Effects of LY-379268 on cocaine self-administration and cocaine-induced reinstatement of drug-seeking behavior. Systemic administration of LY-379268 (3, 6 mg/kg, i.p.) failed to alter cocaine self-administration under FR2 reinforcement schedule in either WT or mGluR2-KO rats (A), but significantly inhibited cocaine self-administration under progressive-ratio (PR) reinforcement schedule in WT rats, not in mGluR2-KO rats (B). mGluR2-KO rats displayed lower reinstatement response to cocaine priming than WT rats (C). Pretreatment with LY-379268 (3 mg/kg, i.p.) produced a significant reduction in cocaine-induced reinstatement of drug-seeking behavior in both WT and mGluR2-KO rats (C). The data are represented as mean ± SEM. * p<0.05, *** p<0.001, compared to the vehicle control group. Also see Figure S2.