Scrapie infection diminishes spines and increases varicosities of dendrites in hamsters: a quantitative Golgi analysis.

An altered morphology of neuronal dendrites has been shown to be associated with many degenerative diseases of the central nervous system (CNS). Scrapie is a CNS degenerative disorder caused by a novel infectious particle or prion. Golgi impregnation studies showed that neurons in the scrapie-infected brains of hamsters contained varicose swellings and diminished numbers of dendritic spines. In order to ascertain whether or not these differences were statistically significant, quantitative methods were applied to brain samples from scrapie-infected hamsters and compared to uninfected controls. Golgi impregnated layer III pyramidal neurons from both motor and visual cortex exhibited two types of changes in infected animals. First, loss of dendritic spines on the apical shaft of both motor and visual neurons were found from 50 to 200 microns from the cell body (p less than 0.001). Second, spherical varicosities on dendritic stalks ranging from 7 to 25 microns in diameter were found. The average number of varicosities per cell was 18.1 in infected animals with varicosities on dendrites of controls numbering less than 3 per cell. Less than 2% of the control cells exhibited these varicosities, while greater than 80% of the scrapie dendrites exhibited varicosities. These changes in scrapie are similar to those reported in Creutzfeldt-Jakob and Alzheimer's disease in human patients.