Baroreflex Sensitivity during the Development of Spontaneous Hypertension in Rats

1982 ◽  
Vol 62 (6) ◽  
pp. 589-594 ◽  
Author(s):  
H. A. J. Struyker-Boudier ◽  
R. T. Evenwel ◽  
J. F. M. Smits ◽  
H. Van Essen
Keyword(s):  
Blood Pressure ◽  
Baroreflex Sensitivity ◽  
Baroreceptor Reflex ◽  
Spontaneous Hypertension ◽  
Wky Rats ◽  
Arterial Blood ◽  
A Value ◽  
Freely Moving ◽  
Wistar Kyoto ◽  
Further Development

1. Baroreflex sensitivity was studied in relation to the development of spontaneous hypertension in rats (SH rats), with normotensive Wistar-Kyoto (WKY) rats as controls. Conscious, freely moving animals were studied at different times, ranging from 4 to 20 weeks after birth. 2. The youngest SH rats (4–6 weeks; n = 10) already had significantly (P < 0.01) higher mean arterial blood pressure (112 ± 2 mmHg) than WKY rats of corresponding age (95 ± 4 mmHg; n = 10). Baroreflex sensitivity did not differ at this age (0.37 ± 0.04 vs 0.38 ± 0.05 ms/mmHg). 3. Mean arterial pressure increased rapidly in SH rats during further development, reaching a value of 166 ± 3 mmHg in 12–20 week old animals (n = 25). In equally old WKY rats blood pressure was significantly (P<0.001) lower (110 ± 6 mmHg, n = 25). Baroreflex sensitivity did not change during development of SH rats (0.40 ± 0.03 ms/mmHg in 12–20 weeks old SH rats), whereas it increased two- to three-fold in WKY rats (0.93 ± 0.08 ms/mmHg, P<0.001). 4. It is concluded that an increase in baroreflex sensitivity is part of the development of a normotensive cardiovascular system, whereas in SH rats responsiveness of the baroreceptor reflex remains depressed during the development and stabilization of hypertension.

Blood pressure responsiveness during the development of hypertension in the conscious spontaneously hypertensive rat

1985 ◽  
Vol 63 (10) ◽  
pp. 1258-1262 ◽  
Author(s):  
Corey B. Toal ◽  
Frans H. H. Leenen
Keyword(s):  
Blood Pressure ◽  
Angiotensin Ii ◽  
Spontaneously Hypertensive Rat ◽  
Blood Pressure Response ◽  
Receptor Occupancy ◽  
Pressure Response ◽  
Spontaneously Hypertensive ◽  
Wky Rats ◽  
Freely Moving ◽  
Wistar Kyoto

Blood pressure responsiveness to iv noradrenaline and angiotensin II was studied in conscious, freely moving, age-matched spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats from 4 to 16 weeks of age. At 4 and 6 weeks the SHR showed small, but nonsignificant increases in responsiveness compared with WKY to both noradrenaline and angiotensin II. At 8 weeks they exhibited similar responses to the WKY. Subsequently, at 12 and 16 weeks decreased responsiveness to noradrenaline (nonsignificant) and angiotensin II (p < 0.05 at 12 and 16 weeks) was observed in SHR versus WKY. At 16 weeks of age, hexamethonium caused potentiation of the blood pressure response to noradrenaline and angiotensin II, but to the same degree in the two strains. Captopril at this age did not elicit potentiation to noradrenaline or angiotensin II in either strain. These results indicate that there is no rise in blood pressure responsiveness to circulating pressor agents, parallel to the development of hypertension in SHR. Increased receptor occupancy or more active attenuating reflexes in SHR versus WKY appear not to be involved in the absence of hyperresponsiveness in intact consious SHR at 16 weeks of age.

Short-term effect of egg-white hydrolysate products on the arterial blood pressure of hypertensive rats

2005 ◽  
Vol 94 (5) ◽  
pp. 731-737 ◽  
Author(s):  
Marta Miguel ◽  
Rosina López-Fandiño ◽  
Mercedes Ramos ◽  
Amaya Aleixandre
Keyword(s):  
Blood Pressure ◽  
Egg White ◽  
Therapeutic Benefit ◽  
Negative Control ◽  
Hypertensive Rats ◽  
Blood Pressure Lowering Effect ◽  
Wky Rats ◽  
Arterial Blood ◽  
Wistar Kyoto

In the present study we evaluate the blood pressure-lowering effect of the following products: the hydrolysate obtained from egg white (EW) by enzymatic treatment with pepsin (HEW), the peptide fraction of HEW with molecular mass lower than 3000 Da (HEW<3000 Da), and three peptide sequences isolated from HEW<3000 Da (Tyr-Ala-Glu-Glu-Arg-Tyr-Pro-Ile-Leu: YAEERYPIL); (Arg-Ala-Asp-His-Pro-Phe-Leu: RADHPFL); and (Ile-Val-Phe (IVF)). These peptides, and also HEW and HEW<3000 Da, had been characterized previously in vitro as potent inhibitors of angiotensin-converting enzyme (ACE). EW and the products mentioned earlier were orally administered by gastric intubation, to 17–20-week-old male spontaneously hypertensive rats (SHR) and normotensive Wistar–Kyoto (WKY) rats. We measured the systolic blood pressure (SBP) and the diastolic blood pressure (DBP) of the rats by the tail cuff method before administration and also 2, 4, 6, 8 and 24h post-administration. Distilled water served as negative control, and we used captopril (50mg/kg) as positive control to carry out similar experiments with a known ACE inhibitor. HEW, HEW<3000 Da and the three peptide sequences decreased SBP and DBP in SHR but they did not modify these variables in WKY rats. The peptide sequences YAEERYPIL, RADHPFL and IVF showed a potency to decrease blood pressure greater than HEW or HEW<3000 Da. The results obtained suggest that the studied products could be used as a functional food with potential therapeutic benefit in the prevention and treatment of hypertension.

Release of norepinephrine from the paraventricular hypothalamic nucleus of hypertensive rats

1988 ◽  
Vol 254 (5) ◽  
pp. H993-H1003 ◽  
Author(s):  
J. M. Qualy ◽  
T. C. Westfall
Keyword(s):  
Blood Pressure ◽  
Age Groups ◽  
Reciprocal Relationship ◽  
Hypothalamic Nucleus ◽  
Sprague Dawley ◽  
Spontaneously Hypertensive ◽  
Paraventricular Hypothalamic Nucleus ◽  
Arterial Blood ◽  
Freely Moving ◽  
Wistar Kyoto

The push-pull cannula was used to examine the release of endogenous norepinephrine (NE) from the paraventricular hypothalamic nucleus (PVH) of unanesthetized freely moving 7- to 10- and 12- to 14-wk-old Sprague-Dawley (SD), Wistar-Kyoto (WKY), and spontaneously hypertensive (SHR) rats. Basal NE release, K+ (56 mM) stimulation-induced NE release, and NE release in response to pressor/depressor drugs were examined in all three strains at both ages. Significant increases in basal and K+-stimulated release of endogenous NE from the PVH were observed in 7- to 10- and 12- to 14-wk-old SHR compared with the normotensive control rats suggesting that enhanced central noradrenergic nerve activity may be involved in the development and maintenance of hypertension in the SHR. In addition, a reciprocal relationship exists with respect to blood pressure and NE release from the PVH, i.e., decreases in blood pressure elicit increases in NE release, and increases in blood pressure elicit decreases in NE release in all three strains at both age groups, suggesting that the noradrenergic pathways of the PVH contribute to the maintenance of arterial blood pressure homeostasis.

scholarly journals Early high-sodium solid diet does not affect sodium intake, sodium preference, blood volume and blood pressure in adult Wistar-Kyoto rats

2011 ◽  
Vol 106 (2) ◽  
pp. 292-296 ◽  
Author(s):  
Marcin Ufnal ◽  
Adrian Drapala ◽  
Mariusz Sikora ◽  
Tymoteusz Zera
Keyword(s):  
Blood Pressure ◽  
Arterial Blood Pressure ◽  
Blood Volume ◽  
Blood Level ◽  
Food Preference ◽  
Plasma Osmolality ◽  
Wky Rats ◽  
Arterial Blood ◽  
Significant Difference ◽  
Wistar Kyoto

A high-Na diet may lead to the development of hypertension in both humans and rats; however, the causes of Na intake in amounts greater than physiologically needed as well as the mechanisms whereby high-Na food elevates blood pressure are not clear. Therefore, we decided to test the hypothesis that a high-Na diet introduced after suckling affects Na intake, food preference, resting blood pressure and blood volume in adult rats. Male Wistar-Kyoto (WKY) rats, 4 weeks old, were divided into three groups and placed on either a high-Na (3·28%), a medium-Na (0·82%) or a regular diet (0·22%) with the same energy content for 8 weeks. Subsequently, food preference, resting arterial blood pressure, blood volume, plasma osmolality and Na blood level were evaluated. When offered a choice of diets, all the groups preferred the regular chow, and there was no significant difference in total Na intake between the groups. When the rats experienced the change from their initial chow to a new one with different Na content, they continued to eat the same amount of food. Body weight, resting arterial blood pressure, blood volume, plasma osmolality and Na blood level were comparable between the groups. In conclusion, the results show that a high-Na diet introduced immediately after suckling does not affect Na preference and Na intake in adult WKY rats. Furthermore, the findings provide evidence that both blood volume and arterial blood pressure are highly protected in normotensive rats on a high-Na diet.

Hyperresponsivitiy of spontaneously hypertensive rat to indirect measurement of blood pressure

1978 ◽  
Vol 234 (6) ◽  
pp. H690-H695 ◽  
Author(s):  
C. C. Chiueh ◽  
I. J. Kopin
Keyword(s):  
Blood Pressure ◽  
Spontaneously Hypertensive Rat ◽  
Plasma Catecholamines ◽  
Indirect Measurement ◽  
Shr Rats ◽  
Spontaneously Hypertensive ◽  
Wky Rats ◽  
Arterial Blood ◽  
Chromatographic Procedure ◽  
Wistar Kyoto

A chronic, indwelling, tail arterial cannula was implated in conscious undisturbed rats for measurement of blood pressure and heart rate and for obtaining blood samples. As an index of sympathetic activity, plasma levels of catecholamines in arterial blood of conscious animals were assayed by a radioenzymatic, paper-chromatographic procedure. Blood pressures of unrestrained spontaneously hypertensive (SHR) rats in their home cages (161 +/- 3/141 +/- 4 mmHg) were not different from those of pentobarbitol-anesthetized, hypertensive animals but were about 25 mmHg lower than awake animals during the restraint required for the tail-cuff procedure. Basal levels of plasma catecholamines in awake, undisturbed or in pentobarbital-anesthetized animals were similar in age-matched SHR and normotensive Wistar-Kyoto (WKY) rats. SHR rats were shown to have greater increase in plasma catecholamines than WKY rats during forced immobilization or restraint for indirect measurement of blood pressure.

Vascular reactivity, tissue levels, and binding sites for endothelin: a comparison in the spontaneously hypertensive and Wistar–Kyoto rats

1991 ◽  
Vol 69 (3) ◽  
pp. 406-413 ◽  
Author(s):  
Gordon T. Bolger ◽  
Francine Liard ◽  
Annette Jodoin ◽  
Jorge Jaramillo
Keyword(s):  
Blood Pressure ◽  
Binding Sites ◽  
Vascular Reactivity ◽  
Spontaneously Hypertensive Rat ◽  
Peripheral Resistance ◽  
Shr Rats ◽  
Spontaneously Hypertensive ◽  
Wky Rats ◽  
Arterial Blood ◽  
Wistar Kyoto

The role of endothelin (ET-1) in mediating the development of blood pressure was investigated in the spontaneously hypertensive (SHR) rat using the Wistar–Kyoto (WKY) rat as the normotensive control. The following were characterized in both rat strains: age-dependent changes in mean arterial blood pressure (MAP), tissue (blood, lung, heart, and kidney) levels of immunoreactive ET-1 like related peptides (ET-1RP), aortic ring responses to ET-1, and specific high-affinity tissue (lung, atrium, ventricle, aorta, and kidney) binding sites for 125I-labelled ET-1. Commencing at age 10 weeks through to 12 weeks, SHR rats but not WKY rats developed a significant increase in MAP (from 152 ± 7 to 189 ± 3 mmHg) (1 mmHg = 133.32 Pa). However, in both WKY and SHR rats immunoreactive levels of ET-1RP increased (100 and 80%, respectively) throughout the same measurement period. The potency of ET-1 to contract aortic rings from SHR rats was slightly but not significantly greater than that for aortic rings from WKY rats, although aortic rings from SHR rats contracted in the presence of 0.5 nM ET-1, while those from WKY rats did not. The levels of immunoreactive ET-1RP were significantly reduced (32%) in the kidney and unchanged in the heart and lung of SHR rats compared with WKY rats. Specific 125I-labelled ET-1 binding sites displayed an increase and a significant decrease (24%) of density in the atrium and ventricle, respectively, a significant increase (31%) of affinity in the lung, and were unchanged in the kidney and aorta of SHR rats compared with WKY rats following the development of hypertension. The lack of a correlation between circulating levels of immunoreactive ET-1RP and the development of hypertension coupled with a lack of significant differences in vascular reactivity suggest that ET-1 is not the sole mediator of hypertension in this animal model. However, the tissue-specific changes in immunoreactive ET-1RP and 125I-labelled ET-1 binding sites suggest that ET-1 may be a partial mediator of hypertension and is subject to compensatory changes in response to the increased total peripheral resistance in SHR rats.Key words: endothelin, hypertension, spontaneously hypertensive rat.

Cerebral hemorrhage and edema following brain biopsy in rats: significance of mean arterial blood pressure

2000 ◽  
Vol 92 (1) ◽  
pp. 100-107 ◽  
Author(s):  
Helene Benveniste ◽  
Katie R. Kim ◽  
Laurence W. Hedlund ◽  
John W. Kim ◽  
Allan H. Friedman
Keyword(s):  
Blood Pressure ◽  
Arterial Blood Pressure ◽  
Mean Arterial Blood Pressure ◽  
Neurosurgical Procedures ◽  
Shr Rats ◽  
Mr Microscopy ◽  
Content Type ◽  
Wky Rats ◽  
Arterial Blood ◽  
Fine Print

Object. It is taken for granted that patients with hypertension are at greater risk for intracerebral hemorrhage during neurosurgical procedures than patients with normal blood pressure. The anesthesiologist, therefore, maintains mean arterial blood pressure (MABP) near the lower end of the autoregulation curve, which in patients with preexisting hypertension can be as high as 110 to 130 mm Hg. Whether patients with long-standing hypertension experience more hemorrhage than normotensive patients after brain surgery if their blood pressure is maintained at the presurgical hypertensive level is currently unknown. The authors tested this hypothesis experimentally in a rodent model.Methods. Hemorrhage and edema in the brain after needle biopsy was measured in vivo by using three-dimensional magnetic resonance (MR) microscopy in the following groups: WKY rats, acutely hypertensive WKY rats, spontaneously hypertensive rats (SHR strain), and SHR rats treated with either sodium nitroprusside or nicardipine. Group differences were compared using Tukey's studentized range test followed by individual pairwise comparisons of groups and adjusted for multiple comparisons.There were no differences in PaCO2, pH, and body temperature among the groups. The findings in this study indicated that only acutely hypertensive WKY rats had larger volumes of hemorrhage. Chronically hypertensive SHR rats with MABPs of 130 mm Hg did not have larger hemorrhages than normotensive rats. There were no differences in edema volumes among groups.Conclusions. The brains of SHR rats with elevated systemic MABPs are probably protected against excessive hemorrhage during surgery because of greater resistance in the larger cerebral arteries and, thus, reduced cerebral intravascular pressures.

scholarly journals Impaired Kv7 channel activity in the central amygdala contributes to elevated sympathetic outflow in hypertension

2021 ◽  
Author(s):  
Zhao-Fu Sheng ◽  
Hua Zhang ◽  
PeiRu Zheng ◽  
Shanyan Chen ◽  
Zezong Gu ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Brain Slices ◽  
Primary Hypertension ◽  
Neuronal Membrane ◽  
Sympathetic Outflow ◽  
Channel Activity ◽  
Central Amygdala ◽  
Expression Levels ◽  
Wky Rats ◽  
Arterial Blood

Abstract Aims Elevated sympathetic outflow is associated with primary hypertension. However, the mechanisms involved in heightened sympathetic outflow in hypertension are unclear. The central amygdala (CeA) regulates autonomic components of emotions through projections to the brainstem. The neuronal Kv7 channel is a non-inactivating voltage-dependent K+ channel encoded by KCNQ2/3 genes involved in stabilizing the neuronal membrane potential and regulating neuronal excitability. In this study, we investigated if altered Kv7 channel activity in the CeA contributes to heightened sympathetic outflow in hypertension. Methods and results The mRNA and protein expression levels of Kv7.2/Kv7.3 in the CeA were significantly reduced in spontaneously hypertensive rats (SHRs) compared with Wistar–Kyoto (WKY) rats. Lowering blood pressure with coeliac ganglionectomy in SHRs did not alter Kv7.2 and Kv7.3 channel expression levels in the CeA. Fluospheres were injected into the rostral ventrolateral medulla (RVLM) to retrogradely label CeA neurons projecting to the RVLM (CeA–RVLM neurons). Kv7 channel currents recorded from CeA–RVLM neurons in brain slices were much smaller in SHRs than in WKY rats. Furthermore, the basal firing activity of CeA–RVLM neurons was significantly greater in SHRs than in WKY rats. Bath application of specific Kv7 channel blocker 10, 10-bis (4-pyridinylmethyl)-9(10H)-anthracnose (XE-991) increased the excitability of CeA–RVLM neurons in WKY rats, but not in SHRs. Microinjection of XE-991 into the CeA increased arterial blood pressure (ABP) and renal sympathetic nerve activity (RSNA), while microinjection of Kv7 channel opener QO-58 decreased ABP and RSNA, in anaesthetized WKY rats but not SHRs. Conclusions Our findings suggest that diminished Kv7 channel activity in the CeA contributes to elevated sympathetic outflow in primary hypertension. This novel information provides new mechanistic insight into the pathogenesis of neurogenic hypertension.

24-hour homeodynamic states of arterial blood pressure and pulse interval in conscious rats

1992 ◽  
Vol 73 (2) ◽  
pp. 754-761 ◽  
Author(s):  
B. J. Janssen ◽  
C. M. Tyssen ◽  
H. A. Struijker Boudier ◽  
P. M. Hutchins
Keyword(s):  
Blood Pressure ◽  
Cardiovascular System ◽  
Arterial Blood Pressure ◽  
Single Mode ◽  
Pulse Interval ◽  
Mean Values ◽  
Frequency Distributions ◽  
Set Point ◽  
Arterial Blood ◽  
Wistar Kyoto

In models that describe the homeostasis of the circulation, arterial blood pressure is usually expressed as a single value, which is regarded as the set point in such systems. The aim of the study was to identify in rats from 24-h beat-to-beat recordings the value of blood pressure that describes best such a set point of the cardiovascular system. Normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR), kept on a 12:12-h lights on-off cycle, were instrumented for computerized 24-h beat-to-beat recording of mean arterial pressure (MAP) and pulse interval (PI). Three-dimensional frequency distributions were constructed by plotting for each beat its MAP vs. its PI. During the dark period, the concurrent distribution of MAP and PI showed two distinct modes while during the light period a single mode was found. Comparable patterns were found in SHRs and WKYs. These three different modes were significantly different from the mathematically calculated mean values of MAP and PI over these periods. Thus in rats the 24-h behavior of the cardiovascular system is better described by dynamic shifts between different modes (homeodynamic states) than by a single set point.

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