Fig. 2.
The effect of intra-accumbens amphetamine during lever pressing bouts in the presence and absence of the cue for both the CS+ and CSrandom groups. Filled circlesrepresent mean ± SEM squared root responses on each lever during presentations of the CS+, and open circles represent responses during the periods immediately before each CS+ presentation.Filled triangles depict responses during presentations of the CSrandom, and open trianglesdepict responses during the periods before each CSrandompresentation. Intra-accumbens amphetamine significantly increased the ability of the CS+ to trigger enhanced responding on the sucrose lever (two-way ANOVA; *p < 0.01 or **p < 0.001; Bonferroni) but not on the control lever. Amphetamine did not change the incentive impact of the CSrandom control cue. In the absence of the CS+ reward cue, amphetamine had only a minimal general motor effect on pressing of both levers.