Conditioned Taste Aversion (CTA)-Induced Saccharin Devaluation

Aversion conditioning was conducted in feeding cages in an experimental room (CTA room) physically different from the room containing the self-administration chambers (choice room) to minimize direct aversive conditioning to the operant chambers and to devalue saccharin in similar conditions as the satiety-induced devaluation test. Animals were allowed to acclimate to this room for 30 min to avoid novelty-induced anxiety. Rats in the D group (N = 10) were given 30 min of free access to a bottle containing 0.2% saccharin whereas rats in the ND group (N = 10) were given free access to a water bottle. After this 30-min period, rats returned to the colony room and were injected with lithium chloride (5 ml/kg, i.p., of 0.3 M LiCl) before being returned to their home cages. The entire procedure was repeated three times until >80% suppression of saccharin drinking. Rats were then left in their home cages for at least 48 h after the last LiCl administration and before being tested for lever-press responding under extinction. For each rat, extinction begins after a delay of 10 min. During extinction, both levers are presented simultaneously and continuously for 10 min. Responding on either lever has no programmed consequence. To confirm the presence of the CTA, immediately after extinction testing, animals were brought back to the CTA room and were all given free access to a bottle containing 0.2% saccharin during 30 min.