Enhancing effects of Ro 15-1788 on straw-climbing behavior as measured with the straw-suspension method: reversal by diazepam

Ro 15-1788 (0.5, 1, 5, or 20 mg/kg), a pure benzodiazepine receptor antagonist, was studied for its effect on the duration of immobility and the number of straw-climbing attempts in a modified forced-swim test with straw-suspension of rats. A single dose of 20 mg/kg of Ro 15-1788 injected IP prolonged only the duration of immobility with no effect on straw-climbing behavior, whereas both doses of 1 and 5 mg/kg of this compound significantly enhanced the number of straw-climbing attempts in an inverted U-shaped manner. Ro 15-1788 at 1 mg/kg significantly reversed the inhibitory effect of 1 mg/kg of diazepam on the number of straw-climbing attempts. It is suggested that the enhancing effect of low doses of Ro 15-1788 on straw-climbing behavior can be regarded as an index of its anxiogenic effect, by acting via central benzodiazepine receptors.