The present invention provides a compound which has the effect of PDE inhibition, and which is useful as a medicament for preventing or treating schizophrenia or so on.A compound of formula (I0):wherein R1represents a substituent, R2represents a hydrogen atom, or a substituent, R3represents a hydrogen atom, or a substituent, Ring A represents an aromatic ring which can be substituted, and Ring B represents a 5-membered heteroaromatic ring which can be substituted, or a salt thereof.本發明係提供具有PDE抑制效果的化合物,其適用為預防或治療精神分裂症等之藥劑。一種式(I0)之化合物,或其鹽:其中,R1表示取代基;R2表示氫原子、或取代基;R3表示氫原子、或取代基;環A表示可經取代之芳香環;以及環B表示可經取代之5員雜芳香環。無元件符號說明
