Figure 5.

Effect of age and voluntary exercise on CX₃CL1/fractalkine levels in the adult mouse hippocampus. A, Under sedentary conditions, a significant decrease in the levels of soluble (i.e., cleaved) CX₃CL1 was observed in 12- and 18-month-old mice compared with their younger (2-month-old) counterparts (*p < 0.05; n = 4 per experimental condition). B, Voluntary wheel running resulted in a small but significant increase in hippocampal CX₃CL1 levels in young mice (*p < 0.05; n = 6 per experimental condition). C, Exercise also increased hippocampal CX₃CL1 levels in aged mice. Voluntary wheel running for a period of 28 d significantly increased CX₃CL1 levels in 12-month-old mice (*p < 0.05; n = 5 per experimental condition), restoring these to the levels normally observed in young, nonrunner hippocampus (compare with A). R, Runner; NR, nonrunner.