Mean distance traveled scores (±SEM) of rats (n = 8 per group) on the pretreatment day. Rats were injected with saline, cocaine, METH, or NPA immediately before a 30-min placement in the activity chambers (left panels). Additional groups of rats were injected with SCH23390 (0.1, 0.5, 1, or 5 mg/kg) 15 min before DA agonist pretreatment (right panels).
a Significantly different from the saline control group (left panels) when collapsed across time blocks 1–6.
b Significantly different from the saline control group (left panels) on the same time block.
c Significantly different from the cocaine alone group (top left panel) on the same time block.
d Significantly different from the METH alone group (middle left panel) on the same time block.