Healing and prevention of relapse of reflux oesophagitis by cisapride.

Altogether, 138 patients were included in a study aimed at evaluating the effect of cisapride on healing and relapse of oesophagitis shown endoscopically. In the first phase of the study cisapride was given in an open fashion at 10 mg four times a day for 8 to 16 weeks, and healing was obtained in 69% of patients. Healing occurred later in patients with grades II to IV oesophagitis. The total score for reflux symptoms decreased by 67%. Eighty of the healed patients were included in the second phase. They were randomly assigned to double blind treatment with either cisapride 10 mg (n = 37) or placebo (n = 43) twice a day. Control endoscopy was performed when symptoms recurred or at the end of the six month trial. The cumulative percentage of patients in remission was higher (p = 0.06, survival analysis) in the cisapride group than in the placebo group, the relapse rates being 20% and 39%. The duration of remission tended to be longer in patients with a lower initial degree of oesophagitis. Adverse effects were no more frequent with cisapride than with placebo. In conclusion, cisapride is efficacious in healing oesophagitis, and, unlike other gastrointestinal prokinetic drugs or low dose cimetidine (400-800 mg daily) or ranitidine (150 mg daily), it may prevent relapse of oesophagitis.

Lymphocytic gastritis--prospective study of its relationship with varioliform gastritis.

Lymphocytic gastritis is a new histopathological entity characterised by a dense lymphocytic infiltration of surface and pit gastric epithelium. Previous retrospective work has suggested that lymphocytic gastritis is related to an endoscopic form of gastropathy comprising enlarged folds, nodules and erosions, commonly denoted as varioliform gastritis. In the present prospective study, the relationship is clearly shown; nearly 82% (54/66) of the varioliform gastritis observed in four different endoscopy units correspond histologically to lymphocytic gastritis. The correlation is even better if cases showing strictly antral localisation are excluded (53/55) - that is, more than 96%. The histological concept of lymphocytic gastritis seems, however, to extend beyond varioliform gastritis as of 67 cases of lymphocytic gastritis diagnosed during the period under study, one third had no particular endoscopic expression.

GABA induces down-regulation of the benzodiazepine-GABA receptor complex in the rat cultured neurons.

Cultured neurons from embryonic rat brain display central type benzodiazepine receptors characterized by high-affinity binding of [3H]flunitrazepam which is allosterically enhanced in the presence of gamma-aminobutyric acid (GABA). A 48 h treatment of the cultured neurons with 1 microM diazepam, 0.1 microM clonazepam or 0.1 microM beta-carboline ester derivatives did not change either Bmax or KD values of the [3H]flunitrazepam specific binding. A 48 h incubation in the presence of GABA (1 mM) or muscimol (0.1 mM) induced a 30% decrease of the Bmax value of [3H]flunitrazepam specific binding without change of the KD value. The down-regulation was dependent on GABA concentrations and temperature, and was partially inhibited by bicuculline but not by the benzodiazepine antagonist Ro 15-1788. The other subunits of the benzodiazepine-GABA-chloride channel receptor complex also seemed to be down-regulated by GABA since there was a decrease of the specific binding of [3H]muscimol and [35S]t-butylbicyclophosphorothionate (TBPS) to the GABAA and chloride channel sites respectively. The GABA-induced down-regulation of the GABA-benzodiazepine receptor seems to be selective since the specific binding of ligands to other receptors was not affected. Our results suggests that activation of the low-affinity GABA subunit which is involved in cellular electrophysiological responses, induced the receptor down-regulation.

Benzodiazepine receptors on cultured neurons: Binding with different [(3)H]ligands on homogenized and intact cells.

Benzodiazepine receptors have been studied on primary neuronal culture of foetal rat brain using different labelled ligands. The agonists [(3)H]flunitrazepam and [(3)H]diazepam, the inverse agonist [(3)H]methyl-?-carboline-3-carboxylate and the antagonist [(3)H]Ro 15-1788 were used. The binding properties of these ligands to homogenate from cultured neurons are very similar to those determined on receptors mediating the pharmacological effects of benzodiazepines in the brain. The [(3)H]ligands behaved differently when the binding was performed with intact cells. Among them, [(3)H]Ro 15-1788 offers two advantages making it fitted for binding to intact cells: it shows a low non-specific binding and a specificity for "central type" of benzodiazepine receptors. On the contrary, [(3)H]diazepam is useless because of its high non-specific binding. In cultured neurons the benzodiazepine receptors are coupled to GABA receptors: this is shown by the enhancement of [(3)H]flunitrazepam binding by GABA and its reduction by bicuculline.

Differentiation between ligand trapping into intact cells and binding on muscarinic receptors.

Binding properties of [3H] dexetimide , L-quinuclidinyl[phenyl-4-3H] benzilate and [3H]methylscopolamine were compared with intact 108 CC 15 cells and membrane preparations of those. The ability of the three ligands to label specifically muscarinic receptors on membrane fractions was quite similar. By contrast, when performed with intact cells, [3H] dexetimide and L-quinuclidinyl [phenyl-4-3H]benzilate revealed higher nonspecific binding which was prevented by methylamine, suggesting a trapping of the ligands within the cells presumably in the lysosomes. To the contrary, such nonspecific 'binding' or trapping was not detectable when [3H]methylscopolamine was used as ligand, a fact which makes this ligand particularly appropriate for labelling cell surface muscarinic receptors. It is concluded that more caution is needed in binding studies when performed with intact cells; indeed, besides specific binding on receptor sites, [3H]ligand can be entrapped within the cell and can even sometimes give the illusion of specific binding. The use of lysosomal agents which do not interfere with specific receptors on membrane preparations should allow one, in most cases, to discard the possibility of a trapping phenomenon in intact cells.

Trapping of labelled ligands in intact cells: a pitfall in binding studies.

Binding on/in whole cells seems to be a more appropriate approach for studying receptor sites in physiological conditions. However, certain difficulties encountered throughout the characterization of [3H]spiperone binding in human lymphocytes led us to reconsider this problem. The IC50 values of [3H]spiperone binding to human lymphocytes did not correlate with those found in rat striatum; domperidone was inactive in lymphocytes whereas it is one of the most potent dopamine antagonists in rat striatal preparations in vitro. In contrast, chloroquine, a lysosomotropic drug, displaced [3H]spiperone at low concentration in intact lymphocytes but did not in the striatum. [3H]Spiperone binding was not displaceable in the membrane preparation of lymphocytes. Similar results were obtained with other intact cells, fibroblasts, hepatocytes and neuroblastoma cells using [3H]spiperone and other ligands, such as [3H]haloperidol, [3H]pyrilamine and [3H]ketanserin. Here again, displaceable binding was only present in intact cells but not in membrane fractions. Such a 'displaceable' binding was not related to receptor sites but may be regarded as non-specific binding which should correspond to a trapping phenomenon presumably in the lysosomes. Binding studies on intact cells need more caution than when performed on membrane preparations; indeed, permeation or trapping of ligands in the nanomolar range represents a serious drawback which, sometimes, can give the illusion of specific binding.

Short-term disappearance of muscarinic cell surface receptors in carbachol-induced desensitization.

A rapid carbachol-induced disappearance of muscarinic cell surface receptors was shown using [3H]methyl scopolamine as ligand on intact 108CC15 hybrid cells or rat cerebellar cells. This phenomenon is temperature-dependent, correlated to agonist stimulation and reversible. In these short time periods (less than or equal to 30 min), no change was observed in the total receptor amount measured on membrane preparations. This disappearance of cell surface receptors could represent the first event in cell desensitization which could be followed by receptor recycling in physiological conditions or by receptor degradation if the stimulation by agonists persists, as in long-term regulation.