Selective anti-aggressive properties of DU 27725: ethological analyses of intermale and territorial aggression in the male rat.

The effects of a new anti-aggressive compound, DU 27725, were evaluated in intermale and territorial aggression. Ethological analysis of intermale aggression showed that DU 27725 (1 to 8 mg/kg IP) strongly decreased aggression, while introductory social behaviour was unaffected or enhanced. The offensive character of aggression disappeared and was replaced by a more defensive pattern. No drastic changes occurred in non-social activities. Sedation, muscle relaxation and motor impairment did not occur at any of the doses tested, suggesting that the anti-aggressive effects were not caused by nonspecific actions of the drug. In territorial aggression, DU 27725 (4 and 8 mg/kg IP) also decreased all aspects of aggression; introductory social behaviour was slightly decreased, and defensive behaviour remained unaffected. At the highest dose (8 mg/kg) sedation was observed. DU 27725 reduced both the number of ultrasonic vocalizations and the number of bites inflicted upon the partners.