Search results for "Histamine H2 receptor"
showing 10 items of 20 documents
Loss of striatal histamine H2receptors in Huntington's: Chorea but not in Parkinson's disease: Comparison with animal models
1993
Autoradiographic techniques were used to study the distribution of histamine H2-receptors as labeled with [125I]iodoaminopotentidine in the brains of patients affected by human neurodegenerative pathologies, as compared with control cases. The highest levels of histamine H2 binding sites in control cases were found in the caudate, putamen, and accumbens nuclei. In Huntington's chorea, the levels of histamine H2 receptor binding sites were found to be markedly decreased in virtually all regions examined, particularly in the putamen and globus pallidus lateralis. The loss of binding sites was related to the grade of the disease. Losses were more marked in grade III disease cases. The possible…
Effect of histamine and histamine analogues on human isolated myometrial strips.
1992
1. The effect of histamine and histamine H1- and H2-receptor agonists on isolated myometrium strips of premenopausal women has been examined. The effect of acetylcholine was also determined. 2. Histamine, 2-pyridylethylamine, 4-methylhistamine and acetylcholine, but not dimaprit, produced a concentration-related contractile response in human isolated myometrial strips. Histamine also produced a further contraction in human isolated myometrial strips precontracted with KCl (55 mM). 3. The contractile response to histamine was antagonized by the histamine H1-receptor antagonist, clemizole (0.1 microM) but was potentiated by the histamine H2-receptor antagonist, ranitidine (10 microM). Clemizo…
H2-Antihistaminika, 25. Mitt. Synthese und H2-antagonistische Wirkung monosubstituierter 1,2,4-Oxadiazol-3,5-diamine
1985
Es wurden die N3- bzw. N5-substituierten 1,2,4-Oxadiazol-3,5-diamine 4a-e und 5a-e dargestellt und auf Histamin-H2-antagonistische Aktivitat untersucht. H2-Antihistaminics, XXV: Synthesis and H2-Antagonistic Activity of Monosubstituted 1,2,4-Oxadiazole-3,5-diamines The N3-or N5-substituted 1,2,4-Oxadiazole-3,5-diamines 4a-e and 5a-e were prepared and tested for histamine H2-antagonistic activity.
Histamine-sensitive adenylate cyclase of human gastric mucosa: a model for H2-receptor excitation.
1978
Recent studies revealed that human gastric mucosa contains a histamine-sensitive adenylate cyclase which is almost completely localized within the acid-secreting area of the stomach. In an attempt to further characterize the effector system of histamine’s action, we compared the effects of H 1 — and H 2-receptor agonists upon the adenylate cyclase in human fundic gastric mucosa.
Lack of Association Between Rs2067474 Polymorphism in the Histamine Receptor H2 Gene and Gastric Cancer In Latvian Population
2018
Abstract Histamine has an important role in the process of the gastric mucosa inflammation acting via histamine receptor H2 (encoded by the gene HRH2). Single nucleotide polymorphism of the enhancer element of HRH2 gene promoter rs2067474 (1018G>A)may be associated with changes of expression of the receptor. We attempted to clarify the association of this polymorphism with gastric cancer and/or atrophic gastritis in the Latvian (Caucasian) population. The study group consisted of 121 gastric cancer patients and 650 patients with no evidence of gastric neoplasia on upper gastrointestinal endoscopy. Genotyping for rs2067474 was performed with the TaqMan probe-based system using a commercia…
Influence of hormonal treatment on the response of the rat isolated uterus to histamine and histamine receptor agonists.
1992
The response of the isolated uterus to histamine and histamine agonists was investigated in progesterone- and oestrogen-treated rats. The uterine inhibitory responses to histamine and 4-methylhistamine (a histamine H2 receptor agonist) were similar in KCl-contracted uteri from progesterone- and oestrogen-treated rats. The histamine H1 receptor agonist, 2-pyridyl-ethylamine, produced a relaxant response only in progesterone dominant uterus. This was inhibited by the histamine H1 receptor antagonist. In the rat isolated uterus which was not preconstricted by KCl, neither histamine, 4-methylhistamine, nor 2-pyridyl-ethylamine produced any effect in the presence or absence of ranitidine. Raniti…
Pharmacological characterization and autoradiographic localization of histamine H2 receptors in human brain identified with [125I]iodoaminopotentidin…
1992
125I-Aminopotentidine (125I-APT), a reversible probe of high specific radioactivity and high affinity and selectivity for the H2 receptor, was used to characterize and localize this histamine receptor subtype in human brain samples obtained at autopsy. On membranes of human caudate nucleus, specific 125I-APT binding at equilibrium revealed a single component, with a dissociation constant of 0.3 nM and maximal capacity of about 100 fmol/mg of protein. At 0.2 nM, 125I-APT specific binding, as defined with tiotidine, an H2-receptor antagonist chemically unrelated to iodoaminopotentidine, represented 40-50% of the total. Specific 125I-APT binding was inhibited by a series of typical H2-receptor…
Mealtime versus nighttime acid inhibition
1992
This study was carried out in order to compare the effects of mealtime and bedtime regimens of ranitidine on gastric acidity. Fifteen duodenal ulcer patients in clinical remission were randomized to receive in single-blind fashion either placebo, ranitidine 300 mg at night (2200 hr) or ranitidine 150 mg three times a day given before each of the three daily meals (1800, 0800 and 1200 hr). Over 24 hr, the two active treatments produced a significantly greater acid inhibition than placebo, while the single daily regimen was superior to the three times a day regimen of ranitidine in terms of both rise in pH values (P less than 0.001) and duration of action expressed as time spent above 3.0 pH …
Histamine binding to H2 receptors stimulates phospholipid methylation in mast cells
1982
Rat peritoneal mast cells incubated in vitro in the presence of L-[methyl-3H] methionine and exposed to histamine undergo a rapid but transient increase in phospholipid methylation. By using specific H1- and H2-receptor antagonists, and histamine analogues differing in their H2-receptor agonist potency, it has been demonstrated that this metabolic event is dependent on histamine binding to H2-receptors.
Effects of histamine on dentate granule cells in vitro
1990
Abstract Hippocampal slices from rat brain were exposed to histamine and related substances in a perfusion chamber. Granule cells of the dentate gyrus were studied with conventional extra- and intracellular recording and a single electrode voltage clamp. Histamine caused, through activation of H 2 -receptors, a small depolarization, an increase in the number of synaptic and action potentials, a block of the long lasting (but not the early) component of spike afterhyperpolarizations and a reduction of the accommodation of action potential firing. These effects were mimicked by forskolin (suggests activation of adenylate cyclase). In voltage clamp, histamine blocked a long lasting calcium-dep…