Encounters with aggressive conspecifics enhance the locomotor-activating effects of cocaine in the rat

Evidence suggests that stress enhances the behavioural actions of cocaine i n the rat. Paradoxically, however, encounters with aggressive conspecifics lead to a pattern of cocaine self-administration indicative of a reduced fu nctional impact of the drug. Hence, we examined the effects of aggressive e ncounters on another behavioural measure-locomotor activity. Encounters bet ween Lister Hooded rats and rats of the aggressive Tryon Maze Dull strain s ignificantly enhanced the locomotor-activating effects of cocaine (20 mg/kg ) in the Lister Hooded rats. The results suggest that the discrepant findin gs derived from self-administration studies are a property of the paradigm rather than a property of the stressor.