Anterograde and Retrograde Degenerative Reactions in Caudate Nucleus and Putamen after Experimental Lesion of the Pallidum in Squirrel Monkey (iSaimiri sciureus/i)

摘要

After stereotactic lesions in the pallidum in 4 squirrel monkeys, electron microscopic material from the striatum was examined for anterograde and retrograde degenerative changes. In the experiment with pallidum internum lesion, only degenerated striatal fibers were observed, more than likely thalamostriatal fibers that pass through the site of the lesion. The three experiments with pallidum externum lesion revealed that the two types of striatal aspiny neurons react with a penumbral degeneration to interruption of their axons. Also, the axospinous type IV striatal synapses, which originate in the center median or parafascicular nucleus of the thalamus, react to interruption of their axons in the pallidum externum with the dark or crystalloid forms of degeneration. The plump axospinous type III synapses, which have previously not been differentiated, were the most frequently altered, showing dark, crystalloid, or pale forms of degeneration. Their degeneration can be attributed directly to the lesions of the pallidum externum nerve cells; thus, an immediate connection between the pallidum externum and the striatum has been demonstrated. A comparison of the retrograde degeneration of striated nerve cells after pallidum externum lesions with that following columnar isolation of striatal tissue revealed two overlapping forms of penumbral degeneration of the aspiny neurons.