under contamination of physiological and measurement noises. The arterial barore ex system may be divided into the neural and peripheral arc subsystems. The neural arc represents the relationship between pressure inputs and efferent sympathetic nerve activity (SNA), which may be regarded as a controller subsystem. The peripheral arc represents the relationship between SNA and AP, which may be regarded as a plant subsystem. The neural arc reveals derivative characteristics whereas the peripheral arc reveals low-pass characteristics. Numerical simulations based on the analytical results indicate that the neural arc compensates for the slow peripheral arc to optimize the arterial barore ex system in achieving both stability and quickness. Impairment of arterial barore ex function is associated with cardiovascular diseases, and arti cial activation of the arterial barore ex system could be a device-based treatment for cardiovascular diseases associated with sympathetic hyperactivity. To improve the efcacy of such device-based therapy, we may need to understand the interactions between stimulated and non-stimulated barore ex systems. Although static sigmoidal nonlinearity of the arterial barore ex with threshold and saturation phenomena is well documented, dynamic nonlinearities are less understood. Further efforts are warranted to fully understand arterial barore ex function and to apply the knowledge to the medical eld.

Section: Application To the Barore Ex Systemmentioning

confidence: 99%

Linear and Nonlinear Analysis of the Carotid Sinus Baroreflex Dynamic Characteristics

Mukkamala

Sugimachi

2019

ABE

Self Cite

“…Previous studies indicate that arterial pressure (AP) increases with logarithm of exogenously infused dose of NE (Kawada et al 2014a or logarithm of plasma NE concentration during electrical stimulation of the spinal cord (Yamaguchi and Kopin 1980). In contrast, AP changes nearly linearly with SNA during acute baroreflex-mediated changes Kawada and Sugimachi 2016). If these results are put together, plasma NE concentration expressed in a logarithmic scale, rather than a normal scale, should linearly correlate with SNA.…”

Section: Introductionmentioning

confidence: 98%

“…In contrast, AP changes nearly linearly with SNA during acute baroreflex‐mediated changes (Kawada et al. ; Kawada and Sugimachi ). If these results are put together, plasma NE concentration expressed in a logarithmic scale, rather than a normal scale, should linearly correlate with SNA.…”

Section: Introductionmentioning

confidence: 99%

Acute arterial baroreflex‐mediated changes in plasma catecholamine concentrations in a chronic rat model of myocardial infarction

Akiyama

et al. 2016

Physiological Reports

Self Cite

While it may be predictable that plasma norepinephrine (NE) concentration changes with efferent sympathetic nerve activity (SNA) in response to baroreceptor pressure inputs, an exact relationship between SNA and plasma NE concentration remains to be quantified in heart failure. We examined acute baroreflex‐mediated changes in plasma NE and epinephrine (Epi) concentrations in normal control (NC) rats and rats with myocardial infarction (MI) (n = 6 each). Plasma NE concentration correlated linearly with SNA in the NC group (slope: 2.17 ± 0.26 pg mL−1 %−1, intercept: 20.0 ± 18.2 pg mL−1) and also in the MI group (slope: 19.20 ± 6.45 pg mL−1 %−1, intercept: −239.6 ± 200.0 pg mL−1). The slope was approximately nine times higher in the MI than in the NC group (P < 0.01). Plasma Epi concentration positively correlated with SNA in the NC group (slope: 1.65 ± 0.79 pg mL−1 %−1, intercept: 115.0 ± 69.5 pg mL−1) and also in the MI group (slope: 7.74 ± 2.20 pg mL−1 %−1, intercept: 24.7 ± 120.1 pg mL−1). The slope was approximately 4.5 times higher in the MI than in the NC group (P < 0.05). Intravenous administration of desipramine (1 mg kg−1) significantly increased plasma NE concentration but decreased plasma Epi concentration in both groups, suggesting that neuronal NE uptake had contributed to the reduction in plasma NE concentration. These results indicate that high levels of plasma catecholamine in MI rats were still under the influence of baroreflex‐mediated changes in SNA, and may provide additional rationale for applying baroreflex activation therapy in patients with chronic heart failure.

“…The mean input pressure imposed on the arterial baroreceptors is a chief determinant of the baroreflex responses. When carotid sinus baroreceptor regions are vascularly isolated and exposed to a nonpulsatile pressure input, the static relationship of AP versus carotid sinus pressure (CSP) approximates an inverse sigmoid curve (4,12,22). In addition to the mean pressure, pulsatility has been known to affect the baroreflex responses (2,10,23,24).…”

mentioning

confidence: 99%

“…The pulse pressure was determined from a preliminary study so that the effect of different waveforms could be clearly detected against spontaneous fluctuations of SNA and AP. The pulse frequency of 1 Hz was used because the dynamic gain of the baroreflex neural arc transfer function from CSP to SNA peaks near 1 Hz in rats (11,12), and the effect of dynamic signal transduction was expected to be largest at this frequency. To examine the reproducibility of the baroreflex responses to the two waveforms, the FSW and BSW were switched every minute.…”

mentioning

confidence: 99%

Effects of different input pressure waveforms on the carotid sinus baroreflex-mediated sympathetic arterial pressure response in rats

Journal of Applied Physiology

Shimizu

Yamamoto

et al. 2017

Self Cite

Although the pulsatility of an input pressure is an important factor that determines the arterial baroreflex responses, whether the difference in the input waveforms can meaningfully affect the baroreflex function remains unknown. This study aimed to compare baroreflex responses between two distinct pressure waveforms: a forward saw wave (FSW) and a backward saw wave (BSW). In seven anesthetized rats, carotid sinus pressure was exposed to the FSW or the BSW with a mean of 120 mmHg, pulse pressure of 40 mmHg, and pulse frequency of 1 Hz. Changes in efferent sympathetic nerve activity (SNA) and arterial pressure (AP) during six consecutive saw wave trials (FSW, BSW, FSW, BSW, FSW, and BSW) were examined. The steady-state SNA value during FSW was 91.1 ± 1.9%, which was unchanged during FSW and FSW but significantly increased during BSW (106.6 ± 3.4%, < 0.01), BSW (110.6 ± 2.5%, < 0.01), and BSW (111.6 ± 2.3%, < 0.01). The steady-state AP value during FSW was 98.2 ± 8.1 mmHg, which was unchanged during FSW and FSW but significantly increased during BSW (106.7 ± 7.4 mmHg, < 0.01), BSW (105.6 ± 7.8 mmHg, < 0.01), and BSW (103.8 ± 7.2 mmHg, < 0.05). In conclusion, the FSW was more effective than the BSW in reducing mean SNA and AP. The finding could be applied to designing an artificial pulsatile pressure such as that generated by left ventricular assist devices. This study examined whether the waveforms of an input pressure alone can affect the baroreflex function by using a forward saw wave and a backward saw wave with the same mean pressure, pulse pressure, and pulse frequency. The forward saw wave was more effective than the backward saw wave in reducing sympathetic nerve activity and arterial pressure. The finding could be applied to designing an artificial pulsatile pressure such as that generated by left ventricular assist devices.