Fig. 2.

Yohimbine challenge induces reinstatement of ethanol- and sucrose-seeking behavior each week for four consecutive weeks. Yohimbine (2 mg/kg i.p.) was administered once weekly for four consecutive weeks and induced a significant increase in active lever pressing in a 10% ethanol-seeking animals (***p<0.001; **p<.01; *p<.05 compared to vehicle: ^##p<.01 compared to week 1 yohimbine reinstatement), b 20% ethanol-seeking animals (***p<0.001; **p< 0.01 compared to vehicle), and c 5% sucrose-seeking animals (***p< 0.001; **p<.01; *p<.05 compared to vehicle). Injection of vehicle had no effect on active or inactive lever responding (n.s., compared to extinction baseline, data not shown) in ethanol and sucrose-seeking animals. d 10% ethanol-trained animals had a significantly higher level of reinstatement in the first week of testing when compared to sucrose animals (*p<.05 compared to the sucrose reinstatement for the corresponding week). Data are presented as mean±SEM, (n=14 for 10% ethanol group, n=10 for 20% ethanol group, and n=16 for sucrose groups). Statistical analysis was performed by repeated-measures ANOVA with Newman–Keuls post hoc testing