Effect of a unilateral lesion of DA neurons onm-CPP-induced oral bouts. The data represent the mean ± SEM of oral bouts recorded for 60 min after drug or vehicle injection (n = 6–8 rats per group). Experiments were performed 4.5–5.5 weeks after the injection of 6-OHDA or its vehicle (sham) in the left substantia nigra. Each rat received only one injection of vehicle or m-CPP (1 mg/kg, i.p.). Lesions of dopaminergic neurons by 6-OHDA increasedm-CPP-induced oral movements (two-way ANOVA; see Results). ***p < 0.001 versus saline-treated rats with a sham-lesion; ###p < 0.001 versusm-CPP-treated rats with a sham lesion; +++p < 0.001 versus saline-treated rats with a 6-OHDA lesion (Scheffe's test).