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  • Histamine H3 receptors  (3)
  • PACS. 77.84.Nh Liquids, emulsions, and suspensions; liquid crystals - 61.30.Cz Theory and models of liquid crystal structure - 61.30.Jf Defects in liquid crystals  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Potencies of antagonists chemically related to iodoproxyfan at histamine H3 receptors in mouse brain cortex and guinea-pig ileum: evidence for H3 receptor heterogeneity? (1996)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 353 (1996), S. 482-488 
    Details
    ISSN: 1432-1912
    Keywords: Key words3H-Nα-Methylhistamine binding ; Mouse brain cortex slices ; Guinea-pig ileum strips ; Histamine H3 receptors ; Iodoproxyfan ; Noradrenaline release ; Acetylcholine release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We determined the affinities of 16 newly synthesized H3 receptor antagonists in an H3 receptor binding assay and the potencies of 12 of these compounds at functional H3 receptors in the mouse brain cortex and guinea-pig ileum. The compounds differ from histamine in that the C-C-N side chain is replaced by a chain of the structure C-C-C-O. The two major aims of the study were (1) to investigate whether the two functional H3 receptors are pharmacologically different and (2) to derive structure-activity relationships. The specific binding of 3H-Nα-methylhistamine to rat brain cortex membranes was monophasically displaced by each of the 16 compounds at pKi values ranging from 7.30 to 9.48. In superfused mouse brain cortex slices preincubated with 3H-noradrenaline, the electrically evoked tritium overflow was slightly decreased by iodoproxyfan and its deiodo analogue; this effect was counteracted by the H3 receptor antagonist clobenpropit. The other compounds did not affect the evoked tritium overflow by themselves. The concentration-response curve of histamine for its inhibitory effect on the electrically evoked tritium overflow was shifted to the right by the 12 compounds with apparent pA2 values ranging from 7.02 to 9.00. The 12 compounds also shifted to the right the concentration-response curve of R-α-methylhistamine for its inhibitory effect on the electrically induced contraction in guinea-pig ileum strips; the apparent pA2 values ranged from 5.97 to 9.00. Iodoproxyfan decreased the electrically induced contraction by itself and this effect was counteracted by the H3 receptor antagonist thioperamide. The apparent pA2 values in the two functional H3 receptor models showed a highly significant correlation (r=0.882; P〈0.001). Highly significant correlations were also obtained when the pKi values of the compounds in the binding assay were compared to their apparent pA2 values in the mouse brain (r=0.799; P〈0.004) and in the guinea-pig ileum (r=0.851; P〈0.001). In each of the three experimental models, iodoproxyfan was the most potent compound; its deiodo analogue was less potent by more than 1.1 log units. The present results show that the compounds under study possess moderate to high affinity and/or (partial) H3 receptor antagonist potency. The two functional H3 receptors in the mouse brain cortex and the guinea-pig ileum may be slightly different; further studies are necessary to clarify whether this difference is due to H3 receptor heterogeneity, species variants or differences in the efficiency of receptor coupling. The marked difference in the affinity/potency between iodoproxyfan and its deiodo analogue may suggest that a highly lipophilic residue in that part of the molecule favours a high affinity/antagonistic potency at H3 receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169166
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Potencies of antagonists chemically related to iodoproxyfan at histamine H3 receptors in mouse brain cortex and guinea-pig ileum: evidence for H3 receptor heterogeneity? (1996)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 353 (1996), S. 482-488 
    Details
    ISSN: 1432-1912
    Keywords: 3H-N a -Methylhistamine binding ; Mouse brain cortex slices ; Guinea-pig ileum strips ; Histamine H3 receptors ; Iodoproxyfan ; Noradrenaline release ; Acetylcholine release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We determined the affinities of 16 newly synthesized H3 receptor antagonists in an H3 receptor binding assay and the potencies of 12 of these compounds at functional H3 receptors in the mouse brain cortex and guinea-pig ileum. The compounds differ from histamine in that the C-C-N side chain is replaced by a chain of the structure C-C-C-O. The two major aims of the study were (1) to investigate whether the two functional H3 receptors are pharmacologically different and (2) to derive structure-activity relationships. The specific binding of 3H-N a -methylhistamine to rat mine for its inhibitory effect on the electrically induced contraction in guinea-pig ileum strips; the apparent pA2 values ranged from 5.97 to 9.00. Iodoproxyfan decreased the electrically induced contraction by itself and this effect was counteracted by the H3 receptor antagonist thioperamide. The apparent pA2 values in the two functional H3 receptor models showed a highly significant correlation (r=0.882; P〈0.001). Highly significant correlations were also obtained when the pKi values of the compounds in the binding assay were compared to their apparent pA2 values in the mouse brain (r=0.799; P〈0.004) and in the guinea-pig ileum (r=0.851; P〈0.001). In each of the three experimental models, iodoproxyfan was the most potent compound; its deiodo analogue was less potent by more than 1.1 log units. The present results show that the compounds under study possess moderate to high affinity and/or (partial) H3 receptor antagonist potency. The two functional H3 receptors in the mouse brain cortex and the guinea-pig ileum may be slightly different; further studies are necessary to clarify whether this difference is due to H3 receptor heterogeneity, species variants or differences in the efficiency of receptor coupling. The marked difference in the affinity/potency between iodoproxyfan and its deiodo analogue may suggest that a highly lipophilic residue in that part of the molecule favours a high affinity/antagonistic potency at H3 receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169166
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Ciproxifan and chemically related compounds are highly potent and selective histamine H3-receptor antagonists (1998)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 358 (1998), S. 623-627 
    Details
    ISSN: 1432-1912
    Keywords: Key words [3H]-Nα-methylhistamine binding ; Rat brain cortex membranes ; Mouse brain cortex slices ; Histamine H3 receptors ; Ciproxifan ; Iodoproxyfan ; Noradrenaline release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We determined the affinities of five newly synthesized histamine H3-receptor antagonists in an H3-receptor binding assay and their potencies in a functional H3-receptor model. Furthermore, we determined their potencies in a histamine H2- and H1-receptor model. The compounds differ from histamine in that the ethylamine side chain is replaced by an aryl-substituted propyloxy chain and they differ from one another by varying substituents of the aryl rest. Iodoproxyfan, a highly potent and selective antagonist at H3 receptors, is structurally related to these five compounds. The specific binding of [3H]-N α-methylhistamine to rat brain cortex membranes was monophasically displaced by each of the five compounds at pK i values ranging from 8.24 to 9.27. Inhibition by histamine of the electrically evoked tritium overflow from mouse brain cortex slices preincubated with [3H]noradrenaline was antagonized by all compounds and the concentration-response curve was shifted to the right with apparent pA 2 values ranging from 7.78 to 9.39. The five compounds under study possess negligible potencies at histamine H2 and H1 receptors studied in the guinea-pig right atrium and ileum, respectively (pD’2 or pK p values ≤5.2). The present paper shows that the five compounds under study possess high affinities and potencies at histamine H3 receptors, four out of the five compounds in this respect being equipotent with iodoproxyfan. Like iodoproxyfan, the five compounds show an at least 1000-fold selectivity for H3 as compared to H2 and H1 receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00005303
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  • 4
    Electronic Resource
    Electronic Resource
    Water droplets in a spherically confined nematic solvent: A numerical investigation (1999)
    Springer
    The European physical journal 10 (1999), S. 515-523 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 77.84.Nh Liquids, emulsions, and suspensions; liquid crystals - 61.30.Cz Theory and models of liquid crystal structure - 61.30.Jf Defects in liquid crystals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Recently, it was observed that water droplets suspended in a nematic liquid crystal form linear chains [Poulin et al., Science 275, 1770 (1997)]. The chaining occurs, e.g., in a large nematic drop with homeotropic boundary conditions at all the surfaces. Between each pair of water droplets a point defect in the liquid crystalline order was found in accordance with topological constraints. This point defect causes a repulsion between the water droplets. In our numerical investigation we limit ourselves to a chain of two droplets. For such a complex geometry we use the method of finite elements to minimize the Frank free energy. We confirm an experimental observation that the distance d of the point defect from the surface of a water droplet scales with the radius r of the droplet like .When the water droplets are moved apart, we find that the point defect does not stay in the middle between the droplets, but rather forms a dipole with one of them. This confirms a theoretical model for the chaining. Analogies to a second order phase transition are drawn. We also find the dipole when one water droplet is suspended in a bipolar nematic drop with two boojums, i.e., surface defects at the outer boundary. Finally, we present a configuration where two droplets repel each other without a defect between them.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510050881
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Director field configurations around a spherical particle in a nematic liquid crystal (1999)
    Springer
    The European physical journal 10 (1999), S. 311-321 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 77.84.Nh Liquids, emulsions, and suspensions; liquid crystals - 61.30.Cz Theory and models of liquid crystal structure - 61.30.Jf Defects in liquid crystals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We study the director field around a spherical particle immersed in a uniformly aligned nematic liquid crystal and assume that the molecules prefer a homeotropic orientation at the surface of the particle. Three structures are possible: a dipole, a Saturn-ring, and a surface-ring configuration, which we investigate by numerically minimizing the Frank free energy supplemented by a magnetic-field and a surface term. In the dipole configuration, which is the absolutely stable structure for micron-size particles and sufficiently strong surface anchoring, a twist transition is found and analyzed. We show that a transition from the dipole to the Saturn ring configuration is induced by either decreasing the particle size or by applying a magnetic field. The effect of metastability and the occurrence of hysteresis in connection with a magnetic field are discussed. The surface-ring configuration appears when the surface-anchoring strength W is reduced. It is also favored by a large saddle-splay constant K24. A comparison with recent experiments [#!itapdb:Poulin1997!#,#!itapdb:Poulin1998!#] gives a lower bound for W, i.e., for the interface of water and pentylcyanobiphenyl (5CB) in the presence of the surfactant sodium dodecyl sulfate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510050860
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    Paper (German National Licenses)
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