Horseradish peroxidase (HRP) was applied to the rat sciatic nerve and the uptake, retrograde transport and interneuronal fate of HRP were examined by light and electron microscopy. Furthermore, FeCl3 which is very toxic to the nervous system was also applied into the rat cerebral sensory motor cortex and examined whth Perls iron staining and Perls + DAB high sensitive iron staining methods for light microscopy. After the injection of iron into the rat sensory-motor cortex, the ultrastructual morphological effects on the neurons and glia cells in the hippocampus were also examined by electron microscopy.
The HRP labeled neurons of the spinal ganglia and spinal anterior motor neurons were observed within 12 hours after application of HRP into the sciatic nerve. The HRP positive brown granules were accumulated in the perinuclear regions. Ultrastructurally, these granules appeared to be multivesicular and lysosomal bodies in the perinuclear regions. These granules were degraded by the lysosomal system disappearing 2 weeks after the injection.
In the cases of FeCl3 injection, many neurons which existed in the vicinity of the injected area also showed iron uptake. These neurons contained abundant small brown materials in the cytoplasm. Ultrastructurally, the pyramidal neurons showed the degenerated changes, the nuclei were pyknotic and the cytoplasmatic materials were amorphous. In the neurons which showed iron uptake, a cause of the epileptic abnormal discharge, there were no degenerative findings. These neurons probably showed the abnormal excitation and seizure discharge and induced the epileptic seizures in the iron-induced epileptic rats models.