Perikaryal neurofilament phosphorylation in axotomized and 6-OH-dopamine-lesioned CNS neurons

The axon reaction in the central nervous system was studied using a monoclonal antibody to phosphorylated neurofilaments. Axotomy was performed by cutting the nigrostriatal pathway. We were able to show that phosphorylated epitopes of neurofilaments, that are usually restricted to axons, could be detected in the perikarya and dendrites of axotomized neurons as early as 3 days postlesion. These neurons remained labelled up to 17 days after axotomy and in some cases even up to 6 weeks. The cytoplasmic changes appearing in the lesioned neurons 8 days after axotomy seem to indicate that these neurons will probably degenerate or survive only in an atrophied, non-functional state as they are unable to regenerate their sectioned axon. Neurochemical lesions, using the neurotoxin 6-OH-dopamine, were performed to establish whether this reaction of perikaryal neurofilament phosphorylation may be a non-specific phenomenon accompanying neuronal degeneration or injury. Although cell loss was important, no labelled neurons could be observed following 6-OH-dopamine treatment. These results indicate that the induction of perikaryal neurofilament phosphorylation is a response to selective types of neuronal injury and concerns selective neuronal populations.