Conditioned place aversion mediated by orally self-administered ethanol in the rat.

The hypothesis was tested that ethanol, self-administered via the oral route, would mediate a conditioned preference for the environment in which the drug was consumed. Ten rats were trained to drink an 8% (weight/volume) ethanol solution in association with one environment and had a different environment paired with the availability of water. Ten control animals had only water available in both environments. The experimental animals drank more ethanol solution than water and achieved doses in excess of their metabolic capacity as confirmed by blood ethanol levels. The drug was functioning as a positive reinforcer, yet the rats avoided the environment in which ethanol was consumed, indicating aversive properties of the drug. The control animals showed no change in preference for the environments associated with water. The conditioned place aversion observed was in accordance with previous studies in which rats were passively dosed using non-oral routes of administration but was paradoxical since the ethanol was actually self-administered.