Effects of congenital hydrocephalus on serotonergic input and barrel cytoarchitecture in the developing somatosensory cortex of rats.

The effects of progressive ventricular dilation on the development of the somatosensory cortex (SmI) were studied in congenital hydrocephalic rats, with regard to early serotonergic innervation and formation of functional cellular columns. In hydrocephalic rats, the time course, immunoreactivity, and patterns of formation and synaptogenesis of serotonin immunoreactive (5-HT-IR) terminal aggregations, which characterize the development of the SmI, were preserved. After disappearance of 5-HT-IR terminals, characteristic barrel cytoarchitecture formed normally at the site where 5-HT-IR terminal aggregations had been present. With the progression of hydrocephalus, the cerebral cortex became extremely thin and its total surface area was greatly increased, while barrels were preserved and their areas did not enlarge. These findings suggest that the basic development and the fundamental cytoarchitecture of the cortex are resistant to adverse effects of hydrocephalus.