Ultrastructure of 6-aminonicotinamide (6-AN)-induced lesions in the central nervous system of rats. II. Alterations of the nervous susceptibility with aging.

Lesions in the CNS induced by 6-aminonicotinamide (6-AN) presented a spongy state of the gray matter and neuronal chromatolysis. With aging of the experimental animals the lesions extended from the phylogenetically early developed structures to those developed later, i.e., from spinal gray matter, dentate nuclei, and brain stem nuclei through limbic structures and striatum to the cerebral cortex. Changes of the neurons were more prominent with aging. Lesions in the CNS of rats at the age, corresponding to the involutional period in the human, were similar to those of Creutzfeldt-Jakob disease (C-J) disease) in the presenile age. In recent years, the resemblance between C-J disease and pellagra encephalopathy had been noted by several authors, and they resemble the lesions caused by 6-AN, an antimetabolite of nicotinamide used in our experiment. This evidence, therefore, has led to the hypothesis that dysfunction of NAD(H)- or NADP(H)-dependent enzymes in the CNS of the aged, even if not the primary cause, may be one possible pathogenetic factor of C-J disease.