We investigated other possible mechanisms for increased ethanol intake in the two-bottle choice paradigm. For example, mice can increase consumption of ethanol because of reduced aversive properties of alcohol as well as an increase (or decrease) in ethanol reward (Chester and Cunningham, 2002; Green and Grahame, 2008). Our studies of CPP showed no changes in rewarding properties of ethanol after LPS pretreatment but showed a reduction of the aversive properties of ethanol as measured by CTA. This is consistent with a large literature relating reduced CTA to increased alcohol consumption (Green and Grahame, 2008). In addition, we found that deletion of some chemokine genes increased alcohol CTA (and decreased alcohol consumption) (Blednov et al., 2005a), providing additional evidence that immune signaling is important for the aversive properties of alcohol.
