Conditioned place aversion mediated by self-administered ethanol in the rat: a consideration of blood ethanol levels.

A previous experiment has shown that rats will avoid environmental cues that have been associated with a history of ethanol self-administration. One possible explanation for this conditioned place aversion may be related to the temporal parameters of that experiment. During the initial segment of each 90-min conditioning/drinking trial (when most of the drinking occurred) the blood ethanol levels (BELs) were low and may well have produced positive effects at that time. However, as the drug continued to be absorbed and BELs increased during the remainder of the 90-min trial, the final (and conditioned) drug effects may have been aversive. In the present experiment the trial length was shortened to a 15-min period so that only low BELs would be temporally paired with the conditioning environment. A conditioned preference for that environment was predicted. Twelve rats were trained to self-administer ethanol in one environment and had water available in a different environment. Eight control animals had only water in both environments. BELs were measured and found to be low (16.8 to 57.6 mg%) and rising during the conditioning trials. However, when given a choice between the two environments, the rats avoided the environment in which they formerly consumed ethanol. No change in preference was noted for the control animals. This result was in accordance with previous findings but did not support the hypothesis that low, excitatory BELs would mediate a conditioned place preference in the rat.