Changes in the serotonin‐, somatostatin‐ and motilin‐immunoreactive cells in the gastrointestinal tract of the bullfrog, Rana catesbeiana, at various developmental stages

In order to investigate the regional distribution and relative frequency of the serotonin‐, somatostatin‐ and motilin‐immunoreactive cells in the gastrointestinal tract (GIT) of the bullfrog (Rana catesbeiana) with developmental stages, group of bullfrogs subdivided into the tadpole with hindlegs, metamorphosed bullfrog with tail, 2wk after metamorphosed bullfrog and adult bullfrog, were stained by immunohistochemical methods (PAP methods). Multifarious changes of the regional distribution and relative frequency of the gastrointestinal endocrine cells were observed as developmental stages but motilin‐immunoreactive cell were not detected in this study. Serotonin‐immunoreactive cells were detected from 2wk after metamorphosed bullfrog in the whole GIT. The positive cells were predominant in the pylorus regions. In the adult bullfrog, these cells increased in fundus. On the other hand, somatostatin‐immunoreactive cells were observed from the tadpole with hindlegs in the stomach regions. In the metamorphosed...