Developmental changes of NADPH-diaphorase neurons in the forebrain of neonatal and adult cat.

We examined morphological changes of neurons stained for NADPH-diaphorase (a marker for nitric oxide synthase, NOS) in maturing cat brains. In the newborn and 2-week-old kittens reactive neurons were dispersed throughout the cortical layers, in the white matter and in subcortical structures, with dense staining in some thalamic nuclei. In the adult, the density of reactive neurons was considerably decreased in the cortex and the white matter. In the thalamus, only some nuclei retained a faint labeling. Morphological changes also occurred at the cellular level. In the neonate, stained cells had prominent, thick processes with numerous beads and varicosities. In the adult, the processes were longer and thinner, with smaller varicosities. These observations provide further evidence that NOS may play a role during development.