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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The relative role of brain catecholamines in the development of hypertension in the spontaneously hypertensive rat (SHR) was studied. Treatments consisted in five weeks old SHR of central injections of 6-hydroxydopamine (6-OHDA), 3 X 200 micrograms either intracerebroventricularly (i.c.v.) or intracisternally (i.c.), or of intraperitoneal (i.p.) injections of DSP-4, either once or three times 50 mg/kg. Compared to the pronounced attenuation of the development of hypertension following i.c.v. 6-OHDA treatment, the i.c. 6-OHDA treatment and the multiple DSP-4 treatment were less effective. A single injection of DSP-4 had only minor effects on blood pressure. Heart rate was markedly lower in i.c.v. 6-OHDA treated SHR, but the other treatments induced no effects on this parameter. Noradrenaline depletion was found in various parts of the brain particularly after i.c.v. 6-OHDA or either DSP-4 treatment. Brain dopamine and adrenaline were depleted to a lesser extent. However, the best correlation between blood pressure and brain catecholamine concentration was found for dopamine in the hippocampus and hypothalamus and for adrenaline in the hypothalamus. Noradrenaline levels were also correlated with blood pressure, but to a lesser extent. These results suggest that the depletion of dopamine or adrenaline in the brain may be of more importance in the effects of neurotoxic treatments on the development of hypertension than the effects on brain noradrenaline. Thus, these experiments lend support to the hypothesis that brain noradrenaline systems may not play an important role in the development of hypertension in the SHR.
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PMID:Brain noradrenaline and the development of hypertension: the effect of treatment with central 6-hydroxydopamine or DSP-4. 309 24

This study was performed to investigate whether ketanserin (a serotonergic receptor antagonist) might affect the sympathetic nerve activity in resistance vessels of hypertension. Isolated perfused mesenteric vasculatures were prepared from spontaneously hypertensive rats (SHRS, Okamoto and Aoki, 20-22 weeks old) and age-matched Wistar Kyoto rats (WKY), and effects of ketanserin on norepinephrine overflow from the adrenergic nerve endings as well as on vascular responsiveness were examined. Pressor responses to electrical nerve stimulation or exogenous norepinephrine were inhibited by ketanserin, in a dose-dependent manner. Norepinephrine overflow during electrical nerve stimulation was also suppressed by ketanserin. Inhibitory degrees of pressor responses and norepinephrine overflow during electrical nerve stimulation by ketanserin were significantly greater in SHRs than those in WKY rats. These results suggest that ketanserin could affect presynaptic neurotransmitter release from the adrenergic nerve endings in resistance vessels. These sympatho-depressive actions might contribute, at least partially, to the hypotensive mechanisms of ketanserin.
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PMID:Ketanserin decreases sympathetic nervous activity in hypertension. 341 14

The purpose of the present study was to analyse the regulatory mechanisms of epinephrine and dopamine on norepinephrine release from the sympathetic nerve endings in the resistance vessels in hypertension. The perfused mesenteric arteries were used for the experiment in spontaneously hypertensive rats (SHR; 7-10 weeks old) and age-matched normotensive Wistar-Kyoto (WKY) rats. Norepinephrine overflow during electrical nerve stimulation was significantly greater in SHR than in WKY rats. A low concentration of epinephrine (5.5 X 10(-9) mol/l) potentiated norepinephrine overflow from the nerve endings in SHR, and this was antagonized by propranolol, while this overflow was reduced by the same concentration of epinephrine in WKY rats. Higher concentrations of epinephrine decreased the norepinephrine overflow both in SHR and WKY rats, and this was antagonized by yohimbine. Dopamine reduced the norepinephrine overflow during electrical nerve stimulation, suppression being significantly less in SHR than in WKY rats. These results suggest that in SHR the increased norepinephrine overflow from sympathetic nerve endings may be partly caused by the facilitatory effect of epinephrine (through presynaptic beta-adrenoceptors) and impaired dopamine-mediated inhibition on the nerve terminals, which might contribute to the enhanced adrenergic activity in hypertension.
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PMID:Effects of epinephrine and dopamine on norepinephrine release from the sympathetic nerve endings in hypertension. 347 13

The development of hypertension in rabbits with bilateral cellophane wrapping of the kidneys was studied in animals with and without surgical denervation of the kidneys. Mean arterial pressure was measured before and 14 and 28 days after surgery. After 14 and 28 days of wrapping, mean arterial pressure had increased 12 +/- 3 mmHg and 31 +/- 3 mmHg in rabbits with innervated kidneys and 7 +/- 2 mmHg and 26 +/- 2 mmHg in rabbits with denervated kidneys, respectively. The increases in arterial pressure were significantly less in the denervated animals. In sham wrap animals, renal denervation also resulted in significantly lower arterial pressure than in sham wrap+sham denervated rabbits. Noradrenaline concentration of denervated kidneys averaged only 4% of that measured in kidneys subjected to sham denervation. The results show that renal denervation slightly attenuated the degree of hypertension developed following renal wrapping. Since renal denervation produced a similar small decrease in arterial pressure in normotensive rabbits it is suggested that the effect is non-specific and probably due to loss of efferent renal sympathetic nerves.
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PMID:Effect of renal denervation on the development of cellophane-wrap hypertension in rabbits. 354 56

Obstructive apnea (asphyxia) is accompanied by acute elevation of systemic blood pressure. The usual nocturnal fall in blood pressure seen during sleep in normals may be absent in patients with repetitive apneas, and daytime systemic hypertension is reported to occur in up to 90% of such patients. Increased sympathetic activity in response to repetitive nocturnal episodes of asphyxia could explain the reversal of the diurnal pressure variation but not the daytime systemic hypertension in this setting. We examined diurnal variation in urinary catecholamines in eight subjects with severe apnea before and after tracheostomy. Five obese hypertensive subjects without apnea served as controls. Three urine specimens, two awake (7 a.m. to 3 p.m. and 3 p.m. to 11 p.m.) and one asleep (11 p.m. to 7 a.m.) were collected preoperatively and again 10-14 days postoperatively when the patient was free of pain and signs of stoma infection. All specimens were analyzed for epinephrine, norepineprine, metanephrine, and normetanephrine by liquid chromatography with electrochemical detection. Urinary epinephrine and metanephrine were not different between subjects and controls. Norepinephrine and normetanephrine were significantly higher in apneic subjects pretracheostomy as compared either with controls or with their own values posttracheostomy. Diurnal variation was not seen before or after tracheostomy. Only two of the controls showed significant diurnal variation in norepinephrine. We conclude that the absence of diurnal variation in catecholamines prior to tracheostomy reflects increased nocturnal sympathetic activity. Elevation of daytime norepinephrine and normetanephrine with return to control levels following tracheostomy implies increased sympathetic activity throughout the day.
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PMID:Urinary catecholamines before and after tracheostomy in patients with obstructive sleep apnea and hypertension. 356 46

Ring segments were obtained from the aorta of spontaneously hypertensive (SHR), Wistar-Kyoto (WKY), and Wistar (WST) rats and from the anterior tibial artery of normotensive and hypertensive dogs. Norepinephrine dose-response curves were generated at lengths relative to that for maximum force (Lmax) and at a specific preload (in grams). The doses of stimulus necessary to elicit 10 and 50% maximum force of contraction (ED10 and ED50) are greater at lengths less than Lmax than at Lmax for all groups. When SHR rings are compared with WKY or WST rings, ED10 or ED50 is the same at either length. The same result was found in comparing normal and hypertensive dogs. ED10 and ED50 from hypertensive groups were the same as their respective control groups when compared at the same preload. We conclude that sensitivity of the rat aorta and dog anterior tibial artery to norepinephrine depends on muscle length, this relationship is not altered in hypertension, and the conclusion on sensitivity in hypertension is the same for excised rings compared at the same length or at the same preload. Contractility (active stress) was lower (rats) or the same (dogs) but thickness was greater in the hypertensive groups than in their controls. The results show that a change in the vessel wall that can cause increased flow resistance and pressure is not in sensitivity or contractility but in wall thickness. Apparent differences in sensitivity from normal and hypertensive animals can be explained by an unchanged length-dependent sensitivity. The results also show that differences in body weight will affect a comparison of wall tension but not of sensitivity.
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PMID:Length-dependent sensitivity of vascular smooth muscle in normotensive and hypertensive animals. 361 13

Adrenergic innervation in the main trunk of the mesenteric artery was studied in stroke-prone spontaneously hypertensive rats (SHRSP) as well as in a new strain of SHRSP (M-SHRSP) and was compared with that of normotensive Wistar Kyoto rats (WKY). Noradrenaline (NA) content and high K-induced NA release in the artery of 6-week-old SHRSP and M-SHRSP were greater than those in the artery of WKY. These results suggest that a higher adrenergic innervation of the artery might be involved in the development of hypertension in SHRSP and M-SHRSP.
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PMID:Noradrenaline content and release in the mesenteric artery of stroke-prone spontaneously hypertensive rats (SHRSP) and a new strain of SHRSP (M-SHRSP). 365 21

Urinary excretion of free noradrenaline and adrenaline during 24 h in 265 individuals was determined and related to sex, age, and hypertension as one indicator of the average sympathetic drive. Noradrenaline was found to correlate positively with age in healthy individuals. Noradrenaline and adrenaline were lower in healthy women than in men during the first half of life expectancy. Catecholamine excretion was similar in men and women in the second half of life expectancy. In hypertensive individuals, catecholamine excretion was slightly higher in the first half, and significantly higher in the second half of life expectancy. We assume that the differences in catecholamine excretion can contribute to the sex-and age-related differences in incidence of cardiovascular diseases, such as hypertension and coronary heart disease.
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PMID:Urinary excretion of free noradrenaline and adrenaline related to age, sex and hypertension in 265 individuals. 369 84

Noradrenaline (NA), adrenaline (A) and dopamine (DA) levels were measured in the heart, kidney and caudal artery of male and female SHR and WKY rats aged 6, 14 and 28 weeks, and the influence of strain, sex and age on catecholamine content determined. Levels of A were elevated in all three regions of SHR compared to WKY rats, independent of age and sex. This may represent increased A accumulation in sympathetic nerves resulting from the increased sympatho-adrenomedullary hyper-reactivity of the SHR strain. DA levels were also elevated in the heart and kidney of SHR rats, independent of sex and age. Na levels were lower in the heart of SHR rats, but this appeared to be partly a consequence of cardiac hypertrophy and partly due to strain difference between older male but not female rats. Thus a simple association between decreased cardiac NA levels and hypertension appeared unlikely. It is emphasised that further genetic studies of F2 backcross rats would be required to establish an etiological association between these differences in catecholamine levels and differences in blood pressure between the SHR and WKY strains.
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PMID:The influence of age and sex on cardiac, renal and caudal artery catecholamine content in spontaneously hypertensive (SHR) and Wistar Kyoto (WKY) rats. 377 90

The effects of sino-aortic denervation (SAD) on cardiac noradrenaline stores, turnover and neuronal re-uptake were examined in normotensive rabbits and rabbits with two-kidney, two wrapped hypertension. Ten to 12 days after SAD, left ventricular (LV) noradrenaline stores were reduced in renal hypertensives to 43% of that of the sham-operated rabbits, although there was no overt evidence of heart failure. This did not occur after SAD of normotensive rabbits. The reduction in noradrenaline content was accompanied by a reduction in [3H]-noradrenaline turnover time (4.4 h) compared with renal hypertensive (7.4 h) and the normotensive subgroups (9.3 h). Noradrenaline turnover rates were elevated by 25% in hypertensive compared with normotensive rabbits. Left ventricular tyrosine hydroxylase, dopamine-beta-hydroxylase and type A monoamine oxidase activities were similar in normotensive and hypertensive rabbits and were unaffected by SAD. Following SAD of hypertensive rabbits cardiac neuronal uptake for alpha-methylnoradrenaline was reduced by 33% compared with either the hypertensive or the normotensive rabbits. Sino-aortic denervation did not affect neuronal uptake in normotensives. These results suggest that following SAD of hypertensive rabbits, cardiac noradrenaline stores are depleted by enhanced cardiac sympathetic activity (reduction in [3H]-noradrenaline turnover time) and a reduction in neuronal re-uptake. It appears that the hypertensive hypertrophied heart is less able to tolerate chronic sympathetic overactivity and/or liability in coronary oxygen supply brought about by SAD.
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PMID:Differential effects of sino-aortic denervations on cardiac noradrenaline stores, turnover and neuronal re-uptake in normotensive and renal hypertensive rabbits. 377 95


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