THE PRESENT INVENTION RELATES TO ETHYNYL DERIVATIVES OF FORMULA (I) WHEREIN X IS N OR C-R¹； Y IS N OR C-R²； Z IS CH OR N； R⁴ IS A 6-MEMBERED AROMATIC SUBSTITUENT CONTAINING 0, 1 OR 2 NITROGEN ATOMS, OPTIONALLY SUBSTITUTED BY 1 TO 3 GROUPS, SELECTED FROM HALOGEN, LOWER ALKYL, LOWER ALKOXY OR NRR’； R¹ IS HYDROGEN, LOWER ALKYL, LOWER ALKOXY, HYDROXY, LOWER HYDROXYALKYL, LOWER CYCLOALKYL OR IS HETEROCYCLOALKYL OPTIONALLY SUBSTITUTED WITH HYDROXY OR ALKOXY； R² IS HYDROGEN, CN, LOWER ALKYL OR HETEROCYCLOALKYL； R AND R’ ARE INDEPENDENTLY FROM EACH OTHER HYDROGEN OR LOWER ALKYL； OR TO A PHARMACEUTICALLY ACCEPTABLE SALT OR ACID ADDITION SALT, TO A RACEMIC MIXTURE, OR TO ITS CORRESPONDING ENANTIOMER AND/OR OPTICAL ISOMER AND/OR STEREOISOMER THEREOF. IT HAS NOW SURPRISINGLY BEEN FOUND THAT THE COMPOUNDS OF GENERAL FORMULA (I) ARE POSITIVE ALLOSTERIC MODULATORS (PAM) OF THE METABOTROPIC GLUTAMATE RECEPTOR SUBTYPE 5 (mGluR5) AND THEY ARE THEREFORE USEFUL FOR THE TREATMENT OF DISEASES RELATED TO THIS RECEPTOR.
