Neurofilamentous abnormalities in motor neurons in spontaneously occurring animal disorders

Cytoskeletal proteins have a characteristic distribution within neurons when immunocytochemical techniques are used on conventional paraffin sections. For example, phosphorylated neurofilaments are located within axons but are not normally present in the majority of perikarya of the central nervous system. This pattern can be altered in disease, and neurofilaments that accumulate within perikarya can be phosphorylated inappropriately. To determine whether retained neurofilaments were phosphorylated inappropriately, we used immunocytochemical techniques to examine several diseases in animals in which neurofilaments accumulate within neuronal perikarya. Our investigations of diseases with disparate etiologies show that, whenever neurofilaments are retained within the neuronal perikarya, they are phosphorylated. These results suggest that phosphorylation of neurofilaments in an inappropriate location, i.e. perikarya, may be a nonspecific disease-related response of neurons that can be initiated by a variety of cellular injuries.