Aggravation by the Capsaicin-Treatment of Gastric Antral Ulcer Induced by the Combination of 2-Deoxy-D-Glucose, Aspirin and Ammonia in Rats

Proton Pump Inhibitors Prevent Gastric Antral Ulcers Induced by NSAIDs via Activation of Capsaicin-Sensitive Afferent Nerves in Mice

BACKGROUND/AIMS

We examined the effects of proton pump inhibitors (PPIs) on gastric antral ulcers induced by non-steroidal anti-inflammatory drugs in re-fed mice and the role of capsaicin-sensitive afferent nerves (CSANs) in the protective effects of PPIs on the antral mucosa.

METHODS

Male mice were administered indomethacin after 2 h of re-feeding of diet after a 24-h fast, and gastric lesions were examined 24 h after indomethacin dosing. The effects of PPIs (lansoprazole and omeprazole), histamine H₂-receptor antagonists (H₂-RAs, famotidine, ranitidine), capsaicin and misoprostol on the formation of antral ulcers induced by indomethacin were examined. Functional ablation of CSANs was caused by pretreatment of mice with a high dose of capsaicin.

RESULTS

Indomethacin produced lesions selectively in the gastric antrum in re-fed conditions. Formation of antral ulcers was not affected by H₂-RAs, but inhibited by PPIs, capsaicin and misoprostol. The anti-ulcer effect of lansoprazole was 30 times stronger than that of omeprazole. Antral ulcers induced by indomethacin were markedly aggravated in mice with ablated CSANs. The effects of PPIs and capsaicin on ulcer formation were inhibited by ablation of CSANs, pretreatment with a capsaicin receptor antagonist (capsazepine/ruthenium red) and an inhibitor of nitric oxide synthesis (L-NAME). However, the inhibitory effect of misoprostol was not prevented by the ablation of CSANs or drugs.

CONCLUSIONS

The results suggested that CSANs play an important role in protection of the antral mucosa and that both lansoprazole and omeprazole are capable of preventing NSAID-induced antral ulcers by activating CSANs.

Effects of vanilloid receptor agonists and antagonists on gastric antral ulcers in rats

Defunctionalization of capsaicin-sensitive afferent nerves by pretreatment with a neurotoxic dose of capsaicin aggravates gastric ulcers in rats. In the present study, we investigated the roles of vanilloid receptors in gastric antral ulcers, using vanilloid receptor agonists and antagonists. Gastric antral ulcers were induced by a combination of diethyldithiocarbamate and 1 N HCl in refed rats. The administration of ruthenium red (1.5 mg/kg, s.c., twice daily) aggravated gastric antral ulcers (ulcer index: control, 33.7+/-13.7 mm(2); ruthenium red, 99.9+/-11.0 mm(2)). A similar result was observed in rats pretreated with a neurotoxic dose of capsaicin. On the other hand, capsaicin (1-10 mg/kg, p.o., twice daily) inhibited antral ulcer formation (ulcer index: control, 99.2+/-20.6 mm(2); capsaicin 10 mg/kg, 37.0+/-11.7 mm(2)). A similar effect was obtained in rats treated with the novel antiulcer drug, lafutidine (3-10 mg/kg, p.o., twice daily), which has gastroprotective activity mediated by capsaicin-sensitive afferent nerves. The antiulcer effects of capsaicin and lafutidine were abolished by ruthenium red and by pretreatment with a neurotoxic dose of capsaicin. These results suggest that vanilloid receptors play a gastroprotective role in gastric antral ulcers. In addition, treatment with ruthenium red may be an alternative tool for defunctionalization of capsaicin-sensitive afferent nerves.