5-HT3 RECEPTOR ANTAGONISTS DO NOT MODIFY COCAINE PLACE CONDITIONING OR THE RISE IN EXTRACELLULAR DOPAMINE IN THE NUCLEUS-ACCUMBENS OF RATS

Three 5-HT3 receptor antagonists, MDL 72222, tropisetron, and ondanset ron were studied for their ability to modify the conditioned place pre ference (CPP) induced by 10 mg/kg IP cocaine in rats. MDL 72222 (0.03- 3 mg/kg SC) and tropisetron (0.01-0.1 mg/kg SC) administered, respecti vely, 30 min and 1 h before each conditioning session, did not affect the acquisition of cocaine CPP. Ondansetron (0.01-0.1 mg/kg SC) admini stered 30 min before each conditioning session or just before testing likewise had no effect. At 0.1 mg/kg SC ondansetron did not modify the increase of extracellular dopamine caused by 10 mg/kg cocaine in the nucleus accumbens. The results suggest that 5-HT3 receptor antagonists have no effect on the rewarding properties of cocaine or on the behav iour elicited by the stimuli previously associated with the drug's act ion.