OBJECTIVETo investigate the growth and development of nitric oxide synthase (NOS)-positive neurons in the cerebellum of human fetus in the midanaphase.

METHODThe positive expression of the NOS-positive neurons in the cerebellum of midanaphase human fetus was observed by immunohistochemistry.

RESULTSBy the sixth to seventh month of gestation, NOS-positive neurons were seen in the ependymal layer of the cerebellum. The nucleus was oval-shaped and the neurons had short and small processes. By the eighth to ninth month, NOS-positive neurons were found in the central layer of the cerebellum and the nucleus was round-, oval-, or fusiform-shaped; meanwhile, the neurons grew larger in size with richer cytoplast and heavier staining. The beaded nerve fibers reached the marginal layer and the layer became thickened on the tenth month, which generally was composed of 5 to 6 layers of NOS-positive neurons that were tightly aligned. Some NOS-positive neurons were in smaller size with the cell body and the nerve fibers grew well.

CONCLUSIONNitric oxide generated by NOS of the NOS-positive neurons in the cerebellum plays an important role in the differentiation, proliferation, and migration of neurons and gliacytes.