Nucleus tractus solitarius and control of blood pressure in chronic sinoaortic denervated rats

1992 ◽  
Vol 263 (2) ◽  
pp. R258-R266 ◽  
Author(s):  
A. M. Schreihofer ◽  
A. F. Sved
Keyword(s):  
Blood Pressure ◽  
Plasma Levels ◽  
Nucleus Tractus Solitarius ◽  
Inhibitory Influence ◽  
Baroreceptor Reflexes ◽  
Alpha Chloralose ◽  
And Control ◽  
Bilateral Destruction ◽  
Conscious Control

To determine the role of the nucleus tractus solitarius (NTS) in the tonic maintenance of arterial pressure (AP) following chronic baroreceptor denervation, the present study examined the effect of inhibition of the NTS on AP in chronic sinoaortic denervated (SAD) and control rats. One to two weeks after complete SAD (no residual arterial baroreceptor reflexes) mean AP was not significantly different from that of control rats. Bilateral microinjections of muscimol and lidocaine into the NTS markedly increased AP in alpha-chloralose-anesthetized control rats. However, microinjections of these neuroinhibitory drugs had no effect on AP in SAD rats. Similarly, 1 h after bilateral destruction of the NTS conscious control rats were hypertensive, while AP in SAD rats was not changed. Plasma levels of vasopressin (VP), which were also elevated in control rats 1 h after NTS lesions, were not significantly altered in SAD rats. These results demonstrate that inhibition of the NTS has no effect on AP or plasma levels of VP in chronic SAD rats. This suggests neither the NTS nor afferents to the NTS supply a tonic inhibitory influence on AP after chronic baroreceptor denervation.

Cardiac baroreflex facilitation evoked by hypothalamus and prefrontal cortex stimulation: role of the nucleus tractus solitarius 5-HT2A receptors

2006 ◽  
Vol 291 (4) ◽  
pp. R1007-R1015 ◽  
Author(s):  
C. Sévoz-Couche ◽  
M. A. Comet ◽  
J. F. Bernard ◽  
M. Hamon ◽  
R. Laguzzi
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Prefrontal Cortex ◽  
Nucleus Tractus Solitarius ◽  
Cardiovascular Responses ◽  
Receptor Activation ◽  
Cardiac Response ◽  
Inhibitory Influence ◽  
Homocysteic Acid

We previously showed that serotonin (5-HT2) receptor activation in the nucleus of the tractus solitarius (NTS) produced hypotension, bradycardia, and facilitation of the baroreflex bradycardia. Activation of the preoptic area (POA) of the hypothalamus, which is involved in shock-evoked passive behaviors, induces similar modifications. In addition, previous studies showed that blockade of the infralimbic (IL) part of the medial prefrontal cortex, which sends projections to POA, produced an inhibitory influence on the baroreflex cardiac response. Thus, to assess the possible implication of NTS 5-HT2 receptors in passive cardiovascular responses, we analyzed in anesthetized rats the effects of NTS inhibition and NTS 5-HT2 receptor blockade on the cardiovascular modifications induced by chemical (0.3 M d,l-homocysteic acid) and electrical (50 Hz, 150–200 μA) stimulation of IL or POA. Intra-NTS microinjections of muscimol, a GABAA receptor agonist, prevented the decreases in blood pressure and heart rate normally evoked by IL or POA activation. In addition, we found that intra-NTS microinjection of R(+)-α-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenylethyl)]-4-piperidine-methanol, a specific 5-HT2A receptor antagonist, did not affect the decreases in cardiovascular baseline parameters induced by IL or POA stimulation but prevented the facilitation of the aortic baroreflex bradycardia normally observed during IL (+65 and +60%) or POA (+70 and +69%) electrical and chemical stimulation, respectively. These results show that NTS 5-HT2A receptors play a key role in the enhancement of the cardiac response of the baroreflex but not in the changes in basal heart rate and blood pressure induced by IL or POA stimulation.

Role of paraventricular and supraoptic nuclei in central cardiovascular regulation in the cat

1980 ◽  
Vol 239 (1) ◽  
pp. R137-R142 ◽  
Author(s):  
J. Ciriello ◽  
F. R. Calaresu
Keyword(s):  
Heart Rate ◽  
Cardiovascular Responses ◽  
Inhibitory Influence ◽  
Sympathetic Nervous Systems ◽  
Aortic Depressor Nerve ◽  
Bilateral Lesions ◽  
Alpha Chloralose ◽  
Supraoptic Nuclei ◽  
Stimulation Of

To investigate the role of the paraventricular (PAH) and supraoptic (SON) nuclei in regulation of the cardiovascular system experiments were done in 26 cats anesthetized with alpha-chloralose, paralyzed, and artificially ventilated. Electrical stimulation of histologically verified sites in the region of the PAH and SON elicited increases in arterial pressure in bilaterally vagotomized animals and increases in heart rate both in spinal (C2) animals and in animals bilaterally vagotomized, In addition, stimulation of either the PAH or SON inhibited the reflex vagal bradycardia elicited by stimulation of the carotid sinus nerve (CSN) and bilateral lesions of these areas increased the magnitude of the response. On the other hand, stimulation and lesions of these hypothalamic regions did not alter the magnitude of the cardiovascular responses to stimulation of the aortic depressor nerve. These results demonstrate that stimulation of the PAH and SON elicit cardiovascular responses due to reciprocal changes in activity of the parasympathetic and sympathetic nervous systems and that these structures maintain a tonic inhibitory influence on the heart rate component of the CSN reflex.

Angiotensin II antagonists in dehydrated rabbits without baroreceptor reflexes

1977 ◽  
Vol 232 (2) ◽  
pp. H110-H113
Author(s):  
N. C. Trippodo ◽  
T. G. Coleman ◽  
A. W. Cowley ◽  
A. C. Guyton
Keyword(s):  
Blood Pressure ◽  
Angiotensin Ii ◽  
Blood Pressure Regulation ◽  
Pressure Effects ◽  
Feedback Gain ◽  
Plasma Sodium ◽  
Pressure Regulation ◽  
Angiotensin Ii Antagonists ◽  
Baroreceptor Reflexes

Blood pressure effects of angiotensin II antagonists were studied in sham-operated and baroreceptor-denervated rabbits in the normal water-replete state or after 6 days of water deprivation (dehydrated). Experiments were performed in awake rabbits. Dehydrated rabbits had significantly higher plasma sodium concentrations, hematocrits, and plasma renin activities, but lower plasma potassium concentrations and body weights than water-replete rabbits. Administration of angiotensin II antagonists caused a significant decrease in mean arterial pressure in dehydrated rabbits (-16 mmHg in sham-dehydrated and -19 mmHg in denervated-dehydrated) but not in water-replete ones, whether the baroreceptor reflexes were intact or not (-1 mmHg in sham replete and -4 mmHg in denervated replete). The open-loop feedback gain of the renin-angiotensin system in blood pressure control was calculated as -1.6. The results demonstrate an important role of angiotensin II in blood pressure regulation during the high-renin, dehydrated state, but not during the normal renin, water-replete state. Abolishment of baroreceptor reflexes did not unmask an important role of normal levels of angiotensin II in blood pressure regulation.

Chronic nucleus tractus solitarius lesions do not prevent hypovolemia-induced vasopressin secretion in rats

1994 ◽  
Vol 267 (4) ◽  
pp. R965-R973 ◽  
Author(s):  
A. M. Schreihofer ◽  
E. M. Stricker ◽  
A. F. Sved
Keyword(s):  
Polyethylene Glycol ◽  
Plasma Volume ◽  
Nucleus Tractus Solitarius ◽  
Baroreceptor Reflex ◽  
Bilateral Vagotomy ◽  
Vasopressin Secretion ◽  
Bilateral Lesions ◽  
Alpha Chloralose ◽  
And Control ◽  
Arterial Baroreceptor

The present study examined the hypothesis that hypovolemia stimulates vasopressin (VP) secretion by removing tonic inhibitory baroreceptor input. Serial hemorrhage (4 samples of 2 ml/300 g body wt taken every 10 min) increased plasma VP levels in conscious rats devoid of cardiac and arterial baroreceptor reflex responses due to chronic bilateral lesions of nucleus tractus solitarius (NTS). The VP response to hemorrhage was similar to that seen in control rats and chronic sinoaortic-denervated (SAD) rats. After subcutaneous injection of 30% polyethylene glycol, NTS-lesioned rats, SAD rats, and control rats had elevated VP levels that correlated with the induced depletion of plasma volume. Additionally, in alpha-chloralose-anesthetized control rats, chronic SAD rats, and chronic NTS-lesioned rats, bilateral vagotomy had minimal effects on basal VP levels, and vagotomy in chronic NTS-lesioned rats did not prevent hemorrhage-evoked increases in VP secretion. These results do not support the idea that hemorrhage-induced VP secretion occurs through reduction in tonic inhibitory baroreceptor input. Instead, neither cardiac nor arterial baroreceptor input appears to be necessary for hypovolemia-induced VP secretion in rats.

The kidney and control of blood pressure

2015 ◽  
Author(s):  
Olga Gonzalez-Albarrán ◽  
Luis M. Ruilope
Keyword(s):  
Blood Pressure ◽  
Arterial Hypertension ◽  
Renal Nerves ◽  
Renal Ischaemia ◽  
Arterial Blood ◽  
Gene Defects ◽  
And Control ◽  
Transplantation Experiments ◽  
Primary Gene

The kidneys can be at the root of the development of arterial hypertension or they can participate in the maintenance of hypertension and its sequels. Renal alterations interfering with the regulation of sodium homeostasis or facilitating the generation of vasoconstrictors, particularly angiotensin II, are involved in the dysregulation of arterial blood pressure that underlies the development of arterial hypertension. The biology of angiotensin is described in detail.The kidneys are also the mediator of hypertension in such examples as renal ischaemia and hyperaldosteronism. The role of renal nerves, and renal depressor substances, are also described.Transplantation experiments in animals and observations in human transplantation, as well as some primary gene defects, show the importance of renal mechanisms in hypertension. Once kidneys have been damaged, they often contribute to an increase in arterial pressure. Salt sensitivity is probably a major part of the mechanism, but it is mediated by multiple pathways.

Role of ouabainlike compound in rats with reduced renal mass-saline hypertension

1994 ◽  
Vol 266 (4) ◽  
pp. H1357-H1362 ◽  
Author(s):  
K. Yamada ◽  
A. Goto ◽  
C. Hui ◽  
N. Yagi ◽  
H. Nagoshi ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Human Plasma ◽  
Plasma Levels ◽  
Renal Mass ◽  
Saline Solution ◽  
Distilled Water ◽  
Subtotal Nephrectomy

Ouabainlike compound (OLC) has recently been identified as a likely mammalian endogenous digitalis-like factor (EDLF) from human plasma. In this study, plasma levels of OLC were determined to assess the role of OLC in a model known as volume-expanded, reduced renal mass (RRM)-saline (S) hypertension in rats with use of a newly developed radioimmunoassay for ouabain. In the first experiment, at 3 wk after subtotal nephrectomy and drinking 1% saline solution, sysolic blood pressure (SBP) of 18 rats with reduced renal mass (RRM-S rats) was significantly higher than in 17 sham-operated saline-drinking control (C-S) rats [154 +/- 4 (SE) vs. 132 +/- 2 mmHg; P < 0.01]. Plasma OLC levels were 355 +/- 68 pmol/l in RRM-S rats, sevenfold higher than in C-S rats (54 +/- 4 pmol/l; P < 0.01). In the second experiment, we measured plasma OLC levels of 10 RRM-S, 12 sham-operated control (C), and 10 subtotally nephrectomized rats drinking distilled water (RRM rats). Concomitant with a marked increase in blood pressure (203 +/- 5 mmHg), RRM-S rats showed significantly higher plasma OLC levels compared with C and RRM rats (RRM-S 114 +/- 24, C 47 +/- 11, and RRM 52 +/- 9 pmol/l; P < 0.05). In both experiments, plasma OLC levels correlated significantly with SBP (P < 0.05). These findings suggest that plasma OLC shows a similar behavior to that of EDLFs or Na(+)-K(+)-adenosinetriphosphatase inhibitors reported in previous publications and may play a role in hypertensive mechanisms in rats with RRM and excess Na intake.

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.

Abstract 102: Role of Renal Tubular NHE3 for Blood Pressure and Salt Homeostasis

Hypertension ◽  
2016 ◽  
Vol 68 (suppl_1) ◽  
Author(s):  
Timo Rieg ◽  
Soren B Poulsen ◽  
Jessica A Dominguez Rieg ◽  
Robert A Fenton
Keyword(s):  
Blood Pressure ◽  
Transport Proteins ◽  
Plasma Aldosterone ◽  
Pressure Regulation ◽  
Urinary Ph ◽  
Blood Ph ◽  
Renal Tubular ◽  
And Control ◽  
Salt Homeostasis

The Na + /H + exchanger isoform 3 (NHE3) is expressed in the intestine and the kidney where it facilitates Na + absorption and H + secretion. The importance of NHE3 in the kidney for NaCl homeostasis and blood pressure regulation, relative to the intestine, is not known. To investigate this, we examined kidney-specific NHE3 knockout mice (NHE3 loxloxPax8Cre ) and control mice (Con, NHE3 loxlox ) under normal, low or high dietary NaCl intake. Under normal dietary NaCl intake, no significant differences were detected between genotypes in body weight, fluid or food intake, blood pH and plasma Na + , K + or aldosterone levels. However, urinary pH was significantly elevated in NHE3 loxloxPax8Cre mice and GFR was significantly lower (457±20 vs 358±17 μl/min, P<0.05). High NaCl intake (4% for 10 days) had no impact on plasma Na + in Con mice; but plasma Na + concentrations in NHE3 loxloxPax8Cre mice were susceptible to the effects of low NaCl (<0.01% for 10 days) (-3.9±1.0 mM, P<0.05) or high NaCl intake (+2.2±0.6 mM, P<0.05) compared to baseline conditions. Low NaCl diet decreased plasma K + levels in Con mice (-0.5±0.2 mM, P<0.05) but to a significantly greater amount in NHE3 loxloxPax8Cre mice (-1.2±0.1 mM, P<0.05). Plasma aldosterone was not significantly different between Con and NHE3 loxloxPax8Cre mice under low (345±96 vs 498±78 pg/ml) or high NaCl intake (60±19 vs 86±20 pg/ml). Low NaCl intake decreased GFR in Con (-110±13 μl/min, P<0.05) and NHE3 loxloxPax8Cre (-99±8 μl/min, P<0.05) mice, whereas high NaCl intake was without effect on GFR in either genotype. Dietary NaCl did not affect blood pressure in Con mice (low NaCl: 102±3; high NaCl: 102±3 mmHg); however, blood pressure was significantly lower in NHE3 loxloxPax8Cre mice and salt-sensitive (low NaCl: 81±2; high NaCl: 91±2 mmHg, P<0.05). Alterations in the abundances of several Na + transport proteins within the kidney tubule system were also apparent in NHE3 loxloxCre mice under different dietary conditions. In conclusion, renal NHE3 is required to maintain blood pressure and steady state plasma Na + levels when dietary NaCl intake is modified.

Angiotensin II attenuates baroreflexes at nucleus tractus solitarius of rats

1986 ◽  
Vol 250 (2) ◽  
pp. R193-R198 ◽  
Author(s):  
R. Casto ◽  
M. I. Phillips
Keyword(s):  
Blood Pressure ◽  
Angiotensin Ii ◽  
Baroreflex Sensitivity ◽  
Nucleus Tractus Solitarius ◽  
Ang Ii ◽  
Spontaneously Hypertensive ◽  
Baroreceptor Reflexes ◽  
Dose Dependent Increase ◽  
Dose Dependent ◽  
The Brain

Microinjection of angiotensin II (ANG II) into the nucleus tractus solitarius (NTS) has been shown to produce a dose-dependent increase in blood pressure and heart rate. We have tested the effect of subpressor infusions of ANG II (10 ng . kg-1 . min-1) in the NTS on reflex bradycardia after intravenous administration of the vasoconstrictor phenylephrine (1-12 micrograms) in normotensive urethan-anesthetized rats. ANG II within the brain is thought to contribute to the decreased baroreflex sensitivity in spontaneously hypertensive rats (SHR). The sensitivity of the baroreflex was significantly decreased by the infusion of ANG II (1.01 +/- 0.08) compared with control (2.41 +/- 0.51) in the normotensive animals. Baroreflex sensitivity was significantly decreased in SHR (0.40 +/- 0.21) compared with normotensive animals. We conclude that ANG II within the NTS can inhibit the function of baroreceptor reflexes in normotensive animals, suggesting that the endogenous peptide may perform an inhibitory role in the baroreflex arc, and this is further evidence that central ANG II is involved in blood pressure of SHR.

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