ABSTRACT
Objective To explore the etiology and pathogenesis of Hirschsprung disease(HD) and the role of nitric oxide in pathophysiology of HD. Methods The whole amount preparations of dilative and transitional segments were stained by NADPH\|diaphorase histochemistry mothod,and colonic walls were digested by dispase. Then the NOS positive nervous structure were observed by light and scanning electron microscope. Results In dilative segment, under light microscope, ganglion and neuron were bigger and more darkly stained. Intraganglionic neurons distributed mostly in peripheral area of ganglion and basal part of ganglionic fiber bundles. Under scanning electron microscope, the neurons were denser, more nerve fibers from them and connected with each other in all dimensions. And more transverse connected fibers between neurons which were arranged along muscle fibers. Myenteric plexus even connected with the submucosal plexus by nerve fibers which passed through circular muscle layer. In transitional segment, under light microscope, intraganglionic neurons cytoplasm were lightly stained and also variedly. The ganglion and neurons of the segment were smaller, and the fibers from them were thinner and paler than those of the dilative segment. Under scanning electron microscope, neurons' density was lower, the fiber connection between neurons and muscle fibers/neurons was lesser. In the transitional segment, neurons and nerve fibers were distributed linearly along the longitudinal muscle fibers. Conclusion Our results indicated that an intimate relationship existed between the development of Hirschsprung disease and abnormal distribution and metabolism of NOS positive neuron in colonic wall. [