Effects of dietary nucleoside-nucleotide mixture on memory in aged and young memory deficient mice

Intestinal mucosa, bone marrow hematopoietic cells and brain have limited capacity for the de novo synthesis of nucleosides (NSs) and nucleotides (NTs). Whereas the role of dietary NS and NT in the former two tissues is known, it is not known in the brain. Therefore we studied the effect of dietary NS and NT mixture on memory in aged mice (Experiment 1) and young memory deficient mice (Experiment 2). Memory retention was studied by step-through type passive avoidance performance (maximum 180 seconds). In Experiment 1 aged (7 month old) senescence accelerated mice (SAM) were fed 20% casein diet (control) or this diet supplemented with 0.5% NS NT mixture for 12 weeks. Memory was studied 1, 2 and 3 days after the electric shock (punishment). In Experiment 2, young (1 month old) memory deficient mice (Dull mice) and normal mice (ddY mice) were fed the same diets as those in Experiment 1 for 12 weeks. Memory retention was studied 1 and 3 days after the punishment. In the aged SAM the average time of avoidance and also the percentages of successful memory 2 and 3 days after the punishment were significantly higher in the NS NT diet group than the control diet group (P