Struggling and flumazenil effects in the swimming test are related to the level of anxiety in mice.

The possible involvement of anxiety and learning/memory processes in escape-directed (struggling) behavior in a two-trial swimming test was investigated in mice, as well as the differential effects that low doses of flumazenil (a benzodiazepine receptor antagonist) could display depending on the animals' anxiety levels. Mice showing less anxiety in the plus-maze test exhibited less struggling behavior in the first swimming trial than the more anxious animals, suggesting a relationship between anxiety and struggling behavior in the swimming test. Flumazenil (5 mg/kg) given before the first swimming trial displayed differential effects depending upon the animals' anxiety levels. Thus, it increased struggling behavior in the first swimming trial in 'low-anxiety' mice whereas the opposite tendency was observed in 'high-anxiety' animals. Struggling decreased in the second swimming trial in all the animals, giving support to the involvement of learning/memory processes in the two-trial swimming test. That reduction in escape-directed behavior was greater in animals treated with flumazenil before the first swimming session, thus indicating a slight enhancement of retention.