Effects of the neonatal treatment with monosodium glutamate on myenteric neurons and the intestine wall in the ileum of rats.

BACKGROUND

The neonatal administration of a 4 mg/g dose of monosodium glutamate (MSG) to rodents leads to neuronal death in the hypothalamus arcuate nucleus, which leads in turn to obesity in the adult animal. However, few studies have investigated the effects on the enteric nervous system. This study evaluated the effects of the neonatal administration of MSG on the frequency and morphometry of the myenteric as well as the ileum wall morphometry of adult Wistar male rats.

METHODS

Whole-mount preparations of ileum samples were stained by the Giemsa or NADH-diaphorase histochemical methods. For histological processing, hematoxylin and eosin staining was used.

RESULTS

The treatment with MSG led to obesity, as shown by the higher values for Lee's index and the weights of periepididimal and retroperitoneal adipose tissues. The Giemsa staining revealed a significantly larger neuronal density in the MSG group, which is explained by smaller physical growth and a reduction in the weight of the small intestine. The mean neuronal profile did not change between groups. The NADH-diaphorase-positive neuronal subpopulation kept its neuronal density but its average cellular profile was reduced in the MSG group. A morphometric analysis of the intestinal wall, muscular layer, villi, and intestinal crypts showed that their characteristics did not change.

CONCLUSIONS

The treatment with MSG did not cause alteration of the total myenteric population of the ileum, but it influenced the NADH-diaphorase-positive subpopulation. From the maintenance of the morphometric parameters of the ileum intestinal wall, we inferred that intestinal function was preserved in obese animals.