Baroreceptor Stimulation and Isometric Exercise in Normotensive and Borderline Hypertensive Subjects

1982 ◽  
Vol 62 (3) ◽  
pp. 307-309 ◽  
Author(s):  
D. H. Suarez ◽  
F. H. Messerli ◽  
H. O. Ventura ◽  
G. Aristimuno ◽  
G. R. Dreslinski ◽  
...  
Keyword(s):  
Arterial Pressure ◽  
Isometric Exercise ◽  
Pressure Increase ◽  
Baseline Heart Rate ◽  
Carotid Baroreceptor ◽  
Subsequent Response ◽  
Baroreceptor Stimulation ◽  
Exercise Induced ◽  
Neck Chamber ◽  
Similar Decrease

1. The effects of carotid baroreceptor stimulation (neck chamber) on systemic haemodynamics were determined for normotensive and borderline hypertensive subjects during periods of resting and isometric exercise. 2. Both groups reacted to baroreceptor stimulation with a similar decrease in mean arterial pressure and cardiac index at rest and during isometric exercise, but baseline heart rate decreased more in borderline hypertensive patients. 3. Baroreceptor stimulation elicited the same haemodynamic response at rest and during exercise-induced arterial pressure increase. Since the magnitude of arterial pressure had no bearing on the subsequent response, these data suggest resetting of baroreceptors during this short-term blood pressure increase.

Plasma Catecholamines and Blood Pressure Responses to the Carotid Baroreceptor Reflex in Essential Hypertension

1979 ◽  
Vol 57 (s5) ◽  
pp. 165s-167s ◽  
Author(s):  
G. Mancia ◽  
G. Leonetti ◽  
G. B. Picotti ◽  
A. Ferrari ◽  
M. D. Galva ◽  
...  
Keyword(s):  
Essential Hypertension ◽  
Arterial Pressure ◽  
Sympathetic Activity ◽  
Plasma Catecholamines ◽  
Variable Pressure ◽  
Carotid Baroreceptor ◽  
Pressure Variable ◽  
Blood Pressure Responses ◽  
Neck Chamber ◽  
Noradrenaline And Adrenaline

1. Slight decreases and increases in carotid baroreceptor activity were induced in subjects with essential hypertension by slight alterations in carotid transmural pressure (variable pressure neck-chamber technique) in order to obtain limited increases and reductions in sympathetic adrenergic activity. 2. When sympathetic activity was reflexly increased there was a rise in arterial pressure but no significant increase in plasma catecholamines. Likewise when sympathetic activity was reflexly reduced there was a fall in arterial pressure but no significant reduction in plasma catecholamines. 3. Plasma noradrenaline and adrenaline significantly and markedly increased in the same subjects when sympathetic activity was increased by activation of both arterial and low pressure baroreceptor reflexes with tilting. 4. It is suggested that measurements of catecholamines in systemic plasma may reveal marked degrees of sympathetic activation but may not be a sensitive index of more moderate changes in sympathetic tone.

Isometric exercise modifies autonomic baroreflex responses in humans

1987 ◽  
Vol 63 (6) ◽  
pp. 2325-2330 ◽  
Author(s):  
D. L. Eckberg ◽  
B. G. Wallin
Keyword(s):  
Sympathetic Activity ◽  
Isometric Exercise ◽  
Base Line ◽  
Nerve Activity ◽  
Carotid Baroreceptor ◽  
Abrupt Changes ◽  
Torr Pressure ◽  
Nerve Muscle ◽  
Neck Pressure ◽  
Neck Chamber

The influence of brief, moderate isometric exercise on the earliest vagal and sympathetic responses to changes of afferent carotid baroreceptor activity was studied in 10 healthy young men and women. Vagal-cardiac nerve activity was estimated from changes of electrocardiographic R-R intervals, and postganglionic peroneal nerve muscle sympathetic activity was measured directly from microneurographic recordings. Carotid baroreceptor activity was altered with 5-s periods of 30 Torr pressure or suction applied to a neck chamber during held expiration. Brief handgrip (30% of maximum) significantly reduced base-line R-R intervals, did not modify reductions of R-R intervals during neck pressure, and significantly reduced increases of R-R intervals during neck suction. Handgrip did not significantly increase base-line sympathetic activity from resting levels, but it significantly diminished increases of sympathetic activity during neck pressure and augmented reductions of sympathetic activity during neck suction. Our results suggest that exercise modifies, in small but significant ways, early sympathetic and vagal responses to abrupt changes of arterial baroreceptor input in humans.

Continuous resetting of the human carotid baroreceptor-cardiac reflex

1987 ◽  
Vol 252 (4) ◽  
pp. R732-R736 ◽  
Author(s):  
G. A. Kasting ◽  
D. L. Eckberg ◽  
J. M. Fritsch ◽  
C. L. Birkett
Keyword(s):  
Arterial Pressure ◽  
Reflex Response ◽  
Chamber Pressure ◽  
Systematic Change ◽  
Circadian Changes ◽  
Ongoing Process ◽  
Carotid Baroreceptor ◽  
Pressure Changes ◽  
Neck Chamber ◽  
Human Carotid

Although human baroreflex responses have been studied during night as well as day, there has been no attempt to distinguish circadian changes of baroreflex function from those related to sleep. We measured carotid baroreceptor-cardiac reflex responses serially during a 24-h period in 11 normotensive volunteers who were awake and cooperative during testing. We applied sequences of ramped R-wave-triggered neck chamber pressure changes from +40 to -65 mmHg, during held expiration, at 3-h intervals. Subjects maintained their usual sleep-wake cycles but were awakened for three 30-min periods for night testing. There was no systematic change of baroreflex slope during the 24-h period. There were, however, parallel shifts of the entire sigmoid baroreceptor-cardiac reflex response relation along its R-R interval and arterial pressure axes associated with small, but significant, circadian changes of baseline R-R intervals and arterial pressures. Thus, although our data do not point toward major circadian variability of baro-reflex responsiveness, they provide evidence for an ongoing process of human baroreflex resetting.

Carotid Sinus Reflex Control of Renin Release in Hypertensive Subjects with High Renin Secretion

1981 ◽  
Vol 61 (5) ◽  
pp. 505-509 ◽  
Author(s):  
G. Mancia ◽  
A. Ferrari ◽  
G. Leonetti ◽  
Luisa Gregorini ◽  
Laura Terzoli ◽  
...  
Keyword(s):  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Plasma Renin ◽  
Renin Secretion ◽  
Renin Release ◽  
Moderate Increase ◽  
Marked Rise ◽  
Carotid Baroreceptor ◽  
Baroreceptor Stimulation ◽  
Reflex Control

1. Carotid baroreceptor manipulation (neckchamber technique) and passive head-up tilting were used in ten patients with renovascular hypertension and in five subjects with essential hypertension under diuretic treatment to study reflex control of renin secretion” at high basal-renin production rates. 2. Reflex effects of carotid baroreceptor manipulation on renin secretion were only minor. During baroreceptor deactivation there was a moderate increase in mean arterial pressure, but an inconsistent change in the renal venous—arterial difference in plasma renin activity (PRA). 3. During baroreceptor stimulation there was a modest fall in mean arterial pressure and a marked rise in the renal venous—arterial difference in PRA. This was opposite to the fall which might have been predicted as a result of the sympathetic depressor influence of the baroreceptor stimulus. Conversely, tilting increased the venous—arterial PRA difference by about 200%. 4. It is concluded that when renin production rate is high carotid baroreceptors exert little control over renin release, just as when renin production is low. Reflex control of renin, however, is very active in subjects with a high renin production, probably due to receptors in the cardiopulmonary region.

Human sinus node responses to repetitive, ramped carotid baroreceptor stimuli

1982 ◽  
Vol 242 (4) ◽  
pp. H638-H644 ◽  
Author(s):  
D. L. Eckberg ◽  
M. J. Eckberg
Keyword(s):  
Heart Rate ◽  
Arterial Pressure ◽  
Sinus Node ◽  
Correlation Coefficients ◽  
Base Line ◽  
Carotid Baroreceptor ◽  
Baroreceptor Stimulation ◽  
Stimulus Train ◽  
Interval Response ◽  
Integral Feature

When arterial pressure rises spontaneously, baroreceptor areas are presented with repetitive stimuli of progressively increasing intensities. We simulated rising arterial pressure in 18 healthy young adults by applying trains of repetitive, ramped, R-wave-coupled neck suction, and we related P-P interval responses to intensities of stimuli with least-squares linear regression. We found that the P-P interval response to the stimulus train we used is immediate and highly linear (most correlation coefficients were above 0.90). In studies in which the base-line heart rate was less than 75 beats/min, cardiac inhibition was maximal in the cardiac cycle in which the stimulus was delivered. Decay of inhibition commences rapidly after the end of baroreceptor stimulation and proceeds with time constants that are independent of maximum levels of inhibition. P-P interval shortening (cardioacceleration) comprises an integral feature of baroreflex responses, such that inhibitory stimuli set in motion oscillations of heart period above and below base-line levels. Our data suggest that the pattern of sinus node responses during transitions of arterial pressure results from a complex interplay among several factors, including baroreflex responsiveness, base-line heart rate, the rate decay of baroreflex inhibition, and the biphasic nature of sinus node responses to inhibitory cholinergic interventions.

Variability of the haemodynamic responses to laboratory tests employed in assessment of neural cardiovascular regulation in man

1985 ◽  
Vol 69 (5) ◽  
pp. 533-540 ◽  
Author(s):  
Gianfranco Parati ◽  
Guido Pomidossi ◽  
Agustin Ramirez ◽  
Bruno Cesana ◽  
Giuseppe Mancia
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Test Performance ◽  
Blood Pressure Response ◽  
Cold Pressor Test ◽  
Cold Pressor ◽  
Cardiovascular Regulation ◽  
Pressor Test ◽  
Carotid Baroreceptor ◽  
Baroreceptor Stimulation

1. In man evaluation of neural cardiovascular regulation makes use of a variety of tests which address the excitatory and reflex inhibitory neural influences that control circulation. Because interpretation of these tests is largely based on the magnitude of the elicited haemodynamic responses, their reproducibility in any given subject is critical. 2. In 39 subjects with continuous blood pressure (intra-arterial catheter) and heart rate monitoring we measured (i) the blood pressure and heart rate rises during hand-grip and cold-pressor test, (ii) the heart rate changes occurring during baroreceptor stimulation and deactivation by injection of phenylephrine and trinitroglycerine, and (iii) the heart rate and blood pressure changes occurring with alteration in carotid baroreceptor activity by a neck chamber. Each test was carefully standardized and performed at 30 min intervals for a total of six times in each subject. 3. The results showed that the responses to any test were clearly different from one another and that this occurred in all subjects studied. For the group as a whole the average response variability (coefficient of variation) ranged from 10.2% for the blood pressure response to carotid baroreceptor stimulation to 44.2% for the heart rate response to cold-pressor test. The variability of the responses was not related to basal blood pressure or heart rate, nor to the temporal sequence of the test performance. 4. Thus tests employed for studying neural cardiovascular control in man produce responses whose reproducibility is limited. This phenomenon may make it more difficult to define the response magnitude typical of each subject, as well as its comparison in different conditions and diseases.

Human arterial responses to isometric exercise: the role of the muscle metaboreflex

2007 ◽  
Vol 112 (8) ◽  
pp. 441-447 ◽  
Author(s):  
Tom S. Davies ◽  
Michael P. Frenneaux ◽  
Ross I. Campbell ◽  
Michael J. White
Keyword(s):  
Plantar Flexion ◽  
Isometric Exercise ◽  
Arterial Tree ◽  
Contralateral Limb ◽  
Post Exercise ◽  
Muscle Metaboreflex ◽  
Calf Exercise ◽  
Exercise Induced ◽  
Arterial Responses

The effects of exercise on the distensibility of large and medium-sized arteries are poorly understood, but can be attributed to a combination of local vasodilator effects of exercise opposed by sympathetic vasoconstrictor tone. We sought to examine this relationship at the conduit artery level, with particular reference to the role of the sympatho-excitatory muscle metaboreflex. The effect of maintained muscle metaboreflex activation on a previously passive or exercised limb femoral artery was investigated. A total of ten healthy volunteers performed 2 min of isometric ankle plantar-flexion at 40% MVC (maximal voluntary force), in conjunction with 2 min of either non-ischaemic isometric HG (handgrip; control condition) or IHG (ischaemic HG) at 40% MVC. IHG was followed by 2 min of PECO (post-exercise circulatory occlusion) to maintain muscle metaboreflex activation. FTPWV [femoral–tibial PWV (pulse wave velocity)] was measured in the exercised or contralateral limb at baseline and immediately following calf exercise. BP (blood pressure) and HR (heart rate) were measured continuously throughout. In the HG condition, BP and HR returned promptly to baseline post-exercise, whereas exercised leg FTPWV was decreased (less stiff) by 0.6 m/s (P<0.05) and the non-exercised leg PWV was not changed from baseline. PECO caused a sustained increase in BP, but not HR, in the IHG condition. Contralateral leg PWV increased (stiffened) during PECO by 0.9 m/s (P<0.05), whereas exercised limb FTPWV was not changed from baseline. In conclusion, muscle metaboreflex activation causes a systemic stiffening of the arterial tree, which can overcome local exercise-induced decreases in arterial PWV.

Sympathetic transients caused by abrupt alterations of carotid baroreceptor activity in humans

1982 ◽  
Vol 242 (2) ◽  
pp. H185-H190 ◽  
Author(s):  
B. G. Wallin ◽  
D. L. Eckberg
Keyword(s):  
Sympathetic Activity ◽  
Chamber Pressure ◽  
Reduced Pressure ◽  
Cardiac Responses ◽  
Carotid Baroreceptor ◽  
Sympathetic Responses ◽  
Nerve Muscle ◽  
Neck Pressure ◽  
Pressure Changes ◽  
Neck Chamber

We examined the role of carotid baroreceptors in the short-term modulation of sympathetic outflow to the muscle vascular bed and parasympathetic outflow to the heart in 10 healthy adults. Afferent carotid baroreceptor activity was modified with 30-mmHg neck suction or pressure applied during held expiration, and efferent sympathetic activity was measured with microelectrodes inserted percutaneously into peroneal nerve muscle fascicles. Sympathetic responses were conditioned importantly by directional changes of carotid transmural pressure: increased pressure (onset of neck suction or offset of neck pressure) inhibited (totally) sympathetic activity, and reduced pressure (offset of neck suction or onset of neck pressure) augmented sympathetic activity. Responses occurred after a latency of about 2 s and did not persist as long as changes of neck-chamber pressure. Cardiac intervals were prolonged by increased carotid transmural pressures and shortened by decreased carotid transmural pressures, but, in contrast to sympathetic responses, cardiac responses adapted only slightly during neck-chamber pressure changes. Our results suggest that in the human a common baroreceptor input is processed differently in central vagal and sympathetic networks. Muscle sympathetic responses to changing levels of afferent baroreceptor traffic are profound but transitory. They appear to be conditioned more by changes of arterial pressure than by its absolute levels.

Sign in / Sign up

Export Citation Format

Share Document