Increased NCAM-180 immunoreactivity and maintenance of L1 immunoreactivityin injured optic fibers of adult mice

The injury related expression of two axon-growth promoting cell adhesion mo lecules (CAMs), NCAM-180 which is developmentally downregulated and L1 whic h is regionally restricted, were compared in optic fibers in the adult mous e. The neuron-specific isoform of NCAM (NCAM-180) is present at very low le vels in unlesioned adult optic axone. At 7 days after nerve crush, immunore activity was strongly and uniformly increased in optic axons within the ner ve and throughout retina. Reactivity in surviving axons had returned to con trol levels at 4 weeks. To induce regrowth of adult retinal ganglion cell a xone retinal explants were placed in culture. Strong NCAM-180 staining was observed on these regenerating optic axone. The neuronal cell adhesion mole cule L1 is restricted to retina and to the unmyelinated segment of the opti c nerve near the optic nerve head in unlesioned adult animals. Following ne rve crush, L1 immunoreactivity was retained within retina and proximal nerv e and novel staining was detected in the more distal segment of the optic n erve up to the lesion site where it persisted for at least eight months. Th e capacity of optic fibers to show increased NCAM-180 immunoreactivity and maintain L1 expression after a lesion may explain why these fibers exhibit relatively good potential for regeneration. (C) 2001 Academic Press.