Stimulatory signals from the central nervous system for ornithine decarboxylase activity in the rat duodenal mucosa

Homeostasis in the small intestinal mucosa balanced between cell proliferation and apoptosis is regulated partly by the central nervous system

The aim of this study was to investigate whether the central nervous system regulates mucosal cell growth and apoptosis in the rat small intestine. Ornithine decarboxylase is a key enzyme for polyamine synthesis, which plays an important role in intestinal mucosal growth. The increase in ornithine decarboxylase activity in the duodenum just before a dark period was abolished by truncal vagotomy. An infusion of 2-deoxy-D-glucose into the third cerebroventricle activated the enzyme activity in the small intestine. Epithelial homeostasis is balanced by the regulation of cell proliferation and cell death. Intestinal mucosal apoptosis decreased in rats with ventromedial hypothalamus lesions, which induced hyperphagia and obesity. In contrast, sustained anorexia induced by 1-deoxy-D-glucosamine increased intestinal apoptosis. These results indicate that the central nervous system, in addition to local factors, is related to the regulation of mucosal homeostasis in the intestinal mucosa.

Lingual factors enhance the increase of ornithine decarboxylase activity in rat jejunal mucosa after feeding

Luminal nutrients are the main factors that stimulate ornithine decarboxylase (ODC) activity in rat intestinal mucosa following feeding. The aim of the present study was to determine whether lingual (oral) factors are related to the increase in jejunal ODC activity after feeding. ODC activity in the jejunum and liver was measured 3 hours after refeeding of 48-hour fasted rats. In the first experiment, rats were refed with a regular pellet, powder, or liquid diet. In the second experiment, rats were infused with the liquid diet through a gastric infusion tube following 48 hours' fasting. In the third experiment, the experimental rats had a gastric fistula that allowed free drainage from the stomach of all ingested liquid diet. In the fourth experiment, a truncal vagotomy was performed 1 week before the experiment. The increase of ODC activity in the jejunum of rats fed with the liquid diet was less than that of rats fed with the pellet diet or powder diet. The increase of ODC activity in the jejunal mucosa of rats infused through the gastric tube was less than that of rats fed per os, and the increase of ODC activity in the liver did not differ between these experimental groups. ODC activity did not increase in rats with a gastric fistula. Vagotomy did not affect the increase of jejunal ODC activity after feeding. In conclusion, the increase of ODC activity after feeding was attenuated in rats in which the diet was given by bypassing the mouth. This indicates that lingual factors enhance the increase of ODC activity in the jejunal mucosa after feeding, but the lingual factors alone do not increase ODC activity in the jejunum.