Background/Aim: Based on animal models, lafutidine, a novel histamine H₂ receptor (H₂R) antagonist, is reported to show potent and long-lasting antagonisms of histamine H₂R-mediated effects. However, no reports have been published concerning its direct interaction with the human H₂R. This study aims at characterizing its interaction with human H₂R. Methods: Chinese hamster ovary cell lines stably expressing human H₂Rs were obtained. The dose-dependent effects of lafutidine and famotidine on [³H]tiotidine binding and histamine-stimulated cAMP production were analyzed. The effects of preincubation with 2.78 × 10^–7M of lafutidine or famotidine for 30 min on histamine-dependent cAMP production and [³H]tiotidine binding were also examined after 0, 1, 2, 4, and 12 h. This concentration is below the C_max of lafutidine (10 mg p.o.) and above the C_max of famotidine (20 mg p.o.). Results: Lafutidine inhibited [³H]tiotidine binding and histamine-stimulated cAMP production as or more potently than famotidine. At higher concentrations lafutidine was more potent than famotidine. In addition, preincubation with 2.78 × 10^–7M lafutidine, but not with 10^–5M famotidine, had marked inhibitory effects which persisted as long as after extensive washing. Conclusion: Lafutidine shows a potent and long-lasting antagonism on the human H₂R.

Works in iconicity (for example Bybee, 1985; Waugh and Newfield, in press;Haiman, 1980Haiman, , 1985aHaiman, , 1985b suggest a strong correspondence (a direct link) belween form and meaning based on their resemblance at all levels of language. One piece of evidence for such a correspondence is reduplication (Sapir, 1921;Moravcsik, 1978). This paper examines a 30minute tape-recorded conversation amongfour Japanese Speakers andshows that, similarly to reduplication, conversational repetition serves äs an iconic sign. The iconic meanings expressed by self-repetition and reduplication are intensity, Iteration, and continuation. This evidences a strong correspondence between form and meaning. Considering the interactional properties of meaning in discourse äs shown by Tannen (1985 and, l claim yet another meaning äs iconic, examining allo-repetition in what I call 'ajoint idea construction\ The iconic meaning expressed by this sign is the indentification of the idea and stance toward that idea between participants. I claim that this evidences a strong correspondence between form and interactional function and call this correspondence 'interactional iconicity'. My study contributes to iconicity research by showing that, there is a strong correspondence not only between form and meaning, but also between form and interactional function. My study also contributes to repetition research by demonstrating conversational repetition äs an iconic sign which represents the seif that is constructed in social interaction.

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