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

2001 ◽  
Vol 281 (1) ◽  
pp. R206-R212 ◽  
Author(s):  
Sarah-Jane Guild ◽  
Paul C. Austin ◽  
Michael Navakatikyan ◽  
John V. Ringwood ◽  
Simon C. Malpas
Keyword(s):  
Blood Flow ◽  
Transfer Function ◽  
Renal Blood Flow ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Nerve Activity ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Dynamic Relationship ◽  
Transfer Function Analysis

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 (<1 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 ± 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.

Inhibition of NO synthesis minimally affects the dynamic baroreflex regulation of sympathetic nerve activity

1997 ◽  
Vol 272 (5) ◽  
pp. H2446-H2452 ◽  
Author(s):  
H. Miyano ◽  
T. Kawada ◽  
T. Shishido ◽  
T. Sato ◽  
M. Sugimachi ◽  
...  
Keyword(s):  
Transfer Function ◽  
Arterial Pressure ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Carotid Sinus ◽  
Function Analysis ◽  
Corner Frequency ◽  
Nerve Activity ◽  
Carotid Sinus Baroreflex ◽  
Transfer Function Analysis

The purpose of this investigation was to examine the role of nitric oxide (NO) in the dynamic baroreflex regulation of cardiac sympathetic nerve activity. In anesthetized rabbits, we imposed random pressure perturbations on the isolated carotid sinuses before and after the intravenous administration of NG-monomethyl-L-arginine. We characterized the dynamic properties relating carotid sinus pressure input to sympathetic nerve activity by means of a transfer function analysis. NG-monomethyl-L-arginine decreased the corner frequency of the transfer function (0.100 +/- 0.054 vs. 0.074 +/- 0.035 Hz; P < 0.05), whereas other parameters such as the steady-state gain and transmission lag time remained unchanged. Although cursory examination of these findings would suggest a possible contribution of NO in the dynamic baroreflex regulation of sympathetic nerve activity, quantitative assessment of the transfer function reveals only a minimal effect on the baroreflex regulation of arterial pressure, particularly under closed-loop conditions. We conclude that NO noticeably affects the dynamic baroreflex regulation of sympathetic nerve activity. However, it may not significantly affect arterial pressure regulation through central modulation of the carotid sinus baroreflex.

Long-term control of renal blood flow: what is the role of the renal nerves?

2001 ◽  
Vol 280 (5) ◽  
pp. R1534-R1545 ◽  
Author(s):  
Carolyn J. Barrett ◽  
Michael A. Navakatikyan ◽  
Simon C. Malpas
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Renal Blood Flow ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Renal Nerves ◽  
Renal Vasculature ◽  
Nerve Activity ◽  
Renal Sympathetic

We have developed a system for long-term continuous monitoring of cardiovascular parameters in rabbits living in their home cage to assess what role renal sympathetic nerve activity (RSNA) has in regulating renal blood flow (RBF) in daily life. Blood pressure, heart rate, locomotor activity, RSNA, and RBF were recorded continuously for 4 wk. Beginning 4–5 days after surgery a circadian rhythm, dependent on feeding time, was observed. When averaged over all days RBF to the innervated and denervated kidneys was not significantly different. However, control of RBF around these mean levels was dependent on the presence of the renal sympathetic nerves. In particular we observed episodic elevations in heart rate and other parameters associated with activity. In the denervated kidney, during these episodic elevations, the increase in renal resistance was closely related to the increase in arterial pressure. In the innervated kidney the renal resistance response was significantly more variable, indicating an interaction of the sympathetic nervous system. These results indicate that whereas overall levels of RSNA do not set the mean level of RBF the renal vasculature is sensitive to episodic increases in sympathetic nerve activity.

Different Responses of Renal Blood Flow and Sympathetic Nerve Activity to Captopril and Nicardipine in ConsciousRenal Hypertensive Rabbits

1995 ◽  
Vol 25 (1) ◽  
pp. 57-64 ◽  
Author(s):  
Hiroo Kumagai ◽  
Hiromichi Suzuki ◽  
Masashi Ichikawa ◽  
Masahiko Nishizawa ◽  
Munekazu Ryuzaki ◽  
...  
Keyword(s):  
Blood Flow ◽  
Renal Blood Flow ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Nerve Activity

Dynamic interactions between arterial pressure and sympathetic nerve activity: role of arterial baroreceptors

2003 ◽  
Vol 285 (4) ◽  
pp. R834-R841 ◽  
Author(s):  
Claude Julien ◽  
Bruno Chapuis ◽  
Yong Cheng ◽  
Christian Barrès
Keyword(s):  
Arterial Pressure ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Noise Sources ◽  
Nerve Activity ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Mayer Waves ◽  
Arterial Baroreceptors

The role of arterial baroreceptors in controlling arterial pressure (AP) variability through changes in sympathetic nerve activity was examined in conscious rats. AP and renal sympathetic nerve activity (RSNA) were measured continuously during 1-h periods in freely behaving rats that had been subjected to sinoaortic baroreceptor denervation (SAD) or a sham operation 2 wk before study ( n = 10 in each group). Fast Fourier transform analysis revealed that chronic SAD did not alter high-frequency (0.75-5 Hz) respiratory-related oscillations of mean AP (MAP) and RSNA, decreased by ∼50% spectral power of both variables in the midfrequency band (MF, 0.27-0.74 Hz) containing the so-called Mayer waves, and induced an eightfold increase in MAP power without altering RSNA power in the low-frequency band (0.005-0.27 Hz). In both groups of rats, coherence between RSNA and MAP was maximal in the MF band and was usually weak at lower frequencies. In SAD rats, the transfer function from RSNA to MAP showed the characteristics of a second-order low-pass filter containing a fixed time delay (∼0.5 s). These results indicate that arterial baroreceptors are not involved in production of respiratory-related oscillations of RSNA but play a major role in the genesis of synchronous oscillations of MAP and RSNA at the frequency of Mayer waves. The weak coupling between slow fluctuations of RSNA and MAP in sham-operated and SAD rats points to the interference of noise sources unrelated to RSNA affecting MAP and of noise sources unrelated to MAP affecting RSNA.

Effect of renal denervation on dynamic autoregulation of renal blood flow

2004 ◽  
Vol 286 (6) ◽  
pp. F1209-F1218 ◽  
Author(s):  
Gerald F. DiBona ◽  
Linda L. Sawin
Keyword(s):  
Blood Flow ◽  
Renal Blood Flow ◽  
Sympathetic Nerve ◽  
Renal Denervation ◽  
Sympathetic Nerve Activity ◽  
Nerve Activity ◽  
Renal Sympathetic Nerve Activity ◽  
Spontaneously Hypertensive ◽  
Renal Sympathetic Nerve ◽  
Renal Sympathetic

Vasoconstrictor intensities of renal sympathetic nerve stimulation elevate the renal arterial pressure threshold for steady-state stepwise autoregulation of renal blood flow. This study examined the tonic effect of basal renal sympathetic nerve activity on dynamic autoregulation of renal blood flow in rats with normal (Sprague-Dawley and Wistar-Kyoto) and increased levels of renal sympathetic nerve activity (congestive heart failure and spontaneously hypertensive rats). Steady-state values of arterial pressure and renal blood flow before and after acute renal denervation were subjected to transfer function analysis. Renal denervation increased basal renal blood flow in congestive heart failure (+35 ± 3%) and spontaneously hypertensive rats (+21 ± 3%) but not in Sprague-Dawley and Wistar-Kyoto rats. Renal denervation significantly decreased transfer function gain (i.e., improved autoregulation of renal blood flow) and increased coherence only in spontaneously hypertensive rats. Thus vasoconstrictor intensities of renal sympathetic nerve activity impaired the dynamic autoregulatory adjustments of the renal vasculature to oscillations in arterial pressure. Renal denervation increased renal blood flow variability in spontaneously hypertensive rats and congestive heart failure rats. The contribution of vasoconstrictor intensities of basal renal sympathetic nerve activity to limiting renal blood flow variability may be important in the stabilization of glomerular filtration rate.

Septic shock induces distinct changes in sympathetic nerve activity to the heart and kidney in conscious sheep

2009 ◽  
Vol 297 (5) ◽  
pp. R1247-R1253 ◽  
Author(s):  
Rohit Ramchandra ◽  
Li Wan ◽  
Sally G. Hood ◽  
Robert Frithiof ◽  
Rinaldo Bellomo ◽  
...  
Keyword(s):  
Septic Shock ◽  
Blood Flow ◽  
Cardiac Output ◽  
Renal Blood Flow ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Large Animal Model ◽  
Large Animal ◽  
Nerve Activity ◽  
Conscious Sheep

Sepsis and septic shock are the chief cause of death in intensive care units, with mortality rates between 30 and 70%. In a large animal model of septic shock, we have demonstrated hypotension, increased cardiac output, and tachycardia, together with renal vasodilatation and renal failure. The changes in cardiac sympathetic nerve activity (CSNA) that may contribute to the tachycardia have not been investigated, and the changes in renal SNA (RSNA) that may mediate the changes in renal blood flow and function are unclear. We therefore recorded CSNA and RSNA during septic shock in conscious sheep. Septic shock was induced by administration of Escherichia coli, which caused a delayed hypotension and an immediate, biphasic increase in heart rate (HR) associated with similar changes in CSNA. After E. coli, RSNA decreased for over 3 h, followed by a sustained increase (180%), whereas renal blood flow progressively increased and remained elevated. There was an initial diuresis, followed by oliguria and decreased creatinine clearance. There were differential changes in the range of the arterial baroreflex curves; it was depressed for HR, increased for CSNA, and unchanged for RSNA. Our findings, recording CSNA for the first time in septic shock, suggest that the increase in SNA to the heart is not driven solely by unloading of baroreceptors and that the increase has an important role to increase HR and cardiac output. There was little correlation between the changes in RSNA and renal blood flow, suggesting that the renal vasodilatation was mediated mainly by other mechanisms.

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