Brain amyloid accumulates in aged rats with kaolin-induced hydrocephalus.

Amyloid beta-peptide (Abeta) accumulation in aged Sprague-Dawley rats (12 months) with kaolin-induced hydrocephalus was investigated by Abeta(1-40) and Abeta(1-42) immunohistochemistry at 2, 6 and 10 weeks after induction. The low-density lipoprotein receptor-related protein-1 transporting Abeta across the blood-brain barrier was assayed. Age-matched controls showed some positive Abeta staining, mainly in the choroid plexus. At 2 weeks after induction, Abeta staining of the arachnoid and subependymal layer was observed. At 6 weeks, larger Abeta accumulations were prominent at the endothelial and perivascular sites. Intraparenchymal Abeta positively stained accumulations occurred at 10 weeks. Microvessel lipoprotein receptor-related protein-1 staining was progressively reduced from 2 to 10 weeks. The pattern of Abeta deposition and lipoprotein receptor-related protein-1 loss suggests reduced Abeta clearance in chronic hydrocephalus.