Inescapable shock induces the opposite changes of the plus-maze test behavior in rats with divergent coping strategy.

Behavior in the elevated plus-maze and plasma corticosterone levels were investigated in Koltushi high-avoidance (KHA) and low-avoidance (KLA) rat strains subjected to inescapable shock (IS) or daily handling for 10 days. These strains have been genetically selected on the basis of divergent acquisition of a conditioned avoidance response in a two-way shuttle-box. Naive KHA rats were more anxious than KLA ones. Following exposure to IS, the time spent in open arms was increased in KHA rats but decreased in KLA rats. After handling, the time spent in open arms increased only in KHA rats and became similar in both strains. There were no differences in plasma corticosterone levels between naive animals. Exposure to either IS or handling increased the plasma corticosterone levels in KLA rats. In KHA rats, handling reduced the plasma corticosterone levels, and exposure to IS had no effect. The present results suggest that the stress-induced changes in anxiety levels depend on the coping strategy of the subject.