LOCALIZATION OF NADPH-DIAPHORASE ACTIVITY IN THE HUMAN VISUAL-CORTEX

The present report describes the activity of NADPH-diaphorase (NADPHd) in area 17 of autopsied normal human visual cortex. Four human brains from autopsy tissue (4-8 h postmortem) were fixed by immersion in 4% paraformaldehyde in 0.1 M sodium phosphate buffer, pH 7.2-7.4, or in 1 0% formalin for 24 h. NADPHd histochemistry was done using the malic e nzyme indirect method. The neuropile pattern of enzyme activity presen ted a clear six-layer appearance. Cell morphology and the laminar dist ribution of 73 NADPHd-positive neurons are described. All neurons foun d in area 17 of human cortex were sparsely spiny or smooth cells, loca ted in all cortical layers except layer 4c. Quantitative analysis of t he branching pattern of the dendritic tree was carried out. A symmetri cal pattern was observed with no particular dendritic bias except for a few white matter and layer 1 cells. Larger dendritic fields were fou nd in white matter cells when compared to the other cortical layers. C omparison of cell densities for gray and white matters showed that 85% of the NADPHd-positive neurons were located in the white matter. NADP Hd was colocalized with nitric oxide synthase which produces nitric ox ide, a short-life neuromediator implicated in synaptic plasticity, neu roprotection: and neurotoxicity. Thus, the spatial distribution of the NADPHd cells is important for posterior functional studies of the neu romediators in the brain.