The comparative effects of benzodiazepines, progabide and PK 9084 on acquisition of passive avoidance in mice.

Acquisition of passive avoidance following aversive conditioning to a dark compartment was measured in mice under the influence of one of seven benzodiazepines, the GABA-mimetic drug progabide or PK 9084, a nonbenzodiazepine ligand on benzodiazepine receptors. The drugs were administered prior to the training trial and retention was measured in the absence of the drug 24 h later. Oral administration (dose in mg/kg in parentheses) of flunitrazepam (0.1), lorazepam (1.0), nitrazepam (3.0), diazepam (10), flurazepam (10) and chlordiazepoxide (30), all prevented retention whereas progabide (100-800) and PPK 9084 (10-100) were ineffective. In comparison to effects on motor capacity none of the benzodiazepines was outstanding in its acquisition interfering effects.