Figure 1.

Effect of cebranopadol on cocaine SA under fixed (A) and progressive (B) ratio of responses. (A) Both doses of cebranopadol decreased the number of cocaine infusions earned (top panel); the effect of cebranopadol was specific, as inactive lever responses were not affected by treatments (bottom panel). (B) When cebranopadol was tested on motivation for cocaine expressed as breakpoint reached in SA session under a progressive-ratio schedule of reinforcement, the dose of 50 µg/kg, but not 25 µg/kg, decreased the break point for cocaine. Values are presented as mean ± SEM. Statistical differences: *p < 0.05 and ***p < 0.001 vs. vehicle; ^#p < 0.05 and ^##p < 0.01 vs. 25 µg/kg. SA, self-administration.