It is yet a further object of the present invention to treat or prevent various neurodegenerative diseases such as Huntington's disease, Amyotrophic Lateral Sclerosis, Alzheimer's disease, Down's Syndrome, Korsakoff's disease, olivopontocerebellar atrophy, HIV-induced dementia and blindness or multi-infarct dementia, by the administration of effective amounts of substituted guanidines, amino guani