The aversive stimulus properties of repeated infusions of cocaine

When the presentation of a novel food to a rat is followed by the administration of certain compounds, including psychomotor stimulants, the animal consumes less of the food on subsequent presentations relative to an animal administered saline. This phenomenon has been termed gustatory avoidance conditioning. Conflicting results have been obtained when cocaine is used in this procedure. Therefore, the possibility that the weak efficacy of cocaine in this paradigm is due to its relatively short duration of action was investigated. Fluid intake was limited to a single 15 min presentation, seven days a week. Following the determination of baseline water in take sweetened milk was given during the session followed by a series of infusions of cocaine through chronic indwelling peritoneal catheters. Four infusions, spaced 15 min apart, of 9.0 mg/kg cocaine induced an avoidance response, while one infusion of 36 mg/kg cocaine followed by three saline infusions did not. This supports the hypothesis that the low efficacy of cocaine in this paradigm is due, at least in part, to its short duration of action.