EXTINCTION OF A CONDITIONED TASTE-AVERSION IN RATS .1. BEHAVIORAL-EFFECTS

The literature is divided over whether a conditioned taste aversion (C TA) can be fully extinguished. In Experiment 1, we created a powerful aversion in 54 rats by pairing the taste of 0.0025 M NaSaccharin (CS) with intraperitoneal injections of 127 mg/kg LiCl (US) on 3 occasions. We then offered 23-h deprived rats NaSaccharin for 10 min/day to obse rve the course of recovery. Extinction occurred in three phases: stati c, dynamic, and asymptotic. During the static phase (mean = 9.6 days), rats consumed the CS at <10% of their preconditioned rate. With dynam ic recovery (6.0 days), they increased acceptance to >80% of precondit ioning levels. Finally, they achieved asymptote (3.1 days) at 100% acc eptance. In Experiment 2, we used 8 additional conditioned rats and 8 unconditioned controls. We followed the same 1-bottle extinction proce dure and, again, obtained 100% acceptance. Then we offered both NaSacc harin and water for 8 days at 23 h/day and monitored lick patterns eve ry 6 s to determine taste preferences. The conditioned animals consume d less NaSaccharin than controls on Day 1, and less NaSaccharin as a p ercentage of total fluid as late as Day 3. For the last 5 days of 2-bo ttle preference testing, there were no significant differences between the groups with regard to 1. volume of NaSaccharin or water consumed, 2. percentage of total fluid taken as NaSaccharin, 3. consumption of each fluid associated with a meal or taken spontaneously, 4. intake du ring the light or dark periods, or 5. the characteristics of ingestion , including number of drinking bouts, duration of bouts, number of lic ks/bout, and rate of licking. Therefore, a robust CTA is subject to co mplete behavioral extinction. Copyright (C) 1997 Elsevier Science Inc.