Spontaneous pressure-flow patterns in the kidney of conscious rats

We have developed a model that permits a quantitative analysis of the contribution of different mechanisms to the spontaneously occurring pressure-flow patterns of a vasculature. In this study we evaluated the spontaneous relationship between arterial pressure (P) and renal blood flow (F) in resting conscious rats during control conditions, autonomic ganglionic blockade (hexamethonium), and nonselective alpha-adrenoreceptor blockade (phentolamine). In a total of 250 trials in 29 rats, we measured the average P and F for each cardiac cycle over 13-min periods (approximately 4,000 cardiac cycles/trial). The P and F values for each cardiac cycle were expressed as percentage change from each 13-min average (beat-to-beat changes). The slope and angle of each consecutive beat-to-beat P-F change were calculated and collated into one of eight zones representing the physiological mechanisms responsible for the concurrent spontaneous changes in P and F. Our results reveal that, in the absence of any chemical or mechanical intervention (control), the renal circulation demonstrated a baroreflex-like P-F pattern approximately 38% of the time. An autoregulatory-like P-F pattern occurred, at the most, 35% of the time. Autonomic ganglionic blockade significantly (P < 0.05) decreased the baroreflex-like pattern and increased the presence of P-F patterns indicative of autoregulation. alpha-Adrenoreceptor blockade resulted in a P-F pattern that was qualitatively similar to that produced by hexamethonium, but with considerably more variability. These results indicate that, in the resting conscious undisturbed state, the autonomic nervous system exerts a tonic influence on the renal circulation that facilitates arterial pressure regulation via a baroreflex-like pattern.

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Spontaneous pressure-flow relationships in renal circulation of conscious dogs

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1993.264.5.h1517 ◽

1993 ◽

Vol 264 (5) ◽

pp. H1517-H1527 ◽

Cited By ~ 1

Author(s):

S. Skarlatos ◽

N. DiPaola ◽

R. A. Frankel ◽

R. W. Pomerantz ◽

P. H. Brand ◽

...

Keyword(s):

Blood Flow ◽

Cardiac Cycle ◽

Renal Circulation ◽

Physiological Mechanisms ◽

Pressure Flow ◽

Percent Change ◽

Conscious Animal ◽

Moment Control ◽

Ganglionic Transmission ◽

Induced Changes

Renal pressure-flow (P-F) relationships are usually evaluated by measuring effects of mechanically induced changes in renal arterial pressure (AP) on renal blood flow (RBF). We devised a method allowing evaluation of renal P-F relationships during normal changes in AP occurring spontaneously in a conscious animal rather than during artificially induced changes in AP. In 18 trials in 6 dogs standing at rest, we measured average AP and RBF for each cardiac cycle over periods of approximately 35 min (approximately 3,100 cardiac cycles/trial). AP and RBF values for each cardiac cycle were expressed as percent change (%delta) from the 35-min average (beat-to-beat changes). Slope and angle of each consecutive beat-to-beat P-F change were calculated and collated into one of eight zones representing the possible physiological mechanisms responsible for concurrent, spontaneous changes in RBF and AP. In a predominance of the cardiac cycles (approximately 43%), the spontaneous AP-RBF relationship was consistent with being mediated by arterial baroreflexes (i.e., increases in AP were accompanied by proportionately greater increases in RBF during 44.4% of cardiac cycles in which AP increased, and decreases in AP were accompanied by proportionately greater decreases in RBF during 41.4% of cardiac cycles in which AP decreased). Blockade of autonomic ganglionic transmission with hexamethonium markedly attenuated this pattern. Our results indicate that renal circulation participates in moment-to-moment control of AP via a predominant baroreflex-like pattern.

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Hemodynamic effects of vasopressin compared with angiotensin II in conscious rats

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1987.252.3.h628 ◽

1987 ◽

Vol 252 (3) ◽

pp. H628-H637 ◽

Cited By ~ 2

Author(s):

J. W. Osborn ◽

M. M. Skelton ◽

A. W. Cowley

Keyword(s):

Heart Rate ◽

Cardiac Output ◽

Angiotensin Ii ◽

Arterial Pressure ◽

Peripheral Resistance ◽

Fold Increase ◽

Adrenergic Blockade ◽

Ganglionic Blockade ◽

Conscious Rats ◽

Potent Vasoconstrictor

The mechanisms whereby arginine vasopressin influences hemodynamic and autonomic function were investigated in conscious rats. In normal rats, 60-min intravenous infusions produced dose-related increases of arterial pressure and total peripheral resistance with marked decreases of both heart rate and cardiac output. Cholinergic blockade with methscopolamine attenuated the bradycardia at higher doses of vasopressin, whereby the fall of cardiac output was not affected. beta-Adrenergic blockade with atenolol attenuated the fall of heart rate seen with lower doses of vasopressin but did not prevent the fall of cardiac output. Ganglionic blockade with methscopolamine and hexamethonium resulted in nearly a 60-fold enhancement of vasopressin pressor sensitivity. This was related to a greater rise of peripheral resistance, since the fall of cardiac output was not altered compared with normal rats. Hemodynamic responses to angiotensin II were determined in other groups of conscious, normal rats and rats with ganglionic blockade. Peripheral resistance increased in the normal rats, whereas the related decreases in cardiac output and heart rate were only 30% of the responses seen with equipressor doses of vasopressin. Ganglionic blockade increased pressor activity only two- to eightfold compared with the 60-fold increase observed with vasopressin. We conclude that vasopressin is a more potent vasoconstrictor than angiotensin II, decreases cardiac output independent of neural mechanisms, and results in withdrawal of sympathetic vascular tone to buffer rises of arterial pressure.

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Effect of insulin on regional vascular resistances in conscious rats

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1996.270.2.r450 ◽

1996 ◽

Vol 270 (2) ◽

pp. R450-R455

Author(s):

E. Qadir ◽

J. P. Porter

Keyword(s):

Skeletal Muscle ◽

Arterial Pressure ◽

Low Dose ◽

Chronic Administration ◽

High Dose ◽

Ganglionic Blockade ◽

Conscious Rats ◽

Before And After ◽

Vascular Beds ◽

Renal Vascular

In the rat, but not in humans and other mammals, chronic administration of insulin produces hypertension. The present aim was to determine the effect of acute insulin infusion on regional vascular resistances and to determine the neurogenic contribution to the response. Conscious rats were infused with insulin (2 or 6 mU/min) before and after ganglionic blockade with chlorisondamine (5 mg/kg). The low dose of insulin produced an increase in arterial pressure and hindquarter vascular resistance; the high dose produced a gradual decrease in arterial pressure and renal resistance. After ganglionic blockade, the hindquarter vasoconstriction produced by the low dose was abolished. The high dose of insulin produced both hindquarter and renal vasodilation. Thus the low dose of insulin had a selective neurogenic vasoconstrictor effect in rat skeletal muscle vascular beds. With higher doses, direct vasodilatory effects in both skeletal muscle and renal vascular beds appeared. This greater sensitivity of the sympathoexcitatory effects of insulin in rats may explain the ability of chronic insulin infusions to increase blood pressure in this species.

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Electrical stimulation of the carotid sinus lowers arterial pressure and improves heart rate variability in l-NAME hypertensive conscious rats

Hypertension Research ◽

10.1038/s41440-020-0448-7 ◽

2020 ◽

Vol 43 (10) ◽

pp. 1057-1067 ◽

Cited By ~ 1

Author(s):

Gean Domingos-Souza ◽

Fernanda Machado Santos-Almeida ◽

César Arruda Meschiari ◽

Nathanne S. Ferreira ◽

Camila A. Pereira ◽

...

Keyword(s):

Heart Rate ◽

Heart Rate Variability ◽

Electrical Stimulation ◽

Arterial Pressure ◽

Carotid Sinus ◽

Conscious Rats ◽

Stimulation Of

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Systematic understanding of acute effects of intravenous guanfacine on rat carotid sinus baroreflex-mediated sympathetic arterial pressure regulation

Life Sciences ◽

10.1016/j.lfs.2016.02.051 ◽

2016 ◽

Vol 149 ◽

pp. 72-78 ◽

Cited By ~ 5

Author(s):

Toru Kawada ◽

Shuji Shimizu ◽

Michael J. Turner ◽

Masafumi Fukumitsu ◽

Hiromi Yamamoto ◽

...

Keyword(s):

Arterial Pressure ◽

Carotid Sinus ◽

Pressure Regulation ◽

Acute Effects ◽

Carotid Sinus Baroreflex ◽

Systematic Understanding ◽

Arterial Pressure Regulation

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Contrasting effects of moderate vagal stimulation on heart rate and carotid sinus baroreflex-mediated sympathetic arterial pressure regulation in rats

Life Sciences ◽

10.1016/j.lfs.2011.07.026 ◽

2011 ◽

Vol 89 (13-14) ◽

pp. 498-503 ◽

Cited By ~ 13

Author(s):

Toru Kawada ◽

Shuji Shimizu ◽

Meihua Li ◽

Atsunori Kamiya ◽

Kazunori Uemura ◽

...

Keyword(s):

Heart Rate ◽

Arterial Pressure ◽

Carotid Sinus ◽

Vagal Stimulation ◽

Pressure Regulation ◽

Carotid Sinus Baroreflex ◽

Arterial Pressure Regulation

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Drug infusion control for mean arterial pressure regulation of critical care patients

2013 IEEE International Conference of IEEE Region 10 (TENCON 2013) ◽

10.1109/tencon.2013.6718882 ◽

2013 ◽

Author(s):

S.A. Nirmala ◽

Ranganath Muthu ◽

B. Veena Abirami

Keyword(s):

Critical Care ◽

Mean Arterial Pressure ◽

Arterial Pressure ◽

Pressure Regulation ◽

Drug Infusion ◽

Critical Care Patients ◽

Arterial Pressure Regulation

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Comments on "Carotid sinus baroreceptor reflex control and the role of autoregulation in the systemic and pulmonary arterial pressure-flow relationships of the dog".

Circulation Research ◽

10.1161/01.res.57.1.198 ◽

1985 ◽

Vol 57 (1) ◽

pp. 198-200 ◽

Cited By ~ 5

Author(s):

R Burattini

Keyword(s):

Arterial Pressure ◽

Carotid Sinus ◽

Pulmonary Arterial Pressure ◽

Baroreceptor Reflex ◽

Pressure Flow ◽

Pulmonary Arterial ◽

Reflex Control ◽

Baroreceptor Reflex Control

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Effect of hypoxic hypoxia on systemic vasculature

Journal of Applied Physiology ◽

10.1152/jappl.1984.56.5.1403 ◽

1984 ◽

Vol 56 (5) ◽

pp. 1403-1410 ◽

Cited By ~ 13

Author(s):

J. Malo ◽

H. Goldberg ◽

R. Graham ◽

H. Unruh ◽

C. Skoog

Keyword(s):

Arterial Pressure ◽

Inferior Vena ◽

Superior Vena ◽

Venous Pressure ◽

Vena Cava ◽

Venous Drainage ◽

Hypoxic Hypoxia ◽

Venous Compliance ◽

Flow Curves ◽

Pressure Flow

Effects of hypoxic hypoxia (HH) on cardiac output (CO), CO distribution, arterial and venous pressure-flow curves, vascular compliance, vascular time constant (tau), and resistance to venous return (RVR) were evaluated on six dogs. The vascular bed was isolated into four compartments depending on venous drainage: superior vena cava (SVC), splanchnic, renal and adrenal, and the remainder of the inferior vena cava (IVC). Low arterial O2 content and PO2 produced a threefold increase in CO at the same mean arterial pressure and a significant redistribution of CO to the SVC. Arterial pressure-flow curves decreased their slope (i.e., flow resistance) by a factor of two in the IVC and renal beds and by a factor of three in the splanchnic and SVC beds. Venous pressure-flow curves for the animal also decreased their slope significantly. HH causes a twofold increase in venous compliance and in mean venous pressure; tau did not change, but RVR halved. Seventy percent of the CO increase is explained by the increase in mean venous pressure and 30% by the reduction in RVR.

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