The present invention provides a compound which has the effect of PDE inhibition, and which is useful as an agent for preventing or treating schizophrenia. The compound is represented by the formula (I): wherein the symbols are defined in the specification.La présente invention concerne un composé qui a un effet d'inhibition de PDE et qui est utile comme agent de prévention ou de traitement de la schizophrénie etc., représenté par la formule (I).
