Induction of conditioned taste aversion with a self-administered substance in rats

Drugs of abuse such as cocaine induce a paradoxical aversive effect when paired with a novel taste. When a novel gustatory cue is paired with drugs of abuse the resulting conditioned effect is the avoidance of the novel taste. A conditioning paradigm was developed in order to pair saccharin with self-administered cocaine. Rats were trained to lever-press for sweetened milk in an operant chamber and then implanted with an intrajugular catheter for cocaine self-administration (SA). After recovery from surgery, food and water access were restricted and the operant behavior was reestablished using contingent milk. Pairings of 10-min saccharin access followed by 1-h cocaine (0.125 mg/kg per injection) SA sessions were alternated daily with pairings of 10-min water access followed by 30-min SA sessions of oral milk and i.v. saline, delivered simultaneously. Pairings were conducted once a day for 10 days. After four sessions of cocaine self-administration there was no significant decrease in saccharin intake. However, rats that avoided saccharin also self-administered more cocaine than non-avoiding rats. These results suggest that the development of taste aversion is accompanied by an acceptance of the drug rather than an aversion to it.