Unilateral injury to the adult rat optic nerve causes multiple cellular responses in the contralateral site

This study was undertaken to examine whether unilateral injury to one optic nerve (ON) elicits a response in the microglia, neuroglia and ganglion cel ls of the retina and ON of the contralateral site as well. Bilateral activa tion of the transcription fatter c-jun could be immunohistochemically detec ted in the ganglion cell, layer 2 days after crush and later. Microglial ce lls were detected with the activation-specific antibodies MUC 102 and OX-42 . They showed an immediate and clear pattern of activation within the contr alateral ON and retina, although this response was less pronounced than in the directly lesioned site. Astrocytes and Muller cells showed a typical up -regulation of glial fibrillary acidic protein in the lesioned retina and o nly focal but virtually no generalized up-regulation in the contralateral e ye. Ganglion cells whose axons had been crushed responded with vigorous axo nal growth after 2 days in culture, in addition to exhibiting in situ react ions. However, ganglion cells of the contralateral retina responded with a moderate regeneration, too, Growth was less pronounced than in the crushed retina but significantly better than in retinas on untreated animals. The r esults suggest that unilateral lesion of the optic nerve elicits a defined response in the major cell types of the contralateral retinofugal system. T he findings suggest that it is advisable to maintain caution in the use of the contralateral optic nerve and retina as a control in experiments dealin g with cellular processes of de- and regeneration. (C) 1999 John Wiley & So ns, Inc.