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. Author manuscript; available in PMC: 2009 Jun 8.
Published in final edited form as: Pharmacol Biochem Behav. 2007 May 5;87(2):267–279. doi: 10.1016/j.pbb.2007.04.023

Figure 1.

Figure 1

Responding for intravenous cocaine delivered on an FR 2 schedule of reinforcement. Open squares and open circles, respectively, represent females and males responding for the 0.3 mg/kg unit dose. Closed squares and closed circles, respectively, represent females and males responding for the 1mg/kg unit dose. (A) The mean ± S.E.M. across sessions for the 4 groups of mice. (B) The predicted values from the 2 level hierarchical model for lever pressing across the 4 sessions by the same mice summarized in Panel A. The hierachical analysis indicated that responding was dose-dependent but did not vary according to sex.