Ultrastructure of reduced nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase-positive neurons in the cat cerebral cortex, amygdala and caudate nucleus

The ultrastructure of reduced nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase-positive neurons in cat cerebral cortex, amygdala and caudate nucleus was investigated by electron microscopy using a modified method applicable to aldehyde-fixed tissues. These NADPH diaphorase-positive neurons were morphologically similar to neurons immunohistochemically positive for somatostatin. They had large amounts of electron-dense formazan reaction products scattered through the whole cytoplasm but not in the mitochondria or nucleus. Similar electron-dense reaction products were visible in the dendrites of these neurons. The results indicate that NADPH diaphorase histochemistry is a useful method for the ultrastructural examination of particular groups of neurons.