Effects of renal sympathectomy on sodium and water excretion in stroke-prone spontaneously hypertensive rats.

American Journal of Physiology-Regulatory, Integrative and Comp

2004

Malpas, Simon C. What sets the long-term level of sympathetic nerve activity: is there a role for arterial baroreceptors? Am J Physiol Regul Integr Comp Physiol 286: R1-R12, 2004; 10.1152/ajpregu.00496.2003.-Much of our knowledge of the influence of the sympathetic nervous system on the control of blood pressure is built on experimental approaches that focus very much on time scales Ͻ24 h. Although direct recordings of sympathetic nerve activity (SNA) over short time scales provide important information, it is difficult to place their relevance over the longer term where the development of chronic changes in blood pressure are likely to be a mixture of hormonal, renal, and neural influences. Recently new experimental approaches are now revealing a possible role for arterial baroreceptors in the chronic regulation of SNA. These studies reveal that chronic increases in blood pressure are associated with chronic changes in SNA that may be due to nonresetting of the blood pressure-SNA baroreflex relationship. This review discusses the implications of such information, highlighting new technologies for long-term recording of SNA that appear to hold much promise for revealing the role of SNA to the kidney for the long-term control of blood pressure. blood pressure; baroreflex; renal THE CONTROL OF ARTERIAL PRESSURE is a complex mixture of the long-and short-term influences of hormones, local vascular factors, and neural mechanisms. With regard to neural influences, much progress has been made in recent years on the central nervous system pathways involved in regulating sympathetic nerve activity (SNA) and the effect of that activity on vascular resistance. However, our knowledge of this control is mostly confined to short time scales of seconds and minutes, with a paucity of studies extending their focus to the longer term aspects (Ͼ24 h). Yet such information is liable to be critical in understanding the pathogenesis of hypertension where the onset of the disease is most likely to be a combination of slowly developing factors. As new tools for assessing sympathetic activity over longer time scales emerge, there is a growing desire and ability to understand longer term aspects of the regulation of SNA. It is recognized that pathways involved in regulating blood volume, osmolarity, and oxygen levels, as well as chronic changes in central nervous system function, are all likely to be important factors in understanding how SNA is controlled. However, given the revival in the hypothesis that arterial baroreflexes play a role in regulating the long-term levels of blood pressure, this review concentrates on the recent research supporting this concept. HISTORY

Section: Current Approaches For Examining the Relevance Of The Sympatmentioning

confidence: 99%

What sets the long-term level of sympathetic nerve activity: is there a role for arterial baroreceptors?

American Journal of Physiology-Regulatory, Integrative and Comp

2004

“…In animal studies, removal of the renal sympathetic nerves has been shown to delay the onset or reduce the magnitude of hypertension. [10][11][12][13][14][15][16] Overall, these results have been interpreted to suggest that an integral relationship exists between functional sympathetic outflow to the kidneys and the chronic regulation of arterial pressure.…”

Section: Sympathetic Nerve Activity To the Kidney Is Increasedmentioning

confidence: 89%

“…Total noradrenaline spillover is increased by approximately 40% in essential hypertension, with half of this increase derived from increases to the heart and kidneys, suggesting selective overactivity in the sympathetic nerves to these organs. In animal studies, removal of the renal sympathetic nerves has been shown to delay the onset or reduce the magnitude of hypertension 10–16 . Overall, these results have been interpreted to suggest that an integral relationship exists between functional sympathetic outflow to the kidneys and the chronic regulation of arterial pressure.…”

Section: Sympathetic Nerve Activity To the Kidney Is Increasedmentioning

confidence: 98%

Long‐term Recording of Sympathetic Nerve Activity: The New Frontier in Understanding the Development of Hypertension?

Guild

Barrett

2005

Clin Exp Pharma Physio

1. With increasing evidence that the sympathetic nervous system plays a critical role in the development of hypertension, focus is turning to how these signals translate to a chronic increase in arterial pressure. 2. The kidney's role in the control of salt and water homeostasis makes it an obvious target for such investigations. However, to date, many studies have been restricted to experiments lasting only a few hours or, at most, a few days, whereas others may use indirect methods of assessing sympathetic activity rather than direct recordings. 3. We review current approaches used to determine the effects of renal sympathetic nerve activity (SNA) on arterial pressure and suggest possible avenues of future investigation. We propose that although afferent inputs, such as from chemoreceptors and baroreceptors, are important for the short-term control of blood pressure via regulation of SNA to multiple organs, it is highly likely that alternative signals are important for setting the long-term level of renal SNA. 4. Emerging evidence indicates circulating angiotensin II is hormone that may act on the central nervous system to regulate renal SNA, renal function and, thus, blood pressure. 5. We propose that an integral part of future studies seeking an understanding of the genesis of hypertension should include chronic direct recordings of renal SNA.

“…This approach has revealed a disproportionate increase in sympathetic activity to the heart and kidneys in hypertension, with half of the increase in noradrenaline being accounted for by increased SNA to the heart and the kidney [15,16•]. In animal studies, removal of the renal sympathetic nerves has been shown to delay the onset or reduce the magnitude of hypertension [17][18][19][20][21]. Overall, these results have been interpreted to suggest that an integral relationship exists between functional sympathetic outflow to the kidneys and the chronic regulation of arterial pressure.…”

Section: Sympathetic Activity To the Kidney Is Increased Selectivelymentioning

confidence: 99%

Renal sympathetic nerve activity in the development of hypertension

Ramchandra²,

Guild³

et al. 2006

Current Science Inc

With increasing evidence that the sympathetic nervous system plays a critical role in the development of hypertension, focus is turning to how these signals translate to a chronic increase in arterial pressure. The kidney's role in the control of salt and water homeostasis makes it an obvious target for such investigations. However, to date many studies have been restricted to experiments that last only a few hours, or at most, a few days, whereas others may use indirect methods of assessing sympathetic activity rather than direct recordings. We review current approaches used to determine the effects of renal sympathetic nerve activity (SNA) on arterial pressure and suggest possible avenues of future investigation. We propose that although afferent inputs, such those as from chemoreceptors and baroreceptors, are important for the short-term control of blood pressure via regulation of SNA to multiple organs, it is highly likely that alternative signals are important for setting the long-term level of renal SNA. Emerging evidence indicates that circulating angiotensin II is a hormone that may act on the central nervous system to regulate renal SNA, renal function, and, therefore, blood pressure. Future studies on the genesis of hypertension should focus more on determining the mediators of long-term levels of renal SNA.