Research Paper Volume 8, Issue 10 pp 2370—2391

Figure 2. Total activity levels were lower in older mice during the dark phase; activity levels of males, but not females differed among age groups during the light phase of the 24-hour light-dark cycle. (A) 4-month -old female mice were more active during the dark (=active) phase than females in all other age groups (p < 0.0001 in all cases). 20-month-old females did not differ from 28 and 32-month-old females (p = 0.088, p = 0.066, respectively) and 28 and 32-month-old females did not differ from each other (p > 0.999) in dark phase activity. (B) 4-month -old males were more active than 20, 28 and 32-month-old males during the dark phase (p = 0.039, p < 0.0001 and p < 0.0001, respectively). 20-month-old males were more active than 28 and 32-month-old males (p = 0.002 in both cases). (C) Female activity levels during the light phase do not differ between the four age groups. (D) Male activity during light phase was highly variable in all age groups. 4-month -old males’ activity levels did not differ from 20 and 32-month old males (p > 0.999 and p = 0.088, respectively). 4-month -olds were more active than 28-month -olds (p = 0.03) and 20-month-olds were more active than both 28 and 32-month-old males (p = 0.002 and p = 0.010, respectively). Post-hoc tests subject to Bonferroni correction for multiple comparisons. Females n = 20, 20, 30 and 27 for 4, 20, 28 and 32 months. Males n = 18, 18, 26 and 23 for 4, 20, 28 and 32 months.