Cocaine-paired lever responding during self-administration, extinction, and reinstatement testing (a-c). (a) Rats from all groups did not significantly differ in rates of cocaine self-administration over FR schedules of reinforcement. (b) Rats from all groups did not significantly differ in cocaine-paired lever responses during extinction sessions. The latency to reach extinction also did not significantly differ between groups. (c) Disruption of hippocampal activity by LFS in the dorsal or ventral hippocampus enhances cocaine priming-induced reinstatement of cocaine-seeking behavior. The bar graphs (Group D without LFS, gray bars; Group E with LFS in the ventral hippocampus, light gray filled); Group F with LFS in the dorsal hippocampus, light gray hatched depict non-reinforced, cocaine-paired lever responses (mean ± SEM) during testing in extinction (Ext), cocaine-primed (cocaine) and saline-primed (saline) reinstatement (Rst). n = 4–10 each group. Data are expressed as mean ± SEM. * significant difference relative to responding during extinction (p < 0.05); # significant difference compared with Group D during reinstatement (p < 0.05); $ significant difference relative to cocaine-primed treatment (p < 0.01).