Effects of diazepam on the carotid sinus baroreflex control of circulation in rabbits

This study investigated control of heart rate (HR) and mean arterial pressure (MAP) at rest and during electrical stimulation (ES) leg cycling exercise (LCE) in paraplegics (Para). Seven men with complete spinal lesions (T5–T11) and six able-bodied (AB) men participated in this study. Beat-to-beat changes in HR and MAP were recorded during carotid sinus perturbation. Carotid baroreflex function curves were derived at rest and during ES-LCE for Para and during voluntary cycling (Vol) for AB. From rest to ES-LCE, oxygen uptake (V˙o 2) increased (by 0.43 l/min) and HR rose (by 11 beats/min), yet MAP remained unchanged. In AB, Vol increased V˙o 2 (by 0.53 l/min), HR (by 22 beats/min), and MAP (by 8 mmHg). ES-LCE did not alter the carotid sinus pressure (CSP)-MAP relationship, but it displaced the CSP-HR relationship upward relative to rest. No rightward shift was observed during ES-LCE. Vol by AB produced an upward and rightward displacement of the CSP-MAP and CSP-HR relationships relative to rest. These findings suggested that the carotid sinus baroreflex was not reset during ES-LCE in Para.

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Carotid sinus baroreflex control of beta-endorphin release in anesthetized dogs

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1989.256.2.r408 ◽

1989 ◽

Vol 256 (2) ◽

pp. R408-R412

Author(s):

M. J. Brunner ◽

K. E. Wehberg ◽

J. C. Williams ◽

C. A. Cahill

Keyword(s):

Carotid Sinus ◽

Venous Blood ◽

Normal Component ◽

Vagal Afferents ◽

Mixed Venous Blood ◽

Baroreflex Control ◽

Beta Endorphin ◽

Carotid Sinus Baroreflex ◽

Before And After ◽

Anesthetized Dogs

A quantitative assessment of the carotid sinus baroreflex release of endogenous plasma beta-endorphin-like immunoreactive material has been established. The carotid sinuses of 12 pentobarbital sodium-anesthetized dogs were isolated bilaterally and perfused with a constant pressure maintained by infusion or withdrawal of normal saline. Mean arterial pressure (MAP) and heart rate (HR) were monitored. Carotid sinus pressure (CSP) was changed from 200 to 50 mmHg in 25 mmHg steps before and after vagotomy. At each interval of CSP, 10 ml mixed venous blood were collected, and beta-endorphin-like peptides were extracted from plasma and assayed. Concentrations of plasma beta-endorphin-like material were determined by radioimmunoassay. Sigmoidal responses of MAP and HR were revealed during changes in CSP. No significant differences in beta-endorphin-like immunoreactivity (beta-END-L-I) were measured at CSP of 200 and 50 in the intact condition (35.9 +/- 3.9 and 35.0 +/- 6.4 fm/ml, respectively). However, after vagotomy, beta-END-L-I measured at 50 mmHg CSP was significantly elevated to 53.3 +/- 5.2 fm/ml compared with the value of 35.5 +/- 7.2 fm/ml at CSP of 200 mmHg. The results suggest that the release of beta-endorphin is modulated by the action of the carotid baroreflex as a normal component of an integrated efferent response. However, this response is normally buffered by reflexes with vagal afferents.

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Baroreflex control of arterial and venous compliances and vascular capacity in hypertensive dogs

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1993.265.1.h96 ◽

1993 ◽

Vol 265 (1) ◽

pp. H96-H102 ◽

Cited By ~ 2

Author(s):

G. G. Bishop ◽

K. Shigemi ◽

J. P. Freeman ◽

M. J. Brunner

Keyword(s):

Arterial Pressure ◽

Carotid Sinus ◽

Arterial Compliance ◽

Characteristic Curve ◽

Venous Blood ◽

Baroreflex Control ◽

Reservoir Volume ◽

Carotid Sinus Baroreflex ◽

Pentobarbital Sodium Anesthesia ◽

Venous Blood Volume

The ability of the carotid sinus baroreflex to elicit reflex changes in vascular capacity was studied in chronically hypertensive (one-kidney, one-clip) and sham-operated normotensive dogs under pentobarbital sodium anesthesia. Vascular compliances and reflex-induced changes in external reservoir volume were measured in response to changes in isolated carotid sinus pressure (CSP). The mean arterial pressure-CSP reflex characteristic curve was shifted to a higher arterial pressure with hypertension with no change in maximum reflex gains. Arterial compliance in both groups increased significantly (P < 0.01) when CSP was increased from 50 to 200 mmHg. Total, arterial, and venous vascular compliances were not different in normotensive and hypertensive groups. Changes in CSP caused no significant changes in either total systemic vascular or calculated venous compliances. A decrease in CSP from 250 to 50 mmHg resulted in an increase in external reservoir volume of 8.02 +/- 1.03 and 7.44 +/- 1.33 ml/kg in normotensive and hypertensive groups, respectively, with changes in venous volume of 11.99 +/- 1.39 and 12.58 +/- 1.52 ml/kg (NS). We conclude that despite the increase in arterial resistance, Goldblatt hypertensive dogs retain the ability to make short-term reflex adjustments in both arterial pressure and venous blood volume.

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Invariance of the resistance to venous return to carotid sinus baroreflex control

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1996.271.3.h1022 ◽

1996 ◽

Vol 271 (3) ◽

pp. H1022-H1030 ◽

Cited By ~ 6

Author(s):

T. Hatanaka ◽

J. T. Potts ◽

A. A. Shoukas

Keyword(s):

Venous Return ◽

Carotid Sinus ◽

Arterial Compliance ◽

Systemic Circulation ◽

Major Site ◽

Apparent Paradox ◽

Baroreflex Control ◽

Lumped Model ◽

Carotid Sinus Baroreflex ◽

Established Fact

Despite the well-established fact that the carotid sinus baroreflex system has profound control over the physical properties of the systemic circulation, the resistance to venous return (RVR) seems to be invariant of such control. We hypothesized that this apparent paradox may be explained from the baroreflex changes in systemic arterial compliance. In 12 pentobarbital-anesthetized mongrel dogs, RVR was measured at controlled carotid sinus pressures (CSP) of 50 and 200 mmHg with normal and artificially increased arterial compliance. Arterial compliance was determined from the arterial pressure decay when systemic blood flow was stopped with total vena caval occlusion. Changing CSP between 50 and 200 mmHg changed RVR significantly only under the condition of artificially increased arterial compliance. A four-parameter lumped model of the systemic circulation revealed that the baroreflex changes in arterial compliance and arterial resistance, which occurred in opposite directions, prevented a change in RVR when CSP was changed. The data also suggested that approximately 75% of RVR was attributed to large and conduit veins, the resistances along which were insensitive to baroreflex control. We concluded that the invariance of RVR results from a combination of 1) baroreflex change in the arterial compliance, 2) baroreflex insensitivity of the resistance along large and conduit veins, and 3) spatially distinct location between the major site of reflex change in capacitance and the major site of compliance.

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Increase in sympathetic activity with age. II. Role of impairment of cardiopulmonary baroreflexes

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1991.260.4.h1121 ◽

1991 ◽

Vol 260 (4) ◽

pp. H1121-H1127 ◽

Cited By ~ 5

Author(s):

G. Hajduczok ◽

M. W. Chapleau ◽

F. M. Abboud

Keyword(s):

Carotid Sinus ◽

Young Group ◽

Left Ventricular ◽

Baroreflex Control ◽

Renal Sympathetic Nerve Activity ◽

Carotid Sinus Baroreflex ◽

Cardiopulmonary Baroreflex ◽

Bilateral Vagotomy ◽

Renal Sympathetic

We have previously shown that arterial baroreflex function is significantly impaired in a group of old beagles [G. Hajduczok, M. W. Chapleau, S. L. Johnson, and F. M. Abboud. Am. J. Physiol. 260 (Heart Circ. Physiol. 29): H1113-H1120, 1991]. In the present study, we determined whether the neural limb of the cardiopulmonary baroreflex control of renal sympathetic nerve activity (RSNA) and the interaction between the arterial and cardiopulmonary reflexes is also impaired with senescence. In the anesthetized state, the aortic nerves were sectioned and carotid sinuses were isolated bilaterally with carotid sinus pressures held at 50 mmHg in both young (1 yr) and old animals (11 yr). In response to graded volume expansion (VE) with 3% dextran (0 to 30 ml/kg iv), the gain of cardiopulmonary baroreflex control of RSNA was significantly lower in the old (5.1 +/- 3%/mmHg) compared with the young (13.4 +/- 3%/mmHg) animals. There were no significant differences in systemic vascular compliance or left ventricular mass index between the two groups. The gain of the carotid sinus baroreflex inhibition of RSNA was significantly attenuated by VE in the young group but was not affected in the old group. Bilateral vagotomy (VX) resulted in a 182 +/- 74% increase in RSNA in the young (P less than 0.05), but VX did not significantly increase RSNA in the old (12 +/- 17%). After VX, the carotid sinus baroreflex gain markedly increased by nearly eightfold in the young group (P less than 0.05) but was not altered in the old dogs.(ABSTRACT TRUNCATED AT 250 WORDS)

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Arterial pressure-flow relationships in hypertensive dogs: effect of carotid sinus baroreflex

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1993.265.3.h986 ◽

1993 ◽

Vol 265 (3) ◽

pp. H986-H992

Author(s):

M. J. Brunner ◽

G. G. Bishop ◽

K. Shigemi ◽

J. P. Freeman ◽

D. Chung

Keyword(s):

Arterial Pressure ◽

Carotid Sinus ◽

Peripheral Resistance ◽

Coefficient Of Determination ◽

Experimental Hypertension ◽

Baroreflex Control ◽

Pressure Flow ◽

Hypertensive Group ◽

Carotid Sinus Baroreflex ◽

Reflex Gain

The effect of the carotid sinus baroreflex reflex on arterial pressure-flow relationships was studied in Goldblatt hypertensive and normotensive dogs on cardiopulmonary bypass. Dogs were anesthetized with pentobarbital sodium, vagotomized, and the carotid sinuses were isolated at controlled carotid sinus pressures (CSP). The mean arterial pressure-flow relationships were measured at different levels of CSP. The arterial pressure-flow relationship was found to be linear except at extreme levels of flow. The slopes derived from the linear regression of the pressure-flow relationships [total peripheral resistance (TPR)] were 1.466 +/- 0.111 and 0.786 +/- 0.13 mmHg.ml-1 x min.kg at CSP of 50 and 200 mmHg in the normotensive group and 1.758 +/- 0.183 and 0.937 +/- 0.114 mmHg.ml-1 x min.kg at CSP of 50 and 250 mmHg in the hypertensive group. The increases in slope measured when CSP was decreased from saturation to threshold were 0.68 mmHg.ml-1 x min.kg (187% increase) in the normotensive group and 0.82 mmHg.ml-1 x min.kg (188% increase) in the hypertensive group. Zero-flow arterial pressures at CSP of 50, 125, and 200 mmHg were found to be 23.1 +/- 2.9, 21.7 +/- 2.2, and 17.1 +/- 1.8 mmHg in the normotensive group and 28.4 +/- 2.2, 23.8 +/- 1.5, and 20.0 +/- 1.2 mmHg in the hypertensive group. A nonlinear model fit was found to give a significantly better fit [coefficient of determination (r2) = 0.932 linear, 0.956 nonlinear] of the arterial pressure-flow relationships. We conclude that, in experimental hypertension, carotid baroreflex control of TPR is shifted to a higher operating point without any reduction in overall reflex gain.

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Fentanyl antagonizes diazepam on carotid sinus baroreflex control of circulation in rabbits

Journal of Anesthesia ◽

10.1007/s0054030070210 ◽

1993 ◽

Vol 7 (2) ◽

pp. 210-217

Author(s):

Masakatsu Sakamoto ◽

Hisatoshi Ohsumi ◽

Takeshi Sumida ◽

Fukuichiro Okumura ◽

Tohru Morioka

Keyword(s):

Carotid Sinus ◽

Baroreflex Control ◽

Carotid Sinus Baroreflex

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Effects of fentanyl on carotid sinus baroreflex control of circulation in rabbits

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1989.256.3.r625 ◽

1989 ◽

Vol 256 (3) ◽

pp. R625-R631

Author(s):

H. Ohsumi ◽

M. Sakamoto ◽

T. Yamazaki ◽

F. Okumura

Keyword(s):

Heart Rate ◽

Mean Arterial Pressure ◽

Carotid Sinus ◽

Peripheral Resistance ◽

Conscious State ◽

Hemodynamic Responses ◽

Baroreflex Control ◽

Bilateral Carotid Occlusion ◽

Bilateral Carotid ◽

Carotid Sinus Baroreflex

The effects of intravenous administration of fentanyl on carotid sinus baroreflex control of hemodynamics were investigated in chronically instrumented rabbits. Carotid sinus baroreflex was assessed by bilateral carotid occlusion (BCO), and the responses of mean arterial pressure (MAP), heart rate (HR), mean ascending aortic flow (MAF), and total peripheral resistance (TPR) were obtained. Hemodynamic responses to BCO were examined with cumulative doses of 5, 10, and 15 micrograms/kg of fentanyl. Fentanyl did not affect MAP and TPR but reduced HR and MAF dose dependently. Fentanyl did not attenuate the MAP response to BCO significantly. In contrast, fentanyl significantly attenuated the TPR response from 0.126 +/- 0.003 to 0.104 +/- 0.005 mmHg.min-1.ml-1 and augmented the HR response from 31 +/- 2 to 47 +/- 3 beats/min in the conscious state and at 15 micrograms/kg of fentanyl, respectively. The administration of atropine after the fentanyl attenuated MAP and HR responses to 79.9 and 27.7% of those of 10 micrograms/kg of fentanyl, respectively. We suggest that these dissociated hemodynamic responses reflect the vagotonic and sympatholytic effects of fentanyl on the baroreflex pathways.

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