[Gastric ulcer formation induced by kainic acid injection into the dorsal motor nucleus of the vagus nerve (DMN) and identification of the neuronal input to the DMN in rats].

Parasympathetic preganglionic cells innervating the stomach are located in the dorsal motor nucleus of the vagus nerve (DMN) in the medulla. The present experiments were carried out to elucidate that the long-lasting excitation of DMN neurons by kainic acid, a long-acting neuronal excitant, induced gastric ulcers and to identify the input neuronal systems projecting to the DMN by means of horseradish peroxidase (HRP) method in rats. Twenty four hours after kainic acid injection into the DMN, gastric ulcerative lesions were induced in 12 out of 14 rats. The ulcer index in experimental group, 10.2 +/- 6.5 mm, was significantly higher than that in the control group, 0.5 +/- 1.0. Mucus content in gastric mucosa was significantly lower than that of the control group. Fourty four hours after HRP injection into the DMN, HRP labeled cells were distributed from medulla to cortex, especially in medullary reticular formation, interpositis cerebellar nucleus, several hypothalamic nuclei, central amygdala nucleus and insular cortex. These results suggest that long-lasting excitation of DMN neurons facilitate gastric ulcer formation and that a decrease in mucus content in gastric mucosa plays an important role in the process of gastric ulcer formation by kainic acid injection into the DMN. Since the cortex, amygdala and hypothalamus has been shown to be closely associated with emotion and stress, it could be speculated that emotional changes and stress might induce the changes of excitability of DMN neurons via higher order neuronal systems.