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  • 1
    Electronic Resource
    Electronic Resource
    Fasting or dexamethasone treatment reduce protease content in rat lung mast cells and modulation of histamine synthesis by H3 receptors (1994)
    Springer
    Inflammation research 42 (1994), S. 7-12 
    Details
    ISSN: 1420-908X
    Keywords: Rat mast cell proteases ; Histamine presynaptic receptor ; Dexamethasone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The sensitivity of mast cells to H3-receptor modulation was studied in rat lung under various hormonal conditions. The heterogeneity of mast cell subpopulations in rat lung was assessed by the tissue content of rat mast cell protease I (RMCP I) and rat mast cell protease II (RMCP II). After 24 h fasting, concentrations of RMCP I were unchanged whereas the concentration of RMCP II was significantly reduced by 49%. The [3H]histamine (HA) synthesis was concomitantly decreased by 35%. In addition, the modulation of [3H]HA, synthesis by the H3 receptor agonist, (R)α-methylHA and by the antagonist, thioperamide, observed in control rats, was lost in fasted rats. Single and repeated, administrations of dexamethasone did not influence RMCPI concentrations, but decreased the concentrations of RMCP II with a parallel decrease in [3H]HA synthesis. The inhibitory effect of (R)α-methylHA on [3H]HA synthesis was also reduced. These results suggest that a subpopulation of RMCP II-containing mast cells, very sensitive to environmental factors, could be the mast cells synthesizing HA in an H3-receptor-dependant manner.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02014292
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  • 2
    Electronic Resource
    Electronic Resource
    Guinea Pig Histamine H1 Receptor. II. Stable Expression in Chinese Hamster Ovary Cells Reveals the Interaction with Three Major Signal Transduction Pathways (1994)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 62 (1994), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: A cDNA encoding a guinea pig histamine H1 receptor was stably expressed in Chinese hamster ovary (CHO) cells. In one resulting clone, named CHO(H1), the H1 receptor was found to be coupled to several major signal transduction pathways. In each case the involvement of a Gi/Go protein with pertussis toxin (PTX) was assessed, as well as the influence of extracellular Ca2+ and of protein kinase C activation by phorbol 12-myristate 13-acetate (PMA). Histamine induced, in a PTX- and PMA-insensitive manner, a biphasic increase in the intracellular Ca2+ level of which only the second sustained phase was dependent on the extracellular Ca2+ level. Histamine also caused a threefold elevation of inositol phosphate production, which was PTX-insensitive, but slightly inhibited by PMA and reduced by 75% in the absence of extracellular Ca2+. Histamine also caused a massive release of arachidonic acid, which occurred in a Ca2+- and PMA-sensitive manner, probably through the activation of a cytosolic phospholipase A2, which partly involves coupling to a PTX-sensitive G protein. In comparison, in HeLa cells endowed with a native H1 receptor, the histamine-induced arachidonic acid release was also Ca2+- and PMA-sensitive, but totally PTX-insensitive. Finally, in CHO(H1) cells, histamine in very low concentrations potentiated the cyclic AMP accumulation induced by forskolin. This response appeared to be insensitive to PTX, extracellular Ca2+, and PMA. These various observations show that stimulation of a single receptor subtype, the guinea pig H1 receptor, can trigger four major intracellular signals through coupling to several G proteins that are variously modulated by extracellular Ca2+ and protein kinase C activation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1994.62020519.x
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  • 3
    Electronic Resource
    Electronic Resource
    Pharmacological Characterization and Autoradiographic Localization of Histamine H2 Receptors in Human Brain Identified with [125I]Iodoaminopotentidine (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 59 (1992), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 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 antagonists that displayed apparent dissociation constants closely similar to corresponding values at the reference biological system, i.e., guinea pig atrium. This indicates that the pharmacology of the H2 receptor is the same in the human brain as on this reference system. However, histamine was about 10-fold more potent in inhibiting 125I-APT binding to membranes of human brain than of guinea pig brain. 125I-APT binding was also inhibited by amitriptyline and mianserin, two antidepressant drugs, in micromolar concentrations corresponding to effective plasma concentrations of treated patients. The distribution of H2 receptors was established autoradiographically with 125I-APT on a series of coronal sections of human brain after assessing the pharmacological specificity of the labeling. The highest density of 125I-APT sites was found in the basal ganglia, various parts of the limbic system, e.g., hippocampus or amygdaloid complex, and the cerebral cortex. H2 receptors displayed a laminar distribution in cerebral cortex and hippocampal formation. A low density of sites was found in cerebellum as well as in hypothalamus, the brain area where all the perikarya and the largest number of axons of histaminergic neurons are found. The widespread distribution of H2 receptors in the human brain is consistent with the alleged modulatory role of histamine mediated by this subtype of receptor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1992.tb08903.x
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  • 4
    Electronic Resource
    Electronic Resource
    Design of an Affinity Matrix for Purification of the Histamine H1 Receptor from Guinea Pig Cerebellum (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 58 (1992), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: H1 receptors from guinea pig cerebellum were solubilized using digitonin, and [125I]iodobolpyramine was used as a probe. [125I]Iodobolpyramine binding to this solubilized preparation occurred with a KD of 0.1 nM and a Bmax of 220 fmol/mg of protein and was inhibited by various H1 ligands with the expected potencies. Using a gel filtration procedure, a very sensitive radioassay was set up for detecting H1 activity in the solubilized preparation: 0.1 nM[125I]iodobolpyramine specific binding represented 〉90% of total binding. Moreover, the synthesis is described of potent H1 antagonists that are mepyramine derivatives with an amino alkyl acylamido alkyl spacer arm. One of them, UCL 1057 (Ki= 0.5 nM), has been coupled to a Sepharose epoxy-activated resin. The resulting affinity matrix adsorbed selectively [125I]iodobolpyramine binding sites from the guinea pig cerebellum soluble preparation. In contrast, a Sepharose–glycine matrix was not able to adsorb these sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1992.tb09317.x
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  • 5
    Electronic Resource
    Electronic Resource
    Guinea Pig Histamine H1 Receptor. I. Gene Cloning, Characterization, and Tissue Expression Revealed by In Situ Hybridization (1994)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 62 (1994), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: An intronless DNA encoding the guinea pig H1 receptor was cloned from a genomic library using probes derived from the bovine H1 receptor. It encodes a protein of 488 amino acids with a calculated molecular mass of 55,619 daltons compared with a size of 56–68 kDa for the photoaffinity-labeled receptor as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. The protein displays a 66% homology with the bovine receptor. Stable expression of the H1 receptor, characterized by the appearance of [3H]mepyramine binding sites with a pharmacology similar to that of the native H1 receptor, was obtained following transfection of Chinese hamster ovary cells. Southern blot analysis, using a variety of restriction enzymes, did not provide any evidence of multiple H1 isoreceptors. Northern blot analysis of a variety of guinea pig peripheral or cerebral tissues identified, in most cases, a single transcript of 3.3 kb, but also, in some tissues, a second transcript of 3.7 kb, possibly generated by the use of different promoter or polyadenylation sites or corresponding to a transcript from a distinct gene. In situ hybridization studies showed the highly contrasted cerebral expression of H1-receptor gene transcripts, which was compared with autoradiographic receptor localization. This allowed the identification of some major cell populations expressing the H1 receptor, e.g., Purkinje cells in cerebellum or pyramidal cells in the hippocampal complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1994.62020507.x
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of Dopaminergic Transmission Interruption on the D2 Receptor Isoforms in Various Cerebral Tissues (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 58 (1992), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: We examined the effects of an interruption of dopamine neurotransmission, by either dopamine receptor blockade or degeneration of dopamine neurons by 6-hydroxydopamine, on the levels of D2 receptor mRNAs. In addition, we evaluated by the polymerase chain reaction (PCR) the relative abundance of the two D2 receptor isoform mRNAs generated by alternative splicing. Daily injections of 4 mg/kg of haloperidol to rats elicited in striatum a rapid and progressive increase in D2 receptor mRNA levels, which reached 70% after a 15-day treatment. By contrast, there was no apparent change in D2 receptor mRNA levels in cerebral cortex and pons-medulla, in spite of an increased density of D2 receptor in the former tissue. Using the PCR with primers flanking the alternative exon, we observed that the relative proportion of the shorter receptor isoform (D2s) mRNA was slightly but significantly enhanced in cerebral cortex (17%) and pons-medulla (18%) after a 15-day haloperidol treatment. Unilateral degeneration of dopamine neurons induced by local injection of 6-hydroxydopamine resulted in a marked decrease in levels of total D2 receptor mRNAs in substantia nigra (—79%) and ventral tegmental (—63%) area, two cell body areas. In the substantia nigra, the longer isoform (D2l) mRNA was significantly more decreased in content than the D2s isoform mRNA, so that there was a large enhancement in the relative abundance of the latter (81%). In contrast, the lesion did not result in any significant change in levels of total D2 receptor mRNAs in striatum, but the relative proportion of D2s receptor mRNA tended to decrease—although nonsignificantly—as a result of a tendency of the D2l receptor mRNA abundance to rise. The present study establishes that two distinct processes of D2 receptor gene expression accompany and may contribute to the hypersensitivity known to develop at D2 receptors following either their chronic blockade by neuroleptics or dopamine denervation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1992.tb09770.x
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  • 7
    Electronic Resource
    Electronic Resource
    Dopaminergic Regulation of Enkephalin Release (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 56 (1991), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The effects of dopamine receptor stimulation on enkephalin release were evaluated in vitro and in vivo by measuring the changes in the levels of [Met5]enkephalin (YGGFM) and Tyr-Gly-Gly (YGG), a characteristic extracellular enkephalin metabolite produced under the action of enkephalinase. In rat striatal slices, D1-receptor agonists or antagonists did not modify enkephalin release. By contrast, D2-receptor agonists enhanced the potassium-induced release of YGGFM and YGG without affecting spontaneous release from nondepolarized slices. This response was prevented by the D2-receptor antagonists haloperidol and RIV 2093, the latter compound being more potent, which suggested the involvement of a putative D2-receptor subtype. Acute administration of apomorphine or selective D2-receptor agonists, but not that of a D1-receptor agonist, enhanced the steady-state level of YGG without affecting the YGGFM level in rat striatum. The effect was blocked selectively by D2-receptor antagonists which, administered alone, had no effect. These observations indicate that D2-receptor stimulation in vitro or in vivo facilitates enkephalin release from striatal neurons, but that endogenous dopamine does not exert any tonic influence upon the opioid peptide neuron activity under basal conditions. However, chronic administration of haloperidol resulted in increases in striatal YGGFM and YGG, an effect presumably reflecting a long-term adaptive process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1991.tb11434.x
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  • 8
    Electronic Resource
    Electronic Resource
    Histamine H1-Receptor in Heart: Unique Electrophoretic Mobility and Autoradiographic Localization (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 55 (1990), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Histamine H1-receptors, visualized in the guinea pig heart by autoradiography using [125I]iodoboipyramine as a specific probe, are abundant in the nodal tissue and cardiac vessels but also occur heterogeneously in the myocardium. Following photoaffinity labeling with [125I]iodoazidophenpyramine and electrophoresis, the ligand binding domain of the heart H1-receptor was shown to be present on a major 68-kDa and a less abundant 54- to 58-kDa protein. The 68-kDa protein displayed a molecular size higher in heart than in all other tissues (56 kDa). This indicates the existence of at least two isoforms of the H1-receptor; the cardiac isoform, however, was pharmacologically indistinguishable from the common isoform studied in cerebellar membranes using available ligands. Its distinct electrophoretic properties suggest that the cardiac isoform may have a unique function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1990.tb04148.x
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  • 9
    Electronic Resource
    Electronic Resource
    Opposing Roles for Dopamine D2 and D3 Receptors on Neurotensin mRNA Expression in Nucleus Accumbens (1994)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 6 (1994), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Using in situ hybridization histochemistry in rat nucleus accumbens, we show that the dopamine D3 receptor mRNA is expressed in the ventromedial part of the shell subdivision, where its gross distribution matches that of neurotensin mRNA. In addition, hybridization studies at the cellullar level show that a large fraction of the neurotensin neurons co-express the D3 receptor mRNA in this restricted area. In contrast, the dopamine D2 receptor mRNA is expressed mainly in the core and marginally in the shell, at the level of the cone. In rats treated by haloperidol and sulpiride, two D2-like receptor antagonists, but not by SCH 23390, a D1-like receptor antagonist, proneurotensin mRNA was increased in the D2 receptor mRNA-rich areas but decreased in the D3 receptor mRNA-rich areas. This suggests that the D2 and D3 receptors control neurotensin mRNA expression negatively and positively, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.1994.tb00329.x
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  • 10
    Electronic Resource
    Electronic Resource
    Effects of acetorphan, an antidiarrhoeal enkephalinase inhibitor, on oro-caecal and colonic transit times in healthy volunteers (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Alimentary pharmacology & therapeutics 6 (1992), S. 0 
    Details
    ISSN: 1365-2036
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Acetorphan is a potent enkephalinase inhibitor displaying antidiarrhoeal activity attributable to its intestinal antisecretory action mediated by endogenous enkephalins. The effect of acetorphan on digestive motility was studied in 12 healthy volunteers. Oro-caecal transit time was evaluated using the sulphasalazine/sulphapyridine method and colonic transit times using radiopaque markers. These measurements were successively performed after one week treatment with an antidiarrhoeal dose of acetorphan (100 mg t.d.s.) or placebo. There was no significant modification in transit time linked to acetorphan treatment: total orocaecal times were 303 ± 32 min vs. 287 ± 27 min and colonic transit times 25.8 ± 5.8 h vs. 31.3 ± 5.5 h after acetorphan and placebo, respectively (means ± S.E.M.). There was no significant modification either in right colonic, left colonic or rectosigmoid segmental transit times, or in the mean number of stools. These results, consistent with those from animal studies, confirm that, unlike classical antidiarrhoeal mu opiate receptor agonists, which act by delaying intestinal transit, acetorphan does not affect the transit. Antidiarrhoeal activity not accompanied by a delayed intestinal transit could have beneficial therapeutic consequences in the management of infectious diarrhoea. In addition, we show that the sulfphasalazine and radiopaque markers methods can be simultaneously applied in the same study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2036.1992.tb00052.x
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