Ultrastructural changes of the substantia nigra, ventral tegmental area and striatum in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice.

The substantia nigra pars compacta (SNc), ventral tegmental area (VTA) and striatum in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated young adult mice were examined for the occurrence of marked ultrastructural changes. In the median SNc dopaminergic neurons, the Golgi apparatus and rough endoplasmic reticulum were dilated and there was a decrease in the number of ribosomes in the rough endoplasmic reticulum (Nissl substance). The mitochondrial cristae were often disarranged. Characteristic electron dense deposits were often observed in the neuronal fibers, many of which were dilated. However, no clear evidence of nuclear degeneration was seen. On the other hand, ultrastructural abnormalities were not seen in the dopaminergic neurons in the VTA. In both the latero-dorsal and latero-ventral striatum, many dilated neuronal fibers, which contained only a few synaptic vesicles and sparse subcellular structures were observed, but no significant ultrastructural changes could be seen in the medial part of the striatum in MPTP-treated mice. Thus, the effect of MPTP treatment is inhomogenous within the mouse striatum, as would be expected from the appearance of ultrastructural changes in only some of the dopaminergic neurons in the SNc.