Distribution of serotonin-immunoreactive cells in the mouse pancreas during development.

The distribution and time of appearance of 5HT-storing cells were studied in samples from the pancreas of mice embryos from 7 to 19 days of gestation. Additionally, 1- and 15-day-old newborns and adult specimens were also examined. Serotonin-immunoreactive cells appeared for the first time in the dorsal pancreatic primordium at 10 days of gestation and increased rapidly in number through E15. From this age, the cellular number diminished in the exocrine pancreatic parenchyma, although an increase of endocrine cells in Wirsung's duct can be detected. At day 15 of extrauterine life, we could only observe some cells in the surface epithelium of pancreatic duct of Wirsung. Islet immunoreactive cells could only be detected in adult animals.