Jf. Flood et al., AGE-RELATED-CHANGES IN LEARNING, MEMORY, AND LIPOFUSCIN AS A FUNCTIONOF THE PERCENTAGE OF SAMP8 GENES, Physiology & behavior, 58(4), 1995, pp. 819-822
SAMP8 (P8) mice are characterized by impaired learning and memory rela
tively early in their life, while CD-1 mice show impairment later in l
ife. A series of paternal backcross strains were developed from a CD-1
dame and P8 sire. Siblings from each backcross were bred to establish
strains with 50% to 97% P8 genes. F4 mice, 4 or 12 mo of age, were tr
ained to avoid foot shock in a T-maze with retention tested 1 wk later
. After testing, brain sections were examined for lipofuscin autofluor
escence. At 4 mo of age, all strains, including the CD-1 and P8 strain
s, showed no significant differences in learning, retention or lipofus
cin deposits. At 12 mo of age, groups with 94%, 97% P8 genes or P8 mic
e (100%) required significantly more trials to learn the task or relea
rn the task 1 wk later than groups with 88% or fewer P8 genes. Lipofus
cin deposits increased in the hippocampus as the percentage of P8 gene
s increased suggesting that many genes control aging of the brain. How
ever, the sudden appearance of impaired learning in the 94% strain sug
gests that the mechanism(s) responsible for the impairment involves a
few recessive genes and are independent of the mechanisms controlling
the general aging of the brain.