Quantitative analysis of the density of Fos-like immunoreactive cells in the GP, EPN, SNr, and subthalamic nucleus (STh) after systemic administration ofm-CPP (1 mg/kg, i.p.) in rats with sham and 6-OHDA-induced lesions. The data are expressed as the mean ± SEM of Fos-like immunoreactive cells per square millimeter on the side of the lesion (white bars) and the contralateral side (black bars) in each experimental group.s/v, Sham/vehicle; s/C, sham/m-CPP; 6/v, 6-OHDA/vehicle;6/C, 6-OHDA/m-CPP (n= 6–8 animals per group). Experiments were performed 4.5–5.5 weeks after the injection of 6-OHDA or its vehicle in the left substantia nigra. The nigrostriatal lesion significantly increased the number of Fos-like immunoreactive cells after m-CPP administration on the side of the lesion only in the EPN (two-way ANOVA; see Results).m-CPP induced by itself a significant increase of Fos-like immunoreactive cells in the subthalamic nucleus (one-way ANOVA; see Results). *p < 0.05 and **p < 0.01 compared with saline-treated rats with a sham-lesion; +p < 0.05 and +++p < 0.001 compared with saline-treated rats with a 6-OHDA-lesion; ##p < 0.01 compared withm-CPP-treated rats with a sham lesion (Scheffe's test).