Choice between saccharin and cocaine as a function of drug history.

<p>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 (<i>P</i><0.05, <i>t</i>-test); +, different from the lowest dose (<i>P</i><0.05, Fisher's LSD test after one-way ANOVA).