Fig. 6.
Baselines before, during, and after repeated oxycodone administration. (A) Baselines significantly shifted to the right during repeated dosing but recovered after a period of drug abstinence. There was a significant effect of baseline day (F4, 32 = 17.57, P < 0.0001) and an interaction between baseline day and frequency (F36, 288 = 3.13, P < 0.0001). (B) Percent day 0 baseline stimulations were also reduced during repeated administration of oxycodone and returned to day 1 baseline responding after a period of drug abstinence (day 34), shown as the white bar (F4, 32 = 22.87, P < 0.0001). Significant differences for frequency-rate curves (A) are denoted by filled symbols (gray: P < 0.05; black: P < 0.01) and by asterisks for the percent baseline stimulations (B; *P < 0.05; ****P < 0.0001). All values represent means ± S.E.M., and error bars on frequency-rate curves are omitted for clarity (n = 9).