Nitric oxide synthase distribution in myenteric plexus of rat digestive tract

AIM To investigate the distribution of nitric oxide synthase (NOS) positive neurons in the myenteric plexus of rat digestive tract. METHODS With NADPH diaphorase (NDP) histochemical staining method and whole mount preparation technic, the density of NOS positive neurons was microscopically measured in rat digestive tract. RESULTS The NOS positive neurons were distributed in whole myenteric plexus of the rat digestive tract. The size and density of the NOS positive cells did not coincide in different regions. The density (cells/mm 2) was 1 8±2 5 (esophagus), 31 4±4 7 (stomach), 26 4±3 1 (duodenum), 29 5±3 9 (jejunum), 33 7±4 4 (ileum), 6 7±2 3 (cecum), 38 6±4 1 (ascending colon), 48 7±5 3 (descending colon) and 36 2±3 3 (rectum). The NOS positive neuro fiber was also most dense in descending colon and most sparse in esophagus, with similar shape of NOS positive neurons, and obviously different size. Most NOS neurons were inside ganglion, with 2-8 cells in each. Some NOS positive neurons were found to be connected each other to form a network. CONCLUSION The density of NOS positive neurons in different regions of digestive tract coincides with the physiological function of digestive tract. The abnormal distribution of NOS positive neurons may be involved in many gastrointestinal diseases.