A nucleoside-nucleotide mixture may reduce memory deterioration in old senescence-accelerated mice

We investigated the effects of a mixture of dietary nucleosides and nucleot ides (NS + NT) on memory in 1- and 7-mo-old senescence-accelerated mice (SA M). Memory retention was studied with passive avoidance (step-through) and active avoidance (shuttle) tests. For 14 wk, mice in the control groups wer e fed a 20 g of casein/100 g diet, whereas the NS + NT groups were fed this diet supplemented with a 0.5 g of NS + NT mixture/100 g. All mice were kil led at wk 14, and we studied the brain histopathology. Lipofuscin, monovacu oles and multiple vacuoles of various brain regions were measured. Body wei ght, food intake and ambulatory activity did not differ between the control and NS + NT groups. In old mice, the time of passive avoidance was signifi cantly higher in the NS + NT group than in the control group at d 1 and 7 ( P < 0.05). However, such an effect of NS + NT was not observed in young mic e. In the active avoidance test, the incidence of successful avoidance in o ld mice was higher in the NS + NT group than in the control group at d 1 an d 2 (P < 0.05). The percentages of specific brain cells containing lipofusc in were lower in NS + NT groups than in the control groups in both young an d old mice (P < 0.05). The number of monovacuoles and multiple vacuoles in specific brain regions tended to be lower (P = 0.1-0.25) in NS + NT than in control groups, with significant differences in the microvacuoles of the m iddle cortex of young mice and in the multiple vacuoles in the hind cortex of old mice (P < 0.05). These results suggest that increased dietary NS + N T may be associated with decreases in the age-induced deterioration of brai n morphology and certain memory tasks.