Cocaine seeking and taking: role of hippocampal dopamine D1-like receptors.

Despite the well-documented involvement of dopamine D1-like receptor stimulation in cocaine-induced goal-directed behaviours, little is known about the specific contribution of D1-like receptor populations in the dorsal hippocampus (DH) to drug context-induced cocaine-seeking or drug-reinforced instrumental behaviours. To investigate this question, rats were trained to lever press for un-signalled cocaine infusions in a distinct context followed by extinction training in a different context. Cocaine-seeking behaviour (non-reinforced lever responding) was then assessed in the previously cocaine-paired and extinction contexts. SCH23390-induced D1-like receptor antagonism in the DH, but not the overlying trunk region of the somatosensory cortex, dose-dependently inhibited drug context-induced cocaine-seeking behaviour, without altering cocaine-reinforced instrumental responding, cocaine intake, food-reinforced instrumental responding, or general motor activity, relative to vehicle treatment. These findings suggest that D1-like receptor stimulation in the DH is critical for the incentive motivational effects and/or memory of cocaine-paired contextual stimuli that contribute to drug-seeking behaviour.