Ethanol Exposure During Either Adolescence or Adulthood Alters the Rewarding Effects of Cocaine in Adult Rats

Objectives: The present studies assessed the effects of adolescent and adult ethanol exposure on the rewarding effects of cocaine as measured with the conditioned place preference procedure.

Methods: Male rats were exposed to intraperitoneal (IP) injections of ethanol or vehicle for 10 days [postnatal days (PNDs) 30-39 or PNDs 70-79; 2 mg/kg]. Place preference conditioning began on PND 65 or PND 105, respectively, and consisted of a baseline test followed by four conditioning cycles with either 0, 5, 10 or 20 mg/kg cocaine. Following the fourth conditioning cycle a final preference test was performed. Changes in time on the drug-paired side between the baseline and final test were analyzed.

Results: Animals exposed to vehicle (during adolescence or adulthood) showed a significant place preference at 20 mg/kg cocaine. Animals exposed to ethanol (during adolescence or adulthood) showed a significant place preference at 10mg/kg cocaine.

Conclusions: Exposure to ethanol (adolescents or adults) sensitized the rewarding effects of cocaine. This may indicate an increase in the abuse liability of cocaine following a history of ethanol exposure.