CROSS-SENSITIZATION BETWEEN COCAINE AND GBR-12909, A DOPAMINE UPTAKE INHIBITOR

In the present experiment, rats which had received repeated injections of 20 mg/kg GBR 12909, a selective dopamine uptake inhibitor, were subjected to challenge doses of GBR 12909 and cocaine which were near or below the threshold for locomotor activation in drug-naive animals. The behavior measured was general motor activity, monitored in photocell testing cages. Results verify earlier findings which showed that rats treated chronically with GBR 12909 display a potentiated locomotor response to low doses of the drug (behavioral sensitization). In addition, it was found that GBR 12909-sensitized rats show a potentiated locomotor response to 5 mg/kg cocaine (cross-sensitization). These results are discussed with regard to various mechanisms which may underlie the sensitization phenomena observed, including possible neurochemical changes at the presynaptic level.