Ketaset-Rompun extends the effective interstimulus interval in long-trace taste-aversion conditioning in rats

The effect of anesthesia (Ketaset-Rompun) interpolated between the conditioned stimulus (CS) and unconditioned stimulus (US) during long-trace taste-aversion conditioning in rats was examined in three experiments. In Experiment 1, rats that were anesthetized immediately after experiencing a saccharin solution formed a taste aversion at a 3-h interval that typically does not support conditioning, a prolongation effect. Prior experience with the anesthetic eliminated the associability of the aversive consequences of the anesthetic but did not eliminate the anesthetic's prolongation effect. Some evidence was also obtained indicating that LiCl produced an aversion at the 3-h interval in unanesthetized rats if they had experience with the anesthetic prior to conditioning. In Experiment 1a, the interval between prior experience and conditioning was extended from 24 to 96 h. Results demonstrated that the evidence for conditioning at 3 h for unanesthetized subjects in Experiment 1 was not a robust finding. By reversing the role of Ketaset-Rompun (KR) and LiCl as prior experience manipulation and US treatment in Experiment 2, the prolongation effect was shown not to be due to the summation of the aversive properties of the anesthetic and the LiCl. Results were interpreted in terms of a hypothesized metabolic pacemaker.