An unbiased conditioned place preference (CPP) assay was carried out as described previously495659. Mice were evaluated for cocaine place preference using 3 chambered CPP Med Associates boxes and software. The two end chambers were made to have distinct visual (gray vs. striped walls) and tactile (small grid vs. large grid flooring) cues to allow differentiation. On the pre-test day animals were allowed to freely explore all three chambers for 20 minutes and those that showed a significant preference for one of the two chambers were excluded from further analysis (<10% of animals tested). Groups were then balanced and adjusted to balance out any pre-existing chamber bias. Place preference conditioning was carried out by pairing an injection of saline with one chamber in the morning, and a second injection of cocaine (5 or 10 mg/kg) with the other chamber in the afternoon for two consecutive days. CPP testing was carried out on the fourth day when each animal was again allowed to explore all chambers freely. Place preference score was taken as time on the cocaine paired side – time on the saline paired side.
