Effects of alprazolam on anxiety-related behavior of rats in a modified forced-swim test employing straw suspension.

The present study was undertaken to examine how the triazolobenzodiazepine derivative, alprazolam, which possesses anxiolytic activity in man and anticonflict effects in animals, could affect both the duration of immobility and the incidence of straw-climbing behavior of rats in a modified forced-swim (MFS) test. After a 5-min test of forced swimming, four straws were suspended just above the surface of the water and subsequently the straw-climbing trials were counted for 5 min as an index of escape behaviors induced by negative emotionality (anxiety and/or fear). Rats were injected IP with either alprazolam (0.1, 0.2, 1, and 2 mg/kg) or its vehicle 30 min before testing. Alprazolam prolonged the duration of immobility and inhibited the straw-climbing counts in a dose-dependent manner. This effect is in the same direction as the effect shown by an anxiolytic benzodiazepine such as diazepam. The results suggest that alprazolam may possess anxiolytic effects at lower doses, whereas at a high dose of 2 mg/kg this compound might elicit sedation, concomitantly with its anxiolytic and/or antipanic effects. In addition, it appears that alprazolam is more potent than diazepam in the MFS test following a single-injection protocol.