Reproducibility of human vagal carotid baroreceptor-cardiac reflex responses

Published information on the reproducibility of human baroreflex responses in the absence of interventions is limited. Therefore, we analyzed retrospectively vagally mediated carotid baroreceptor-cardiac reflex responses of 34 healthy young adult volunteers whom we studied twice, 7-10 days apart (all 34 subjects) or 10 wk apart (8 subjects). We delivered a sequence of neck pressure changes during held expiration: A computer-driven bellows initially raised pressure to approximately 40 mmHg for five heart beats, and then reduced pressure in a stepwise series of R-wave-triggered 15-mmHg decrements to about -65 mmHg. R-R interval changes were plotted as functions of the carotid distending (systolic less neck) pressure occurring within each interval. Each experimental session yielded one stimulus-response relation, which comprised the average of seven separate trials. Six measures were derived from these relations: minimum, maximum, and range of R-R intervals; maximum slope; and operational point [(R-R interval shortening/R-R interval range) x 100%]. Linear regression correlation coefficients for measurements made on two occasions were all highly significant (range: 0.64-0.99). Our results indicate that human vagally mediated carotid baroreceptor-cardiac reflex responses, studied serially under exacting experimental conditions, are highly reproducible.

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

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1982.242.2.h185 ◽

1982 ◽

Vol 242 (2) ◽

pp. H185-H190 ◽

Cited By ~ 27

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.

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Short-duration spaceflight impairs human carotid baroreceptor-cardiac reflex responses

Journal of Applied Physiology ◽

10.1152/jappl.1992.73.2.664 ◽

1992 ◽

Vol 73 (2) ◽

pp. 664-671 ◽

Cited By ~ 132

Author(s):

J. M. Fritsch ◽

J. B. Charles ◽

B. S. Bennett ◽

M. M. Jones ◽

D. L. Eckberg

Keyword(s):

Short Duration ◽

Space Shuttle ◽

Orthostatic Intolerance ◽

Sinus Node ◽

Reflex Responses ◽

Carotid Baroreceptor ◽

Body Weights ◽

Before And After ◽

Neck Pressure ◽

Pressure Changes

Orthostatic intolerance is a predictable but poorly understood consequence of space travel. Because arterial baroreceptors modulate abrupt pressure transients, we tested the hypothesis that spaceflight impairs baroreflex mechanisms. We studied vagally mediated carotid baroreceptor-cardiac reflex responses (provoked by neck pressure changes) in the supine position and heart rate and blood pressure in the supine and standing positions in 16 astronauts before and after 4- to 5-day Space Shuttle missions. On landing day, resting R-R intervals and standard deviations, and the slope, range, and position of operational points on the carotid transmural pressure-sinus node response relation were all reduced relative to preflight. Stand tests on landing day revealed two separate groups (one maintained standing arterial pressure better) that were separated by preflight slopes, operational points, and supine and standing R-R intervals and by preflight-to-postflight changes in standing pressures, body weights, and operational points. Our results suggest that short-duration spaceflight leads to significant reductions in vagal control of the sinus node that may contribute to, but do not account completely for, orthostatic intolerance.

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Autonomic pathophysiology in heart failure: carotid baroreceptor-cardiac reflexes

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1990.259.3.h689 ◽

1990 ◽

Vol 259 (3) ◽

pp. H689-H696 ◽

Cited By ~ 7

Author(s):

S. M. Sopher ◽

M. L. Smith ◽

D. L. Eckberg ◽

J. M. Fritsch ◽

M. E. Dibner-Dunlap

Keyword(s):

Heart Failure ◽

Healthy Subjects ◽

Pressure Change ◽

Plasma Norepinephrine ◽

Heart Failure Patients ◽

Stimulus Response ◽

Carotid Baroreceptor ◽

Average Maximum ◽

Neck Pressure ◽

Pressure Suction

We evaluated reflex cardiac responses mediated by carotid baroreceptors in 14 patients with treated congestive heart failure and 14 age-matched healthy subjects. We used a neck chamber to deliver two types of pressure change: 5 s of continuous 50-mmHg suction and an R wave triggered, ramped neck pressure-suction sequence. Reflex latencies (functions of baroreflex arc duration) were comparable in heart failure patients and healthy subjects. However, the average maximum baroreflex slope (gain) was less in heart failure patients than healthy subjects (2.0 vs. 3.5 ms/mmHg, P less than 0.010), the R-R interval response range was smaller (91 vs. 188 ms, P = 0.002), and the resting R-R interval position on stimulus-response relation (operational point) was significantly (13 vs. 40%, P = 0.001) closer to threshold. Stepwise regression analysis suggested that baseline R-R interval variability, used as an index of ongoing vagal-cardiac nerve traffic, and the inverse of antecubital vein plasma norepinephrine level, used as an index of sympathetic nerve activity, contributed significantly to the prediction of abnormal carotid baroreceptor-cardiac reflex responses. Thus our results suggest that in heart failure patients, carotid baroreceptor-cardiac reflex abnormalities are related significantly to ongoing abnormalities of vagal and sympathetic cardiovascular outflow.

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Carotid baroreflex resetting during drug-induced arterial pressure changes in humans

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1989.256.2.r549 ◽

1989 ◽

Vol 256 (2) ◽

pp. R549-R553 ◽

Cited By ~ 1

Author(s):

J. M. Fritsch ◽

R. F. Rea ◽

D. L. Eckberg

Keyword(s):

Arterial Pressure ◽

Systolic Pressure ◽

Chamber Pressure ◽

Base Line ◽

Drug Induced ◽

Maximum Slope ◽

Reflex Responses ◽

Cardiac Responses ◽

Carotid Baroreflex ◽

Pressure Changes

We studied human baroreflex resetting during 25 min of drug-induced arterial pressure changes in 10 healthy volunteers. Average (+/- SE) base-line systolic pressure of 113 +/- 4 fell to 102 +/- 3 during nitroprusside infusions and rose to 135 +/- 6 mmHg during phenylephrine infusions. Average base-line R-R intervals of 932 +/- 37 shortened to 820 +/- 39 during nitroprusside infusions and lengthened to 1,251 +/- 61 ms during phenylephrine infusions. Carotid baroreceptor-cardiac reflex responses were evaluated with a complex series of neck chamber pressure changes, and R-R intervals were plotted as functions of carotid distending pressure. Baroreceptor-cardiac reflex relations shifted on both R-R interval and arterial pressure axes during drug infusions, but there was no significant change of the maximum slope or range of R-R interval responses. The position of baseline R-R intervals on the reflex relation (operational point) changed significantly. Resting R-R intervals were closer to threshold during pressure reductions and closer to saturation for baroreceptor-cardiac responses during pressure elevations. These results document short-term partial resetting of human baroreceptor-cardiac reflex responses as early as 25 min after the onset of arterial pressure changes.

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Impairment of carotid-cardiac vagal baroreflex in wheelchair-dependent quadriplegics

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1991.260.3.r576 ◽

1991 ◽

Vol 260 (3) ◽

pp. R576-R580 ◽

Cited By ~ 10

Author(s):

V. A. Convertino ◽

W. C. Adams ◽

J. D. Shea ◽

C. A. Thompson ◽

G. W. Hoffler

Keyword(s):

Buffer Capacity ◽

Prolonged Exposure ◽

Bed Rest ◽

Maximum Slope ◽

Stimulus Response ◽

Carotid Baroreceptors ◽

Blood Pressures ◽

Pressure Changes ◽

Neck Chamber ◽

Interval Response

The incidence of orthostatic hypotension can increase after prolonged exposure to chair rest and bedrest and is associated with post-bed rest impairment of the carotid-cardiac baroreflex response. We therefore hypothesized that the hypotension observed in humans confined to wheelchairs may be manifested by a reduced baroreflex sensitivity. We compared baroreflex responses of 16 wheelchair-dependent (WCD) quadriplegics with those of 15 able-bodied subjects (ABS) matched for age, height, and weight. Beat-to-beat R-R intervals were measured during application of graded pressures from 40 to -65 mmHg using a neck chamber for noninvasive stimulation of the carotid baroreceptors. Changes of R-R intervals were plotted against carotid distending pressures. The maximum slope of the stimulus-response relationship was greater (P less than 0.0001) in ABS (6.1 +/- 0.6 ms/mmHg) than in WCD (2.6 +/- 0.4 ms/mmHg). The range of the R-R interval response, i.e., the capacity to buffer blood pressure changes, was only 138 +/- 19 ms in WCD compared with 253 +/- 19 ms in ABS (P less than 0.001). Mean sitting systolic-to-diastolic blood pressures in WCD (92/60 mmHg) were less (P less than 0.0001) than in ABS (120/77 mmHg), although there were no significant differences between groups in supine resting blood pressures. Chronic loss of stimulation to carotid baroreceptors by routine standing posture is associated with attenuated sensitivity and reduced buffer capacity of the arterial baroreflex and hypotension during sitting in WCD patients.

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Device for rapid quantification of human carotid baroreceptor-cardiac reflex responses

Journal of Applied Physiology ◽

10.1152/jappl.1986.60.2.727 ◽

1986 ◽

Vol 60 (2) ◽

pp. 727-732 ◽

Cited By ~ 52

Author(s):

J. M. Sprenkle ◽

D. L. Eckberg ◽

R. L. Goble ◽

J. J. Schelhorn ◽

H. C. Halliday

Keyword(s):

Reflex Response ◽

Chamber Pressure ◽

Pressure System ◽

New Device ◽

Reflex Responses ◽

Carotid Baroreceptor ◽

Human Volunteers ◽

Pressure Changes ◽

Neck Chamber ◽

Human Carotid

We designed, constructed, and evaluated a new device to characterize the human carotid baroreceptor-cardiac reflex response relation rapidly. We designed this system for study of reflex responses of astronauts before, during, and after space travel. The system comprises a new tightly sealing silicone rubber neck chamber, a stepping motor-driven electro-deposited nickel bellows pressure system, capable of delivering sequential R-wave-triggered neck chamber pressure changes between +40 and -65 mmHg, and a microprocessor-based electronics system for control of pressure steps and analysis and display of responses. This new system provokes classic sigmoid baroreceptor-cardiac reflex responses with threshold, linear, and saturation ranges in most human volunteers during one held expiration.

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EXPRESS: When Symmetric and Curved Visual Contour Meet Intentional Instructions: Hedonic Value and Preference

Quarterly Journal of Experimental Psychology ◽

10.1177/17470218211021593 ◽

2021 ◽

pp. 174702182110215

Author(s):

Erick G. Chuquichambi Apaza ◽

Guido B. Corradi ◽

Enric Munar ◽

Jaume Rosselló-Mir

Keyword(s):

Cognitive Processing ◽

Experimental Session ◽

Hedonic Tone ◽

Stimulus Response ◽

Negative Valence ◽

Visual Contour ◽

Positive Valence ◽

Positive And Negative Valence ◽

Implicit And Explicit ◽

Explicit Measures

Symmetry and contour take part in shaping visual preference. However, less is known about their combined contribution to preference. We examined the hedonic tone and preference triggered by the interaction of symmetry and contour. Symmetric/curved, symmetric/sharp-angled, asymmetric/curved, and asymmetric/sharp-angled stimuli were presented in an implicit and explicit task. The implicit task consisted of an affective stimulus-response compatibility task where participants matched the stimuli with positive and negative valence response cues. The explicit task recorded liking ratings from the same stimuli. We used instructed mindset to induce participants to focus on symmetry or contour in different parts of the experimental session. We found an implicit compatibility of symmetry and curvature with positive hedonic tone. Explicit results showed preference for symmetry and curvature. In both tasks, symmetry and curvature showed a cumulative interaction, with a larger contribution of symmetry to the overall effect. While symmetric and asymmetric stimuli contributed to the implicit positive valence of symmetry, the effect of curvature was mainly caused by inclination toward curved contours rather than rejection of sharp-angled contours. We did not find any correlation between implicit and explicit measures, suggesting that they may involve different cognitive processing.

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Baroreflex responses to acute changes in blood volume in humans

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1990.259.4.r792 ◽

1990 ◽

Vol 259 (4) ◽

pp. R792-R798 ◽

Cited By ~ 23

Author(s):

C. A. Thompson ◽

D. L. Tatro ◽

D. A. Ludwig ◽

V. A. Convertino

Keyword(s):

Lower Body Negative Pressure ◽

Venous Pressure ◽

Peripheral Resistance ◽

Cardiac Response ◽

Stimulus Response ◽

Cardiopulmonary Baroreflex ◽

Low Levels ◽

Acute Changes ◽

Pressure Changes ◽

Forearm Vascular Resistance

To test the hypothesis that acute changes in plasma volume affect the stimulus-response relations of high- and low-pressure baroreflexes, eight men (27-44 yr old) underwent measurements for carotid-cardiac and cardiopulmonary baroreflex responses under the following three volemic conditions: hypovolemic, normovolemic, and hypervolemic. The stimulus-response relation of the carotid-cardiac response curve was generated using a neck cuff device, which delivered pressure changes between +40 and -65 mmHg in continuous steps of 15 mmHg. The stimulus-response relationships of the cardiopulmonary baroreflex were studied by measurements of forearm vascular resistance (FVR) and peripheral venous pressure (PVP) during low levels of lower body negative pressure (0 to -20 mmHg). Altered vascular volume had no effect on response relations of the carotid-cardiac baroreflex but did alter the gain of the cardiopulmonary baroreflex (-7.93 +/- 1.73, -4.36 +/- 1.38, and -2.56 +/- 1.59 peripheral resistance units/mmHg for hypovolemic, normovolemic, and hypervolemic, respectively) independent of shifts in baseline FVR and PVP. These results indicate greater demand for vasoconstriction for equal reductions in venous pressure during progressive hypovolemia; this condition may compromise the capacity to provide adequate peripheral resistance during severe orthostatic stress. Fluid loading before reentry after spaceflight may act to restore vasoconstrictive capacity of the cardiopulmonary baroreflex but may not be an effective countermeasure against potential post-flight impairment of the carotid-cardiac baroreflex.

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