Attenuation of defensive threat and attack in wild rats (Rattus rattus) by benzodiazepines

A battery of tests designed to elicit reactions to a variety of non-painful threat stimuli was used to study the effects of chlordiazepoxide (5–20 mg/kg), diazepam (1–5 mg/kg) and midazolam (1–10 mg/kg) on the defensive repertoire of wild Rattus rattus. The most consistent effect of benzodiazepine treatment, across compounds and tests, was a marked reduction in defensive threat and attack behaviors, with midazolam effective over a wider range of situations. In contrast, effects on freezing and flight reactions were more variable, differing substantially as a function of stimulus context. The general profile of observed changes in defense cannot be explained in terms of either non-specific behavioral suppression or a global reduction in defensiveness. Rather, our findings suggest that benzodiazepines may primarily induce a shift within the defense repertoire.