Discharge characteristics and rapid resetting of autoactive aortic baroreceptors in rats.

Munch, P. A.

doi:10.1113/jphysiol.1992.sp019430

Cited by 10 publications

(10 citation statements)

References 18 publications

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“…It has been proposed that the two types of fibers may act differentially, having different "purposes," allowing arterial pressure to be buffered over a wide operating range and both rapid and slow changes in arterial pressure to be buffered (84). Importantly, there is evidence that the two fiber types may differ in their ability to reset (69,85). It should also be noted that the typical methods for monitoring afferent baroreceptor activity, namely single or so-called whole nerve recordings, are biased toward A fibers with their larger spikes (1, 6), despite the fact that histological studies have shown that C fibers outnumber A fibers in baroreceptor nerves in both the rabbit (79) and rat (7).…”

Section: Possible Mechanisms Regulating the Long-term Level Of Sna: Amentioning

confidence: 99%

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

Malpas

2004

American Journal of Physiology-Regulatory, Integrative and Comp

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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

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Section: Possible Mechanisms Regulating the Long-term Level Of Sna: Amentioning

confidence: 99%

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

Malpas

2004

American Journal of Physiology-Regulatory, Integrative and Comp

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“…While the presence of activity in aortic baroreceptors at low pressures has been reported previously [2,3,11], there is no report that has quantified or explained this behaviour at low pressure. We have now demonstrated that approximately one-third of the aortic baroreceptors in the rabbit have a non-monotonic J-shaped response curve.…”

Section: Discussionmentioning

confidence: 78%

“…Thus the J-shaped multifibre response curve may be attributable, at least in part, to the behaviour of a substantial subpopulation of aortic baroreceptors within the ADN [13]. Indeed, there are limited reports of fibres possessing these appropriate firing characteristics [2,3,11].…”

Section: Introductionmentioning

confidence: 99%

“…Stress and strain in the wall of the artery are determined by the arterial pressure, and it is these variables that are monitored by the baroreceptors. Circumferential distortion of the vessel, which occurs at lower and mid-range arterial pressures, is reported primarily by baroreceptors coupled to myelinated afferent fibres (A-fibre baroreceptors) [1][2][3][4][5][6][7]. Baroreceptors coupled to unmyelinated afferent fibres (C-fibre baroreceptors) appear to respond primarily to compression of the arterial wall [8] and report arterial pressure in the middle and higher range of pressure [9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

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The relationship between aortic baroreceptor activity and arterial pressure is not monotonic

2011

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Previous reports indicate that when aortic pressure (AP) falls below the threshold (P (th)) for baroreceptor sensitivity, activity in the aortic depressor nerve (ADN) may increase. To quantify and explain this anomalous behaviour, we analysed curves describing the relationship of baroreceptor fibre activity in rabbit left ADN to AP. Data were obtained in anaesthetised New Zealand White rabbits. Occlusion and release of cuffs around the inferior vena cava and descending aorta generated AP ramps (25-140 mmHg). Response curves were obtained for 173 fibres in 26 animals. Thirty percent of curves had a nadir (J-shaped curve), and in 40% activity was always present. In fibres showing activity below P (th), firing was predominantly diastolic, switching to systolic firing at P (th). The unusual behaviour of a substantial fraction of aortic baroreceptors below P (th) accounts for the J-shaped response curve of the whole ADN. We suggest that fibres that fire during diastole at pressures below P (th) may have sensory endings close to the origin of the left subclavian artery. As a consequence of this anatomical location, low pressures can impose strain on these receptors, which is then relieved by the systolic pulse.

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“…16 In the present study, we recorded the whole nerve activity during natural pulsatile pressure and observed a sigmoidal-shaped curve for the MAP-aortic nerve activity relation. We therefore plotted aortic nerve activity at 5-mm Hg intervals of MAP and fitted the data to a logistic function curve 14 ' 15 by using a nonlinear regression program (PROC NUN, SAS Institute Inc) on a computer (PS/2 model 50Z, IBM Co).…”

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confidence: 58%

Effects of antihypertensive agents on baroreceptor function in early hypertensive rats.

et al. 1994

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To investigate the effects of antihypertensive treatment with four currently used agents (trichlormethiazide, atenolol, nicardipine, and enalapril) on the arterial baroreceptor function at the early phase of hypertension, we administered the agents to spontaneously hypertensive rats and WistarKyoto rats from 8 to 10 weeks of age and examined the aortic nerve activity function. In untreated spontaneously hypertensive rats, the relation between the arterial pressure and aortic nerve activity was shifted to the right, that is, to a higher pressure level (threshold pressure, 90±3 versus 76±1 mm Hg, P<.05), and the maximum gain which was obtained by logistic function analysis was depressed (1.55±0.08% versus 2.18±0.13% maximum/mm Hg, f<.01) as compared with untreated Wistar-Kyoto rats. An equivalent decrease in arterial pressure with each of the four agents (-20±l mm Hg, P<.01) B aroreceptor activity transmitted to the central nervous system (CNS) is a primary signal concerning moment-to-moment alterations in arterial pressure and represents a fundamental mechanism in the neural control of the circulation because it triggers reflex inhibition of sympathetic nerve activity and excitation of parasympathetic nerve activity that buffers the rise in pressure. It is known that the baroreceptor function is depressed in several forms of hypertension. 1 " 3 Impaired baroreceptor input to the CNS elicits instability of the circulation, 4 which tends in turn to lead to increases in cardiovascular morbidity and mortality. Agents that effectively potentiate the baroreceptor function are considered preferable in the treatment of hypertension. Early studies have shown that conventional antihypertensive therapy with combinations of drugs (diuretics, vasodilators, and adrenergic antagonists) increased the baroreceptor sensitivity in spontaneously hypertensive rats (SHRs). classes of antihypertensive agents might exert distinct effects on the baroreceptor function through specific pharmacological actions when administered chronically to hypertensive subjects. To test this hypothesis, we treated SHRs with one of four currently used agents (a diuretic, a j3-adrenergic blocker, a calcium channel blocker, and an ACE inhibitor) for 2 weeks and examined the effects on the aortic baroreceptor function. Moreover, we used relatively young SHRs (10 weeks of age) in which the characteristics of the aorta are less damaged by hypertension 3

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Discharge characteristics and rapid resetting of autoactive aortic baroreceptors in rats.

Cited by 10 publications

References 18 publications

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

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

The relationship between aortic baroreceptor activity and arterial pressure is not monotonic

Effects of antihypertensive agents on baroreceptor function in early hypertensive rats.

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