2.3 Serum corticosterone detection
The concentration of serum corticosterone was measured by ELISA assay
kits (R&D Systems, Inc., Minneapolis, MN, USA) according to the
manufacturer’s protocol. The limit of detection for corticosterone
concentration was 0.39Â ng/ml. The intra-assay and inter-assay
coefficients of variation for corticosterone were 5.0 and 7.2%,
respectively.