Fig. 3.
Corticosterone (CORT) responses. a Time course of CORT (in ng/ml) for high-, low-freezing, and control animals. There was a significant difference in CORT level changes over time among three groups (Two-way repeated ANOVA, Fgroup × time (6,108) = 2.84, p = 0.023). Control animals showed no appreciable CORT change across time (One-way repeated ANOVA, Ftime (3,56) = 0.8, p = 0.50). High-freezing animals exhibited a relatively short CORT response, peaking at 30 min and returning to baseline at 60 min (Tukey-Kramer test, 30 min vs. 60 min: p = 0.049; 0 min vs. 60 min: p = 0.54; 60 min vs. 120 min: p = 0.93). The peak amplitude of CORT response at 30 min was comparable between high- and low-freezing animals (Tukey-Kramer test, p = 0.59). However, relative to high-freezing rats, the CORT response in low-freezing animals was prolonged, maintained at a high level at 60 min (Tukey-Kramer test, 30 min vs. 60 min: p = 1; 0 min vs. 60 min: p = 0.0005) and had a delayed return to baseline at 120 min (Tukey-Kramer test, 60 min vs. 120 min: p = 0.0098; 0 min vs. 120 min: p = 1). In addition, low freezers’ CORT level was significantly higher at 60 min than high freezers (Tukey-Kramer test, p = 0.0039). b Low-freezing animals showed a significant higher total CORT response than high-freezing (p = 0.031) and control (p = 0.017) animals. c Significant correlation between the total CORT responsive (y-axis) and freezing time (x-axis) during exposure across all fox-urine exposed animals (r = −0.43, p = 0.035). d Significant correlation (r = −0.36, p = 0.019) between the total CORT response (y-axis) and EPM score (open/open + closed arm time, x-axis) measured 6 days post exposure across all animals tested. Bars indicate s.e.m. Source data of Fig. 3 are provided as a Source Data file