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. 2021 Nov;379(2):108–116. doi: 10.1124/jpet.121.000655

Fig. 1.

Fig. 1.

Number of infusions earned during 90-minute self-administration sessions by adult male Sprague-Dawley rats (n = 16/drug) responding for 0.032 mg/kg/infusion MDPV (circles), 0.32 mg/kg/infusion cocaine (squares), 0.0032 mg/kg/infusion fentanyl (diamonds), 0.032 mg/kg/infusion nicotine (downward triangles), or 1 mg/kg/infusion ketamine (upward triangles) during the initial 10 sessions on a FR1:TO 5-second schedule of reinforcement and final 10 sessions of infusions earned under a FR5:TO 5-second schedule of reinforcement. Symbols represent mean (±1 S.E.M.) number of infusions earned across 20 sessions of self-administration. Abscissa: session number (day) where the left sessions 1–10 were responding under FR1 and right sessions 1–10 were responding under FR5. Ordinates: mean number of infusions earned. A two-way repeated measures ANOVA found no significant difference between the mean number of infusions earned during the final three sessions of responding under FR1 compared with FR5 [F(1,105) = 0.07; P = 0.79].