NADPH diaphorase cells in the mammalian inner retina

The distribution of the enzyme NADPH diaphorase was examined histochemically in the retina of the rat, rabbit, cat, owl monkey, squirrel monkey, rhesus macaque, and human being. In all species tested the enzyme was concentrated in cells 10-12 microns in diameter at the vitread margin of the inner nuclear layer. The population was sparse (less than 2,000 cells/rat retina). In several species additional minor populations were observed. While a clear function for NADPH diaphorase has yet to be described, an abundance of the enzyme characterizes a similar subpopulation of retinal cells in a wide variety of mammals.