NITRIC-OXIDE SYNTHASE IN RAT-BRAIN - AGE COMPARISONS QUANTITATED WITHNADPH-DIAPHORASE HISTOCHEMISTRY

We examined age-related differences in nicotinamide adenine dinucleoti de phosphate diaphorase (NADPH-d) containing neurons and neuropil in t he striatum and hippocampus of male Fischer 344 rats at 6, 12, and 26 mo of age. NADPH-d staining is considered to he a marker for neurons a nd neuronal processes containing nitric oxide synthase. Rat brains wer e processed for NADPH-d histochemistry and analysed morphometrically u sing computerized image analysis. The following NADPH-d histochemical parameters were examined: neuronal density, neuronal size, and neuropi l staining optical density of selected regions. In the striatum, signi ficant age-related declines were observed in NADPH-d-positive neuronal density and in neuropil staining, while neuronal size increased betwe en 6 and 12 mo and then declined between 12 and 26 mo. In tile hippoca mpus no significant age-related changes were rioted in NADPH-d-positiv e neuronal density or size, or in the optical density of the molecular layer of the hippocampal dentate gyrus. Thus, age differences in NADP H-d histochemistry appear to be regionally specific in the Fischer 344 rat.