Rapid resetting of aortic nerves in conscious rabbits

Undesser, K. P.; Lynn, Melvyn; Bishop, Vernon S.

doi:10.1152/ajpheart.1984.246.2.h302

Cited by 13 publications

(7 citation statements)

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“…The thresholds of arterial baroreceptors are rapidly reset during druginduced pressure changes of this magnitude and duration, and they continue to operate over a higher pressure range with no reduction in gain. 3 ' 5 Therefore, a change in arterial baroreceptor gain cannot explain the reduction in baroreceptor reflex gain seen in these experiments. However, sustained periods of elevated arterial baroreceptor input produced either by electrical stimulation of the aortic nerve or by phenylephrine-induced pressure elevation cause a sustained sympathoinhibition after the return of pressure to control levels.…”

mentioning

confidence: 79%

Cardiac afferents attenuate renal sympathetic baroreceptor reflexes during acute hypertension.

1990

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We have studied the effect of acute hypertensive episodes on the renal sympathetic baroreceptor reflex in conscious rabbits and the role played by cardiac afferents and endogenous opiate mechanisms. Renal sympathetic nerve activity was recorded during brief perivascular ballooninduced ramp changes in mean arterial pressure before and during 40-minute elevations in resting pressure. Methoxamine infusion was adjusted to increase pressure by +30 and +45 mm Hg in the presence of autonomic blockade of the heart with atenolol and methscopolamine. Experiments were repeated in other rabbits after blocking cardiac afferents with 5% intrapericardial procaine or during intravenous naloxone (4-6 mg/kg, then 0.12 mg/kg/min). We found a progressively severe attenuation of the renal sympathetic baroreceptor reflex during increasing elevations in resting pressure. The upper plateau and range of the reflex curve were both reduced by one third and two thirds during moderate and severe hypertension, respectively. The average gain fell by 64% and 87%, and the range-independent gain and hypotensive reversal response were also reduced. There was no resetting of the reflex to higher pressures as would be expected. One third of the reflex inhibition was prevented by blocking cardiac afferents; none of it was affected by intravenous naloxone, which had previously been shown to reverse the renal baroreceptor reflex depression elicited by hemorrhagic hypotension. Factors possibly responsible for the remaining two thirds of the hypertension-induced sympathoinhibition are suggested to be either central depression of sympathetic tone after elevation of arterial baroreceptor discharge during the hypertensive episode or additional inhibitory afferent input arising from the pulmonary circulation. {Hypertension 1990;16:131-139) C hanges in resting blood pressure lasting longer than a few minutes cause shifts in the thresholds of arterial baroreceptors and baroreceptor reflex curves that occur in the same direction as the changes in pressure.1 " 6 This rapid resetting of baroreceptor reflexes can largely be explained by the resetting of the arterial baroreceptors themselves. However, during moderate falls and rises in resting pressure, resetting of the renal sympathetic and cardiac baroreceptor reflexes is greater than baroreceptor resetting, and during somewhat larger increases in resting pressure of approximately 20 mm Hg, resetting of the renal baroreceptor reflex is suppressed in the face of continued baroreceptor

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confidence: 79%

Cardiac afferents attenuate renal sympathetic baroreceptor reflexes during acute hypertension.

1990

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“…One possibility is that the A fibers are important in buffering rapid changes in pressure, and reset readily whereas the C fibers are more important in preventing high pressures and are less likely to reset (48). In explaining the greater shift in the response curve at threshold pressures than at higher pressures seen in whole nerve recordings, both Undesser et al (55) and Heesch et al (19) speculated that the low-threshold receptors may reset more readily than high-threshold baroreceptors.…”

Section: Differential Baroreflex Resettingmentioning

confidence: 99%

Problems, possibilities, and pitfalls in studying the arterial baroreflexes’ influence over long-term control of blood pressure

Barrett

Malpas

2005

American Journal of Physiology-Regulatory, Integrative and Comp

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While there is no disputing the critical role of baroreflexes in buffering rapid changes in arterial pressure, their role in long-term pressure control has become an area of controversy. Recent experiments using novel techniques have challenged the traditional view that arterial baroreflexes are not involved in setting chronic arterial pressure levels. Resetting of the arterial baroreflex, often used as an argument against the arterial baroreflex playing a role in long-term pressure control is rarely complete. The arterial baroreflex is just one of the many neural, hormonal, and intrinsic mechanisms involved in arterial pressure control and while the removal of the arterial baroreflex alone has little effect on mean arterial pressure it is too simplistic to suggest that the baroreflex has no role in long-term pressure control. Renal sympathetic nerve activity appears to be particularly resistant to resetting in response to ANG II-induced hypertension. Given the important role of the kidneys in long-term pressure control, we suggest there is a clear need to develop experimental techniques whereby sympathetic nerve activity to the kidneys and other organs can be monitored over periods of weeks to months.

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“…This is in keeping with the concept of an acute reset capability of the arterial baroreceptors (cf. Korner 1979, Coleridge et al 1981, Heesch et al 1984, Undesser et al 1984, which may also account for the increased baroreflex sensitivity induced by exercise. Heesch et al (1984) suggested that when a baroreceptor area is biased by increased transmural pressure, the low-threshold baroreceptor units reset to a greater extent than do the high pressure units, which, in turn, leads to an increased slope of the pressuredischarge curve.…”

Section: Ejects Of Exercisementioning

confidence: 99%

Effects of blood‐volume distribution on the characteristics of the carotid baroreflex in humans at rest and during exercise

Eiken

Sun

Mekjavic

1994

Acta Physiologica Scandinavica

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Seven supine subjects were studied at rest and during mild to moderate dynamic leg exercise with and without unloading of the cardiopulmonary baroreceptors accomplished by exposing the lower portion of the body to a subatmospheric pressure of 20 mmHg (Lower Body Negative Pressure, LBNP). The function of the cardiac branch of the carotid baroreflex was studied over its full operational range by measuring R-R intervals during application of pulse synchronous graded pressures (40 to -65 mmHg) in a neck-chamber device. Raising the carotid transmural pressure (systolic arterial pressure minus neck-chamber pressure) induced increasing R-R intervals in all conditions. In conformity with previous results from our laboratories it was found that the maximal rate of change in relative R-R intervals and the corresponding transmural pressure were higher during exercise than at rest, indicating that exercise increased the carotid baroreflex sensitivity and shifted its optimal buffering range to higher arterial pressures. LBNP did not affect the characteristics of the reflex at rest nor during exercise. It is concluded that reduced central venous pressure with consequent selective cardiopulmonary receptor disengagement exerts no influence on the carotid baroreflex control of heart rate (HR), as tested over the entire arterial pressure-effector response relation, either at rest or during mild-moderate exercise.

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Rapid resetting of aortic nerves in conscious rabbits

Cited by 13 publications

References 0 publications

Cardiac afferents attenuate renal sympathetic baroreceptor reflexes during acute hypertension.

Cardiac afferents attenuate renal sympathetic baroreceptor reflexes during acute hypertension.

Problems, possibilities, and pitfalls in studying the arterial baroreflexes’ influence over long-term control of blood pressure

Effects of blood‐volume distribution on the characteristics of the carotid baroreflex in humans at rest and during exercise

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