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. 2007 Aug 1;2(8):e698. doi: 10.1371/journal.pone.0000698

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Lenoir et al.

This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.

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a, Reversal of preference in rats which had acquired a preference for lever C under the S-/C+ condition. The first 3 days (-3 to -1) correspond to baseline choice under the S-/C+ condition. The next 10 days correspond to choice after the shift to the S+/C+ condition. b, Choice between levers C and S (mean±SEM) after cocaine intake escalation. Insert: Choice between levers C and S as a function of the dose. c, Cocaine self-injections (mean±SEM) during the hour preceding choice in the modified discrete-trials choice procedure. d, Choice between levers C and S (mean±SEM) during cocaine intoxication. e, Representative individual distributions of cocaine rewards (downward ticks) or saccharin rewards (upward ticks) within the last testing session. The vertical dashed line separates the 1-hour exclusive access to cocaine self-administration (C+ only) from the subsequent 8 discrete choices (S+/C+ condition). *, different from the indifference level (P<0.05, t-test); +, different from the lowest dose (P<0.05, Fisher's LSD test after one-way ANOVA).