Activation of Group II Metabotropic Glutamate Receptors Attenuates Both Stress and Cue-Induced Ethanol-Seeking and Modulates c-fosExpression in the Hippocampus and Amygdala

Abstract

Major precipitating factors for relapse to drug use are stress and exposure to drug-related environmental stimuli. Group II (mGlu(2/3)) metabotropic glutamate receptors (mGluRs) are densely expressed within circuitries mediating the motivating effects of stress and drug cues and, therefore, may participate in regulating drug-seeking linked to both of these risk factors. Thus, we tested the hypothesis that pharmacological activation of group II mGluRs modifies both stress- and cue-induced ethanol-seeking, using reinstatement models of relapse. In parallel, brain c-fos expression was examined to identify neural substrates for the behavioral effects of group II mGluR activation. The selective mGlu(2/3) agonist LY379268 (1R,4R,5S,6R-2-oxa-4-aminobicyclo[3.1.0]hexane-4,6-dicarboxylate) (0.3, 1.0, and 3.0 mg/kg, s.c.) dose dependently blocked the recovery of extinguished ethanol-seeking induced by either footshock stress or ethanol-associated discriminative stimuli. These effects were accompanied by modulation of c-fos expression in the hippocampus, central nucleus of the amygdala, bed nucleus of the stria terminalis, and medial parvocellular paraventricular nucleus of the hypothalamus. The results implicate group II mGluRs as a shared neuropharmacological substrate for ethanol-seeking elicited by both drug cues and stress and identify group II mGluRs as promising treatment targets for relapse prevention.