The effects of life-long food restriction on spatial memory in young and aged Fischer 344 rats measured in the eight-arm radial and the Morris water mazes

Abstract

The effect of life-long 60% ad lib food restriction on performance in two tasks involving spatial memory, the eight-arm radial maze and the Morris water maze, was studied in young and aged Fischer 344 rats. Restricted (R) and ad lib (AL) feeding groups were compared at 8, 16, and 24 months of age on both tasks. A 30-month-old R group was also tested in the Morris water maze. In the eight-arm maze, although 24-month-old animals performed more poorly than 8- and 16-month-old animals during the first week of testing, overall accuracy of performance did not vary significantly as a function of age. Twenty-four-month-old animals took longer to make 10 choices than did younger animals, and there was a significant interaction between feeding regimen and age, reflecting the fact that at the two younger ages, R groups performed more quickly than the AL groups. In the Morris water maze, both distance swum and time to find the platform increased with age. Life-long food restriction led to small but significant improvements in performance in the water maze in aged rats. R groups showed evidence for better retention over 24-hour intervals than did AL groups. By 30 months of age, however, R animals showed impaired performance relative to younger R groups. These differential findings on the two tasks, as they were used here, suggest that there was greater impairment with age on the spatial memory task requiring retention of information over long intervals than there was on the task primarily involving working memory within a trial. Life-long food restriction would appear to delay the impairments of age, but not prevent them.