ABSTRACT-We have examined the effect of orally administered capsaicin on gastric motility in the rat to investigate a possible relationship between motility change and cytoprotection induced by this agent. Capsaicin, given orally (1-30 mg/kg), dosedependently inhibited hemorrhagic band-like lesions induced by ethanol (60% in 150 mM HQ. This protection was significantly mitigated by desensitization of afferent neurons following capsaicin pretreatment 2 weeks before the experiment, and it was also significantly attenuated by prior administration of indomethacin, but not by spantide. Intragastric administration of capsaicin (30 mg/kg) significantly inhibited gastric motility and increased the mucosal blood flow, but had no effect on the transmucosal potential difference of the stomach. These functional changes induced by capsaicin were also less marked in the afferent neuronal desensitized rat, and they were significantly attenuated by indomethacin but not by spantide. These results suggest that the mucosal protection by intragastric capsaicin may be associated with the inhibition of gastric motility and the increase of mucosal blood flow. These responses may be induced by activation of primary afferent neurons which are probably sensitized by endogenous prostaglandins.
The present study was undertaken in rats using 2-deoxy-D-glucose (2DG) as a stimulator of gastric motility and a low dose of indomethacin as a prostaglandin (PG) synthesis inhibitor to investigate the roles of gastric motility and PG deficiency in the pathogenesis of indomethacin-induced gastric lesions. Subcutaneously administered indomethacin at 5 mg/kg did not induce any visible damage in the mucosa within 4 hr, but at 25 mg/kg produced linear hemorrhagic lesions along the long axis of the stomach. 2DG (100 mg/kg/hr), given intravenously, produced linear nonhemorrhagic lesions along the mucosal folds and, in the presence of 5 mg/kg of indomethacin, caused severe hemorrhagic lesions in the same areas of the stomach. Gastric motility was markedly enhanced by both indomethacin (25 mg/kg) and 2DG, while acid output and mucosal blood flow were increased only by the latter. Mucosal PGE2 levels were significantly reduced by indomethacin (25 mg/kg) but not by 2DG. Indomethacin at 5 mg/kg alone had no or little effect on any parameter except PG levels, which were reduced to similar degrees as caused by 25 mg/kg of the agent. Time-course development of the lesions was closely associated with those changes in gastric motility after administration of indomethacin (25 mg/kg) and 2DG. These results suggest that the enhanced gastric motility is, by itself, sufficient to induce damage (nonhemorrhagic) in the mucosa and that a PG deficiency alone does not induce any damage but is required for further extension to hemorrhagic lesions of nonhemorrhagic ones that are initially induced by enhanced gastric motility.(ABSTRACT TRUNCATED AT 250 WORDS)
Abstract-We assembled a new system using a lucite chamber and rat stomach for simultaneous measurement of transmucosal potential difference (PD) and luminal pH as indicators of the mucosal integrity and the secretory activity, respectively. The biological preparation involved only the glandular mucosa and responded to a variety of mucosal damaging agents by different degrees of PD reduction, pH increases and histological damages.When the mucosa was exposed for 10 min to 1 M NaCI, the reduced PD was restored with time, reaching the baseline values within 2 hr with histological restitution.Titration of gastric effluent showed that after the exposure, acid secretion ceased and a considerable amount of HC03 was evident in the lumen, followed by re-secretion of acid. These secretory changes corresponded with those of luminal pH; this remained elevated for 1 hr after the exposure and returned to the basal values 2 hr later. The histological restitution as well as the PD recovery after damage were significantly interfered with by indometh acin (5 mg/kg, s.c.) or vasopressin (10 unit/kg/hr, i.v.), respectively, at the dose which inhibited the increased pH responses caused by 1 M NaCI or reduced the mucosal blood flow. These results suggest that this system may be useful for studying physiological changes of gastric mucosa after acute injury and for screen ing drugs that may have an effect on the repair process.
Pathogenesis of indomethacin-induced gastric lesions was investigated in the rat by measuring lesions, gastric motility, and terminal blood glucose levels and correlating them with each other. Subcutaneously administered indomethacin (3-25 mg/kg) dose-dependently produced lesions in the stomach with concomitant gastric hypermotility and reduction of blood glucose levels. When the lesion score and the motility were plotted against terminal glucose levels, a highly significant relationship was found among these three factors (P less than 0.01). Gastric lesions and hypermotility induced by indomethacin (25 mg/kg) were suppressed significantly by 16,16-dmPGE2 (10 micrograms/kg) with no effect on the glucose levels, while intravenous infusion of glucose (25% w/w, 1.4 ml/hr) prevented these responses and restored the reduced glucose levels above the basal values. In addition, both 16,16-dmPGE2 and glucose infusion afforded a significant protection against gastric lesions induced by indomethacin even in the acid-perfused stomach (150 mM HCl). These results confirmed gastric hypermotility as a key element in the pathogenesis of indomethacin-induced lesions and further suggested that indomethacin may sensitive gastric contractility through glycoprivic receptors by inducing hypoglycemia and PG deficiency.
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