A Developmental Study On The NKA-immunoreactive Expression In The Digestive Tract Of Rats

Objective: To explore the expression and change on the neurokinin A (NKA) of rat digestive tract during the development. Method: PAP immunocytochemistry method was used to detect systematically the expression of NKA in rat esophagus, stomach, duodenum, jejunum, ileum and colon from 13th day of embryo to adult stage. Results: 1. In rat esophagus, the positive varicosities and fibres could be observed in the circular muscle layer and the muscularis mucosae layer at 21st day before birth. With the development of rat digestive tract, neurokinin A-immunoreactivity(NKA-IR) positive nerves could be observed gradually in the epithelium, submucosa, longitudinal muscle layer, myenteric plexus and submucosal plexes, while mature nerve fibres could be seen at one month after birth. 2. In rat stomach, the positive reaction of NKA initially happened in the myenteric plexus at the 14th day of embryo, and then appeared on circular muscles, longitudinal muscles, submucosal, muscularis mucosae, lamina propria and epithelium. 30 days after birth, expression of NKA is same as seen in adaulthood. 3. In rat small intestinal, the NKA-IR could first be found in the myenteric plexus of the duodenum, jejunum and ileum at 14th , 15th and 17th day before birth respectively. Then the NKA-IR occurred in the longitudinal muscle layer, circular muscle layer, intestinal villus, intestinal gland, muscularis mucosae, submucosa, submucosal plexes, mucosa plexus and deep muscular plexus. The ontogeny of NKA-IR in jejunum and ileum later slightly than seen in the duodenum (about 1 day). On 30 days after birth, they have showed the distribution feature of adult. 4. In rat colon, the NKA-IR initially appeared in the myenteric plexus at the 17th day of embryo.Subsequently, the NKA-IR could be observed in longitudinal muscles, circular muscles, muscularis mucosae, lamina propria, mucosa plexus and suhmucosa in succession with the development of colon. The distribution character similar to mature could be found at 30 days after birth. 5. The NKA-IR positive cells showed the typical feature of morphology and distribution of gastrointestinal endocrine cells. Conclusion: 1. The ontogeny and development of NKA in rat digestive tract mainly appeared in the last 1 week before birth and 4 weeks after birth, whereas NKA still would quantitatively change in later development. The neurokinin A in different sections of digestive tract do not occur spontaneously, but in different ways. 2. There are two key periods during the development of NKA in rat digestive tract. The first crucial stage is from 1 week before birth to 1 week after birth. The second important stage is in the end of the 4th week after birth. 3. In enteric nerve system (ENS), the origin of NKA nerve has both of intrinsic and extrinsic. 4. NKA may play an important role in the development of rat digestive tract, and may be closely related to the establishment of digestive tract function. 5. The NKA-IR cells may be the endocrine cell which produces NKA in rat digestive tract.