Figure 1.

Effect of different durations of stress on serum glucocorticoid levels. Compared with the control group, the level of serum glucocorticoid significantly increased after stress exposure for 3 days, peaked at 7 days, and remained high at 14 days. However, with prolonged stress exposure, serum glucocorticoid level significantly decreased at 21 days compared with 14 days. The results are shown as mean ± SEM, ^*P < 0.05, ^**P < 0.01 vs. control group. ^&P < 0.05 vs. RS+IS group at 14 days. d, day(s); RS+IS, restraint stress combined with ice water swimming.