[Bilateral carotid artery ligation in rat serial pathology of the optic nerve]

Ischemic disease is common in the central nervous system, and has been extensively studied both clinically and neuropathologically. Experimental models have been designed for the reproduction of cerebral infarct. Advanced optic nerve atrophy was recently described in Long-Evans pigmented rat 16 weeks following bilateral carotid artery ligation. Marked change in the retina and its vessels had previously been observed by the fundoscopy and the fluorescein angiography. Serial alteration of the optic nerve was studied on the same experimental model for one month; each two rats for two days, one week, two weeks, one month after the operation, in which the common carotid arteries were ligated just before the bifurcation. A mid-portion of the optic nerve attached to the brain was dissected out and cross-sections were prepared to examine under the light and the electron microscope. Unequivocal pathology was demonstrated in six among eight rats operated. There was no significant change both in remaining two rats and two sham-operated controls. Two-days-postoperative rats developed obvious optic nerve swelling with vacuolar appearance. They consisted of numerous distended axons, containing empty space or flocculus materials. Both intra- and extracellular edema were seen at this time, when vascular beds were transiently disrupted. Necrotic cells and other residual materials were also present in the wide interstitial space. In the following one or two weeks, the edema disappeared and many distended axons contained a lot of organelles, such as mitochondria and/or neurofilaments. In the same period severely damaged axons collapsed, occasionally concomitant with homogeneous dense axoplasm.(ABSTRACT TRUNCATED AT 250 WORDS)