Edematous changes in the central nervous system of zitter rats with genetic spongiform encephalopathy.

The pathogenesis of progressive spongy degeneration in zitter rats with genetic spongiform encephalopathy was examined histopathologically and biochemically in the context of edematous change in the central nervous system (CNS). Histopathological studies revealed that vacuolation in the CNS of zitter rats progressed with aging and the severity of spongy degeneration was markedly divergent in different areas in the CNS. Edematous change was confirmed by a consistently higher water content in the brain of zitter rats than in that of normal SD/J rats at all ages. Furthermore, a close relationship between spongy degeneration and edematous change in the CNS was demonstrated by regional measurement of specific gravity (SPGR) of brain tissues and quantification of the spongy degeneration by computer-image analysis. The brain regions with lighter SPGR were more severely affected by spongy degeneration. These results suggest that edematous change is related to the pathogenesis of spongy degeneration in the CNS of the zitter rat.