Postnatal Development of the Stomach in the Japanese Field Vole, Microtus montebelli

Summary The postnatal development of the stomach in the Japanese field vole, Microtus montebelli, were studied with the light and scanning electron microscopes. Three kinds of cells constituting the fundic glands, that is, mucous neck cells, parietal cells and chief cells were distinguished clearly by light microscopy to have been differentiated around 14 days old. At 4 days old, the structure of pyloric glands was similar to that of adult stage. The investigation on the development of esophageal sac, fundic stomach and pyloric stomach was made by measuring each area of the vertical section. The fundic stomach grew more rapidly than the esophageal sac and pyloric stomach. The ratio of esophageal sac to fundic stomach and pyloric stomach in the area was about 1.5: 2: 1 at 20 days old. In the fundic glands, 5‐hydroxytriptamine (5‐HT)‐ and somatostatin‐immunoreactive cells appeared first at 6 days old and at birth, respectively and in the pyloric glands, gastrin‐, 5‐HT‐ and somatostatin‐immunoreactive cells appeared at 19th day fetus. Gastrin‐immunoreactive cells showed a rapid increase in the pyloric glands after birth. The distribution and frequency of endocrine cells were similar to that of adult at about 20 days old. The fimbria showed bank‐like appearance at the beginning and thereafter they showed the process‐like structure. The fimbria in both the appearance and the length at 60 days old was similar to that of adult stage. As a whole, the stomach of the field vole seemed to became mature at 20 days old in the aspects of gastric endocrine cells and morphology of gastric wall, although the fimbria formation was not accomplished at the same period.