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

Epidemiological studies indicate that there are biological interrelationships between blood pressure and blood lipids that may influence the mechanisms whereby hypertension is associated with an increased risk of coronary artery disease. Serotonin (5-HT) and thromboxane A2, which are released from aggregating platelets, mediate platelet-induced vasoconstriction, which itself significantly contributes to coronary artery constriction in vivo. Platelet aggregatory response to serotonin is modulated by disparate effects of lipoprotein fractions. This corresponds to the recognized differences in degree of atherogenicity of low- (LDL) and high-density lipoprotein (HDL). Amplification of serotonin-induced platelet aggregation by LDL and its inhibition by HDL support the hypothesis that 5-HT-mediated effects represent a mechanism clinically relevant to both chronic progression of atherosclerosis (particularly at sites of vascular injury and atherosclerotic plaques) and acute thrombotic events. Calcium antagonists differ in their platelet-inhibition potency, including their effects on platelet response to 5-HT and LDL. Verapamil and isradipine inhibit platelet aggregation induced by 5-HT at therapeutic concentrations. Isradipine also inhibits the amplifying effect of LDL on 5-HT-induced aggregation. These platelet effects of calcium antagonists appear to be neither group- nor class-specific but, rather, drug-specific.
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PMID:Platelet activation by low-density lipoprotein and serotonin: effects of calcium antagonists. 137 30

In vitro and animal experiments suggest that a constitutional increase in vascular responsiveness to serotonin (5-HT) may play a role in the development of essential hypertension. We have studied the potential alterations in vascular responsiveness to the direct and catecholamine-potentiating effects of exogenous 5-HT in patients with essential hypertension, by comparing in vivo responsiveness of superficial hand veins to local infusions of 5-HT or to coinfusions of 5-HT and noradrenaline in unmedicated hypertensive patients and in healthy control subjects. The dorsal hand vein compliance technique was employed. There was no significant difference between patients and control subjects in the maximal 5-HT-induced venoconstriction or in the doses required for half-maximal venoconstriction (ED50) for 5-HT. Coinfusions of a constant dose of 5-HT caused a significant leftward shift in the dose response curve for noradrenaline as compared with noradrenaline alone. This was indicated by a 9.7 +/- 13.7 fold and a 10.4 +/- 13.8 fold increase in the ED50 for noradrenaline in the patient and control groups, respectively (p = 0.89 between study groups). Our results argue against a generalized increase in responsiveness to the direct or catecholamine-potentiating effect of 5-HT in vivo in vascular smooth muscle, associated with hypertension.
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PMID:Effects of serotonin and noradrenaline on superficial hand veins in patients with primary hypertension and in healthy volunteers. 147 Feb 20

Because platelet activation and serotonin have been implicated in preeclamptic hypertension, we investigated the effect of pregnancy on the contractile response to this agent. Prior studies have shown that the vascular contractions to norepinephrine, angiotensin II, and thromboxane are reduced during normal pregnancy by the altered release of endothelium-derived vasoactive substances. We hypothesized that the contraction to serotonin would also be reduced during pregnancy by an endothelium-dependent mechanism. Isolated ring segments from uterine and carotid arteries of near-term pregnant and nonpregnant guinea pigs were studied after stimulating a small amount of active tone with prostaglandin F2 alpha. Serotonin (10(-8) to 10(-5) M) contractile responses of both arteries were reduced by pregnancy. Regardless of pregnancy status, the contractile responses of the uterine artery to serotonin were severalfold greater than that of the carotid artery whose maximum averaged only 10% of the 120 mM KCl contraction. Denudation of uterine artery abolished acetylcholine-stimulated relaxation in vessels from pregnant and nonpregnant animals. However, serotonin-induced contractions were enhanced by denudation only in ring segments obtained from pregnant animals. Nitric oxide synthase inhibition by either NG-monomethyl-L-arginine (L-NMMA) or N omega-nitro-L-arginine and cyclooxygenase inhibition by indomethacin had no effect on serotonin-induced contraction of intact uterine artery regardless of pregnancy. L-NMMA modestly enhanced the intact carotid arterial response to 10(-5) M serotonin independent of pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Pregnancy reduces serotonin-induced contraction of guinea pig uterine and carotid arteries. 148 1

The past decade has seen important progress in understanding the localization, pharmacology, and function of serotonin (5-HT) receptor subtypes. At least seven subclasses have been shown to exist, and evidence is emerging to suggest further subclassification. Serotonin is involved in numerous physiological processes (e.g. feeding, sleep, pain, sexual behavior, temperature regulation) and pathophysiological ones. Serotonin reuptake blockers have been found effective in the alleviation of depression and attacks of panic, and are at varying stages of clinical evaluation in the treatment of obsessive compulsive disorder, chronic pain, and bulimia nervosa. Selective potent serotonin receptor agonists and antagonists show promise in the treatment of migraine, nausea and vomiting, schizophrenia, anxiety, hypertension, and Raynaud's disease.
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PMID:[New therapeutic possibilities with drugs affecting serotonin receptors]. 150 27

Sodium (Na+)-dependent hypertension was studied in hypoxia in an effort to determine the basis for hypoxia-mediated attenuation of hypertension. Hypoxia attenuated spontaneous hypertension while Na+ increased blood pressure in SHR. A lack of interaction between the effects of hypoxia and Na+ indicated additivity of effects. As a result, hypoxia-exposed, Na(+)-supplemented SHR had similar blood pressure as did normoxic, nonsupplemented SHR although both groups had lower blood pressure than normoxic, Na(+)-supplemented SHR. Hypoxia decreased serotonin turnover (5-HIAA/5-HT) in the brain stem of SHR while supplemental Na+ had no influence on this measurement. Hypoxic exposure in DOCA-treated rats failed to prevent the development of hypertension although hypoxia decreased 5-HIAA/5-HT in the brain stem of hypoxic rats, irrespective of DOCA treatment. The finding in SHR that Na+ counteracts the protection of hypoxia could be argued to support a similar mechanism of action for hypoxia and sodium. However, the results with DOCA treatment clearly refute such an interpretation. Our findings indicate that the pressor influence of Na+ does not occur through the modulation of brain stem 5-HIAA/5-HT.
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PMID:Hypoxic attenuation of brain stem serotonin does not influence sodium-induced hypertension. 160 Jun 39

A two week administration of the glucocorticoid betametasone to male Wistar rats produced a mild hypertensive state. The brain of these rats showed some significant changes in amine and metabolite content with respect to normotensive controls. Epinephrine and metanephrine were increased in the rostral ventrolateral medulla and in the preoptic area. Epinephrine also increased in the septal area. Normetanephrine decreased in the rostral ventrolateral medulla. Dopamine and homovanillic acid increased in septal and preoptic areas. Dopamine alone increased in rostral ventrolateral medulla. Serotonin and 5-hydroxyindole-3-acetic acid increased in the septal area and dorsal medulla. These changes suggest significant alterations in the aminergic activity of the brain circuitry known to regulate cardiovascular functions; the changes may play a basic role in the development and maintenance of glucocorticoid-induced hypertension.
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PMID:Brain amines in glucocorticoid-induced hypertension in the rat. 162 93

The effects of svate on platelet morphology and aggregation were studied and compare with Radix Salviae Miltiorrhizae. The results showed that svate remarkably inhibited platelet aggregation in patients with coronary heart disease and hypertension. Svate could increase plasma 6-keto-PGF1 alpha and decrease plasma TXB2. After treatment with svate, levels of platelet cAMP was increased. Svate enhanced platelet 5-HT and reduced plasma 5-HT. Electron microscopic study showed that the percentage of discoid and dendritic platelets were increased, while those of spread and aggregate platelets were decreased following svate therapy. It was found that svate is superior to Radix Salviae Miltiorrhizae in inhibition of platelet function. The results indicate that svate inhibits platelet aggregation and release through increasing prostacyclin generation in the vascular wall, raising platelet cAMP and inhibition of TXA2 production.
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PMID:[Effects of svate on platelet morphology and function in patients with coronary heart disease and hypertension]. 165 75

We investigated the hypertensive changes in renal arteries isolated from 21-week-old spontaneously hypertensive rats (SHR), and from age-matched normotensive Wistar-Kyoto rats (WKY). The maximum contraction of renal arteries from SHR in response to norepinephrine (NE), serotonin (5-HT) and KCl was greater than that of arteries from WKY. The threshold and EC50 concentrations of NE, 5-HT and KCl were not significantly different between SHR and WKY. Contraction induced by removal of K+ was inhibited by 10(-8) M prazosin. Less than 10(-7) M NE in K(+)-free solution did not cause contraction. Addition of 5.9 mM KCl to K(+)-free solution in the presence of 10(-5) M NE induced relaxation, which was followed by contraction to about the same level as that before KCl addition. The duration of the K(+)-induced relaxation in SHR (22.4 +/- 0.9 min) was slightly, but significantly shorter than that in WKY (26.6 +/- 0.8 min) arteries. In K(+)-free solution with reduced Na+, the duration of the relaxation induced by KCl was shorter than that in the normal solution, for both SHR (13.8 +/- 0.3 min) and WKY (14.1 +/- 0.5 min). Such differences could be caused by increased influx and decreased efflux of Ca2+, which depend on the Na+ concentration and are related to the Na(+)-Ca2+ exchange. The results suggest that enhanced renal vascular reactivity in hypertension may depend on structural changes and increased Na+ pump activity.
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PMID:Sodium pump activity and contraction of renal artery from spontaneously hypertensive rats. 166 26

The effects of serotonin (5-hydroxytryptamine; 5-HT) on the cardiovascular system are complex. These effects, consisting of bradycardia or tachycardia, hypotension or hypertension, and vasodilation or vasoconstriction are mediated by three main sets of receptors called 5-HT1-like, 5-HT2, and 5-HT3. In addition, recent findings suggest the participation of a putative 5-HT4 receptor. Though selective 5-HT1A receptor agonists can lower heart rate (and arterial blood pressure), 5-HT usually lowers heart rate by eliciting an initial short-lasting hypotension due to bradycardia (von Bezold-Jarisch-like reflex) via 5-HT3 receptors located on sensory vagal nerve endings in the heart. Once this bradycardia reflex is suppressed--for example, during deep anesthesia, vagotomy, or spinal section--5-HT can increase heart rate in different species by a variety of mechanisms. Myocardial 5-HT1-like, 5-HT2, and 5-HT4 receptors appear to be involved in the cat, rat, and pig, respectively. 5-HT-induced tachycardia in the dog and rabbit is due mainly to release of catecholamines and involves 5-HT2 receptors on the adrenal medulla and 5-HT3 receptors on postganglionic cardiac sympathetic nerve fibers. Recently, 5-HT3 receptors also have been implicated in the 5-HT-induced tachycardia in the conscious dog. The blood pressure response to 5-HT is usually triphasic and consists of a von Bezold-Jarisch-like reflex, a middle pressor phase, and a longer-lasting hypotension. The pressor response is a consequence of vasoconstriction mediated via 5-HT2 receptors; however, vasoconstriction in the dog saphenous vein and cephalic arteries and arteriovenous anastomoses is due to stimulation of 5-HT1-like receptors. The depressor response exclusively involves 5-HT1-like receptors located at four different sites: (a) central nervous system (decrease in sympathetic and increase in vagal nervous activity), (b) sympathetic nerve terminals (reduction of transmitter release), (c) vascular smooth muscle (vasodilatation), and (d) vascular endothelium (release of a relaxant factor, probably nitric oxide). Arteriolar dilatation, together with the constriction of arteriovenous anastomoses, leads to an increase in nutrient (tissue; capillary) blood flow. The 5-HT1-like receptors are heterogeneous in nature; however, apart from the resemblance of the central nervous system 5-HT1-like receptor causing hypotension and bradycardia to the 5-HT1A binding subtype, the relationship of the other 5-HT1-like receptors to 5-HT1 binding subtypes is still debatable.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Cardiovascular effects of serotonin agonists and antagonists. 170 84

Enalapril (Renitec, Merck-Sharp-Dohne, Rahway, USA) administered alone (Group I), or in combination (Group II) in a dosage normalizing blood pressure (BP) was investigated for its ability to inhibit adrenergic and serotonergic systems in a one-year study. BP normalization was achieved. Serotonin (5-hydroxytryptamine, 5HT) levels in platelet rich and poor plasma, urinary excretion of 5HT, adrenaline and noradrenaline decreased. Correlations between the changes in BP and the inhibition of serotonergic and adrenergic systems were found in the acute phase in Group I. In chronic effect the reduction of BP correlated with inhibition of the serotonergic system in both groups. Changes in adrenergic and serotonergic systems correlated in the acute phase in both groups; during chronic treatment only in Group II. It is concluded that a concurrent antihypertensive effect and the inhibition of sympathetic activity and 5HT amplifying mechanism (antiatherogenic effect) are of clinical importance for hypertension treatment and prevention of its complications.
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PMID:Modulation of serotonergic and adrenergic systems by long-term antihypertensive treatment with enalapril. 171 98


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