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. Author manuscript; available in PMC: 2010 Oct 1.
Published in final edited form as: Psychopharmacology (Berl). 2009 Aug 4;206(3):447–456. doi: 10.1007/s00213-009-1622-4

Figure 2.

Figure 2

Changes in the dose-response curve for self-administered cocaine after 14 days of continuous d-amphetamine (5 mg/kg/day) treatment. All points represent the mean (±SEM) breakpoints under a PR schedule. The final ratio values corresponding to breakpoints are represented on the additional y axis. a) Initial dose-response curve established in all animals (N = 32) after training sessions were completed. b) 14-day d-amphetamine treatment period during which animals were divided into four groups to self-administer one of four cocaine doses (▼: 0.19, ▲: 0.38, ■: 0.75, or ●: 1.5 mg/kg/inj). c) Final dose-response curves for each of the four groups after removal of d-amphetamine mini-pumps. Open symbols represent a significant difference from the same dose in the initial dose-response curve.