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. Author manuscript; available in PMC: 2016 Jun 3.
Published in final edited form as: Psychopharmacology (Berl). 2014 Feb 21;231(16):3189–3195. doi: 10.1007/s00213-014-3501-x

Fig. 1.

Fig. 1

Schematic illustrating time course of experiments in this study. Rats acquired nicotine SA (0.03 mg/kg, 23h/day) under an escalating fixed-ratio (FR) schedule of reinforcement from FR1 to FR5 for at least 20 days. Then, rats abstained from nicotine for 7 days during which, on alternating days, the restraint (30 min) was applied to rats in the stress group, while not in the non-stress group. Thereafter, in experiment 1 (EXP 1), reacquisition of nicotine SA was first elevated under a progressive ratio (PR) schedule during a 23h session that began immediately post-final stress (i.e. 4th session); this was followed by an FR5 schedule for 5 days. In EXP 2, the reacquisition sessions (FR5) began 24 h after the final stress (i.e. 4th session). No PR session was conducted. In EXP 3, only 2 sessions of restraint were administered during abstinence. Reacquisition was assessed beginning 24 h or 5 days after the second stress. In EXP 4, the time course was as same as in experiment 2, but nicotine reinforcement was not available during reacquisition.