A morphologic analysis of neurons and neuropil in the dorsal lateral geniculate nucleus of aged rats.

Light and electron microscopy were used to investigate the morphology of neuropil and neuronal cell bodies of the dorsal lateral geniculate nucleus (LGNd) of aged rats. Light microscopic examination reveals that, despite the optic tract showing signs of degeneration, the LGNd is scarcely affected. Thus, a slight but significant reduction in the diameters of both soma and nuclei is observed in aged neurons of the LGNd. Ultrastructural analysis demonstrates a few degenerating profiles of the neuropil. Neurons resembling relay cells exhibit typical features of aged neurons. Cells showing a very infolded nucleus, most of the ER cisternae connected with the nuclear envelope, abundant free polyribosomes and subsurface cisterns associated with mitochondria are similar to interneurons of adult rats. Therefore, aging and partial loss of visual input appear to induce small changes in the morphology of most of LGNd neurons.