Gastric mucosal susceptibility to erosive action of acid in stressed rats and its modification by various treatments.

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Abstract
We studied gastric mucosal susceptibility (GMS) to erosive action of acid in stressed rats in response to surgical or pharmacological treatments. The optimal experimental conditions, which were less severe for animals but sensitive for detecting change in GMS to erosive action of acid, were determined ; after 60 min of restraint and water (25°) immersion stress, the pylorus was ligated, a test solution of isotonic saline or hydrogen ion of 50 meq/l was instilled into the stomach at a volume of 3 ml, and gastric lesions were examined after 60 min of exposure to the test solution. Change in GMS was estimated as a difference in erosion severity between saline- and acid-instilled groups. Acid instillation caused a significant increase in formation of gastric erosions only when rats were exposed to stress. Vagotomy, methylatropine (10 mg/kg, s.c.), chlorpromazine (10 mg/kg, s.c.), and aluminum hydroxide (2.0 g/kg, p.o.) which were performed or administered before stress inhibited a formation of gastric erosions in the saline-instilled group as compared with their own control treatment, but only vagotomy and methylatropine markedly protected the stressed rat against an increase in GMS to erosive action of acid. Adrenalectomy performed before stress rather intensified the severity of gastric erosions in the saline-instilled group but moderately inhibited an increase in GMS. The present results demonstrated an increase in GMS to erosive action of acid in stressed rats and strongly suggested that this change may be mediated chiefly by vagal activity although involvement of sympatho-adrenal activity was not ruled out. The role of acid in forming gastric erosions during stress was also discussed.

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