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. Author manuscript; available in PMC: 2026 Jul 1.
Published in final edited form as: Neuroscience. 2026 Jun 9;610:147–162. doi: 10.1016/j.neuroscience.2026.06.002

Fig. 1. Schematic of experimental cohorts.

Fig. 1.

a. Cohort 1. Following arrival, adult rats (N=24) were acclimated and then handled. The CPP behavior followed a 14-day sequence: (Preconditioning; PRE): On day 1 rats were given free access to the entire CPP apparatus (30 min). Conditioning: On days 2 – 9, rats had four 2-day training sessions. Rats were divided into 4 groups (Sal female, Oxy female, Sal male, Oxy male; N = 4/grp). On the first day of each session, Oxy rats were administered oxycodone (3mg/kg, i.p.) and restricted to one compartment of the apparatus (30 min). On the second day of each session, the Oxy rats were administered saline and restricted to the other compartment (30 min). Sal rats were injected with saline before each conditioning session. CPP test: On day 14, the doors separating the compartments were removed. The rats were not injected and were put in the central neutral gray compartment and their behavior was monitored for 30 min. Rats were immediately euthanized after the CPP test. b. Cohort 2. The experimental design was identical that described in a, except that rats were subjected to CIS after acclimation and handling and before the CPP behavior.