METH pretreatment on basal GLU concentrations in the SN: effect of haloperidol challenge. Rats were administered METH (10 mg/kg 4 times, every 2 h) or 0.9% saline (1 ml/kg 4 times, every 2 h) 2 d before the dialysis experiment. Basal GLU concentrations are expressed as picograms per 20 μl of dialysate. Data shown are mean ± SEM. METH pretreatment caused a significant increase in basal GLU concentrations in the SN compared with saline pretreatment (inset; significance was determined via a t test; *p < 0.05; n = 4 for both groups). Dialysate GLU concentrations are expressed in picograms per 20 μl as the absolute difference from baseline concentrations. Data shown are mean ± SEM. A haloperidol challenge injection (0.5 mg/kg, i.p.) was administered after baseline collection (indicated by a black arrow). HAL produced an overall greater increase in extracellular GLU concentrations in the METH-pretreated group compared with the saline-pretreated group. Significance was determined via a two-way ANOVA with repeated measures. *p < 0.05, significant overall treatment effect; #p < 0.05, significant difference between the METH and saline groups. n = 4 for both groups.