Induced hydrocephalus in postnatal rats following an intracerebral injection of ricin.

A single injection of peroxidase-labelled Ricinus communis agglutinin (RCA-HRP) was given intracerebrally in 5-day old postnatal rats to determine its effects on neural tissues. The rats were sacrificed at various time intervals ranging from 1 hour to 8 weeks after the injection. 5 days after the injection, the lateral ventricle ipsilateral to the injection was progressively enlarged. The size of the ventricle continued to expand so that 10-15 days after the injection the ventricle on the contralateral side was also affected. In longer surviving rats, i.e 3-8 weeks after the injection, both the ventricles were extremely dilated resulting in the thinning of the cerebral cortex. Scanning electron microscopy of the dilated ventricles showed signs of disruption of the ependyma in some regions. A number of cells including macrophages, neurons, glioblasts, astrocytes and oligodendrocytes were present on the ependyma. Their identification was confirmed by scanning- and transmission electron microscopy. Transmission electron microscopy of the cerebral cortex subjacent to the dilated ventricles showed the presence of many degenerating neurons, 2-5 hours after the injection of RCA-HRP. The neurons displayed typical features of degeneration, i.e. displacement of nucleus, dilatation of cisternae of rough endoplasmic reticulum, and swelling and disintegration of mitochondria. In conclusion, following a single intracerebral injection of RCA-HRP, drastic neuronal degeneration was elicited near the site of injection and this resulted in the dilatation of the lateral ventricles similar to hydrocephalus.