Unloading arterial baroreceptors causes neurogenic hypertension

2002 ◽  
Vol 282 (4) ◽  
pp. R1044-R1053 ◽  
Author(s):  
Terry N. Thrasher
Keyword(s):  
Carotid Sinus ◽  
Control Period ◽  
Plasma Renin ◽  
Systemic Hypertension ◽  
Neurogenic Hypertension ◽  
Arterial Baroreceptors ◽  
Flow Through ◽  
Common Carotid Arteries

We developed a new model to examine the role of arterial baroreceptors in the long-term control of mean arterial pressure (MAP) in dogs. Baroreceptors in the aortic arch and one carotid sinus were denervated, and catheters were implanted in the descending aorta and common carotid arteries. MAP and carotid sinus pressure (CSP) averaged 104 ± 2 and 102 ± 2 mmHg (means ± 1 SE), respectively, during a 5-day control period. Baroreceptor unloading was induced by ligation of the common carotid artery proximal to the innervated sinus ( n = 6 dogs). MAP and CSP averaged 127 ± 7 and 100 ± 3 mmHg, respectively, during the 7-day period of baroreceptor unloading. MAP was significantly elevated ( P < 0.01) compared to control, but CSP was unchanged. Heart rate and plasma renin activity increased significantly in response to baroreceptor unloading. Removal of the ligature to restore normal flow through the carotid resulted in normalization of all variables. Ligation of the carotid below a denervated sinus ( n = 4) caused a significant decrease in CSP but no systemic hypertension. These results indicate that chronic unloading of carotid baroreceptors can produce neurogenic hypertension and provide strong evidence that arterial baroreceptors are involved in the long-term control of blood pressure.

Arterial baroreceptors control plasma vasopressin responses to graded hypotension in conscious dogs

2000 ◽  
Vol 278 (2) ◽  
pp. R469-R475 ◽  
Author(s):  
Terry N. Thrasher ◽  
Hong-Gen Chen ◽  
Lanny C. Keil
Keyword(s):  
Inferior Vena ◽  
Control Period ◽  
Vena Cava ◽  
Plasma Renin ◽  
Conscious Dogs ◽  
Inferior Vena Caval ◽  
Arterial Baroreceptors ◽  
Treatment Conditions ◽  
The Individual

We studied the role of cardiac and arterial baroreceptors in the reflex control of arginine vasopressin (AVP) and renin secretion during graded hypotension in conscious dogs. The dogs were prepared with Silastic cuffs on the thoracic inferior vena cava and catheters in the pericardial space. Each experiment consisted of a control period followed by four periods of inferior vena caval constriction, during which mean arterial pressure (MAP) was reduced in increments of ∼10 mmHg. The hormonal responses were measured in five dogs under four treatment conditions: 1) intact, 2) acute cardiac denervation (CD) by intrapericardial infusion of procaine, 3) after sinoaortic denervation (SAD), and 4) during combined SAD+CD. The individual slopes relating MAP to plasma AVP and plasma renin activity (PRA) were used to compare the treatment effects using a 2 × 2 factorial analysis. There was a significant ( P < 0.01) effect of SAD on the slope relating plasma AVP to MAP but no effect of CD and no SAD × CD interaction. In contrast, the slope relating PRA and MAP was increased ( P < 0.05) by SAD but was not affected by CD. These results support the hypothesis that stimulation of AVP secretion in response to graded hypotension is primarily driven by unloading arterial baroreceptors in the dog.

Suppression of the glutamate receptor delta 2 subunit produces a specific impairment in cerebellar long-term depression

1996 ◽  
Vol 76 (5) ◽  
pp. 3578-3583 ◽  
Author(s):  
A. Jeromin ◽  
R. L. Huganir ◽  
D. J. Linden
Keyword(s):  
Glutamate Receptor ◽  
Antisense Oligonucleotide ◽  
Metabotropic Glutamate Receptors ◽  
Metabotropic Glutamate Receptor ◽  
Calcium Influx ◽  
Long Term Depression ◽  
Metabotropic Glutamate ◽  
Flow Through

1. The role of the glutamate receptor subunit delta 2 in the induction of cerebellar long-term depression (LTD) was investigated by application of antisense oligonucleotides. The delta 2 subunit is selectively localized to Purkinje cells (PCs), with the highest levels being in the PC dendritic spines, where parallel fibers are received and where cerebellar LTD is expressed. 2. Immunocytochemical analysis of calbindin-positive PCs revealed that both the dendritic and somatic expression of delta 2 was reduced in antisense-but not in sense-treated cultures. An antisense oligonucleotide directed against the related subunit delta 1 did not affect the expression of delta 2 in PCs. 3. Cerebellar LTD may be reliably induced in a preparation of cultured embryonic cerebellar neurons from the mouse when parallel and climbing fiber stimulation are replaced by brief glutamate pulses and strong, direct depolarization of the PC, respectively. Application of an antisense oligonucleotide directed against delta 2 completely blocked the induction of LTD produced by glutamate/ depolarization conjunctive stimulation. A delta 2 sense oligonucleotide or an antisense oligonucleotide directed against the related delta 1 subunit had no effect. 4. The effect of the delta 2 antisense oligonucleotide was not related to attenuation of calcium influx via voltage-gated channels or calcium mobilization via metabotropic glutamate receptors, as assessed with fura-2 microfluorimetry. Current flow through alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-receptor-associated ion channels also appeared unaltered. All three of these processes have previously been shown to be required for cerebellar LTD induction. The observation that delta 2 is involved in a metabotropic-glutamate-receptor-independent signaling pathway that is required for LTD induction supports the view that delta 2 participates in the formation of a novel postsynaptic receptor complex.

Nutrient control of cardiac rate in infant rats: role of arterial baroreceptors

1985 ◽  
Vol 249 (4) ◽  
pp. R443-R448 ◽  
Author(s):  
M. A. Hofer
Keyword(s):  
Blood Pressure ◽  
Carotid Sinus ◽  
Nutrient Deprivation ◽  
Base Line ◽  
Cardiac Rate ◽  
Suckling Rats ◽  
Arterial Baroreceptors ◽  
Infant Rats ◽  
And Control

A surgical procedure is described for the deafferentation of carotid sinus (CS) and aortic depressor (AD) baroreceptors in 2-wk suckling rats. Baroreflex testing in unanesthetized pups showed that cardiac rate responses to acute elevations of blood pressure were reduced to less than 9% of controls after combined denervation (CSAD), 28% after AD and 47% after CS denervation at 4 h. After 24 h of nutrient deprivation, resting cardiac rates of sham operated controls fell a mean of -148 beat/min, significantly more than CS, AD, or CSAD groups (P less than 0.01). Baroreflex test responses in individuals correlated significantly with their later responses to nutrient deprivation (r = 0.67, P less than 0.01). There were no significant differences in base-line cardiac rate, systolic blood pressure, or cardiac rate during 24 h intragastric milk infusion between deafferented and control pups. These experiments suggest that arterial baroreceptors are important in the cardiovascular adjustments after nutrient deprivation in suckling rats.

Long-Term Electronic Cigarette Exposure Induces Cardiovascular Dysfunction Similar to Tobacco Cigarettes: Role of Nicotine and Exposure Duration

2021 ◽  
Author(s):  
Mohamed A. El-Mahdy ◽  
Elsayed M. Mahgoup ◽  
Mohamed G. Ewees ◽  
Mahmoud S. Eid ◽  
Tamer M. Abdelghany ◽  
...  
Keyword(s):  
Exposure Duration ◽  
Electronic Cigarette ◽  
Exposure Model ◽  
Heart Weight ◽  
Systemic Hypertension ◽  
Nicotine Exposure ◽  
Cardiac Tissues ◽  
Air Control

Electronic cigarette (e-cig) vaping (ECV) has been proposed as a safer alternative to tobacco cigarette smoking (TCS); however, this remains controversial due to a lack of long-term comparative studies. Therefore, we developed a chronic mouse exposure model, which mimics human vaping and allows comparison to TCS. Longitudinal studies were performed to evaluate alterations in cardiovascular function with TCS and ECV exposure durations of up to 60 weeks. For ECV, e-cig liquid with box-mod were used and for TCS, 3R4F-cigarettes. C57/BL6 male mice were exposed 2 hours/day, 5 days/week to TCS, ECV, or air-control. The role of vape nicotine levels was evaluated using e-cig-liquids with 0, 6 or 24 mg/ml nicotine. Following 16 weeks exposure, increased constriction to phenylephrine and impaired endothelium-dependent and endothelium-independent vasodilation were observed in aortic segments, paralleling the onset of systemic hypertension, with elevations in systemic vascular resistance. Following 32 weeks, TCS and ECV induced cardiac hypertrophy. All of these abnormalities further increased out to 60 weeks of exposure, with elevated heart weight and aortic thickness along with increased superoxide production in vessels and cardiac tissues of both ECV and TCS mice. While ECV-induced abnormalities were seen in the absence of nicotine, these occurred earlier and were more severe with higher nicotine exposure. Thus, long-term vaping of e-cig, can induce cardiovascular disease similar to TCS, and the severity of this toxicity increases with exposure duration and vape nicotine content.

Thyroid status affects 5-HT2A receptor modulation of breathing before, during, and following exposure of hamsters to acute intermittent hypoxia

2007 ◽  
Vol 293 (5) ◽  
pp. R2070-R2080 ◽  
Author(s):  
Abrea A. Varney ◽  
Evelyn H. Schlenker
Keyword(s):  
Body Temperature ◽  
Intermittent Hypoxia ◽  
Thyroid Status ◽  
Subcutaneous Injections ◽  
Ventilatory Responses ◽  
Receptor Modulation ◽  
Flow Through ◽  
Long Term Facilitation

The BIO 14.6 hamster (dystrophic), animal model of limb girdle muscular dystrophy, exhibits low plasma triiodothyronine levels, muscle weakness, and decreased breathing. After exposure to acute intermittent bouts of hypoxia, dystrophic hamsters depress ventilation relative to baseline resulting in ventilatory long-term depression (LTD). Control hamsters may increase ventilation relative to baseline resulting in ventilatory long-term facilitation (LTF). Serotonin (5-HT) receptors, especially the 5-HT2A subtype, are involved in the development of LTF. The purpose of this study was to evaluate the role of 5-HT2A receptors in ventilatory and metabolic responses before, during, and following intermittent hypoxia in eleven euthyroid, nine dystrophic, and eleven propylthiouracil (PTU)-induced hypothyroid male hamsters. Animals received subcutaneous injections of vehicle or 0.5 mg/kg MDL (5-HT2A receptor antagonist). Plethysmography was used to evaluate ventilatory responses of the three groups to air, five bouts of 5 min of 10% oxygen, each interspersed with 5 min of air, followed by 60 min of exposure to air. CO2 production was measured using the flow-through method. Vehicle-treated dystrophic and PTU-treated hamsters exhibited LTD. MDL decreased body temperature in all groups. After MDL treatment, the euthyroid group exhibited LTD. MDL treatment in the dystrophic, but not in the PTU-treated hamsters, maintained tidal volume, but did not reverse LTD. CO2 production was increased in the euthyroid group with MDL treatment. Thus, 5-HT2A receptors affect body temperature, ventilation, and metabolism in hamsters. The differential responses noted in this study may be in part dependent on thyroid hormone status.

Effect of changes in carotid sinus pulse pressure on catecholamine blood levels

1963 ◽  
Vol 204 (3) ◽  
pp. 467-470 ◽  
Author(s):  
Jiro Nakano ◽  
Christian De Schryver
Keyword(s):  
Pulse Pressure ◽  
Plasma Levels ◽  
Carotid Sinus ◽  
Blood Levels ◽  
Arterial Pulse ◽  
Arterial Blood ◽  
The Common ◽  
The Mean ◽  
Common Carotid Arteries

A study was made on the effect of changes in arterial pulse pressure per se on catecholamine secretion in the anesthetized dog. "Elasticity" bottles were inserted bilaterally in the common carotid arteries in order to change the magnitude of the pulse pressure in the carotid sinus areas without changing the mean arterial blood pressure. It was observed that a marked decrease in the pulse pressure resulted in significant increases in heart rate ( P < 0.005) and catecholamine plasma levels ( P < 0.005). The mechanism and role of this increase in plasma levels of catecholamines are discussed.

Cardiac and arterial baroreceptor influences in release of vasopressin and renin during hemorrhage

1987 ◽  
Vol 252 (6) ◽  
pp. H1120-H1126 ◽  
Author(s):  
A. W. Quail ◽  
R. L. Woods ◽  
P. I. Korner
Keyword(s):  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Plasma Renin Activity ◽  
Arginine Vasopressin ◽  
Plasma Renin ◽  
Hormone Response ◽  
Response Curves ◽  
Arterial Baroreceptors ◽  
Cardiac Receptors

We studied the role of arterial and cardiac baroreceptors on mean arterial pressure (MAP) and release of arginine vasopressin (AVP) and plasma renin activity (PRA) during hemorrhage in conscious rabbits. Each rabbit was bled at 2% of its blood volume (BV) per minute until 35% had been removed, after which the blood was reinfused. Each rabbit was studied on three occasions, 7 days apart, and in each experiment, BV-MAP and BV-hormone response curves were constructed. The response to hemorrhage was examined when the input from arterial and cardiac baroreceptors were both intact; arterial baroreceptors only were intact (cardiac receptors were blocked with intrapericardial procaine); cardiac receptors only were intact (after sinoaortic denervation); neither receptor was intact. Resting AVP and PRA levels were unaffected by the various deafferentation procedures. AVP steeply increased only after more than 25% BV had been removed; this response was entirely mediated by cardiac baroreceptors. Increases in PRA occurred at BV loss greater than 15% and were largely independent of baroreceptor input. Maintenance of MAP during hemorrhage was mostly due to drive from the arterial baroreceptors. Thus AVP secretion during hemorrhage contributes little to the maintenance of MAP, and the hypovolemic stimulus to AVP release comes entirely from the cardiac baroreceptors.

Nutrient economics and trophic status of Lakes Sorell and Crescent, Tasmania

1976 ◽  
Vol 27 (1) ◽  
pp. 151
Author(s):  
DMH Cheng ◽  
PA Tyler
Keyword(s):  
Trophic Status ◽  
Nutrient Inputs ◽  
Short Term ◽  
Management Plans ◽  
Increase Productivity ◽  
Flow Through ◽  
Polymictic Lakes ◽  
Enriched Cultures

Effects of various nutrients on short-term photosynthetic carbon uptake and longer-term yield of algae were assayed for two similar, connected lakes (Lake Sorell flowing into Lake Crescent) with contrasting plankton populations. Phosphorus (P) and phosphorus plus nitrogen (P+N) were the only nutrients to stimulate 14C uptake, and more for Lake Crescent than for Lake Sorell, over 3-h incubations, and P+N was only marginally more effective than P alone. Added SiO2 was inhibitory in short-term but not in long-term incubations. During 3-day incubations, P, N and P+N increased 14C uptake for Lake Sorell but usually not for Lake Crescent. Micronutrients and chelators also accelerated 14C incorporation for Lake Sorell but not for Lake Crescent. No nutrient tested singly increased the ultimate yield of algae, but P+N, Na2CO3 and SiO2 added incrementally produced marked, incremental increases in yield, and more so in Lake Sorell than in Lake Crescent. Addition of micronutrients had no further stimulatory effect. Removal of tripton from lake samples seriously impaired yields, even in P+N-enriched cultures. Incremental replacement of tripton produced incremental restoration of yields. Volume for volume, Lake Crescent water contained more tripton and a more organic tripton than Lake Sorell water. Weight for weight, Lake Crescent tripton stimulated faster growth than Lake Sorell tripton but ultimate yields were the same. Micronutrients and chelators together could substitute for native tripton, the role of which seems to be the maintenance of micronutrients in solution in the oxidizing milieu of the polymictic lakes. The greater productivity and greater phytoplankton biomass of Lake Crescent rests on its greater tripton load, derived from greater scouring of sediments, its flow through from Lake Sorell and an abundant fringing marshland. It is likely that the distinctive floras of the two lakes are adapted to the different nutrient conditions, so that flow-through inocula of Lake Sorell algae cannot become established in Lake Crescent. As Lakes Sorell and Crescent are already mesotrophic and eutrophic respectively, and since additions of P and P+N considerably increase productivity and yield, management plans for this recreational area should seek to limit nutrient inputs.

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