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. Author manuscript; available in PMC: 2014 Jul 2.
Published in final edited form as: J Pharmacol Exp Ther. 2005 Sep 6;315(3):1320–1330. doi: 10.1124/jpet.105.090423

Figure 1.

Figure 1

Progressive ratio break point values for drug (left panel) and money (middle panel) and amount of drug self-administered (right panel) as a function of dose and drug. Break point values could range between 0 and 2800. Data points represent the mean across 6 participants and 2 choice sessions. Error bars represent ± 1 standard error of the mean (S.E.M.). Filled symbols indicate significant differences from placebo (open squares); * indicates significant differences from the lowest active dose; # indicate significant differences from the intermediate active dose (P<0.05).