Altered histofluorescent pattern of noradrenergic innervation of the cerebellum of the mutant mouse Purkinje cell degeneration.

The Purkinje target cells for noradrenergic fibers originating in the locus coeruleus are considered to be of importance in the regulation of noradrenergic input to the cerebellum. The availability of a mouse mutant, Purkinje cell degeneration provides a non-surgical means for studying cellular regulation of innervation. Using a glyoxylic acid histofluorescent method for visualizing noradrenergic fibers, the observations have been made that the density of green histofluorescent neurites is markedly increased in both the granule and molecular layers of the cerebellum of Purkinje cell degeneration mice, following spontaneous degeneration of the Purkinje cells. However, because of tissue shrinkage, tissue concentration of norepinephrine also increases, but total tissue content of norepinephrine is unchanged in whole cerebellum and outer cerebellar cortex. These findings indicate that the relative number of noradrenergic afferents to the molecular layer of the cerebellum is not reduced following spontaneous degeneration of Purkinje cells. Therefore, Purkinje target cells do not appear to be essential for maintenance of afferent inputs in mature cerebellum.