INTRASTRIATAL INJECTION OF THE METABOTROPIC GLUTAMATE-RECEPTOR ANTAGONIST MCPG ATTENUATES ACUTE AMPHETAMINE-STIMULATED NEUROPEPTIDE MESSENGER-RNA EXPRESSION IN RAT STRIATUM

In chronically cannulated rats, microinjection of a competitive metabo tropic glutamate receptor (mGluR) antagonist, (+)-alpha-methyl-4-carbo xyphenylglycine (MCPG), into the dorsal striatum at doses of 0.4, 2 an d 10 mu g/l mu l did not affect basal levels of preprodynorphin, subst ance P and preproenkephalin mRNAs in the dorsal striatum as revealed b y quantitative in situ hybridization. However, intrastriatal MCPG (0.0 8, 0.4 and 2 mu g/l mu l) dose-dependently attenuated increases in the three mRNA expression induced by acute amphetamine injection (2 mg/kg , i.p.). MCPG had no significant effect on spontaneous, and amphetamin e-stimulated, behavioral activities. These data indicate that activati on of MCPG-sensitive mGluRs is necessary for upregulation of striatal neuropeptide mRNA expression in response to amphetamine exposure. Howe ver, the mGluR activity is not implicated in maintaining basal levels of the peptide gene expression in the striatum.