Modified Bielschowsky and immunohistochemical studies on senile plaques in aged dogs

Aged dogs developed senile plaques (SP) in the brain which were similar to those occurring in aged humans. These SP were studied with a modified Bielschowsky stain and immunohistochemical methods using polyclonal antibodies raised against beta-protein and glial fibrillary acidic protein (GFAP). Serial sections stained by immunohistochemical and modified Bielschowsky stains showed that all areas of slight beta-protein immunoreactivity were intensely stained by the modified Bielschowsky stain. Most SP were observed in the neocortex of the cerebrum. Plaque densities were highest in the cingulate and temporal cortices. There were occasional SP in the subcortical nuclei including the caudate nucleus and putamen, and hippocampus. Based on the morphological characteristics demonstrated by the modified Bielschowsky stain, SP in the brains of the dogs were grouped into 3 types: diffuse, mature and perivascular plaques, of which diffuse plaques were predominant. Various degrees of astroglial reaction were observed in all subtypes of SP except diffuse plaques. These findings indicate that dog may serve as a model for study of the pathogenesis of SP.