[Ultrastructural observations of the dorsal lateral geniculate nucleus following non-surgical retinal lesion of the rats].

By intravitreal injection of arsenous pentoxide (As2O5), which had been used in the pulpectomy in the dentistry, the retina, including the ganglion cell layer, fell selectively into necrosis and the lesions were uniform throughout all part of the retina. Following these non-surgically induced retinal lesions, the dorsal lateral geniculate nucleus of the rats was examined by electron microscope over varying periods of time. From 2 days after the injection, dark atrophic axon terminals appeared in the dorsal lateral geniculate nucleus and these terminals were in most instances surrounded by swollen astrocytic processes with glycogen particles. The quantity of the degenerating terminals maximized at 6 to 7 days after injection and then decreased by 60 days. It was also shown that various features of the degenerating terminals were related to the postsynaptic dendrites. In early stages these degenerating axon terminals had dense, swollen mitochondria and many synaptic vesicles in the electron dense matrix. Then these terminals were deeply indented to the apposed dendrites and by this indentation the astrocytic process seemed to insinuate into the synaptic junction. In these situations, the cytoplasm of astrocytes increased in electron density around the terminals. The postsynaptic density and the subsynaptic organellas were clearly shown to be identical through the course of the degeneration. There were also dendro-astroglial junctions, and these junctions seemed to be one of the features of degeneration of the terminals. It was suggested that there was an obvious course of the degenerating terminals separated from their post-synaptic sites without disruption of integrity of the post-synaptic membrane specialization by astrocytic cell process in Wallerian degeneration.(ABSTRACT TRUNCATED AT 250 WORDS)