Abstract
Intermediate filaments of the CNS, neurofilament and glial filament, vary in amount with cell types and locations and with normal and pathological conditions. In order to establish whether these differences depend on the amount of their cytoplasmic messenger RNA (mRNA), we tried to detect the mRNA of the peptides constituting these filaments by Northern blot analysis and by in situ hybridization. We found mRNAs of both peptides in the perinuclear zone of nerve cells or glial cells of the rat brain. Thus, intermediate filament peptides are synthesized in the perikaryal cytoplasm, and not in the processes where the filaments exist. The neurons with thicker and longer axons tended to have larger amounts of NF-L mRNA in the cytoplasm. In the retrograde degeneration of rat facial nucleus, the amount of NF-L mRNA decreased, indicating a decline of its synthesis in the stage of axon regeneration. GFAP mRNA increased in the area of the damaged facial nucleus. The GFAP gene of the protoplasmic astroglia located in these areas may be induced by the brain damage, and this may lead to the formation of gliosis in the gray matter.
