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 or so on.A compound represented by the formula (I):wherein ring A represents an optionally substituted 6-membered ring； any one or two of from Z1 to Z4 represents -N=, and the others represent -CH=；Y represents an oxygen atom, a sulfur atom, an optionally substituted methylene group or -NRc-；Rc represents a hydrogen atom, or a substituent； and R represents(1) a group represented by the formula:wherein R1 represents a phenyl group or 5- to 10-membered heterocyclic group, each of which is optionally substituted； L represents a sulfur atom, an oxygen atom, an optionally substituted methylene group, -CO-, -NRa-, -CH2O-, -NRaCOO-, -NRaCONRb-, -NRaCOCH2-, -NRaCO-,； Ra and Rb are the same or different and each represents a hydrogen atom, or an optionally substituted C1-6 alkyl group, or L and R1 in combination optionally form an optionally substituted bi- or tri-cyclic fused heterocyclic group； and ring B1 represents a benzene ring, a pyridine ring, a pyrimidine ring, a pyrazine ring or a pyridazine ring, each of which is optionally substituted； or(2) a group represented by the formula:wherein R2 represents a phenyl group or 5- to 10-membered heterocyclic group, each of which is optionally substituted； ring B2 represents a benzene ring, a pyridine ring, a pyrimidine ring, a pyrazine ring or a pyridazine ring, each of which is optionally substituted； and ring D represents an optionally further substituted 5- or 6-membered ring； or a salt thereof.本發明提供一種化合物，其具有抑制PDE之效果，以及一種有效作為預防或治療精神分裂症等之製劑。一種下式(I)表示之化合物或其鹽：其中，環A表示視需要經取代之6員環；選自Z1至Z4之任一者或二者表示-N=，以及其它者表示-CH=；Y表示氧原子、硫原子、視需要經取代之亞甲基或-NRc-；Rc表示氫原子，或者取代基；以及R表示(1) 以下列化學式表示之基團：其中，R1表示苯基或5至10員雜環基，各該等基係視需要經取代；L表示硫原子、氧原子、視需要經取代之亞甲基、-CO-、-NRa-、-CH2O-、-NRaCOO-、-NRaCONRb-、-NRaCOCH2-、-NRaCO-、Ra及Rb為相同或不同，且各自表示氫原子，或者視需要經取代之C1-6烷基，或者L及R1組合而視需要形成視需要經取代之二或三環之稠和雜環基；以及環B1表示苯環、吡啶環、嘧啶環、吡環或嗒環，且各該等
