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. Author manuscript; available in PMC: 2020 May 1.
Published in final edited form as: Physiol Behav. 2017 Oct 31;203:33–41. doi: 10.1016/j.physbeh.2017.10.026

Figure 1.

Figure 1

Time-line of experimental events as a function of postnatal day (PND). Rats arrived on PND 22, and after recovery from the catheter implantation surgery (PND 28), began a 5-day acquisition period (PND 30) during which 20 infusions of nicotine were available/day under a fixed ratio 1 schedule. Rats then began a 10-day extended access self-administration period (23-hr/day; PND 35) during which there was no limit on the number of infusions available/day. During the 10-day abstinence period rats had 2-hour/day access to an unlocked running wheel (exercise), a saccharin solution (saccharin), or without access to a wheel or saccharin (control; PND 45–54). After the last exercise/saccharin/control session rats were returned to their self-administration boxes. Nicotine-seeking was assessed the next day (PND 55) in females during estrus versus non-estrus phases (assessed 30-min prior to the session) using a within-session extinction/cue-induced reinstatement procedure.