Fig. 1.
Mean ± SEM (a) active and (b) inactive lever presses for amphetamine (0.03 mg/kg/infusion) between EC, IC, and SC rats during FR-1 responding following MTEP (0.3, 1.0, 3.0 mg/kg) or saline. Caret sign (^) indicates that IC rats self-administered less amphetamine following 3.0 mg/kg MTEP than following saline. Asterisk (*) indicates that in the absence of treatment, EC rats self-administered less amphetamine than IC rats (p<.05). b There were no significant differences in inactive lever responding between EC, IC, or SC rats