Effect Of α‐Adrenoceptor Blockade On The 0.4 Hz Sympathetic Rhythm In Conscious Rats

Barrès, Christian; Neto, Edmundo Pereira de Souza; Julien, Claude

doi:10.1046/j.1440-1681.2001.03561.x

Cited by 15 publications

(10 citation statements)

References 13 publications

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“…19,20 The present study allows extending this conclusion to a situation of centrally induced sympathetic activation accompanying exposure to a mild environmental stressor, which is particularly relevant to daily life situations. A quantitative approach of the various determinants of Mayer wave's amplitude, especially mean SNA level versus baroreflex sensitivity, is now required.…”

Section: Perspectivesmentioning

confidence: 68%

“…9,19 After acute administration of the ␣-adrenoceptor blockade, phentolamine, the baroreceptor reflex loop is opened at the vascular neuroeffector junction, and the reflex sympathetic activation occurring in response to the decrease in AP is not accompanied by a parallel increase in the amplitude of SNA oscillations at Mayer wave's frequency. On the contrary, these oscillations are strongly attenuated or even abolished, 19,20 which further favors a major role of the baroreceptor reflex in their production. During centrally induced sympathetic activation, it is not known whether the amplification of SNA oscillations at Mayer wave's frequency requires the functional integrity of the baroreceptor reflex.…”

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confidence: 99%

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Steady-State and Dynamic Responses of Renal Sympathetic Nerve Activity to Air-Jet Stress in Sinoaortic Denervated Rats

2004

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Abstract-This study examined the role of arterial baroreceptors in mediating the relationship between changes in the mean level and the amplitude of slow oscillations of renal sympathetic nerve activity (RSNA) during environmental stress. In 7 sham-operated (control) and 7 chronically (2 weeks before study) sinoaortic baroreceptor denervated (SAD) conscious rats, arterial pressure (AP) and RSNA were simultaneously recorded during two 15-minute periods, before and during the application of a mild environmental stressor (jet of air). Air-jet stress induced a similar degree of sympathoexcitation in both groups of rats. During stress in control rats, AP and RSNA spectral power in the mid-frequency (MF) range (0.27 to 0.74 Hz) increased, mainly as a consequence of an amplification of strongly coherent oscillations of Ϸ0.4 Hz frequency. In SAD rats, MF fluctuations of AP and RSNA were reduced but not abolished before stress, tended to increase during stress, and were linearly related under both experimental conditions. However, in the MF range, there was no well-defined oscillation at any specific frequency. At the peak coherence frequency (Ϸ0.4 Hz), the gain of the transfer function from RSNA to AP did not change during stress in control rats and was similar to that measured in SAD rats, indicating that it mainly reflected the properties of the feedforward effect of RSNA on AP (ie, vascular reactivity). In summary, the parallelism between stress-induced changes in the mean level of RSNA and the amplitude of slow RSNA oscillations requires the functional integrity of the baroreceptor reflex, which is consistent with the hypothesis that slow AP and RSNA rhythms are resonant oscillations within the baroreceptor reflex loop.

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Section: Perspectivesmentioning

confidence: 68%

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confidence: 99%

Steady-State and Dynamic Responses of Renal Sympathetic Nerve Activity to Air-Jet Stress in Sinoaortic Denervated Rats

2004

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“…The kinetics of vasoconstriction evoked by P2X receptor stimulation is faster than the kinetics evoked by ␣-adrenoceptor stimulation (1), especially because P2X receptors are ligand-gated ion channels (27), whereas ␣-adrenoceptors are G protein-coupled receptors. Accordingly, acute ␣-adrenoceptor blockade shifts Mayer waves and accompanying oscillations of renal sympathetic nerve activity (RSNA) from 0.4 to ϳ0.6 Hz in conscious rats (3). Reciprocally, P2 receptor blockade eliminates 0.4-Hz AP oscillations, whereas it enhances AP oscillations at lower frequencies, especially in the 0.15-to 0.2-Hz range (10).…”

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confidence: 99%

Role of purinergic cotransmission in the sympathetic control of arterial pressure variability in conscious rats

Emonnot

Bakhos²,

Chapuis³

et al. 2006

American Journal of Physiology-Regulatory, Integrative and Comp

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Previous studies have shown that the sympathetically mediated oscillations of arterial pressure (AP), the so-called Mayer waves, are shifted from 0.4 to 0.6 Hz after acute alpha-adrenoceptor blockade in conscious rats. This raises the possibility that, under physiological conditions, Mayer waves are mediated by the conjoint action of norepinephrine and other sympathetic cotransmitters. To evaluate the possible role of the cotransmitter ATP in determining the frequency of Mayer waves, AP and renal sympathetic nerve activity (RSNA) were simultaneously recorded in 10 conscious rats with cardiac autonomic blockade before and after acute blockade of P2 receptors with pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid. P2 receptor blockade did not alter the mean level and overall variability of AP and RSNA but shifted peak coherence between AP and RSNA from 0.43 +/- 0.02 to 0.22 +/- 0.01 Hz. A model of the sympathetic limb of the arterial baroreceptor reflex was designed to simulate Mayer waves at 0.2 and 0.6 Hz, with norepinephrine and ATP, respectively, acting as the sole sympathetic cotransmitter. When both cotransmitters acted in concert, a single oscillation was observed at 0.4 Hz when the gain ratio of the adrenergic to the purinergic components was set at 15. The model thus accounted for an important role for ATP in determining Mayer wave frequency, but not in sustaining the mean level of AP or controlling its overall variability.

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“…Another important finding of studies on baroreceptor denervated rats is that the mid‐frequency (~0.4 Hz) BP oscillations, the so‐called Mayer waves and their associated RSNA oscillations, are markedly attenuated in these animals 17,19 . A similar observation has been made in conscious rats after acute α‐adrenoceptor blockade, 20 a situation where the baroreflex loop is opened at the level of the vascular neuroeffector junction. It is thus proposed that Mayer waves reflect both the feedback from BP to SNA and the feedforward from SNA to BP 21 .…”

Section: Effect Of Sinoaortic Denervation On Rsna Variabilitymentioning

confidence: 59%

Baroreflex Control of Sympathetic Nerve Activity and Blood Pressure Variability

Julien

2008

Clin Exp Pharma Physio

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1. The simultaneous recording of blood pressure (BP) and renal sympathetic nerve activity (RSNA) in conscious sinoaortic baroreceptor denervated rats has revealed that the sympathetic component of the baroreceptor reflex both limits the amplitude of slow BP fluctuations and generates a faster BP oscillation (approximately 0.4 Hz in rats), the so-called Mayer wave. 2. Using BP and RSNA time series collected in conscious baroreceptor denervated rats and parameters of the transfer function relating RSNA to BP, it has been possible to predict BP and RSNA variabilities actually observed in baroreceptor-intact rats. The most accurate simulation was obtained when the baroreflex gain was set at 20-30% of a critical value leading to the production of self-sustained oscillations of BP and RSNA at Mayer wave's frequency. 3. Recent studies performed on conscious rats have indicated that the gain of the RSNA-BP baroreflex function curve is altered during sleep-wake cycle, grooming, exercise and exposure to environmental stress. These observations raise the possibility that the sympathetic baroreflex sensitivity might be continuously modulated as part of normal behavioural responses. 4. To examine this hypothesis, a method has been developed to obtain a continuous index of sympathetic baroreflex sensitivity. The method is based on the calculation of the gain of the transfer function relating RSNA oscillations to the BP pulse at heart rate frequency. This new spontaneous index correlates with the baroreflex gain measured by the vasoactive drug injection technique and is inversely related to overall indices of BP variability. In addition, it shows large, spontaneous variations over time.

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Effect Of α‐Adrenoceptor Blockade On The 0.4 Hz Sympathetic Rhythm In Conscious Rats

Cited by 15 publications

References 13 publications

Steady-State and Dynamic Responses of Renal Sympathetic Nerve Activity to Air-Jet Stress in Sinoaortic Denervated Rats

Steady-State and Dynamic Responses of Renal Sympathetic Nerve Activity to Air-Jet Stress in Sinoaortic Denervated Rats

Role of purinergic cotransmission in the sympathetic control of arterial pressure variability in conscious rats

Baroreflex Control of Sympathetic Nerve Activity and Blood Pressure Variability

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