Anxiety-like subjective effect of ethanol antagonist RO 15-4513 demonstrated in pentylenetetrazol discrimination.

Ro 15-4513, a benzodiazepine-receptor ligand which antagonizes ethanol, was tested in the pentylenetetrazol discrimination, a bioassay for anxiogenic drugs. Rats were trained with food reward to discriminate pentylenetetrazol (PTZ) from saline in a two-lever operant task. In lever-selection tests, rats selected the PTZ lever both after PTZ and after Ro 15-4513. The PTZ-like stimulus produced by Ro 15-4513 was blocked by diazepam and by the benzodiazepine receptor blocker Ro 15-1788. Substitution for the anxiogenic drug PTZ, and blockade by the anxiolytic diazepam, support the hypothesis that Ro 15-4513 is anxiogenic; blockade by Ro 15-1788 suggests that the PTZ-like stimulus produced by Ro 15-4513 occurs through its action at the benzodiazepine receptor.