The study examined the effects of the
benzodiazepine receptor partial agonist,
Ro 19-8022, on anxiety-like, aggressive, social and locomotor behaviours in timid ('anxious') and aggressive mice in the social conflict test. To test the hypothesis that
Ro 19-8022 acts as a partial agonist in this model, i.e. it reduces anxiety-like and aggressive behaviours without affecting motor coordination, its effects were compared to those of the full agonist,
nitrazepam. Both
Ro 19-8022 and
nitrazepam decreased anxiety-like behaviour in timid mice and aggressive behaviour in aggressive mice. The effect of the full agonist,
nitrazepam, was dose-dependent while the effect of the partial agonist,
Ro 19-8022, was lower in magnitude and reflected its partial agonistic properties. Both drugs stimulated social behaviour in both groups of mice, presumably due to disinhibition of anxiety or aggression. The marked difference was in their effects on motor coordination, as
nitrazepam, but not
Ro 19-8022, produced motor impairment at higher doses. Thus,
Ro 19-8022 produces
anxiolytic-like and potent anti-aggressive effects without causing muscle relaxation or
ataxia in the present model. Our data confirm that the main behavioural differences between partial and full
benzodiazepine receptor agonists are in their side-effect profiles.