An antidepressant comprising, as an active ingredient, a compound having an antagonistic effect on group II metabotropic glutamate receptors, as well as a 2-amino-3-alkoxy-6-fluoro-bicycloÄ3.1.0Ühexane-2,6-dicarboxylic acid derivative of Formula ÄIÜ: <CHEM> Äwherein R<1> and R<2>, which may be the same or different, each represent a hydroxyl group, a C1-10 alkoxy group, etc.; R<3> represents a C1-10 acyl group, a C1-6 alkoxy-C1-6 acyl group, etc.; and R<4> and R<5>, which may be the same or different, each represent a hydrogen atom, a C1-10 alkyl group, etc.Ü or a pharmaceutically acceptable salt or hydrate thereof.
6-FLUOROBICYCLO 3.1.0 HEXANE DERIVATIVES