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  • 1
    ISSN: 1435-1463
    Keywords: 8-hydroxy-2-(di-n-propylamino)tetralin ; 5-HT ; blood pressure rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) is a new serotonin (5-HT) receptor agonist that binds selectively to the 5-HT1A binding site. In the present paper we investigated the cardiovascular effects of 8-OH-DPAT in the normotensive Sprague-Dawley rat and in the spontaneously hypertensive rat. The acute i.v. administration of 8-OH-DPAT (5–150Μg/kg) was in both rat strains associated with a biphasic blood pressure response and a bradycardia. The initial pressor response was due to a direct vascular effect of 8-OH-DPAT involving activation ofα-adrenoceptors since it was present in pithed rats and in reserpine pretreated rats and since it was attenuated by prazosin. The longer lasting hypotension was not due to a direct vascular relaxation or a presynaptic inhibition of transmitter release since the hypotension was not evident in pithed rats and since 8-OHDPAT did not influence the pressor responses to electrical stimulation in pithed rats. Rather, the combination of hypotension and bradycardia would suggest a central site of action although the intracerebroventricular (lat. ventricles) route of administration was not more efficient (to induce hypotension) than i.v. administration. At least the bradycardia was mediated by changes in vagal as well as sympathetic discharge since it was prevented by pretreatment with atropine and propranolol in combination but not by pretreatment with either agent alone. The cardiovascular effects of 8-OH-DPAT were not prevented by pretreatment with methergoline, methiothepin, pirenperone or cianserine or by 5-HT depletion by means of p-chlorophenylalanine, which suggests that the putative 5-HT receptor that is responsible for the hypotension and bradycardia to 8-OH-DPAT is not of a presynaptic type and does not have the pharmacological characteristics of a general 5-HT1 receptor.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1435-1463
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Chronic oral treatment (8 weeks) with the selective 5-hydroxytryptamine2 (5-HT2)-receptor blocking agent, ritanserin, did not reduce blood pressure in the spontaneously hypertensive rat (SHR) during basal conditions or during stress (jet air). In pithed rats the pressor responses to 5-HT but not to phenylephrine or sympathetic stimulation of the sympathetic outflow were completely antagonized. These observations indirectly suggests that the 5-HT2-receptor blocking properties of the antihypertensive agent ketanserin cannot alone account for the antihypertensive effects in SHR that are observed during chronic treatment with this agent.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2048
    Keywords: Anabaena ; Cyanobacteria ; Glutamine synthetase ; Immuno-gold localization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Localization of glutamine synthetase in thin sections of nitrogen-fixing Anabaena cylindrica was performed using immuno-gold/transmission electronmicroscopy. The enzyme was present in all of the three cell types possible; vegetative cells, heterocysts and akinetes. The specific gold label was always more pronounced in heterocysts compared with vegetative cells, and showed a uniform distribution in all three types. No specific label was associated with subcellular inclusions such as carboxysomes, cyanophycin granules and polyphosphate granules. When anti-glutamine synthetase antiserum was omitted, no label was observed.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 32 (1987), S. 259-265 
    ISSN: 1432-1041
    Keywords: ketanserin ; ketanserin-ol ; pharmacokinetics ; hypertension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of ketanserin and its main metabolite ketanserin-ol, and the antihypertensive effects of intravenous, single oral and chronic oral (40 mg once daily) administration of ketanserin, have been investigated in a single blind study of 10 patients with uncomplicated mild hypertension. Ketanserin had a terminal half-life of 29.2 h, a plasma clearance of 518 ml/min and a volume of distribution of 18.0 l/kg. Chronic oral intake of 40 mg ketanserin (tablet formulation) gave a peak concentration of unchanged ketanserin of 88 ng/ml after 1.1 h. Its absolute bioavailability was 48%. During chronic therapy the maximal concentration of ketanserin-ol was 208 ng/ml and its half-life of elimination was 35.0 h. As this metabolite can be oxidized back to ketanserin, it contributes to the prolonged half-life of unchanged ketanserin seen during chronic therapy. The blood pressure was reduced by approximately 15% by oral ketanserin. The maximal reduction in blood pressure coincided with the peak concentration of unchanged ketanserin. During chronic therapy with 40 mg once daily blood pressure was reduced over 24 h. The heart rate was slightly reduced and the cardiovascular responses and the plasma noradrenaline concentrations during isometric exercise were only slightly influenced by ketanserin therapy. Thus, unchanged ketanserin has a relatively long half-life during chronic oral therapy and its pharmacokinetics in middle-aged hypertensive patients is similar to that in normal young volunteers.
    Type of Medium: Electronic Resource
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