The GABAergic effect of low doses of lorazepam on social behavior

The aim of this work was to test the antiaggressive effects of lorazepam and to determine whether these effects were mediated by benzodiazepine receptors. In a first experiment, male mice were injected with lorazepam in a range of low doses (0.05, 0.1, 0.2, and 0.6 mg/kg) or saline solution. In a second experiment, 1 mg/kg of Ro 15‐1788, a benzodiazepine receptor antagonist, and a saline solution were injected before the behavioral test. Results showed that 0.6 mg/kg of lorazepam was the only dose that decreased the total duration of threat (P < .01) and social investigation (P < .05) and that 1 mg/kg of Ro 15‐1788 had no effects. In the third experiment, animals received two injections: 0.6 mg/kg of lorazepam plus 1 mg/kg of Ro 15‐1788, 0.6 mg/kg of lorazepam plus saline solution, or saline solution plus saline solution. Those treated with lorazepam and saline solution spent less time digging (P < .001), threatening (P < .001), and attacking (P < .05) and more time avoiding the opponent (P < .01) or being immobile (P < .001) than the controls. Ro 15‐1788 was successful in completely antagonizing the behavior modulated by lorazepam. Aggr. Behav. 28:248–256, 2002. © 2002 Wiley‐Liss, Inc.