Electron Microscopic Observation of Terminal Degeneration in the Neostriatum after Destruction of the Substantia Nigra in the Rat

Abstract

Following unilateral destruction of the substantia nigra of the rat, terminal degenerations in the neostriatum were examined under an electron microscope. The early changes that appeared at 15hrs after destruction were characterized by the increased electron density of the terminals and an accumulation of glycogen particles in the astrocytal processes surrounding such terminals and in the perivascular areas. The postsynaptic sides of the early degenerating terminals were often presumed to be dendritic spines with a fluffy material and the spine apparatus. Some were small dendrites with neurotubules.The degenerating terminals gradually increased the electron density, and irregularly shaped dense bodies appeared in these terminals. At 2 and 3 days after destruction, degenerating terminals became shrunken into dense bodies of 0.5-0.7μ in diameter. They were completely enclosed by the astrocytal swollen processes with glycogen particles, and then digested by these glial processes. At 7 days after destruction, there was no dense degenerating terminal, whereas the degeneration of myelinated axons remained till 2 weeks, showing dense axoplasm and disintegrated lamellar structures of the myelin sheaths. These results indicate that the terminal degeneration of the dopamine neuron in the neostriatum appears within a few days and disappears after 7 days, corresponding well to those results obtained by the Fink-Heimer method.