(A) Amphetamine (AMPH) (combined) is an omnibus group that includes the three AMPH control groups (AMPH Systemic, 0.0 μg/0.5 μl/side IWP-2 groups from B and C): AMPH systemic received IP injections of AMPH (1.5 mg/kg) and the 0.0 μg/0.5 μl/side IWP-2 control groups received microinjections of AMPH (20.0 μg/0.5 μl/side). The inhibitor of Wnt Production-2 (IWP-2) alone group did not receive AMPH. The numbers on the x-axis of (B) and (C) are the doses of IWP-2, in μg/0.5 μl/side. All acquisition (ACQ) groups (B) were conditioned with IWP-2 administered 30 min prior to microinfusion of AMPH on drug days. All expression (EXP) groups (C) were conditioned with AMPH and administered IWP-2 only on test session.

Asterisks above the bar represent a significant difference on test session from pre-conditioning based on simple effects analyses of each group following observation of a significant group × phase interaction in the analyses of variance of all groups (*p < 0.05, **p < 0.01, ***p < 0.001); † p = 0.051.