Effect of Huntington's and Alzheimer's diseases on the transport of nicotinic acid or nicotinamide across the human blood-brain barrier.

Although Elvehjem et al. (1937) discovered that nicotinamide relieved the neurological symptoms of pellagra in dogs, and in spite of the discovery by Hankes and Elvehjem (1949) that nicotinamide or tryptophan reversed the neurological syndrome produced in rats by a diet high in phenylalanine, the importance of nicotinamide and related compounds in neurology remained dormant for almost two decades. The recent surge of interest in the effects of the tryptophan-kynurenine-nicotinamide pathway compounds in neurology (Stone and Connick, 1985) and the transport of these compounds through the blood-brain-barrier prompted a study of the transport of nicotinic acid or nicotinamide through the blood-brain barrier and a subsequent study of the rate of metabolism of these two compounds in the human brain in various neurological disease states.