Effects of mGluR1 antagonism in the dorsal hippocampus on drug context-induced reinstatement of cocaine-seeking behavior in rats
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- Xie, X., Ramirez, D.R., Lasseter, H.C. et al. Psychopharmacology (2010) 208: 1. doi:10.1007/s00213-009-1700-7
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The functional integrity of the dorsal hippocampus (DH) is necessary for drug context-induced reinstatement of cocaine seeking. However, the neuropharmacological mechanisms of this phenomenon are poorly understood.
Given the known significance of group I metabotropic glutamate receptors (mGluRs), including the mGluR1 subtype, in drug-induced behaviors, the present study was designed to evaluate the contribution of mGluR1s in the DH to drug context-induced reinstatement of extinguished cocaine-seeking behavior.
Sprague–Dawley rats were trained to lever press for unsignaled cocaine infusions in a distinct environmental context (cocaine-paired context) followed by extinction training in a distinctly different environmental context (extinction context). Using a counterbalanced partial within-subjects testing design, rats were re-exposed to the cocaine-paired context or the extinction context while cocaine-seeking behavior (nonreinforced active lever pressing) was assessed. Prior to each test session, rats received bilateral microinfusions of the highly potent mGluR1-selective antagonist JNJ16259685 (0.6, 30, or 120 pg/0.5 μl per hemisphere) or vehicle into the DH or the overlying somatosensory cortex trunk region (SStr; anatomical control).
Intra-DH, but not intra-SStr, JNJ16259685 infusions dose dependently attenuated drug context-induced reinstatement of cocaine seeking relative to vehicle treatment, without attenuating instrumental behavior in the extinction context, general motor activity, or food-reinforced instrumental behavior in control experiments.
Stimulation of mGluR1s in the DH is necessary for incentive motivational and/or memory processes that contribute to drug context-induced cocaine-seeking behavior. These findings indicate that the mGluR1 is an interesting target from an addiction treatment perspective.