LY404039 is a potent and selective group II metabotropic glutamate receptors mGluR2/3 agonist (Ki = 15 nM against against [3H]LY341495 for binding rat neurons; Ki = 149 nM and 92 nM, respectively, using membrane from human mGluR2- or mGluR3-expressing cells) with >100-fold selectivity over 16 other receptors/transproters, including iGluRs and EAAT1/2/3. LY404039 inhibits forskolin-stimulated c-AMP production in RGT cells expressing human mGluR2 (EC50 = 23 nM) or mGluR3 (EC50 = 48 nM) with little or no potency toward mGluR1a/5a/4a/6/7a/8a-expressing cells (EC50 >10 μM). LY404039 is orally available (Cmax 1528.5 ng/mL, Tmax 2 h; 10 mg/kg p.o. in rats) and exhibits antipsychotic and anxiolytic efficacy in rats (3-30 mg/kg) in vivo.