ATTENUATION OF PRECIPITATED MORPHINE-WITHDRAWAL SYMPTOMS BY ACUTE ICVADMINISTRATION OF A GROUP IIMGLUR AGONIST

1 We previously showed that chronic i.c.v. antagonism of metabotropic glutamate receptors (mGluRs) concurrently with s.c. morphine significa ntly attenuated precipitated withdrawal symptoms. Conversely, acute i. c.v. injection of a selective group II mGluR antagonist just before th e precipitation of withdrawal exacerbated abstinence symptoms. 2 In th e present study, we showed that acute i.c.v. administration of the non -selective mGluR agonist 1-aminocyclopentane-1,3-dicarboxylic acid ((1 S,3R)-ACPD), as well as the group II selective agonist 1'R,2'R,3'R)-2- (2',3'-dicarboxycyclopropyl)glycine (DCG-IV), significantly attenuated the severity of precipitated withdrawal symptoms. 3 From these result s we hypothesize that chronic opioid treatment may indirectly induce a desensitization of group II mGluRs, which contributes to the developm ent of dependence.