Additive neuroprotection by metabotropic glutamate receptor subtype-selective ligands in a rat Parkinson's model

Pharmacological activation of group III metabotropic glutamate receptors (mGluR) or inhibition of group I mGluR by subtype-selective ligands is neuroprotective in experimental models of Parkinson's disease. The aim of this study was to investigate whether targeting both receptor subtypes simultaneously produces enhanced neuroprotection. Rodents bearing a 6-hydroxydopamine lesion were intranigrally administered either the group III mGluR agonist L-(+)-2-amino-4-phosphonobutyric acid or the group I mGluR antagonist 2-methyl-6-(phenylethynyl)pyridine, alone or in combination. Coadministration of L-(+)-2-amino-4-phosphonobutyric acid and 2-methyl-6-(phenylethynyl)pyridine resulted in robust nigrostriatal neuroprotection that was significantly increased compared with either compound alone. These data suggest that targeting multiple mGluR subtypes with low doses of selective ligands may provide an enhanced therapeutic response in experimental models of Parkinson's disease.