Abstract
The rat brain was fixed by OsO4 immersion after brief glutaraldehyde perfusion, and the caudate nucleus, the putamen and the globus pallidus were observed with the electron microscope.
Numerous small cells (10-15μ) and a few large cells of two kinds (15-20μ) could be seen electron-microscopically in the neostriatum. The small cells showed the comparatively simple fine structure, while the large cells possessed the abundant, complicated cytoplasm. The two kinds of large cells were quite different from each other and this contrast might be due to their functional differences. The globus pallidus was composed of one kind of large neuron (20-40μ) and there were numerous sections of thick dendrites characteristically scattered throughout the neuropil.
Around the small cell as well as large cell, few axo-somatic synapses could be seen, but a great number of small axo-dendritic synapses or spine synapses were recognized in the neuropil. Especially one axon-two or more dendrites synapses more frequently occurred. On the other hand, the pallidal neuron, from the cell body to the end of the dendritic terminal, was covered with numberless axonal boutons to make the axo-somatic synapses or axo-dendritic trunk synapses. Accordingly there were mainly plural axons-one dendrite synapses in the paleostriatum, though one axon-plural dendrites synapses were more abundant in the neostriatum.
In both the neo- and the paleo-striatum, there were several kinds of axon terminals which belonged to some striatal neurons or some other nuclei of the brain, and it could be realized that the most part of the axon terminals in the neostriatum contained the small even (about 450Å in diameter) dense vesicles, and in the paleostriatum, the large uneven (500-800Å in diameter) light vesicles.
The dense vesicle had several fine dense granules (50-80Å in diameter) on its membrane, and they were considered to increase the density of vesicles. They were assumed to be characteristic for the neostriatum.
