Cocaine-induced taste aversions: effect of route of administration.

Female Long-Evans rats were given 20-min access to saccharin followed by either intraperitoneal (IP) or subcutaneous (SC) cocaine (18, 32 or 50 mg/kg) or vehicle. Aversions induced by IP-administered cocaine were relatively weak, with subjects at all doses decreasing consumption by only 35% after four conditioning trials. On the other hand, aversions induced by SC-administered cocaine were robust, with subjects at the two highest doses (32 and 50 mg/kg) decreasing saccharin consumption by 95 and 98%, respectively, on the final aversion test. Although several possibilities exist for the differential ability of IP and SC cocaine to induce taste aversions (e.g., longer duration of action with SC cocaine and the convulsant property of IP cocaine), the basis for this difference remains unknown. A secondary finding was the effect of route of administration on body weight. While all subjects receiving IP cocaine maintained or increased in body weight, subjects receiving the two highest doses of SC cocaine decreased in body weight by 3 and 5%, respectively. The differential effect of IP and SC cocaine on body weight may be due to cocaine's action on drinking and feeding or cocaine's leptogenic property. Independent of the mechanism underlying the differential ability of IP and SC administration to induce taste aversions and affect body weight, it is clear that route of administration may play an important role in the effects of cocaine.