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

The interaction between noradrenergic and serotonergic mechanisms on the central regulation of blood pressure in the rat was studied, using central experimental hypertension produced by chemical lesions of the locus coeruleus (LC) with 6-hydroxydopamine (6-OHDA). The hypertension (LC-hypertension) was blocked by pretreatment with 6-OHDA intraventricularlly administered and also with desipramine. An increase of serotonin (5-HT) turnover in the cortex and especially in the spinal cord was revealed in the hypertension. Intraperitoneally administered para-chlorophenylalanine elevated blood pressure and reduced 5-HT and 5-hydroxyindole acetic acid content in the cortex and especially in the spinal cord, indicating a decrease 5-HT turnover. Intraventricularlly administered 5, 6-dihydroxytryptamine (5, 6-DHT) resulted in only bradycardia but not an elevation in blood pressure and did not block the development of LC hypertension, and lowered 5-HT content in the cortex and especially in the spinal cord. Intraspinally administrated 5, 6-DHT evoked mild but significant elevation in blood pressure but not in heart rate, and lowered 5-HT content only in the spinal cord. Furthermore, the disappearance of the LC was histologically observed in the rats with LC hypertension. The results of these experiments demonstrate that (1) LC hypertension is probably due to a specific lesion of the LC with 6-OHDA, (2) LC hypertension is accompanied by an increase of 5-HT turnover in the cortex and especially in the spinal cord, which may participate in a depressor function in LC hypertension, (3) ablation of bulbospinal serotonergic neurons produce mild elevation in blood pressure. (4) the balance between the activity of central noradrenerfic and serotonergic neurons may play a role in maintaining normotension, and their unbalance may induce hypertension.
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PMID:Interaction between noradrenergic and serotonergic mechanisms on the central regulation of blood pressure in the rat: a study using experimental central hypertension produced by chemical lesions of the locus coeruleus. 15 55

Bovine albumin (BA: 2 mg/kg-1, i.v.) produced a fall in systemic arterial blood pressure accompanied by central venous hypertension and bradycardia in pentobarbital-anaesthetized, spontaneously breathing, bovine albumin-sensitized adult domestic fowl. Trasylol (a potent inhibitor of kallikreins) suppressed acute systemic anaphylaxis. Polyphloretin phosphate (an effective antagonist of PGF2alpha) also inhibited the cardiovascular responses to antigen and PGF2alpha. Sodium meclofenamate and phenylbutazone showed varying degree of blockade of cardiovascular responses to exogenously administered chemical mediators (bradykinik, PGF2alpha, SRS-A and to a lesser extent of histamine, 5-HT and acetylcholine) and antigen. Indomethacin (virtually devoid of receptor blocking activities toward exogenously injected chemical mediators) inhibited anaphylaxis. The results of this investigation strongly suggested an important role of vasoactive lipids and polypeptides in avian anaphylaxis.
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PMID:Acute systemic anaphylaxis in adult domestic fowl--possible role of vasoactive lipids and peptides. 31 23

This review paper deals with the transport of the protein tracer horseradish peroxidase across cerebral vessels under normal and various experimental conditions. Electronmicroscopical investigations have revealed that, under normal conditions, a minor vesicular transfer of intravenously injected peroxidase occurs across the endothelium in segments of arterioles, capillaries and venules, especially in arterioles with a diameter about 15-30 mu. This normally occurring vesicular transport is susceptible to various experimental conditions. Thus the transfer of tracer increases when a hypertonic solution is injected into the internal carotid artery presumably due to vesicular transport. Extensive acute hypertension of short duration also increases the vesicular transfer of peroxidase from blood to brain. Identical observations are obtained when the hypertension is evoked by intravenous injection of phentolamine and by electrically induced seizures. During the postischemic period, one hour after release of the occlusion of an internal carotid artery in the Mongolian gerbil the vesicular transport of peroxidase is increased across the endothelium of cerebral vessels. The explanation may be release of serotonin from blood platelets during the occlusion. The serotonin could then increase the blood pressure locally in the brain resulting in an enhanced permeability. Serotonin, after perfusion through the cerebral ventricular system, is also able to increase the normally occurring vesicular transfer. The most likely mechanism behind this phenomenon seems at the moment to be local hypertension evoked by serotonin-induced vasoconstriction of arterioles. Finally, the enhanced vesicular transport across cerebral endothelium caused by porto-caval anastomosis is mentioned and the possible role of disturbances in the metabolism of amines as responsible for the extravasation is discussed.
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PMID:The blood-brain barrier to horseradish peroxidase under normal and experimental conditions. 33 57

The accumulation of 5-hydroxytryptophan (5-HTP) following decarboxylase inhibition was measured in hypothalamus (HYP), pons-medulla (PM) and spinal cord (SC) of 4- and 8-week-old spontaneously hypertensive (SH) and normotensive (WKY) rats. Using this method, a significant increase in the in vivo activity of tryptophan hydroxylase was observed in the PM and SC of 4-week-old, but not 8-week-old SH rats. These findings show a transient elevation in rate of 5-HT synthesis prior to the onset of hypertension, which does not appear to continue during the maintenance phase.
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PMID:In vivo rate of serotonin synthesis in brain and spinal cord of young, spontaneously hypertensive rats. 75 7

5-Hydroxytryptamine (5-HT) administered intraventricularly (i.vent.) in rats produced hypertension without considerable changes in heart rate. After transsection of the spinal cord or i.vent. administration of methysergide, 5-HT failed to produce the pressor effect. Thus, the hypertension results from the activation of 5-HT receptor sites of the rat brain.
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PMID:Hypertension mediated by the activation of the rat brain 5-hydroxytryptamine receptor sites. 97 59

In rats anestetized with urethane and under ganglionic blockade by hexamethonium (20 mg/kg, i.v.), the i.v. injection of serotonin (60 mug/kg) determined apnea, ECG alterations and a brief hypotensive response which is similar to that as elicited when 5-HT is given to intact rats. During the hypertension which follows that initial response, apnea is still present along with more severe ECG changes. After that, blood pressure falls into a prolonged hypotension, which is invariably accompanied by death. Neither norepinephrine, nor respiratory analeptics (CoramineR, RemeflinF) were able to prevent the fatal outcome. Only artificial respiration was found to be useful in some instances. It was concluded that the association serotonin plus lidocaine becomes lethal when given to ganglion-blocked rate, and this toxic effect can be ascribed mainly to the respiratory depressor activity of the drugs.
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PMID:Lethal effect of the serotonin-xylocaineR association in ganglion-blocked rats. 101 1

A cardiogenic hypertensive chemoreflex was studied in 38 anesthetized and three unanesthetized dogs. Serotonin (100 mug/ml) injected into either the left atrium or small brancehes of the proximal left coronary artery produced a maximal response, with 96 +/- 18 mm Hg increment in mean aortic pressure within 6 +/- 2 seconds, lasting about 1 min; a later phase of the same hypertension lasted 9 +/- 5 minutes more and could partially be produced with serotonin injected into the thoracic aorta. Injections into the distal left coronary artery produced only the Bezold-Jarisch reflex. Concomitant with the immediate hypertension there were vagal and sympathetic efferent effects in both the sinus node and the atrioventricular (A-V) junction. Either of these effects could be selectively eliminated and the other augmented by direct local perfusion with an appropriate cholinergic (atropine 10 mug/ml) or adrenergic beta-receptor (propranolol 10 mug/ml) blocking agent. Bilateral vagotomy markedly attenuated but did not eliminate the acute hypertension, but it abolished both chronotropic and dromotropic effects. Phentolamine (2 mg/min i.v.) markedly diminished the hypertensive response. Guanethidine or reserpine pretreatment markedly diminished the hypertensive response; reserpine eliminated the electrophsiologic effects but guanethidine did not. Infiltration of serotonin around the main left coronary partially reproduced the reflex, but similar infiltration of xylocaine hydrochloride blocked the reflex. Serial section histologic studies of the region around the main left coronary atery in seven dog hearts and nine human hearts demonstrated the presence of a small structure resembling a chemoreceptor; its blood supply originated from the left coronary artery. Some possible clinical implications are discussed.
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PMID:Analysis of components in a cardiogenic hypertensive chemoreflex. 114 1

The effects of intracerebroventricular injections of 5,6-DHT on the development and maintenance of hypertension in spontaneously hypertensive rats has been investigated. 5,6-DHT, injected into 6 week old rats, retarded the development of hypertension for at least 6 weeks; this effect was not accompanied by inhibition of the pressor response produced by stimulation of the total peripheral sympathetic outflow. 5,6-DHT, injected into 14-15 week old rats with established hypertension, produced a short-lived fall in blood pressure. These findings suggest that central 5-HT neurones are involved in the development of hypertension in spontaneously hypertensive rats.
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PMID:Effect of intracerebroventricular 5,6-dihydroxytryptamine on blood pressure of spontaneously hypertensive rats. 127 31

There is considerable evidence that on the anterior surface of the heart (which is usually supplied by the left anterior descending and the proximal part of the left circumflex coronary arteries), sympathetic efferent reflexes characterized by tachycardia and/or hypertension predominate following experimental or pathological perturbations. These cardiovascular reflexes are accompanied by an increase in presumed nociceptive afferent traffic and, in pathological condition, by pain. In these experiments, there is generally no effect of vagotomy on afferent nerve traffic, and lower cervical and upper thoracic sympathectomies help provide relief from angina. On the other hand, experimental or pathological perturbations involving the inferior-posterior surface of the heart (supplied by the right and distal parts of the left circumflex coronary arteries), are characterized by vagal efferent reflexes, resulting in bradycardia and/or hypotension. These reflexes are accompanied by an increase in vagal afferent nerve traffic and, in pathological conditions, by pain. In these experiments, vagotomy generally abolishes such cardiovascular reflexes, and lower cervical and upper thoracic sympathectomies are not effective in the relief from angina. Although cardiac sympathetic afferents are unquestionably involved in the central transmission of nociceptive information from the heart, it is also likely that there is a contributing role from the vagus in cardiac pain. It is important experimentally to understand the natural stimulus that gives rise to angina. In the clinical situation, a decrease in coronary blood flow or an increase in the metabolic demands of the myocardium due to increased work are obvious precipitating factors which lead to myocardial ischemia. In the experimental situation, occlusion of the coronary arteries is often used as a stimulus which mimics myocardial ischemia. As people who frequently experience angina have varying degrees of coronary artery disease, it is difficult to accept that the state of the coronary arteries of the normal experimental animal bear any resemblance to the state of the coronary arteries under pathological conditions. That is, the gain of homeostatic reflexes, the basal concentrations of neuroactive substances in the plasma, the myocardium and the afferent terminals, the excitability of the afferents, access of chemical mediators (e.g. bradykinin, 5-HT, adenosine, histamine, prostaglandins, potassium, lactate), to afferents, and the overall function of the animal are all significantly different. We have no idea how control mechanisms have been altered in the person with severe coronary artery disease compared to the normal patient or the "normal" experimental animal.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:A critical review of the afferent pathways and the potential chemical mediators involved in cardiac pain. 135 Dec 70

1. The abilities of various serotonergic drugs to bind with the 5-HT receptor of Ascaris suum muscle and to affect cyclic AMP levels in muscle tissue were examined. 2. Ligands which selectively interact with either the 5-HT1 or the 5-HT2 receptor in mammalian systems interact with the 5-HT receptor from A. suum muscle and increase cyclic AMP levels. 3. No binding of 5-HT3 ligands to 5-HT receptors from A. suum muscle was observed. 4. The 5-HT receptor of A. suum muscle should be called the 5-HTN (for Nematoda) receptor because its pharmacological and biochemical behaviors were different from those of mammalian 5-HT receptors.
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PMID:Identification of a novel 5-HTN (Nematoda) receptor from Ascaris suum muscle. 135 23


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