THE EFFECT OF INHERITED HYDROCEPHALUS AND SHUNT TREATMENT ON CORTICALPYRAMIDAL CELL DENDRITES IN THE INFANT H-TX RAT

The neuronal basis for neurological deficits in infantile hydrocephalu s is poorly understood. Changes in the dendritic architecture of pyram idal cells of the auditory cortex have been measured at 21 days after birth in H-Tx rats. Tissue was prepared by the rapid Gels method from hydrocephalic and control littermates, together with hydrocephalic rat s with ventriculo-subcutaneous shunts placed at 3-4 days or at 10 days after birth. Layer V pyramidal cells were analyzed quantitatively on a light microscope at a magnification of 250 or 400 x. When compared t o control, the hydrocephalic rats had a 30% reduction in the cortical thickness whereas in the shunt-treated rats it was similar to control. For both the apical and the basal dendrites, the distance extended fr om the soma was reduced in hydrocephalic rats by 49-57%, and the total length of the dendritic trees was decreased by 61 and 77%, respective ly. Rats shunt-treated at 3-4 days had small dendrite changes which, i n most cases, were not significantly different from control. Rats shun t-treated at 10 days had dendrites which were indistinguishable from u ntreated hydrocephalic rats. Dendritic branch patterns were also affec ted; the number and mean length of branch segments were reduced in bot h the hydrocephalic and the 10-day shunt group, with only small change s in the earlier group. Overall, the basal dendrites were more severel y affected than the apical dendrites. It is concluded that infantile h ydrocephalus results in severe neuronal abnormalities which can largel y, but not completely, be prevented by shunt treatment performed in th e early stages. (C) 1996 Academic Press, Inc.