UNILATERAL ATROPHY OF THE OPTIC-NERVE ASSOCIATED WITH RETROGRADE AND ANTEROGRADE DEGENERATIONS IN THE VISUAL PATHWAYS IN SLC- WISTAR RATS

Unilateral degenerative atrophy of the optic nerve (ON) occurred in 6 of 80 male and 4 of 80 female Sie: Wistar rats. Two of these cases com pletely lost the intracranial portion of the unilateral ON and the rem ainder had the small ON, The optic disc and ON were located histologic ally in the posterior pole of the eyeball of 2 rats with no intracrani al ON. ON lesions in all cases were characterized by a reduced number of axons with a small number of myelinated axons and marked astroglios is. There were also swelling, fragmentation and spheroid formation of axons, as well as thickening of the connective tissue sheaths and vess el palls in the ON. One side of the optic chiasma and optic tract cont ralateral to the affected ON reduced in volume, became degenerated and were accompanied by gliosis. Focal or diffuse degeneration of the ret ina was observed in the eyeballs with affected ON. Retinal ganglion ce lls decreased in the number showing chromatolysis. These retinae becam e thin and developed degeneration of both inner and outer portions wit h sclerotic changes in the retinal vessels. The ophthalmic and ciliary arteries in the eyeballs with affected ON often developed proliferati ve or occlusive endoarteritis, suggesting that retinal lesions may hav e resulted not only from axonal degeneration in the ON but also from i schemia. Histologic lesions suggestive of transneuronal degeneration w ere found in the contralateral lateral geniculate body and rostral col liculus. Based on the data presented, it was presumed that a primary l esion may have been induced in the ON by a circulatory disturbance and followed by retrograde and anterograde degenerations in the visual pa thways.