Relationship between the rewarding and aversive effects of morphine and amphetamine in individual subjects

Drugs of abuse have been reported to produce both rewarding and aversive effects, as evidenced by their ability to induce both conditioned place preferences (CPPs) and conditioned taste aversions (CTAs), respectively. Although several attempts have been made to assess the relationship between the rewarding and aversive effects of drugs in independent groups, it is unknown to what extent (if any) preferences and aversions are related in individual animals. The present study assessed this relationship by examining the ability of morphine (5 and 10 mg/kg) and amphetamine (3 and 5 mg/kg) to induce both place preferences and taste aversions in the same animal, using a concurrent CTA/CPP design. There was no consistent relationship between the ability of morphine or amphetamine at either dose to increase time spent on the drug-paired side and the ability to suppress consumption of the drug-paired taste. These results support the position that drugs of abuse have multiple stimulus effects, both rewarding and aversive, that condi- tion place preferences and taste aversions independently.