WALLERIAN DEGENERATION IN RABBIT OPTIC NERVE: CELLULAR LOCALIZATION IN THE CENTRAL NERVOUS SYSTEM OF THE S‐100 AND 14‐3‐2 PROTEINS

Abstract— The S‐100 and 14‐3‐2 proteins, which are found only in nervous tissues, were measured in degenerating rabbit optic nerve at 0, 5 10, 20, 40, 60, 80, 100, 150 and 200 days after unilateral enucleation in order to obtain indications of the cellular localization of these proteins in the central nervous system. S‐100 increased and 14‐3‐2 decreased (both approximately 70 per cent) in cut nerves by 200 days of degeneration. Changes in amounts of the proteins were related to cellular alterations which characterize the degenerative process, as demonstrated by electron microscopy. In uncut nerves (intact eye) from these experimental animals, S‐100 increased and 14‐3‐2 decreased slightly at 5 days, after which time the levels of each returned to those approximating the content in corresponding nerves from unoperated control animals. No appreciable change in total soluble proteins was measured in degenerating or intact nerves. Since S‐100 increased and 14‐3‐2 decreased in the degenerating optic nerve as it became relatively enriched in glial constituents but impoverished in axonal content, it is suggested that S‐100 is primarily a glial protein and 14‐3‐2 predominantly a neuronal protein in the central nervous system.