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

In the present paper the neuronal systems of the medulla oblongata containing phenylethanolamine-N-methyltransferase- and neuropeptide Y-like immunoreactivity have been characterized in adult (3-month-old) and old (24-month-old) male rats. The phenylethanolamine-N-methyltransferase and neuropeptide Y-immunoreactive neurons have been visualized by means of immunocytochemistry (peroxidase-antiperoxidase technique) and analysed in a quantitative fashion by means of morphometrical (phenylethanolamine-N-methyltransferase- and neuropeptide Y-immunoreactive cell groups) and microdensitometrical (phenylethanolamine-N-methyltransferase-immunoreactive cell groups) approaches developed on the IBAS II image analyser (Zeiss-Kontron). During aging there is (a) a reduction in the area covered by the phenylethanolamine-N-methyltransferase-immunoreactive neuropil for both the C1 and C2 adrenaline cell groups; (b) a reduction in the area covered by the phenylethanolamine-N-methyltransferase-immunoreactive cell bodies, which is highly significant only for the C2 cell group; (c) a decrease in the area covered by the phenylethanolamine-N-methyltransferase-positive cell cluster for both C1 and C2 cell groups; (d) a decrease in the degree of phenylethanolamine-N-methyltransferase immunoreactivity present in the C1 and C2 cell groups; (e) a decay of neuropeptide Y immunoreactivity in the C1 and C2 groups, while the C3 group is unaffected by aging as evaluated by number of phenylethanolamine-N-methyltransferase- and neuropeptide Y-immunoreactive cell body profiles. These results indicate heterogeneities in the responses of the adrenaline-neuropeptide Y cell groups to the aging process. The possible functional consequences of aging-induced changes in the cardiovascular adrenergic neurons are discussed, especially in relation to development of hypertension.
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PMID:Morphometrical and microdensitometrical studies on phenylethanolamine-N-methyltransferase- and neuropeptide Y-immunoreactive neurons in the rostral medulla oblongata of the adult and old male rat. 317 85

Histamine levels, histidine decarboxylase and histamine-N-methyltransferase activities were determined in various brain areas of young (9-week old) and adult (18-week old) normotensive rats (WKY) and hypertensive rats (SHR). When compared with WKY, histamine levels were increased in the anterior and posterior hypothalamus of young and adult SHR, as well as in the brainstem of young SHR. Histidine decarboxylase activity was unchanged in the posterior hypothalamus and in the medulla oblongata of young and adult SHR as well as in the anterior hypothalamus of young SHR, but it was slightly decreased in the anterior hypothalamus of adult SHR. Histidine decarboxylase activity was enhanced in the cortex-midbrain of young, as well as adult SHR, histamine-N-methyltransferase in the cortex-midbrain of young SHR. The following differences were found between young and adult rats: histamine levels were elevated in the cortex-midbrain of adult WKY and SHR. In the cortex-midbrain and brainstem of adult WKY and SHR histidine decarboxylase activity was also increased, while histamine-N-methyltransferase activity was elevated in the cortex-midbrain of adult WKY. The findings show changes in histamine levels, histidine decarboxylase and histamine-N-methyltransferase activities in SHR and suggest involvement of histaminergic neurons in hypertension. The activity of histaminergic neurons of adult rats seems to be higher than that of young animals.
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PMID:Histamine, histidine decarboxylase and histamine-N-methyltransferase in brain areas of spontaneously hypertensive rats. 324 96

A computer-assisted morphometrical and microdensitometrical analysis has been performed on cardiovascular noradrenaline (NA), adrenaline (A) and neuropeptide (Y (NPY) neurons in adult and 24-month-old male rats and on hypotensive (LL), normotensive (LN) and hypertensive (LH) male rats of the Lyon strain using the indirect immunoperoxidase procedures. It was found that in NPY/phenylethanolamine-N-methyltransferase (PNMT) costoring neurons of the CI area of the rostral medulla oblongata NPY-like immunoreactivity showed a more marked reduction than the PNMT immunoreactivity. Furthermore, within the parvocellular part of the paraventricular hypothalamic nucleus. NPY immunoreactive nerve terminal profiles were much more affected than the PNMT immunoreactive profiles during aging as revealed by a marked reduction in the number of profiles and by a marked reduction of absorbency values in the microdensitometrical analysis. Thus, in the NPY/PNMT costoring neurons of the A C1 group of the ventrolateral medulla projecting, for example, to the hypothalamus, the peptide transmission line may have a special vulnerability to the aging processes which may contribute to the development of hypertension in old people in view of a vasodepressor role of many central NPY/PNMT neurons. An extensive morphometrical and microdensitometrical analysis of the various catecholamine (CA) cell groups of the medulla oblongata of the LL, LN and LH rats of the Lyon strain was performed. In a comparison between LL and LH rats the A2 cell group of the LH strain showed a trend for an increase in the mean tyrosine hydroxylase (TH) immunoreactive cell body area and the C3 group showed a significant increase in the number of PNMT immunoreactive profiles.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Evidence for discrete alterations in central cardiovascular catecholamine and neuropeptide Y immunoreactive neurons in aged male rats and in genetically hypertensive male rats of the Lyon strain. 330 51

The activities of the catecholamine synthesizing enzymes have been determined in discrete brain areas and in peripheral tissues of rats, at different times after clipping the left renal artery (two-kidney Goldblatt hypertension, 2KGH) and in sham operated animals. Three days after clipping the only enzymatic change was a slight decrease in plasma dopamine-beta-hydroxylase (DBH) activity. Ten days after clipping no change in enzymatic activity was found at the central level. However, the DBH and the phenylethanolamine-N-methyltransferase (PNMT) activities were increased in the adrenal medulla (+49.0%, P less than 0.001 and +36.6%, P less than 0.001, respectively) and DBH activity was also increased in the superior cervical ganglia (+22.8%, P less than 0.01). These data suggest that sympathetic hyperactivity is present in 2KGH rats when hypertension is established. In addition, as this type of hypertension does not alter the PNMT activity in brainstem areas, it seems that the alterations in PNMT activity reported for genetically hypertensive rats are unlikely to be secondary to the elevated blood pressure.
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PMID:Central and peripheral catecholamine synthesizing enzymes during the development of two-kidney, one clip hypertension in rats. 615 68

Bilateral injection of the inhibitor of histamine-N-methyltransferase, SKF 91488, which is also known as homodimaprit (5 micrograms), into the preoptic area of the rat produced delayed hypertension, tachycardia and hyperthermia. Some animals exhibited pulmonary edema. These effects were only noted 18-24 hr after an injection and were not an artifact of the injection, since the administration of artificial cerebrospinal fluid produced none of these effects. At the time noted, lesions of the rostral hypothalamus, including the preoptic area, were evident. Injection of a vasopressin antagonist, intravenously, did not lower the blood pressure of the hypertensive animals nor did previous bilateral adrenal demullation prevent or delay the hypertension or tachycardia. Therefore, it does not appear that hypersecretion of either vasopressin or adrenal catecholamines contributed to the cardiovascular effects. Peripheral pretreatment with the sympathetic neurotoxin 6-hydroxydopamine however, did prevent the delayed rise in blood pressure following an injection of homodimaprit. From these studies, it is concluded that the injection of homodimaprit produces lesions in the preoptic area, resulting in hypertension that is maintained by excessive activation of the sympathetic nervous system.
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PMID:The effect of intrahypothalamic injection of homodimaprit on blood pressure. 623 59

Lesions in the tissue at the anteroventral end of the third ventricle (AV3V area) prevent the development of a variety of forms of experimental hypertension. This region receives afferents from several cell groups which have been implicated in cardiovascular regulation, including the nucleus of the solitary tract and neurons in the ventrolateral medulla. About 70% of the nucleus of the solitary tract neurons which could be retrogradely labeled from the AV3V area stained immunohistochemically for tyrosine hydroxylase, but not phenylethanolamine-N-methyltransferase, and were therefore presumably noradrenergic. About half of the neurons in the rostral part of the ventrolateral medulla which innervated the AV3V area stained for both enzymes, and thus were apparently adrenergic. These medullary catecholaminergic inputs to the AV3V area may be of importance in explaining recent data concerning the roles of both regions in experimental hypertension.
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PMID:Medullary catecholamine inputs to the anteroventral third ventricular cardiovascular regulatory region in the rat. 632 72

SKF 64139, an inhibitor of phenylethanolamine-N-methyltransferase (PNMT), has a marked hypotensive effect in models of sodium-dependent hypertension. The mechanism of this effect is obscure, the compound having in addition alpha-adrenoceptor blocking properties. We compared the acute effects of SKF 64139 with those of LY 134046, another PNMT inhibitor with minimal alpha-blocking capacity, in desoxycorticosterone-salt hypertensive rats. The former agent produced profound hypotension whereas the latter caused only bradycardia. Both induced a similar pronounced suppression of PNMT activity in the C1 and C2 region of the medulla oblongata. These results suggest that the alpha-adrenergic effect rather than PNMT inhibition accounts for the acute lowering of blood pressure in this model.
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PMID:Acute cardiovascular effects of two central phenylethanolamine-N-methyl-transferase inhibitors in unanesthetized desoxycorticosterone-salt hypertensive rats. 648 38

The enzymatic activities of dopamine-beta-hydroxylase (DBH) and phenylethanolamine-N-methyltransferase (PNMT) were determined in adrenals of spontaneously hypertensive rats (SHR) and controls of the Wistar-Kyoto-strain (WKY) of different ages. In SHR of all examined age groups (10, 14 and 26 weeks) lower enzyme activities were found than in WKY rats of the same ages. That was more evident for PNMT than for DBH, SHR show a clear asymmetric distribution or PNMT with higher values in the left adrenals. This concerns 10, 14 and 26-week-old animals. An asymmetric distribution of DBH with higher values in the right adrenals were shown only in 14 and 26 weeks old rats. The asymmetric distribution was generally more obvious in SHR. This fact could be related to changes in the control of the connections between hypophysis and adrenals during development of hypertension.
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PMID:[Asymmetrical content of dopamine-beta-hydroxylase and phenylethanolamine-N-methyltransferase in the adrenals of spontaneously hypertensive and normotensive Wistar-Kyoto rats]. 663 46

Sodium depletion, a maneuver that is accompanied by a 14-fold elevation of plasma renin activity (PRA), alters the norepinephrine concentration of the canine area postrema (AP), a circumventricular organ of the 4th ventricle known to be sensitive to circulating angiotensin II. The norepinephrine concentration of the AP after 3 weeks of sodium depletion decreased by 43%, whereas the concentration of epinephrine and dopamine and the activity of phenylethanolamine-N-methyltransferase (PNMT) did not change. In the pyramidal tract (PT) and choroid plexus (CP) catecholamines were present in significantly lower amounts than in the AP; their concentrations were unaffected by sodium depletion in the PT, but in the CP the norepinephrine concentration was reduced. Serotonin was present in the AP but its concentration was unaltered by sodium depletion. These findings provide evidence that sodium depletion produced an alteration in the concentration of norepinephrine of the area postrema without any change in the concentration of epinephrine, dopamine or serotonin.
Hypertension
PMID:Catecholamines and serotonin in the area postrema of normal and sodium-depleted dogs. 702 13

The New England Deaconess Hospital (NEDH) rat provides a valuable model with which to study pheochromocytoma (P); 59% of male rats 700 to 900 days old and 81% of those 900 days or older developed spontaneous P. One transplantable P (P259), when implanted into other NEDH rats, markedly increased plasma norepinephrine and dopamine as well as blood pressure, and usually caused death within 4 weeks. Even without P, about 83% of NEDH rats became hypertensive by 131/2 weeks of age and remained moderately hypertensive until 2 years of age when some animals developed spontaneous P and hypertension became severe. Whether a common mechanism is responsible for early appearance of hypertension and later development of P remains to be determined. Hypophysectomized NEDH rats remained normotensive or slightly hypotensive despite marked elevations of plasma norepinephrine and dopamine caused by P259 implantation; furthermore, survival was prolonged to 3 months. Catecholamine concentrations in plasma and RBC were usually quite similar, indicating that red blood cells play a significant role in inactivating circulating catecholamines. Unlike the normal adrenal, P259 in NEDH rats contains mainly norepinephrine and dopamine with little epinephrine; it appears that P259 is deficient in the enzyme phenylethanolamine-N-methyltransferase (PNMT), which converts norepinephrine to epinephrine. Why hypophysectomy prevents hypertension and prolongs life in rats with P259 implants is unclear; adrenal cortical and thyroid deficiency may play a role. Preliminary observations indicate that hypophysectomy can prevent spontaneous development of P in NEDH rats.
Hypertension
PMID:Effect of pheochromocytoma and hypophysectomy on blood pressure and catecholamines in NEDH rats. 706 5


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