Neuronal effects of experimentally induced hydrocephalus in newborn rats

✓ To determine the effects of increased cerebrospinal fluid (CSF) pressure on neuronal morphology, obstructive hydrocephalus was induced by injecting kaolin into the fourth ventricle and cisterna magna of 1-day-old rats. The animals were sacrificed 10 to 12 days later, at which time severe ventriculomegaly and cortical thinning were apparent in the parieto-occipital region. Tissue from this area was processed by rapid Golgi methods. Well impregnated pyramidal neurons were examined by light microscopy, and their somatic and dendritic features compared to those of age-matched littermate controls. The somata of medium pyramidal neurons were unaffected, but their basilar dendrites had fewer branches and those that remained were shorter. A variable reduction in dendritic spines occurred, such that some branches were totally denuded while others exhibited spine densities similar to those seen in control animals. The most striking alteration was the occurrence of frequent dendritic varicosities. These enlargemen...