The expression of neuronal nitric oxide synthase in the brain of the mouse during embryogenesis.

The distribution of neuronal nitric oxide synthase (nNOS) in the process of normal mouse brain growth from embryonic (E) Day 11 to postnatal (P) Day 1 was investigated by means of immunohistochemical and immunofluorescent methods. Our results demonstrated that nNOS positive neurons appeared early in superficial cortex at E11. At E13, nNOS positive neurons were located in lateral hypothalamus and amygdala, and temporarily in medullar and ventral hypothalamic neuroepithelia. From E15 to P0, nNOS positive neurons were distributed in superior and inferior colliculi, positive staining could also be seen in superior and inferior tectal neuroepithelium at E15. From E17 to birth, the medial geniculate nucleus had a high density of nNOS labeling. The distribution of nNOS gradually increased and extended laterally in embryo brain, which in turn implies that NO might be involved in the development of mouse brain.