Conditioned place aversion induced by intragastric administration of ethanol in rats.

Most experiments investigating ethanol-induced place conditioning in rats have produced conditioned place aversion (CPA). In one of the few reports of ethanol-induced conditioned place preference (CPP) in rats, selectively bred alcohol-preferring (msP) rats showed CPP in a biased procedure when ethanol was administered via intragastric (IG) catheter but not when ethanol was administered via intraperitoneal injection or by gavage. This finding suggests the importance of both route of administration and genetic variables to the outcome of place conditioning studies. We conducted three experiments examining place conditioning induced by IG ethanol in genetically heterogeneous rats to test the generality of the earlier finding. We employed an unbiased procedure that is more sensitive to detecting preference changes in either direction (preference or aversion). Ethanol-naive (Experiment 1) and ethanol-experienced Sprague-Dawley rats (Experiment 2) showed robust CPA. In Experiment 3, infusion rate was varied to see if the CPA observed in Experiments 1 and 2 was a result of the rapidity of the transition from the sober to the intoxicated states. Both groups showed strong CPA. Overall, the present findings are consistent with previous findings of CPA in heterogeneous rats, suggesting that the aversive postabsorptive effects of ethanol produce CPA.