Conditioned defensive burying as a model for identifying anxiolytics.

Rats exposed to a presumably aversive stimulus such as electric shock respond by heaping litter on the source, a behavior known as conditioned defensive burying (CDB). Because some anxiolytics suppress this behavior, CDB has been proposed as a screening method for anxiolytics. We tested the effects of the conventional anxiolytics chlordiazepoxide (4-32 mg/kg) and meprobamate (75-125 mg/kg), the novel anxiolytic buspirone (8-64 mg/kg), the antidepressant imipramine (4-16 mg/kg), the opiate analgesic morphine (2-8 mg/kg), and the antipsychotic chlorpromazine (1-16 mg/kg) on CDB. Chlordiazepoxide, meprobamate, imipramine, and morphine significantly suppressed CDB, but chlordiazepoxide did so only at a dose that reduced general activity. Buspirone and chlorpromazine did not suppress CDB at doses that reduced activity. There were some methodological differences from previous studies. We conclude that the test as constituted in this study lacks drug-class specificity. The necessity of distinguishing between specific reduction of burying and general reduction of activity is emphasized.