OBJECTIVETo investigate the development of nitric oxide synthase (NOS)-positive neurons in the frontal lobe of the cerebrum of human fetus in midanaphase.

METHODSThe positive expression of the NOS-positive neurons in the frontal lobe of cerebrum of human fetus was observed by immunohistochemistry.

RESULTSBy the 7th to 8th month of gestation, NOS-positive neurons in the cortical plate of frontal lobe demonstrated themselves inequality of sizes and morphological difference in the deeper layers with interspersed distribution and increased NOS response, and the distribution of beaded nerve fiber was observed between neurons of cerebral tissues. By the 9th to 10th month of gestation, NOS-positive neurons in the deeper layers of cortical plate of frontal lobe developed slightly in size of the cell body with richer cytoplast, full shape and deeper dyeing and extrusive beaded nerve fibers, and the NOS-positive neurons scattered in the shallow layer of cortical plate presented with round or oval shape. The nucleus developed bigger but with sparse cytoplasm and clear nerve process.

CONCLUSIONNOS-positive neurons in the deeper layer of cortical plate of lobus frontal consist of largely network of neural system and produce micro-environment with higher concentration of NO, which favors the differentiation, proliferation, migration, and development of various neurons.