Figure 3.

Selective σ₁R agonist self-administration after cocaine experience, but not after experience with food reinforcement. Each point represents the mean ±SEM. (a, b) Self-administration of selective σ₁R agonists when each response produced an injection. Reversal of active and inactive levers, extinction, and reacquisition each had the effects expected for a reinforcing agent. (c) Dose–effect curve for PRE-084 self-administration before and after experience with cocaine self-administration. No dose of PRE-084 was self-administered at rates greater than those for saline in cocaine-naive rats. Following cocaine self-administration, the dose–effect curve of PRE-084 self-administration was typical of those obtained with traditional drugs of abuse. (d) A food reinforcement history was not sufficient to induce reinforcing effects of PRE-084. *p<0.05, ***p<0.001, compared with responding on the inactive lever (post-hoc Bonferroni t-test). (e) Performances of a representative subject in real time (details of recording as in figure 2c). The first record is from the last session of responding maintained by food reinforcement. The second record is from the immediately following session, the first opportunity to self-administer 0.32 mg/kg/injection of PRE-084 after experience with food reinforcement, showing the extinction of responding previously maintained by food reinforcement. The 10th sessions confirm no acquisition of PRE-084 self-administration.