Figure 2.

A. Difference in nicotine infusions per session between the extinction burst group (n = 31) and non-bursting (n = 53) extinction group of animals that were both trained to self-administer nicotine (0.03mg/kg/infusion) in 1-h/day sessions. *p<0.05, Student’s t-test. B. Response rates (responses/min) for each 5-min block from the EXT1 session for the high-intake and low-intake (> 12.75 and < 12.75 infusions during nicotine self-administration, respectively). C. Response rates (responses/min) for the high intake and the low intake animals across the EXT1-3 sessions. D. Nicotine infusions per session over the nicotine self-administration acquisition sessions with FR-1, -2 and -5 scheduling between the high intake and low intake group. *p<0.05, ***p<0.001, Bonferroni’s multiple comparison test following a significant RM two way-ANOVA (for B, C and D). All data expressed as means (±SEM).