The indusium griseum in Alzheimer's disease: an immunocytochemical study

The immunocytochemical features of the indusium griseum (IG) were compared with the corresponding hippocampus in 5 patients with Alzheimer's disease (AD) and 5 age-matched nondemented individuals using antibodies against beta-amyloid, the A68 protein (Alz-50 antibody), tau, ubiquitin and synapsin I. beta-Amyloid-positive plaques were prominent in the AD hippocampus but were not present in the IG. Numerous Alz-50, tau and ubiquitin-positive neurofibrillary tangles and dystrophic neurites were observed in the AD hippocampus but were infrequent in the IG. Synapsin I immunoreactivity was significantly reduced in both the AD hippocampus and the AD IG when compared to age-matched patients. These findings suggest that the IG may be resistant to factors that trigger production of abnormal AD-associated proteins. Loss of synaptic input alone may not account for the AD-associated changes in the hippocampus since synaptic depletion was seen in both the hippocampus and the unaffected AD IG.