Prenatal development of nitric oxide synthase in the mouse spinal cord

Nitric oxide synthase was localized in the spinal cord of the mouse embryo by immunocytochemistry. The first cell population which expressed the enzyme were preganglionic sympathetic neurons in the dorsolateral ventral horn at embryonic day 12. One day later, nitric oxide synthase was detected in neurons corresponding to the developing intermediolateral nucleus of the sacral spinal cord and in a group of cells surrounding the ventral part of the neuroepithelium. Positive cells appeared at day 14 in dorsal portions of the intermediate zone. The ventral horn of cervical and lumbar parts of the spinal cord contained several clusters of stained cells, presumably including motoneurons, which apparently disappear in the postnatal period. These results suggest that nitric oxide might possess different functions for subpopulations of developing spinal neurons.