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. Author manuscript; available in PMC: 2014 Nov 15.
Published in final edited form as: Behav Brain Res. 2013 Oct 10;257:275–285. doi: 10.1016/j.bbr.2013.10.003

Fig. 2.

Fig. 2

The top graphs reflect operant responses for food (±SEM) across IVSA days in adolescent-onset (n = 6–10), naïve adult (n = 6–13), and adult rats that were pre-exposed to nicotine during adolescence (n = 9). Rats were given 23-h access to perform operant responses for saline (open symbols) or escalating doses of nicotine (filled symbols; 0.03, 0.06, or 0.09 mg/kg/0.1 mL infusion) for 4-day intervals separated by 3-day periods of abstinence. The rats received 2 cycles of the IVSA regimen. The bottom graph reflects mean responses (±SEM) separated by the weekly dosing regimen of nicotine IVSA. Only Cycle 1 is presented in order to compare group differences in operant responses when the adolescent rats were still in the adolescent period. Asterisks (*) denote significant group differences from saline IVSA. Number signs (#) denote significant group differences from naïve adults (P ≤ 0.05).