Figure 3

Age-associated impairments in performance in polyriboinosinic-polyribocytidilic acid (PolyI:C) mice in the Y-maze test. (A-B) ANOVA of the % alternation showed a significant main effect for treatment (F _1,54  = 90.1, P < 0.001) and age (F _1,54  = 39.8, P < 0.001), and a treatment × age interaction (F _3,54  = 70.6, P < 0.001), but no effect for sex (F _1,54  = 0.0002, P = 0.988). Fisher's LSD post-hoc analysis confirmed the significant impairment in working-memory performance in the 20 month-old PolyI:C-exposed subjects compared with NaCI-treated subjects in (females: P < 0.001, males: P = 0.003). (C-D) ANOVA of the total distance travelled identified a significant main effect for age (F _1,54 = 10.0, P = 0.003) and sex (F _1,54 = 16.5, P < 0.001), but no main effect for treatment (F _1,54  = 0.51, P = 0.480), indicating that the memory impairment was not confounded by differences in locomotor activity. Post-hoc analysis indicated that males travelled significantly shorter distances than did females (P = 0.0003, Fisher's LSD Post-hoc analysis). (E-F) Similarly, ANOVA of the total number of entries into the Y-maze arms showed no significant main effect for treatment (F _1,54  = 0.53, P = 0.470), but a main effect for sex (F _1,54 = 11.1, P = 0.002), reflecting the lower activity of males relative to females (P = 0.002, Fisher's LSD post-hoc analysis). Besides the effect for age, which closely approached significance (F _1,54 = 3.8, P = 0.056), a significant age × sex interaction emerged (F _3,54  = 4.2, P = 0.045), indicating the lower activity of old males relative to females. Values are given as mean ± SEM; n = 13 to 18 per age and treatment; ***P < 0.001, **P < 0.01.