Baroreflex Control of Sympathetic Nerve Activity and Blood Pressure Variability

Abstract

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.

Hypertension in rat offspring subjected to perinatal protein malnutrition is not related to the baroreflex dysfunction

“…It has been well documented that proper functioning of the cardiovascular system is dependent on different controller systems, including the autonomic nervous system and peripheral sensors, in particular under the influence of arterial baroreceptors . It is assumed, therefore, that changes in the AP, as found in hypertension, could be the result of dysfunction of the cardiovascular control systems, including the BR . It is known that variations in the SAP and IP frequency bands are dependent on biological modulators.…”

“…3,19,20 It is assumed, therefore, that changes in the AP, as found in hypertension, could be the result of dysfunction of the cardiovascular control systems, including the BR. 6,7,[21][22][23] It is known that variations in the SAP and IP frequency bands are dependent on biological modulators. Thus, the BP and HR are constantly subject to fluctuations induced by autonomic tone, determined by the sympathetic and parasympathetic activities.…”

“…This is a health care issue where the SNS has an important place in the development and clinical presentation of the patients . A reduction in the inhibitory influence of the aortic and carotid baroreceptors on SNS activity resulting in hyperactivity of this system is thought to contribute to the development of hypertension …”

“…5 A reduction in the inhibitory influence of the aortic and carotid baroreceptors on SNS activity resulting in hyperactivity of this system is thought to contribute to the development of hypertension. 6,7 Other factors may be involved in the genesis of hypertension.…”

Baroreflex control of lumbar and renal sympathetic nerve activity in conscious rats

“…We conclude that in conscious rats, the baroreflex control of lumbar and renal SNA shows quantitative differences but is modulated in a mostly coordinated way. arterial pressure; baroreceptor reflex; sympathetic nervous system; transfer function THE ARTERIAL BARORECEPTOR reflex plays a major role in the short-term control of arterial pressure (AP) mainly through the modulation of efferent sympathetic nerve activity (SNA) to regional circulations (12). In rats, studies aimed at characterizing the baroreflex control of SNA under physiological conditions, i.e., in the conscious state, have been based mostly on recordings of renal SNA (RSNA; 3,5,7,10,13,16,20,23,25), mainly because of the purely postganglionic nature of this activity.…”