Early ventriculoperitoneal shunt--effects on learning ability and synaptogenesis of the brain in congenitally hydrocephalic HTX rats.

The learning ability of congenitally hydrocephalic HTX rats in which hydrocephalus had been arrested by the insertion of a V-P shunt 7 days after birth (early shunt) was assessed by means of the light-darkness discrimination test when the animals reached maturity. Early shunt placement resulted in marked reduction in size of abnormally enlarged ventricles and the prevention of both decreasing spine density and decay of synaptic vesicle protein (SVP-38) in the affected cerebral cortex. The learning ability of such animals was also found not to be impaired compared with that of animals in a sham-operation group. On the basis of these investigations, it is concluded that early shunt placement may have a beneficial role in preventing not only impairment of synaptogenesis of the brain by progressing hydrocephalus, but also learning disability. Recent biochemical investigation of the developing brains of hydrocephalic HTX rats revealed problems that cannot be resolved by early shunt insertion, and these are also discussed.