Abstract:Distribution and morphological characteristics of 5-hydroxytryptamine (5-HT) cells in the digestive tract of Bufo raddei were observed by avidin-biotin-peroxidase complex immunohistochemical method. The results were as follows: 5-HT cells distributed throughout the whole digestive tract with the highest density in the stomach pylorus, the second highest in the fundus, and the lowest in the rectum. The distributive density of 5-HT cells in esophagus, cardia, fundus, and pylorus was significantly higher than that of any other region of small intestine and rectum. The ratio range between open and closed populations of 5-HT cells recorded along the digestive tract was 2.48-4.71. Most cells along the digestive tract belonged to the open population, which were pyramid-like, shuttle-like, or irregular in shape. The closed population was occasionally observed, round or oval in shape. Morphological characteristics of 5-HT cells in the digestive tract of B.raddei are similar to those of other amphibians, but the distributive pattern of these cells has its own characteristics, and this may be related to the diet and life habitat of this species, which is good at feeding on small animals with weak activities.