Arterial baroreflex control of cardiac and renal sympathetic nerve activities is uniform in frequency domain

1991 ◽  
Vol 261 (2) ◽  
pp. R296-R300 ◽  
Author(s):  
S. Harada ◽  
S. Ando ◽  
T. Imaizumi ◽  
Y. Hirooka ◽  
K. Sunagawa ◽  
...  
Keyword(s):  
Phase Shift ◽  
Transfer Function ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Arterial Baroreflex ◽  
Frequency Range ◽  
Nerve Activity ◽  
Baroreflex Control ◽  
Renal Sympathetic Nerve ◽  
Renal Sympathetic

To investigate wideband dynamic properties of arterial baroreflex control of cardiac and renal sympathetic nerve activities, we assessed the transfer function using a "white-noise technique." In pentobarbital sodium-anesthetized cats, we simultaneously recorded, as the output, cardiac sympathetic nerve activity (CSNA) and renal sympathetic nerve activity (RSNA), while aortic pressure (AP) was randomly perturbed to impose input pressure changes with broad frequencies. We calculated the transfer function from AP to CSNA or to RSNA over the frequency range of 0.01-5 Hz through the spectral analysis of the input and output. We found that the gain, phase shift, and coherence of those transfer functions were statistically indistinguishable. The gain was rather flat below 0.05 Hz, steadily increased above 0.05 Hz, and plateaued above 0.3 Hz. The phase shift was out of phase up to 0.05 Hz and led by approximately 4 degrees above 0.05 Hz. The coherence was high (above 0.7) below 0.3 Hz and became lower above 0.3 Hz. These results suggest that arterial baroreflex control is uniform and similar between the two activities in the frequency range of 0.01-0.7 Hz.

A transfer function method for the continuous assessment of baroreflex control of renal sympathetic nerve activity in rats

2007 ◽  
Vol 293 (5) ◽  
pp. R1938-R1946 ◽  
Author(s):  
Roy Kanbar ◽  
Valérie Oréa ◽  
Bruno Chapuis ◽  
Christian Barrès ◽  
Claude Julien
Keyword(s):  
Transfer Function ◽  
Sympathetic Nerve ◽  
Function Method ◽  
Sympathetic Nerve Activity ◽  
Nerve Activity ◽  
Baroreflex Control ◽  
Renal Sympathetic Nerve Activity ◽  
Transfer Function Method ◽  
Renal Sympathetic Nerve ◽  
Renal Sympathetic

The present study examined whether the gain of the transfer function relating cardiac-related rhythm of renal sympathetic nerve activity (RSNA) to arterial pressure (AP) pulse might serve as a spontaneous index of sympathetic baroreflex sensitivity (BRS). AP and RSNA were simultaneously recorded in conscious rats, either baroreceptor-intact (control, n = 11) or with partial denervation of baroreflex afferents [aortic baroreceptor denervated (ABD; n = 10)] during 1-h periods of spontaneous activity. Transfer gain was calculated over 58 adjacent 61.4-s periods (segmented into 10.2-s periods). Coherence between AP and RSNA was statistically ( P < 0.05) significant in 90 ± 3% and 56 ± 10% of cases in control and ABD rats, respectively. Transfer gain was higher ( P = 0.0049) in control [2.39 ± 0.13 normalized units (NU)/mmHg] than in ABD (1.48 ± 0.22 NU/mmHg) rats. In the pooled study sample, transfer gain correlated with sympathetic BRS estimated by the vasoactive drug injection technique ( R = 0.75; P < 0.0001) and was inversely related to both time- (standard deviation; R = −0.74; P = 0.0001) and frequency-domain [total spectral power (0.00028–2.5 Hz); R = −0.82; P < 0.0001] indices of AP variability. In control rats, transfer gain exhibited large fluctuations (coefficient of variation: 34 ± 3%) that were not consistently related to changes in the mean level of AP, heart rate, or RSNA. In conclusion, the transfer function method provides a continuous, functionally relevant index of sympathetic BRS and reveals that the latter fluctuates widely over time.

Central mechanisms of acute ANG II modulation of arterial baroreflex control of renal sympathetic nerve activity

2002 ◽  
Vol 282 (5) ◽  
pp. H1592-H1602 ◽  
Author(s):  
Max G. Sanderford ◽  
Vernon S. Bishop
Keyword(s):  
Sympathetic Nerve ◽  
Intravenous Infusion ◽  
Sympathetic Nerve Activity ◽  
Ang Ii ◽  
Arterial Baroreflex ◽  
Nerve Activity ◽  
Baroreflex Control ◽  
Renal Sympathetic Nerve Activity ◽  
Renal Sympathetic Nerve ◽  
Renal Sympathetic

Short-term intravenous infusion of angiotensin II (ANG II) into conscious rabbits reduces the range of renal sympathetic nerve activity (RSNA) by attenuating reflex disinhibition of RSNA. This action of ANG II to attenuate the arterial baroreflex range is exaggerated when ANG II is directed into the vertebral circulation, which suggests a mechanism involving the central nervous system. Because an intact area postrema (AP) is required for ANG II to attenuate arterial baroreflex-mediated bradycardia and is also required for maintenance of ANG II-dependent hypertension, we hypothesized that attenuation of maximum RSNA during infusion of ANG II involves the AP. In conscious AP-lesioned (APX) and AP-intact rabbits, we compared the effect of a 5-min intravenous infusion of ANG II (10 and 20 ng · kg−1 · min−1) on the relationship between mean arterial blood pressure (MAP) and RSNA. Intravenous infusion of ANG II into AP-intact rabbits resulted in a dose-related attenuation of maximum RSNA observed at low MAP. In contrast, ANG II had no effect on maximum RSNA in APX rabbits. To further localize the central site of ANG II action, its effect on the arterial baroreflex was assessed after a midcollicular decerebration. Decerebration did not alter arterial baroreflex control of RSNA compared with the control state, but as in APX, ANG II did not attenuate the maximum RSNA observed at low MAP. The results of this study indicate that central actions of peripheral ANG II to attenuate reflex disinhibition of RSNA not only involve the AP, but may also involve a neural interaction rostral to the level of decerebration.

Arterial baroreflex during pregnancy and renal sympathetic nerve activity during parturition in rabbits

1998 ◽  
Vol 274 (5) ◽  
pp. H1635-H1642 ◽  
Author(s):  
Kathleen P. O’Hagan ◽  
Susan M. Casey
Keyword(s):  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Arterial Baroreflex ◽  
Nerve Activity ◽  
Baroreflex Control ◽  
Renal Sympathetic Nerve Activity ◽  
Renal Sympathetic Nerve ◽  
Reflex Gain ◽  
Maximal Gain ◽  
Renal Sympathetic

The arterial baroreflex control of renal sympathetic nerve activity (RSNA) was evaluated in nine term pregnant (P) and 12 nonpregnant (NP) conscious New Zealand White rabbits. In an additional four P rabbits, the RSNA response to spontaneous parturition was measured. The blood pressure (BP)-RSNA relationship was generated by sequential inflations of aortic and vena caval perivascular occluders. Rest BP (P: 61 ± 2 vs. NP: 73 ± 2 mmHg) and the centering point of the baroreflex (P: 57 ± 2 vs. NP: 70 ± 2 mmHg) were lower ( P < 0.05) in term pregnancy. Baroreflex range (P: 246 ± 14% vs. NP 263 ± 24% of rest RSNA) was not affected by pregnancy. However, maximal reflex gain was moderately depressed (−44%) in P rabbits (P: −15 ± 1 vs. NP: −27 ± 4% of rest RSNA/mmHg; P < 0.05) due to a significant reduction in the slope coefficient. Delivery of a fetus was associated with strong renal sympathoexcitation. Peak RSNA averaged 80 ± 37% of smoke-elicited RSNA or 1,221 ± 288% of rest RSNA (mean ± SD). These results suggest that, in contrast to rat pregnancy, depressed arterial baroreflex control of RSNA in rabbit pregnancy is due primarily to a reduction in maximal gain rather than a reduction in the maximal sympathetic response to hypotension.

Arterial baroreflex dynamics in normotensive and spontaneously hypertensive rats

1992 ◽  
Vol 263 (3) ◽  
pp. R524-R528 ◽  
Author(s):  
S. Harada ◽  
T. Imaizumi ◽  
S. Ando ◽  
Y. Hirooka ◽  
K. Sunagawa ◽  
...  
Keyword(s):  
Transfer Function ◽  
Sympathetic Nerve ◽  
Spontaneously Hypertensive Rats ◽  
Sympathetic Nerve Activity ◽  
Arterial Baroreflex ◽  
Frequency Range ◽  
Hypertensive Rats ◽  
Nerve Activity ◽  
Baroreflex Control ◽  
Spontaneously Hypertensive

To investigate dynamic or frequency-dependent characteristics of arterial baroreflex control of efferent sympathetic nerve activity in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY), we assessed the transfer function from aortic pressure (AP) to renal sympathetic nerve activity (RSNA) using a “white-noise technique.” In pentobarbital sodium-anesthetized rats, we recorded RSNA as the output, while AP was randomly perturbed to impose input pressure changes with broad frequencies. We calculated the transfer function from AP to RSNA over the frequency range of 0.01-5 Hz through the spectral analysis of the input and output. The results indicated that the gain, phase shift, and coherence of the transfer function for SHR and for WKY were similar and statistically indistinguishable. The gain was relatively constant below 0.05 Hz but increased steadily by fivefold as frequency increased in the frequency range of 0.05-0.8 Hz. The phase was out of phase where coherence was high. The coherence was high (greater than 0.5) in the frequency range of 0.04-0.8 and 1.00-1.03 Hz but was low in other frequencies. These results suggest that dynamic or frequency-dependent characteristics of arterial baroreflex control of RSNA were not altered in SHR as compared with WKY.

Transfer function analysis between arterial pressure and renal sympathetic nerve activity at cardiac pacing frequencies in the rat

2007 ◽  
Vol 102 (3) ◽  
pp. 1034-1040 ◽  
Author(s):  
Valérie Oréa ◽  
Roy Kanbar ◽  
Bruno Chapuis ◽  
Christian Barrès ◽  
Claude Julien
Keyword(s):  
Transfer Function ◽  
Arterial Pressure ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Cardiac Pacing ◽  
Nerve Activity ◽  
Renal Sympathetic Nerve Activity ◽  
Renal Sympathetic Nerve ◽  
Baseline Conditions ◽  
Renal Sympathetic

This study examined the possible influence of changes in heart rate (HR) on the gain of the transfer function relating renal sympathetic nerve activity (RSNA) to arterial pressure (AP) at HR frequency in rats. In seven urethane-anesthetized rats, AP and RSNA were recorded under baseline conditions (spontaneous HR = 338 ± 6 beats/min, i.e., 5.6 ± 0.1 Hz) and during 70-s periods of cardiac pacing at 6–9 Hz applied in random order. Cardiac pacing slightly increased mean AP (0.8 ± 0.2 mmHg/Hz) and decreased pulse pressure (−3.6 ± 0.3 mmHg/Hz) while leaving the mean level of RSNA essentially unaltered ( P = 0.680, repeated-measures ANOVA). The gain of the transfer function from AP to RSNA measured at HR frequency was always associated with a strong, significant coherence and was stable between 6 and 9 Hz ( P = 0.185). The transfer function gain measured under baseline conditions [2.44 ± 0.28 normalized units (NU)/mmHg] did not differ from that measured during cardiac pacing (2.46 ± 0.27 NU/mmHg). On the contrary, phase decreased linearly as a function of HR, which indicated the presence of a fixed time delay (97 ± 6 ms) between AP and RSNA. In conclusion, the dynamic properties of arterial baroreflex pathways do not affect the gain of the transfer function between AP and RSNA measured at HR frequency in the upper part of the physiological range of HR variations in the rat.

Baroreflex control of renal sympathetic nerve activity during air-jet stress in rats

2007 ◽  
Vol 292 (1) ◽  
pp. R362-R367 ◽  
Author(s):  
Roy Kanbar ◽  
Valérie Oréa ◽  
Christian Barrès ◽  
Claude Julien
Keyword(s):  
Emotional Stress ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Sigmoid Function ◽  
Nerve Activity ◽  
Baroreflex Control ◽  
Renal Sympathetic Nerve Activity ◽  
Renal Sympathetic Nerve ◽  
Air Jet ◽  
Renal Sympathetic

The effects of acute emotional stress on the sympathetic component of the arterial baroreceptor reflex have not yet been described in conscious animals and humans. Arterial pressure (AP) and renal sympathetic nerve activity (RSNA) were simultaneously recorded in 11 conscious rats before and during exposure to a mild environmental stressor (jet of air). Baroreflex function curves relating AP and RSNA were constructed by fitting a sigmoid function to RSNA and AP measured during sequential nitroprusside and phenylephrine administrations. Stress increased mean AP from 112 ± 2 to 124 ± 2 mmHg, heart rate from 381 ± 10 to 438 ± 18 beats/min, and RSNA from 0.80 ± 0.14 to 1.49 ± 0.23 μV. The RSNA-AP relationship was shifted toward higher AP values, and its maximum gain was significantly ( P < 0.01) increased from 9.0 ± 1.3 to 16.2 ± 2.1 normalized units (NU)/mmHg. The latter effect was secondary to an increase ( P < 0.01) in the range of the RSNA variation from 285 ± 33 to 619 ± 59 NU. In addition, the operating range of the reflex was increased ( P < 0.01) from 34 ± 2 to 41 ± 3 mmHg. The present study indicates that in rats, the baroreflex control of RSNA is sensitized and operates over a larger range during emotional stress, which suggests that renal vascular tone, and possibly AP, are very efficiently controlled by the sympathetic nervous system under this condition.

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