DIFFERENTIAL-EFFECTS OF AMPHETAMINE ON THE ATTACK AND DEFENSE COMPONENTS OF PLAY FIGHTING IN RATS

Treatment with d-amphetamine has been shown to cause a decrease in pla y fighting by juvenile rats. Previous studies, however, did not determ ine if all behavioral components of play were equally diminished. In t his study, the effects of amphetamine on both the attack and defense p atterns of play fighting were analyzed. Experiment 1 shows that a 0.5 mg/kg dose, injected subcutaneously in the nape, decreases both attack and defense. In contrast, Experiment 2 shows that the same dose, inje cted subcutaneously in the hip, decreases the level of attack to a sim ilar level, but does not significantly affect defense. This suggests t hat while the 0.5 mg/kg dose of amphetamine is primarily affecting the attack components of play, via its action on the central nervous syst ems, the reduced likelihood of defense for those rats injected in the nape probably results from a local anesthetic effect, which numbs the area of the body defended during play fighting. Further doses (0.15 & 1.0 mg/kg), injected in the hip, were also tested. The highest dose de creased both components of play. The lowest dose had no effect on eith er attack or defense. It is suggested that the attack and defensive co mponents of play fighting may be mediated by different neural systems.