Comparison of NADPH diaphorase activity in the brains of hamsters infectedwith scrapie strains 139H or 263K or with normal hamster brain homogenate

Previous studies showed that the histopathological changes found in the bra ins of scrapie-infected animals included amyloid plaque formation, vacuolat ion, gliosis and neuronal and neurite degeneration. There were differences in the histopathological findings as a function of the scrapie strain-host combination. NADPH-diaphorase (NADPH-d) has been shown to be a selective hi stochemical marker for neurons containing nitric oxide (NO) synthase. Neuro nal cell damage caused by NOS in brain has been reported to be associated w ith many neurodegenerative diseases. In this study, we used NADPH-d histost aining to investigate changes in the NOS system in brains of 139H- and 263K -infected hamsters and compared the results to normal hamster brain (NHB) i njected animals. We observed that some of the NADPH-d histostaining neurons in the cortex of scrapie -infected hamsters appeared to be atrophic: the n eurons were smaller and had fewer neurites. The NADPH-d histostaining inten sity of neurons or astrocytes in septum, thalamus, hypothalamus and amygdal a of 139H- and 263K-infected hamsters was greater than in control hamsters. Astrocytes in the thalamus, hypothalamus and lower part of the cortex (lay ers 4 to 6) in 263K-infected hamsters were more intensely stained for NADPH -d than in either 139H-infected hamsters or controls. Our results suggest t hat changes in NADPH-d system might play a role in the diversity of scrapie induced neurodegenerative changes.