A method to evaluate dynamic cerebral pressure-flow relationships in the conscious rat

2021 ◽  
Vol 131 (4) ◽  
pp. 1361-1369
Author(s):  
Debra Fong ◽  
Kelly Gradon ◽  
Carolyn J. Barrett ◽  
Sarah-Jane Guild ◽  
Yu Chieh Tzeng ◽  
...  
Keyword(s):  
Vena Cava ◽  
Vasoactive Agents ◽  
Conscious Rat ◽  
Pressure Flow ◽  
Conscious Rats ◽  
Novel Technique

We present a novel technique to overcome the use of vasoactive agents when studying cerebrovascular dynamics in the conscious rat. Our method of vena cava occlusion to reduce BP was associated with decreased iCBF and no change in iCVR. In contrast, comparable BP falls with intravenous SNP increased iCBF and reduced iCVR. Thus, the dynamic cerebral pressure-flow relationship shows a narrower, less level autoregulatory plateau than conventionally thought. We confirm our method allows repeatable assessment of cerebrovascular dynamics in conscious rats.

Influence of right atrial stretch on plasma renin activity in the conscious rat

1987 ◽  
Vol 65 (2) ◽  
pp. 257-259 ◽  
Author(s):  
Susan Kaufman
Keyword(s):  
Plasma Renin Activity ◽  
Superior Vena ◽  
Vena Cava ◽  
Extracellular Fluid ◽  
Plasma Renin ◽  
Renin Activity ◽  
Right Atrial ◽  
Balloon Inflation ◽  
Conscious Rat ◽  
Basal Plasma

Rats were prepared with inflatable balloons at the superior vena cava – right atrium junction. After recovery 1 week later, when blood was taken from conscious, normovolaemic animals plasma renin activity was found not to be influenced by right atrial stretch. Plasma renin activity was then measured in rats in which an extracellular fluid deficit had been produced by peritoneal dialysis against a hyperoncotic, isotonic solution. Although basal plasma renin activity was elevated (6.8 ± 0.9 from 1.5 ± 0.2 ng∙mL∙h, n = 19), no depression was observed in the experimental group after 15 or 90 min of balloon inflation. In rats pretreated with isoprenaline (10 μg/kg body wt.) plasma renin activity was also increased over basal levels, but again balloon inflation caused no reduction in plasma renin activity. It would appear that right atrial stretch has little, if any, influence on renin release in the conscious rat.

Abstract P222: Venous Dilation Contributes to 5-HT-induced Hypotension

Hypertension ◽  
2015 ◽  
Vol 66 (suppl_1) ◽  
Author(s):  
Bridget M Seitz ◽  
Teresa Krieger-Burke ◽  
Stephanie W Watts
Keyword(s):  
Blood Pressure ◽  
Imaging System ◽  
Isometric Force ◽  
Peripheral Resistance ◽  
Vena Cava ◽  
Mesenteric Arteries ◽  
Conscious Rat ◽  
Cross Sectional ◽  
Induced Hypotension ◽  
Vascular Bed

Serotonin (5-hydroxytryptamine, 5-HT) infusion in a normal conscious rat decreases mean arterial pressure (MAP), in part by reduction in total peripheral resistance. Microsphere experiments have shown 5-HT increases blood flow within the splanchnic vascular bed, with the greatest being in the intestine and spleen. Interestingly, 5-HT does not cause a direct relaxation of resistant (small or large) mesenteric arteries. The present study addresses the possibility of the venous circulation contributing to the 5-HT induced fall in blood pressure. Our working hypothesis is venous dilation, specifically dilation of veins measurable within the splanchnic vascular bed, contributes to 5-HT-induced hypotension. Using an ultrasound imaging system (Vevo 2100 imaging system; 21 MHz probe,Visual Sonics Inc.), telemetry-implanted, anesthetized male Sprague Dawley rats underwent cross-sectional imaging which was controlled for respiration and cardiac cycles. The following vessels were imaged: abdominal aorta (AA); portal vein (PV); abdominal inferior vena cava (IVC); and superior mesenteric vein (SMV). Following the collection of baseline MAP and vessel diameter measurements, Alzet osmotic mini-pumps containing vehicle (saline; n=9) or 5-HT (25 ug/kg/min; n=9) were implanted for 1 week. After, 24 hours of infusion, 5-HT increased the vein diameter (SMV 17.48±2%; PV 17.67±2%; IVC 46.87±8%) and maintained the AA diameter ( AA 0.93±1%) from baseline while reducing MAP (vehicle 101.93±3; 5-HT 84.68±2 mm Hg; p<0.05).One-week post removal of all osmotic mini-pumps, there was no difference in the MAP or diameter of all noted vessels between the two treatment groups. To correlate with in vivo findings, the PV and IVC, when isolated in a tissue bath for measurement of isometric force and contracted with endothelin 1, relaxed in a concentration dependent fashion to 5-HT and 5-carboxamidotryptamine (5-HT 1/7 receptor agonist;1 nM-10 uM). Collectively, these findings highlight the contribution of splanchnic venous dilation in 5-HT-induced hypotension and propose a possible mechanism for 5-HT reduction in blood pressure.

Effect of hypoxic hypoxia on systemic vasculature

1984 ◽  
Vol 56 (5) ◽  
pp. 1403-1410 ◽  
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.

Simple validation for the hepatic venous cannula implanted chronically in conscious rats

1991 ◽  
Vol 71 (1) ◽  
pp. 359-364 ◽  
Author(s):  
M. T. Huang
Keyword(s):  
Inferior Vena Cava ◽  
Inferior Vena ◽  
Superior Vena ◽  
Tritiated Water ◽  
Vena Cava ◽  
Systemic Circulation ◽  
Tracer Injection ◽  
Conscious Rats ◽  
Tygon Tubing ◽  
Venous Cannula

A method for the detection of vena caval contamination in blood taken from hepatic venous cannulas in conscious rats was described. The procedures included 1) bolus injection of tritiated water (50 microCi) through a cannula into the abdominal inferior vena cava and 2) continuous blood sampling (less than 0.2 ml) from the hepatic venous cannula for 2 min into a 180-cm piece of Tygon tubing, starting concurrently with tracer injection. The washout of tritium was determined from samples in 15-cm sections of Tygon tubing. Because circulation from the inferior vena cava to the hepatic vein is interceded by the systemic circulation, the washout of tritium from a valid hepatic venous cannula should resemble the pattern determined elsewhere in the systemic circulation. In the current study, the reference systemic washout was determined in the superior vena cava of a group of rats similarly injected with tritiated water in the inferior vena cava. The maximum of tritium washout derived from a valid hepatic venous cannula should fall in the range encompassed by one standard deviation of the mean of the maximum of the reference (1,400 to 1,930 cpm/sample). The maximum of the washout pattern derived from the invalid cannula, which lay adjacent to the site of injection, was expected to exceed this range. On the basis of these criteria, hepatic blood flow (HBF) was determined by sulfbromophthalein (BSP) extraction in groups of rats with valid and invalid cannulas. HBF in rats with valid hepatic venous cannulas was 2.58 +/- 0.15 in the conscious state and 2.76 +/- 0.26 ml.min-1.g wet wt-1 in the ketamine-anesthetized state.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals A novel technique to study the time course of morphological and functional vascular responses to hypertension in conscious rats

2010 ◽  
Vol 24 (S1) ◽  
Author(s):  
Harald Martin Stauss ◽  
Katie M Leick ◽  
Jason W Burkle ◽  
Diane L Rotella ◽  
Kevin R Rarick ◽  
...  
Keyword(s):  
Time Course ◽  
Vascular Responses ◽  
Conscious Rats ◽  
Novel Technique

Spontaneous pressure-flow patterns in the kidney of conscious rats

1993 ◽  
Vol 265 (6) ◽  
pp. H2151-H2159 ◽  
Author(s):  
S. Skarlatos ◽  
P. J. Metting ◽  
S. L. Britton
Keyword(s):  
Arterial Pressure ◽  
Cardiac Cycle ◽  
Flow Patterns ◽  
Renal Circulation ◽  
Physiological Mechanisms ◽  
Pressure Flow ◽  
Ganglionic Blockade ◽  
Conscious Rats ◽  
Mechanical Intervention ◽  
Arterial Pressure Regulation

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.

Baroreflex buffering of pressor response to vasopressin is mediated by V1, not V2, receptors in conscious rats

1993 ◽  
Vol 264 (2) ◽  
pp. R345-R349
Author(s):  
K. Shimizu ◽  
J. Schwartz ◽  
B. P. McGrath
Keyword(s):  
Heart Rate ◽  
Receptor Agonist ◽  
Pressor Response ◽  
Conscious Rat ◽  
Conscious Rats ◽  
Pressor Responses ◽  
Autonomic Blockade ◽  
V2 Receptor ◽  
Intact Rats

Arginine vasopressin (AVP) enhances reflex buffering of its own pressor response, thus attenuating its vasoconstrictor potential in vivo. To investigate the extent to which this effect of AVP is mediated by V1 or V2 receptors, mean arterial pressure (MAP) and heart rate (HR) changes were examined in response to graded injections of AVP or [Phe2,Orn8]oxytocin, a potent, selective V1-receptor agonist, in the absence and presence of infusion of [Val4,D-Arg8]VP, a selective V2-receptor agonist. Responses were compared in intact and autonomically blocked conscious rats. During autonomic blockade with methscopolamine and hexamethonium, the pressor sensitivities to AVP and [Phe2,Orn8]oxytocin were similarly increased. Infusion of the V2-receptor agonist had no effect by itself on MAP or HR in conscious intact rats. It also did not alter the pressor responses to the V1 agonist, in either intact or autonomically blocked rats. In the presence of the V2 agonist, the decrease in heart rate induced by the V1 agonist was enhanced. These results indicate that reflex buffering of the pressor response to AVP in the conscious rat is mediated by V1 and not V2 receptors. However, V2 receptors may be involved in modulating the heart rate response to AVP.

scholarly journals A novel technique for right ventricular lead placement in a patient with a persistent left superior vena cava

EP Europace ◽  
2007 ◽  
Vol 9 (3) ◽  
pp. 200-201 ◽  
Author(s):  
Marcos Daccarett ◽  
Rakesh K. Pai ◽  
Moeen Abedin ◽  
Nathan M. Segerson ◽  
Mohamed H. Hamdan
Keyword(s):  
Right Ventricular ◽  
Superior Vena Cava ◽  
Superior Vena ◽  
Vena Cava ◽  
Left Superior Vena Cava ◽  
Persistent Left Superior Vena ◽  
Novel Technique ◽  
Lead Placement ◽  
Ventricular Lead
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