Axonal swellings in cerebellar white matter of groggy mutant rat.

In the groggy mutant rat, a number of axonal swellings appeared in the cerebellar white matter from 180 days of age onward. Since these axonal swellings were immunostained with an antibody against calbindin D28k, the axons forming these swellings were considered to belong to Purkinje cells. They were also immunostained with an anti-neurofilament antibody, and ultrastructurally characterized by the presence of myelin sheaths around them and abnormal accumulations of filamentous structures, mitochondria and smooth endoplasmic reticula (SER) in their axoplasm. The SER were considered to convey acid phosphatase (ACPase) to the swelling's axoplasm, where ACPase was set free from the SER throughout the axoplasm and engaged in the digestion of cytoplasmic organelles. The groggy rat is useful model model for the study of the mechanism of the age-related formation of axonal swellings.