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. Author manuscript; available in PMC: 2018 Jun 1.
Published in final edited form as: Psychopharmacology (Berl). 2017 Mar 31;234(12):1815–1828. doi: 10.1007/s00213-017-4590-0

Figure 9.

Figure 9

Mean lever presses (±SEM) on the active (closed circle) and inactive (open square) levers across sessions in Experiment 4 collapsed across Sex and Social Condition in rats with access to (a) saline (0.00 mg/kg, Sal) or nicotine at doses of 0.015 (b) or 0.03 (c) mg/kg, IV. An FR1 schedule of reinforcement was in effect during sessions 1-3 and a progressive ratio schedule was in effect during sessions 4-20 that increased from an FR1 to FR2 to FR 3 depending on individual performance with the criterion for advancement of 5 reinforcers obtained within 60 min. See Table 1 for n/condition. Asterisks (*) represent a difference between active and inactive lever, test of simple effects, ps<0.05.