Paired helical filaments in spinal ganglion neurons of elderly rats.

Ultrastructural study of spinal ganglion neurons in elderly rats (aged from 24 to 32 months) allowed the observation of spontaneously occurring paired helical filaments (PHFs). On the basis of this finding the rat may provide an animal model for the study of the morphogenesis and nature of the PHFs which are characteristic of human senile dementia of the Alzheimer type.