To examine stress responsive hormones, we used one-way ANOVA to compare each group after foot shock stress, and no group differences in plasma ACTH or CORT levels were found. In comparison with stress control group (the stress/heroin control group), however, significant elevations in both plasma ACTH and CORT levels were found in all the H-RI, L-RI and NR groups (p<0.05) after foot shock (Table 2).