NADPH-diaphorase reveals presumptive sympathetic primary afferents in the developing human spinal cord

The regional distribution of nitric oxide synthase activity in the spinal cord of the dog

The aim of this study was to examine the distribution of calcium-dependent nitric oxide synthase activity (cNOS) in the white and gray matter in cervical, thoracic, lumbar and sacral segments of the spinal cord and cauda equina of the dog. The enzyme's activity, measured by the conversion of [3H]arginine to [3H]citrulline revealed considerable region-dependent differences along the rostrocaudal axis of the spinal cord in general and in cervical (C1, C2, C4, C6 and C8) and lumbar (L1-L3, L4-L7) segments in particular. In the non-compartmentalized spinal cord, the cNOS activity was lowest in the thoracic and highest in the sacral segments. No significant differences were noted in the gray matter regions (dorsal horn, intermediate zone and ventral horn) and the white matter columns (dorsal, lateral and ventral) in the upper cervical segments (C1-C4), except for a significant increase in the ventral horn of C4 segment. In C6 segment, the enzyme's activity displayed significant differences in the intermediate zone, ventral and lateral columns. Surprisingly, extremely high cNOS activity was noted in the dorsal horn and dorsal column of the lowest cervical segment. Comparing the enzyme's activity in upper and lower lumbar segments of the spinal cord, cNOS activity prevailed in L4-L7 segments in the dorsal horn and in all the above mentioned white matter columns.

Neurons expressing NADPH-diaphorase in the developing human spinal cord

The present study used nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase histochemistry to identify populations of neurons containing nitric oxide synthase and to describe their putative migration during development of the human spinal cord. As early as week 6 (W6) of gestation, diaphorase expression was observed in sympathetic preganglionic neurons (SPNs) and interneurons of the ventral horn. As development proceeded, the SPNs translocated dorsally to form the intermediolateral nucleus, and the interneurons remained scattered throughout the ventral horn. In addition to the dorsal translocation of SPNs, a unique dorsomedially directed migratory pathway was observed. At later stages of development, other groups of SPNs were identified laterally in the lateral funiculus and medially in the intercalated and central autonomic regions. In addition, two "U-shaped" groups of diaphorase-labeled cells were identified around the ventral ventricular zone at W7. Cells of these groups appeared to translocate dorsally over the next weeks and presumably give rise to interneurons within the deep dorsal horn and surrounding the central canal. Furthermore, during W7-14 of gestation, the deep dorsal horn contained a number of diaphorase-positive cells, whereas the superficial dorsal horn was relatively free of staining. These data demonstrate that nitric oxide is present very early in human spinal cord development and that two unique cell migrations initially observed in rodents have now been identified in humans. Furthermore, nitric oxide may be expressed in some populations of neurons as they migrate to their final positions, suggesting that this molecule may play a role in neuronal development.