Motor performance and regional brain metabolism of spontaneous murine mutations with cerebellar atrophy.

Three spontaneous mutations with cerebellar atrophy were evaluated for motor coordination and regional brain metabolism, as assessed by cytochrome oxidase (CO) activity. Despite similar neuropathological characteristics, the behavioral phenotype of Lurcher is less severe than that of staggerer, possibly caused by the slower onset of their neuronal degeneration. Although fewer cerebellar cells degenerate in hot-foot than in Lurcher, their motor deficits are more severe, indicating the presence of dysfunctional cells. CO activity in the deep cerebellar nuclei was increased in Lurcher and staggerer but unchanged in hot-foot, probably due to the severe loss of GABAergic input from Purkinje cells in the first two mutants but not the third. Altered CO activity in cerebellar-related pathways was linearly correlated with motor performance, indicating that the activity of this enzyme is associated not only with neuronal activity but also with motor performance.