[Prospects for future development in the pharmacology of gastric ulcer models and of gastric acid secretion in experimental animals].

Prospects for future development in the field of gastrointestinal pharmacology were briefly discussed on the base of the present progress in our own research on animal models of gastric ulcer and the mechanism of gastric acid secretion. We established a few novel methods to induce extensive ulceration restricted to the gastric antral area in rats by a combination of drug-induced vagal stimulation with necrotizing agents or anti-inflammatory drugs, as well as with ammonia in relation to the etiological role of Helicobacter pilori. In these models, it was found that the gastric antral area become sensitive to mucosal aggression under vagal stimulation and refeeding after starvation and that the mucosal primary afferent nervous system was involved in the integration of gastric mucosal defense mechanisms. Among many experimental gastric ulcer models, the gastric antral ulcer is important for future study because of its unique analogy with human ulcer in its location of incidence and pathology. We also established methods to measure gastric acid secretion in the isolated gastric mucosa or whole stomach of rat or mouse, as well as acid secretion in anesthetized rats. By using these methods, the signal transduction route of vagus nerve stimulation to parietal cells was studied. The importance of mediation of enterochromaffin cells in gastric acid secretion was clearly confirmed. In the studies on receptor mechanisms in the central nervous system regulating gastric acid secretion, critical roles of GABA, barbiturate, glutamate, neurosteroids and opioid receptors were clarified. From these results, several remaining problems were suggested and these must be resolved in future research.