Figure 2.

Footshock stress-induced aversion is mediated by the dynorphin/KOR system. Significant aversion was evident to a compartment previously paired with shock compared with unshocked controls. Unshocked controls spent nearly equal time in both compartments during the 15 min session. Wild-type (WT) mice pretreated with the κ-opioid antagonist norBNI (10 mg/kg, i.p.) did not show significant place aversion after shock training. Mice lacking dynorphin (Pdyn, −/−) also failed to develop a significant place aversion after shock training. **p < 0.01, significantly different from saline/no shock group (n = 5–8 animals per group).