Diazepam changes risk assessment in an anxiety/defense test battery

An anxiety/defense test battery was designed to assess defensive reactions of laboratory rats to situations associated with nonpainful threat (exposure to a cat). The battery measured three defense patterns, movement inhibition, risk assessment behaviors, and inhibition of nondefensive behaviors, in two tasks. Diazepam (4.0 mg/kg) altered four of five risk assessment measures, but failed to show an anxiolytic effect on movement inhibition, and had minimal and inconsistent effects on inhibition of nondefensive behaviors. The risk assessment changes with diazepam were all consistent with an anxiolytic action of diazepam. These results provide a partial contrast to the general lack of anxiolytic action of diazepam in a fear/defense test battery designed to measure reactions to a discrete, present, threat stimulus, and suggest a greater diazepam effect on risk assessment than on other aspects of defensive responding. Sex differences indicating higher defensiveness for female than male rats were obtained on many of these measures.