Dopamine D3 as well as D2 receptor ligands attenuate the cue-induced cocaine-seeking in a relapse model in rats.

Environmental cues associated with the previously abused drug elicit craving and relapse to drug use in humans. Several reinstatement paradigms are used in animals to examine the relapse-preventing efficacy of possible medical treatments. The purpose of the present study was to investigate the effect of D3 dopamine receptor ligands in a relapse model where animals with stable cocaine self-administration behavior were exposed to all the environmental and reinforcement-contingent discrete cues associated for the previous cocaine-intake in a single extinction session after 3-week long abstinence period. The following compounds were studied: SB-277011-A as a selective D3 antagonist, BP-897 as a D3 partial agonist/D2 antagonist and haloperidol as a preferential D2 receptor antagonist. In addition, in the same paradigm we investigated the effect of the above ligands on relapse to natural reward-seeking behavior using sucrose as natural reward. SB-277011-A (5 and 20 mg/kg), BP-897 (1 mg/kg) and haloperidol (0.2 mg/kg) significantly inhibited the secondary cues-induced cocaine-seeking behavior. None of the above drugs significantly influenced the cue-controlled sucrose-seeking behavior. These results confirm the importance of the D3 as well as the D2 dopamine receptor in modulating the cue-induced cocaine relapse and the possible usefulness of the D3 dopamine receptor ligands as potential medication in cocaine addicts.