HISTOCHEMICAL CHARACTERIZATION OF NADPH-DIAPHORASE ACTIVITY IN AREA-17 OF DIURNAL AND NOCTURNAL PRIMATES AND RODENTS

NADPH-diaphorase (NADPH-d) activity was studied comparatively in area 17 of four mammalian species, two primates and two rodents. Three brai n hemispheres each from adult capuchin-monkeys, owl-monkeys, agoutis a nd guinea pigs were fixed with aldehyde fixatives by perfusion and 200 -mu m sections were submitted to NADPH-d histochemistry, using the ind irect malic enzyme method. In all species studied the neuropil pattern of enzyme activity presented a clear layered appearance. In primates, histochemical staining was most intense in layer IVc, while in rodent s the highest intensity of the neuropil reaction was in supragranular layers (II and III). Comparison of cell density in grey and white matt er showed that the majority of NADPH-d-positive neurones were located in the white matter of primates but not of rodents. Since NADPH-d is a nitric oxide synthase the results are very important for comparative functional studies of neuromediators and their correlations with lamin ar and modular organization of area 17 of the mammalian brain.