Figure 6.

Male Fischer 344 rats remained sedentary (Sed) or were allowed voluntary access to running wheels for 6 weeks. Following 6 weeks of the sedentary or exercise conditions, wheels in the cages of the exercised rats either remained unlocked and mobile (Run 0), or were rendered immobile with a metal stake. Rats were then exposed to no stress (No Stress) or uncontrollable stress (Stress) the next day, or 4, 14, or 24 days later. Behavioral testing occurred 24 h later, so that exercised rats were forced to remain sedentary for either 0 days (Run 0), 5 days (Run 5), 15 days (Run 15), or 25 days (Run 25) prior to behavioral testing. A. – D. Freezing behavior prior to (Pre Freezing) and immediately following 2 foot shocks in a shuttle box expressed by non-stressed and stressed rats immediately following 6 weeks of wheel running or sedentary conditions (A), or 5 (B), 15 (C), or 25 (D) days following forced exercise cessation. The sedentary data are repeated in each graph for ease of comparison. E. The average % time spent freezing during the 20 minute post-shock freezing period. Values represent group means ± SEM. * p < 0.05 relative to the Sed No stress, Run 0 No Stress, and Run 0 Stress groups. ** p < 0.001 relative to the Sed No stress, Run 0 No Stress, and Run 0 Stress, Run 5 No Stress, and Run 5 Stress groups.