This study investigated the effects of group II metabotropic glutamate receptor agonist, 2R, 4R-4-aminopyrrolidine-2,4-dicarboxylate (2R, 4R-APDC), on cell proliferation in the dentate gyrus of adult rats. 2R, 4R-APDC at a dose of 1 and 10 nmol/day resulted in decreased bromodeoxyuridine immunoreactive cells in the dentate gyrus. In addition, we found that APDC treatment had no effect on the number of BrdU+ and GFAP(+)-labeled cells or BrdU+ and NeuN(+)-labeled cells compared with controls. These data suggest that group II metabotropic glutamate receptor is an important site for glutamate's regulation on cell proliferation in the dentate gyrus, but 2R, 4R-APDC had no effects on newborn cell's ability to differentiate into neurons or astrocytes.