A) Daily running activity measured as number of wheel revolutions per day for young adult and mature adult rats. Asterisk denotes a significant difference between young adult and mature adult animals on a given running day, hatch denotes a significant difference of running activity between a given day of activity and the first day of wheel access. B) Percent change in running activity in young adult and mature adult rats from the first day of running to the last day of running. C) Daily wheel running patterns of young adult rats on day one (filled circle) and day 28 (open circle) of wheel access. Asterisk denotes a significant difference in activity between groups at a given time of day. D) Daily wheel running patterns of mature adult rats on day one (filled square) and day 28 (open square) of wheel access. Asterisk denotes a significant difference in activity between groups at a given time of day. *p<0.05, **p<0.01, ***p<0.001, ****p<0.0001, #p<0.05, ##p<0.01, ###p<0.001, ####p<0.0001